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Common ostrich
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Common ostrich
Temporal range: 15–0 Ma
PreЄЄOSDCPTJKPgN
Early Miocene-Present
Struthio camelus - Etosha 2014 (3).jpg
South African ostrich male (left) and females (S. camelus australis)
Conservation status
Least Concern (IUCN 3.1) common ostrich 1 common ostrich
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Struthioniformes
Family: Struthionidae
Genus: Struthio
Species: S. camelus
Binomial name
Struthio camelus
Linnaeus, 1758 common ostrich 2 common ostrich
Subspecies
S. c. camelus Linnaeus, 1758 common ostrich 2 common ostrich North African
ostrich
S. c. australis Gurney, 1868 common ostrich 2 common ostrich Southern ostrich
S. c. massaicus Neumann, 1898 common ostrich 2 common ostrich Masai ostrich
†S. c. syriacus Rothschild, 1919 common ostrich 2 common ostrich Arabian ostrich
Struthio camelus distribution.svg
Struthio camelus distribution map
S. c. camelus S. molybdophanes
S. c. massaicus S. c. australis
The common ostrich (Struthio camelus), or simply ostrich, is a species of large
flightless bird native to Africa. It is one of two extant species of ostriches,
the only living members of the genus Struthio in the ratite order of birds. The
other is the Somali ostrich (Struthio molybdophanes) was recognized as a
distinct species by BirdLife International in 2014 after having been considered
a very distinctive subspecies of ostrich. common ostrich 2 common ostrich common
ostrich 3 common ostrich
The common ostrich shares the order Struthioniformes with the kiwis, emus,
rheas, and cassowaries. However, phylogenetic studies have shown that it is the
sister group to all other members of Palaeognathae and thus the flighted
tinamous are the sister group to the extinct moa. common ostrich 4 common
ostrich common ostrich 5 common ostrich It is distinctive in its appearance,
with a long neck and legs, and can run for a long time at the speed of 55 km/h
common ostrich 6 common ostrich or even up to about 70 km/h (19 m/s; 43 mph),
common ostrich 7 common ostrich the fastest land speed of any bird. common
ostrich 8 common ostrich The common ostrich is the largest living species of
bird and lays the largest eggs of any living bird (extinct elephant birds of
Madagascar and the giant moa of New Zealand laid larger eggs).
The common ostrich's diet consists mainly of plant matter, though it also eats
invertebrates. It lives in nomadic groups of 5 to 50 birds. When threatened, the
ostrich will either hide itself by lying flat against the ground, or run away.
If cornered, it can attack with a kick of its powerful legs. Mating patterns
differ by geographical region, but territorial males fight for a harem of two to
seven females.
The common ostrich is farmed around the world, particularly for its feathers,
which are decorative and are also used as feather dusters. Its skin is used for
leather products and its meat is marketed commercially, with its leanness a
common marketing point. common ostrich 7 common ostrich
Contents
1 Description
2 Taxonomy
2.1 Subspecies
3 Distribution and habitat
4 Behaviour and ecology
4.1 "Head in the sand" myth
4.2 Feeding
4.3 Mating
4.4 Predators
5 Physiology
5.1 Respiration
5.1.1 Anatomy
5.1.2 Function
5.2 Circulation
5.2.1 Heart anatomy
5.2.2 Blood composition
5.3 Osmoregulation
5.3.1 Physiological challenges
5.3.2 System overview
5.3.2.1 Kidney function
5.3.2.2 Water intake and turnover
5.3.2.3 Nasal glands
5.3.2.4 Biochemistry
5.4 Thermoregulation
5.4.1 Physical adaptations
5.4.2 Internal adaptations
5.4.3 Breathing adaptations
5.4.4 Metabolism
6 Status and conservation
7 Ostriches and humans
7.1 Hunting and farming
7.2 Attacks
7.3 Racing
8 References
9 Further reading
10 External links
Description
Common ostriches usually weigh from 63 to 145 kilograms (139–320 lb), or as much
as two adult humans. common ostrich 7 common ostrich common ostrich 9 common
ostrich The Masai ostriches of East Africa (S. c. massaicus) averaged 115 kg
(254 lb) in males and 100 kg (220 lb) in females, while the nominate subspecies,
the North African ostrich (S. c. camelus), was found to average 111 kg (245 lb)
in unsexed adults. Exceptional male ostriches (in the nominate subspecies) can
weigh up to 156.8 kg (346 lb). At sexual maturity (two to four years), male
common ostriches can be from 2.1 to 2.8 m (6 ft 11 in to 9 ft 2 in) in height,
while female common ostriches range from 1.7 to 2.0 m (5 ft 7 in to 6 ft 7 in)
tall. common ostrich 7 common ostrich New chicks are fawn in colour, with dark
brown spots. common ostrich 10 common ostrich During the first year of life,
chicks grow at about 25 cm (9.8 in) per month. At one year of age, common
ostriches weigh approximately 45 kilograms (99 lb). Their lifespan is up to
40–45 years.
The feathers of adult males are mostly black, with white primaries and a white
tail. However, the tail of one subspecies is buff. Females and young males are
greyish-brown and white. The head and neck of both male and female ostriches is
nearly bare, with a thin layer of down. common ostrich 9 common ostrich common
ostrich 10 common ostrich The skin of the female's neck and thighs is pinkish
gray, common ostrich 10 common ostrich while the male's is gray or pink
dependent on subspecies.
Close-up of head: Note the highly modified feathers
Close-up of head: Note the long eyelashes to protect the eyes
Foot: Note the frequently missing nail on the outer toe
Ostrich skull
Claws on the wings
Ostrich skeleton
male running in Namibia
The long neck and legs keep their head up to 2.8 m (9 ft) above the ground, and
their eyes are said to be the largest of any land vertebrate: 50 mm (2.0 in) in
diameter; common ostrich 11 common ostrich helping them to see predators at a
great distance. The eyes are shaded from sunlight from above. common ostrich 12
common ostrich common ostrich 13 common ostrich However, the head and bill are
relatively small for the birds' huge size, with the bill measuring 12 to 14.3 cm
(4.7 to 5.6 in). common ostrich 7 common ostrich
Their skin varies in colour depending on the subspecies, with some having light
or dark gray skin and others having pinkish or even reddish skin. The strong
legs of the common ostrich are unfeathered and show bare skin, with the tarsus
(the lowest upright part of the leg) being covered in scales: red in the male,
black in the female. The tarsus of the common ostrich is the largest of any
living bird, measuring 39 to 53 cm (15 to 21 in) in length. common ostrich 7
common ostrich The bird has just two toes on each foot (most birds have four),
with the nail on the larger, inner toe resembling a hoof. The outer toe has no
nail. common ostrich 14 common ostrich The reduced number of toes is an
adaptation that appears to aid in running, useful for getting away from
predators. Common ostriches can run at a speed over 70 km/h (43 mph) and can
cover 3 to 5 m (9.8 to 16.4 ft) in a single stride. common ostrich 15 common
ostrich The wings reach a span of about 2 metres (6 ft 7 in), and the wing chord
measurement of 90 cm (35 in) is around the same size as for the largest flying
birds. common ostrich 7 common ostrich
The feathers lack the tiny hooks that lock together the smooth external feathers
of flying birds, and so are soft and fluffy and serve as insulation. Common
ostriches can tolerate a wide range of temperatures. In much of their habitat,
temperatures vary as much as 40 °C (72 °F) between night and day. Their
temperature control relies in part on behavioural thermoregulation. For example,
they use their wings to cover the naked skin of the upper legs and flanks to
conserve heat, or leave these areas bare to release heat. The wings also
function as stabilizers to give better maneuverability when running. Tests have
shown that the wings are actively involved in rapid braking, turning and zigzag
maneuvers. common ostrich 16 common ostrich They have 50–60 tail feathers, and
their wings have 16 primary, four alular and 20–23 secondary feathers. common
ostrich 7 common ostrich
The common ostrich's sternum is flat, lacking the keel to which wing muscles
attach in flying birds. common ostrich 17 common ostrich The beak is flat and
broad, with a rounded tip. common ostrich 9 common ostrich Like all ratites, the
ostrich has no crop, common ostrich 18 common ostrich and it also lacks a
gallbladder. common ostrich 19 common ostrich They have three stomachs, and the
caecum is 71 cm (28 in) long. Unlike all other living birds, the common ostrich
secretes urine separately from faeces. common ostrich 20 common ostrich All
other birds store the urine and faeces combined in the coprodeum, but the
ostrich stores the faeces in the terminal rectum. common ostrich 20 common
ostrich They also have unique pubic bones that are fused to hold their gut.
Unlike most birds, the males have a copulatory organ, which is retractable and
20 cm (8 in) long. Their palate differs from other ratites in that the sphenoid
and palatal bones are unconnected. common ostrich 7 common ostrich
Taxonomy
The common ostrich was originally described by Carl Linnaeus from Sweden in his
18th-century work, Systema Naturae under its current binomial name. common
ostrich 21 common ostrich Its scientific name is derived from Latin, struthio
meaning "ostrich" and camelus meaning "camel", alluding to its dry habitat.
common ostrich 22 common ostrich
The common ostrich belongs to the ratite order Struthioniformes. Other members
include rheas, emus, cassowaries, moa, kiwi and the largest known bird ever, the
now-extinct elephant bird (Aepyornis). However, the classification of the
ratites as a single order has always been questioned, with the alternative
classification restricting the Struthioniformes to the ostrich lineage and
elevating the other groups.
Subspecies
Four living subspecies are recognised:
Common ostrich (S. camelus) complex:
Subspecies of common ostrich
Subspecies Description Image
North African ostrich (S. c. camelus), also called the red-necked ostrich or
Barbary ostrich Lives in North Africa. Historically it was the most widespread
subspecies, ranging from Ethiopia and Sudan in the east throughout the Sahel
common ostrich 23 common ostrich to Senegal and Mauritania in the west, and
north to Egypt and southern Morocco, respectively. It has now disappeared from
large parts of this range, common ostrich 24 common ostrich and it only remains
in 6 of the 18 countries where it originally occurred, leading some to consider
it Critically Endangered. common ostrich 25 common ostrich It is the largest
subspecies, at 2.74 m (9.0 ft) in height and up to 154 kilograms (340 lb) in
weight. common ostrich 26 common ostrich The neck is pinkish-red, the plumage of
males is black and white, and the plumage of females is grey. common ostrich 26
common ostrich
Northern Africa: Algeria, Central African Republic, Chad, Egypt, Ethiopia,
Libya, Mali, Mauritania, Morocco, South Sudan, Sudan, Togo and Tunisia
Western Africa: Benin, Burkina Faso, Cameroon, Ghana, Niger, Nigeria and Senegal
Yaen001.jpg
South African ostrich (S. c. australis), also commonly known as black-necked
ostrich or southern ostrich Is found south of the rivers Zambezi and Cunene. It
is farmed for its meat, leather and feathers in the Little Karoo area of Cape
Province. common ostrich 27 common ostrich
Southern Africa: Angola, Botswana, Democratic Republic of the Congo, Namibia,
South Africa, Zambia and Zimbabwe
Ostrich (Struthio camelus) male (13994461256).jpg
Masai ostrich (S. c. massaicus), also known as the pink-necked ostrich or East
African ostrich It has some small feathers on its head, and its neck and thighs
are pink. During the mating season, the male's neck and thighs become brighter.
Its range is essentially limited to southern Kenya and eastern Tanzania common
ostrich 23 common ostrich and Ethiopia and parts of southern Somalia. common
ostrich 26 common ostrich
Eastern Africa: Burundi, Democratic Republic of the Congo, Ethiopia, Kenya,
Rwanda, Somalia, Tanzania and Uganda
Ostrich Struthio camelus Tanzania 3742 cropped Nevit.jpg
Arabian ostrich (daggerS. c. syriacus), also known as Syrian ostrich or Middle
Eastern ostrich Was formerly very common in the Arabian Peninsula, Syria, common
ostrich 23 common ostrich and Iraq; it became extinct around 1966.
Western Asia: Iran, Iraq, Israel, Jordan, Kuwait, Oman, Qatar, Saudi Arabia,
Syria, United Arab Emirates, and Yemen
Arabian Ostrich hunt.jpg
Somali ostrich
Subspecies Description Image
Somali ostrich (S. molybdophanes), also known as blue-necked ostrich Found in
southern Ethiopia, northeastern Kenya, and Somalia. common ostrich 23 common
ostrich The neck and thighs are grey-blue, and during the mating season, the
male's neck and thighs become brighter and bluer. The females are more brown
than those of other subspecies. common ostrich 26 common ostrich It generally
lives in pairs or alone, rather than in flocks. Its range overlaps with S. c.
massaicus in northeastern Kenya. common ostrich 26 common ostrich
Northeastern Africa: Djibouti, Eritrea, Ethiopia, Kenya and Somalia
Struthio molybdophanes.jpg
Some analyses indicate that the Somali ostrich is now considered a full species
by the Tree of Life Project, The Clements Checklist of Birds of the World,
BirdLife International, and the IOC World Bird List recognize it as a different
species. A few authorities, including the Howard and Moore Complete Checklist of
the Birds of the World do not recognize it as separate. common ostrich 3 common
ostrich common ostrich 28 common ostrich Mitochondrial DNA haplotype comparisons
suggest that it diverged from the other ostriches not quite 4 mya due to
formation of the East African Rift. Hybridization with the subspecies that
evolved southwestwards of its range, S. c. massaicus, has apparently been
prevented from occurring on a significant scale by ecological separation, the
Somali ostrich preferring bushland where it browses middle-height vegetation for
food while the Masai ostrich is, like the other subspecies, a grazing bird of
the open savanna and miombo habitat. common ostrich 29 common ostrich
The population from Río de Oro was once separated as Struthio camelus spatzi
because its eggshell pores were shaped like a teardrop and not round. However,
as there is considerable variation of this character and there were no other
differences between these birds and adjacent populations of S. c. camelus, the
separation is no longer considered valid. common ostrich 30 common ostrich
common ostrich 31 common ostrich This population disappeared in the latter half
of the 20th century. There were 19th-century reports of the existence of small
ostriches in North Africa; these are referred to as Levaillant's ostrich
(Struthio bidactylus) but remain a hypothetical form not supported by material
evidence. common ostrich 32 common ostrich
Distribution and habitat
Common ostriches formerly occupied Africa north and south of the Sahara, East
Africa, Africa south of the rainforest belt, and much of Asia Minor. common
ostrich 7 common ostrich Today common ostriches prefer open land and are native
to the savannas and Sahel of Africa, both north and south of the equatorial
forest zone. common ostrich 33 common ostrich In southwest Africa they inhabit
the semi-desert or true desert. Farmed common ostriches in Australia have
established feral populations. common ostrich 1 common ostrich common ostrich 34
common ostrich The Arabian ostriches in the Near and Middle East were hunted to
extinction by the middle of the 20th century. Attempts to reintroduce the common
ostrich into Israel have failed. common ostrich 35 common ostrich Common
ostriches have occasionally been seen inhabiting islands on the Dahlak
Archipelago, in the Red Sea near Eritrea.
Research conducted by the Birbal Sahni Institute of Palaeobotany in India found
molecular evidence that ostriches lived in India 25,000 years ago. DNA tests on
fossilized eggshells recovered from eight archaeological sites in the states of
Rajasthan, Gujarat and Madhya Pradesh found 92% genetic similarity between the
eggshells and the North African ostrich, so these could have been fairly distant
relatives. common ostrich 36 common ostrich common ostrich 37 common ostrich
Behaviour and ecology
Pair "dancing"
File:Ostriches-Sleep-like-Platypuses-pone.0023203.s003.ogv
Ostriches sleeping, with REM sleep and slow-wave sleep phases. common ostrich 38
common ostrich
Common ostriches normally spend the winter months in pairs or alone. Only 16
percent of common ostrich sightings were of more than two birds. common ostrich
7 common ostrich During breeding season and sometimes during extreme rainless
periods ostriches live in nomadic groups of five to 100 birds (led by a top hen)
that often travel together with other grazing animals, such as zebras or
antelopes. common ostrich 33 common ostrich Ostriches are diurnal, but may be
active on moonlit nights. They are most active early and late in the day. common
ostrich 7 common ostrich The male common ostrich territory is between 2 and 20
km2 (0.77 and 7.72 sq mi). common ostrich 10 common ostrich
With their acute eyesight and hearing, common ostriches can sense predators such
as lions from far away. When being pursued by a predator, they have been known
to reach speeds in excess of 70 km/h (43 mph), common ostrich 7 common ostrich
and can maintain a steady speed of 50 km/h (31 mph), which makes the common
ostrich the world's fastest two-legged animal. common ostrich 39 common ostrich
common ostrich 40 common ostrich When lying down and hiding from predators, the
birds lay their heads and necks flat on the ground, making them appear like a
mound of earth from a distance, aided by the heat haze in their hot, dry
habitat. common ostrich 41 common ostrich common ostrich 42 common ostrich
When threatened, common ostriches run away, but they can cause serious injury
and death with kicks from their powerful legs. common ostrich 33 common ostrich
Their legs can only kick forward. common ostrich 43 common ostrich
"Head in the sand" myth
Contrary to popular belief, ostriches do not bury their heads in sand to avoid
danger. common ostrich 44 common ostrich This myth likely began with Pliny the
Elder (AD 23–79), who wrote that ostriches "imagine, when they have thrust their
head and neck into a bush, that the whole of their body is concealed." common
ostrich 45 common ostrich This may have been a misunderstanding of their
sticking their heads in the sand to swallow sand and pebbles to help digest
their fibrous food, common ostrich 46 common ostrich or, as National Geographic
suggests, of the defensive behavior of lying low, so that they may appear from a
distance to have their head buried. common ostrich 47 common ostrich Another
possible origin for the myth lies with the fact that ostriches keep their eggs
in holes in the sand instead of nests, and must rotate them using their beaks
during incubation; digging the hole, placing the eggs, and rotating them might
each be mistaken for an attempt to bury their heads in the sand. common ostrich
48 common ostrich
Feeding
They mainly feed on seeds, shrubs, grass, fruit and flowers; common ostrich 7
common ostrich common ostrich 10 common ostrich occasionally they also eat
insects such as locusts. Lacking teeth, they swallow pebbles that act as
gastroliths to grind food in the gizzard. When eating, they will fill their
gullet with food, which is in turn passed down their esophagus in the form of a
ball called a bolus. The bolus may be as much as 210 ml (7.1 US fl oz). After
passing through the neck (there is no crop) the food enters the gizzard and is
worked on by the aforementioned pebbles. The gizzard can hold as much as 1,300 g
(46 oz), of which up to 45% may be sand and pebbles. common ostrich 10 common
ostrich Common ostriches can go without drinking for several days, using
metabolic water and moisture in ingested plants, common ostrich 49 common
ostrich but they enjoy liquid water and frequently take baths where it is
available. common ostrich 33 common ostrich They can survive losing up to 25% of
their body weight through dehydration. common ostrich 50 common ostrich
Mating
Common ostriches become sexually mature when they are 2 to 4 years old; females
mature about six months earlier than males. As with other birds, an individual
may reproduce several times over its lifetime. The mating season begins in March
or April and ends sometime before September. The mating process differs in
different geographical regions. Territorial males typically boom in defence of
their territory and harem of two to seven hens; common ostrich 51 common ostrich
the successful male may then mate with several females in the area, but will
only form a pair bond with a 'major' female. common ostrich 51 common ostrich
The cock performs with his wings, alternating wing beats, until he attracts a
mate. They will go to the mating area and he will maintain privacy by driving
away all intruders. They graze until their behaviour is synchronized, then the
feeding becomes secondary and the process takes on a ritualistic appearance. The
cock will then excitedly flap alternate wings again, and start poking on the
ground with his bill. He will then violently flap his wings to symbolically
clear out a nest in the soil. Then, while the hen runs a circle around him with
lowered wings, he will wind his head in a spiral motion. She will drop to the
ground and he will mount for copulation. common ostrich 7 common ostrich Common
ostriches raised entirely by humans may direct their courtship behaviour not at
other ostriches, but toward their human keepers. common ostrich 52 common
ostrich
Only 15% of the surviving chicks reach 1 year of age
Ostrich chick
Common ostrich chick, recently hatched from egg
Common ostrich hen with chicks
Female incubating eggs in a shallow nest on the ground
Ostrich nest
Egg
Fried egg
The female common ostrich lays her fertilised eggs in a single communal nest, a
simple pit, 30 to 60 cm (12–24 in) deep and 3 m (9.8 ft) wide, common ostrich 53
common ostrich scraped in the ground by the male. The dominant female lays her
eggs first, and when it is time to cover them for incubation she discards extra
eggs from the weaker females, leaving about 20 in most cases. common ostrich 7
common ostrich A female common ostrich can distinguish her own eggs from the
others in a communal nest. common ostrich 54 common ostrich Ostrich eggs are the
largest of all eggs, common ostrich 55 common ostrich though they are actually
the smallest eggs relative to the size of the adult bird — on average they are
15 cm (5.9 in) long, 13 cm (5.1 in) wide, and weigh 1.4 kilograms (3.1 lb), over
20 times the weight of a chicken's egg and only 1 to 4% the size of the female.
common ostrich 56 common ostrich They are glossy cream-coloured, with thick
shells marked by small pits. common ostrich 17 common ostrich
The eggs are incubated by the females by day and by the males by night. This
uses the colouration of the two sexes to escape detection of the nest, as the
drab female blends in with the sand, while the black male is nearly undetectable
in the night. common ostrich 17 common ostrich The incubation period is 35 to 45
days, which is rather short compared to other ratites. This is believed to be
the case due to the high rate of predation. common ostrich 56 common ostrich
Typically, the male defends the hatchlings and teaches them to feed, although
males and females cooperate in rearing chicks. Fewer than 10% of nests survive
the 9 week period of laying and incubation, and of the surviving chicks, only
15% of those survive to 1 year of age. common ostrich 10 common ostrich However,
among those common ostriches who survive to adulthood, the species is one of the
longest-living bird species. Common ostriches in captivity have lived to 62
years and 7 months. common ostrich 57 common ostrich
Predators
As a flightless species in the rich biozone of the African savanna, the common
ostrich must face a variety of formidable predators throughout its life cycle.
Animals that prey on ostriches of all ages may include cheetahs, lions,
leopards, African hunting dogs, and spotted hyenas. common ostrich 7 common
ostrich Common ostriches can often outrun most of their predators in a pursuit,
so most predators will try to ambush an unsuspecting bird using obstructing
vegetation or other objects. A notable exception is the cheetah, which is the
most prolific predator of adult common ostriches due to its own great running
speeds. common ostrich 58 common ostrich
Predators of nests and young common ostriches include jackals, various birds of
prey, warthogs, mongoose and Egyptian vultures. common ostrich 51 common ostrich
common ostrich 59 common ostrich If the nest or young are threatened, either or
both of the parents may create a distraction, feigning injury. common ostrich 56
common ostrich However, they may sometimes fiercely fight predators, especially
when chicks are being defended, and have been capable of killing even lions in
such confrontations. common ostrich 47 common ostrich
Physiology
Respiration
Anatomy
Diagrammatic location of the air sacs of the common ostrich
Morphology of the common ostrich lung indicates that the structure conforms to
that of the other avian species, but still retains parts of its primitive avian
species, ratite, structure. common ostrich 60 common ostrich The opening to the
respiratory pathway begins with the laryngeal cavity lying posterior to the
choanae within the buccal cavity. common ostrich 61 common ostrich The tip of
the tongue then lies anterior to the choanae, excluding the nasal respiratory
pathway from the buccal cavity. common ostrich 61 common ostrich The trachea
lies ventrally to the cervical vertebrae extending from the larynx to the
syrinx, where the trachea enters the thorax, dividing into two primary bronchi,
one to each lung, in which they continue directly through to become mesobronchi.
common ostrich 61 common ostrich Ten different air sacs attach to the lungs to
form areas for respiration. common ostrich 61 common ostrich The most posterior
air sacs (abdominal and post-thoracic) differ in that the right abdominal air
sac is relatively small, lying to the right of the mesentery, and dorsally to
the liver. common ostrich 61 common ostrich While the left abdominal air sac is
large and lies to the left of the mesentery. common ostrich 61 common ostrich
The connection from the main mesobronchi to the more anterior air sacs including
the interclavicular, lateral clavicular, and pre-thoracic sacs known as the
ventrobronchi region. While the caudal end of the mesobronchus branches into
several dorsobronchi. Together, the ventrobronchi and dorsobronchi are connected
by intra-pulmonary airways, the parabronchi, which form an arcade structure
within the lung called the paleopulmo. It is the only structure found in
primitive birds such as ratites. common ostrich 61 common ostrich
The largest air sacs found within the respiratory system are those of the
post-thoracic region, while the others decrease in size respectively, the
interclavicular (unpaired), abdominal, pre-thoracic, and lateral clavicular
sacs. common ostrich 62 common ostrich The adult common ostrich lung lacks
connective tissue known as interparabronchial septa, which render strength to
the non-compliant avian lung in other bird species. Due to this the lack of
connective tissue surrounding the parabronchi and adjacent parabronchial lumen,
they exchange blood capillaries or avascular epithelial plates. common ostrich
60 common ostrich Like mammals, ostrich lungs contain an abundance of type II
cells at gas exchange sites; an adaptation for preventing lung collapse during
slight volume changes. common ostrich 60 common ostrich
Function
The common ostrich is an endotherm and maintains a body temperature of 38.1–39.7
°C (100.6–103.5 °F) in its extreme living temperature conditions, such as the
heat of the savanna and desert regions of Africa. common ostrich 63 common
ostrich The ostrich utilizes its respiratory system via a costal pump for
ventilation rather than a diaphragmatic pump as seen in most mammals. common
ostrich 61 common ostrich Thus, they are able to use a series of air sacs
connected to the lungs. The use of air sacs forms the basis for the three main
avian respiratory characteristics:
Air is able to flow continuously in one direction through the lung, making it
more efficient than the mammalian lung.
It provides birds with a large residual volume, allowing them to breathe much
more slowly and deeply than a mammal of the same body mass.
It provides a large source of air that is used not only for gaseous exchange,
but also for the transfer of heat by evaporation. common ostrich 61 common
ostrich
Ostrich portrait showing its large eyes and long eyelashes, its flat, broad
beak, and its nostrils
Inhalation begins at the mouth and the nostrils located at the front of the
beak. The air then flows through the anatomical dead space of a highly vascular
trachea (c. 78 cm (31 in)) and expansive bronchial system, where it is further
conducted to the posterior air sacs. common ostrich 64 common ostrich Air flow
through the parabronchi of the paleopulmo is in the same direction to the
dorsobronchi during inspiration and expiration. Inspired air moves into the
respiratory system as a result of the expansion of thoraco abdominal cavity;
controlled by inspiratory muscles. During expiration, oxygen poor air flows to
the anterior air sacs common ostrich 62 common ostrich and is expelled by the
action of the expiratory muscles. The common ostrich air sacs play a key role in
respiration since they are capacious, and increase surface area (as described by
the Fick Principle). common ostrich 64 common ostrich The oxygen rich air flows
unidirectionally across the respiratory surface of the lungs; providing the
blood that has a crosscurrent flow with a high concentration of oxygen. common
ostrich 64 common ostrich
To compensate for the large "dead" space, the common ostrich trachea lacks
valves to allow faster inspiratory air flow. common ostrich 65 common ostrich In
addition, the total lung capacity of the respiratory system, (including the
lungs and ten air sacs) of a 100 kg (220 lb) ostrich is about 15 L (3.3 imp gal;
4.0 US gal), with a tidal volume ranging from 1.2–1.5 L (0.26–0.33 imp gal;
0.32–0.40 US gal). common ostrich 62 common ostrich common ostrich 65 common
ostrich The tidal volume is seen to double resulting in a 16-fold increase in
ventilation. common ostrich 61 common ostrich Overall, ostrich respiration can
be thought of as a high velocity-low pressure system. common ostrich 62 common
ostrich At rest, there is small pressure differences between the ostrich air
sacs and the atmosphere, suggesting simultaneous filling and emptying of the air
sacs. common ostrich 65 common ostrich
The increase in respiration rate from the low range to the high range is sudden
and occurs in response to hyperthermia. Birds lack sweat glands, so when placed
under stress due to heat, they heavily rely upon increased evaporation from the
respiratory system for heat transfer. This rise in respiration rate however is
not necessarily associated with a greater rate of oxygen consumption. common
ostrich 61 common ostrich Therefore, unlike other birds, the common ostrich is
able to dissipate heat through panting without experiencing respiratory
alkalosis by modifying ventilation of the respiratory medium. During hyperpnea
ostriches pant at a respiratory rate of 40–60 cycles per minute, versus their
resting rate of 6–12 cycles per minute. common ostrich 62 common ostrich Hot,
dry and moisture lacking properties of the common ostrich respiratory medium
affects oxygen's diffusion rate (Henry's Law). common ostrich 64 common ostrich
Common ostriches develop via Intussusceptive angiogenesis, a mechanism of blood
vessel formation, characterizing many organs. common ostrich 60 common ostrich
It is not only involved in vasculature expansion, but also in angioadaptation
common ostrich 66 common ostrich of vessels to meet physiological requirements.
common ostrich 60 common ostrich The use of such mechanisms demonstrates an
increase in the later stages of lung development, along with elaborate
parabronchial vasculature, and reorientation of the gas exchange blood
capillaries to establish the crosscurrent system at the blood-gas barrier.
common ostrich 60 common ostrich The blood–gas barrier (BGB) of their lung
tissue is thick. The advantage of this thick barrier may be protection from
damage by large volumes of blood flow in times of activity, such as running,
common ostrich 67 common ostrich since air is pumped by the air sacs rather than
the lung itself. As a result, the capillaries in the parabronchi have thinner
walls, permitting more efficient gaseous exchange. common ostrich 61 common
ostrich In combination with separate pulmonary and systemic circulatory systems,
it helps to reduce stress on the BGB. common ostrich 60 common ostrich
Circulation
Heart anatomy
The common ostrich heart is a closed system, contractile chamber. It is composed
of myogenic muscular tissue associated with heart contraction features. There is
a double circulatory plan in place possessing both a pulmonary circuit and
systemic circuit. common ostrich 64 common ostrich
The common ostrich’s heart has similar features to other avian species like
having a conically shaped heart, and being enclosed by a pericardium layer.
common ostrich 68 common ostrich Moreover, similarities also include a larger
right atrium volume, and a thicker left ventricle to fulfil the systemic
circuit. common ostrich 68 common ostrich The ostrich heart has three features
that are absent in related birds:
The right atrioventricular valve is fixed to the interventricular septum, by a
thick muscular stock, which prevents back-flow of blood into the atrium when
ventricular systole is occurring. common ostrich 68 common ostrich In the fowl
this valve is only connected by a short septal attachment. common ostrich 68
common ostrich
Pulmonary veins attach to the left atrium separately, and also the opening to
the pulmonary veins are separated by a septum. common ostrich 68 common ostrich
Moderator bands, full of purkinje fibers, are found in different locations in
the left and right ventricles. common ostrich 68 common ostrich These bands are
associated with contractions of the heart and suggests this difference causes
the left ventricle to contract harder to create more pressure for a completed
circulation of blood around the body. common ostrich 68 common ostrich
The atrioventricular node position differs from other fowl. It is located in the
endocardium of the atrial surface of the right atrioventricular valve. It is not
covered by connective tissue, which is characteristic of vertebrate heart
anatomy. It also contains fewer myofibrils than usual myocardial cells. The AV
node connects the atrial and ventricular chambers. It functions to carry the
electrical impulse from the atria to the ventricle. Upon view, the myocardial
cells are observed to have large densely packed chromosomes within the nucleus.
common ostrich 69 common ostrich
The coronary arteries start in the right and left aortic sinus and provide blood
to the heart muscle in a similar fashion to most other vertebrates. common
ostrich 70 common ostrich Other domestic birds capable of flight have three or
more coronary arteries that supply blood to the heart muscle. The blood supply
by the coronary arteries are fashioned starting as a large branch over the
surface of the heart. It then moves along the coronary groove and continues on
into the tissue as interventricular branches toward the apex of the heart. The
atria, ventricles, and septum are supplied of blood by this modality. The deep
branches of the coronary arteries found within the heart tissue are small and
supply the interventricular and right atrioventricular valve with blood
nutrients for which to carry out their processes. The interatrial artery of the
ostrich is small in size and exclusively supplies blood to only part of the left
auricle and interatrial septum. common ostrich 30 common ostrich common ostrich
31 common ostrich
These purkinje fibers (p-fibers) found in the hearts moderator bands are a
specialized cardiac muscle fiber that causes the heart to contract. common
ostrich 71 common ostrich The purkinje cells are mostly found within both the
endocardium and the sub-endocardium. common ostrich 71 common ostrich The
sinoatrial node shows a small concentration of purkinje fibers, however,
continuing through the conducting pathway of the heart the bundle of his shows
the highest amount of these purkinje fibers. common ostrich 71 common ostrich
Blood composition
The red blood cell count per unit volume in the ostrich is about 40% of that of
a human; however, the red blood cells of the ostrich are about three times
larger than the red blood cells of a human. common ostrich 72 common ostrich The
blood oxygen affinity, known as P50, is higher than that of both humans and
similar avian species. common ostrich 72 common ostrich The reason for this
decreased oxygen affinity is due to the hemoglobin configuration found in common
ostrich blood. common ostrich 72 common ostrich The common ostrich’s tetramer is
composed of hemoglobin type A and D, compared to typical mammalian tetramers
composed of hemoglobin type A and B; hemoglobin D configuration causes a
decreased oxygen affinity at the site of the respiratory surface. common ostrich
72 common ostrich
During the embryonic stage Hemoglobin E is present. common ostrich 73 common
ostrich This subtype increases oxygen affinity in order to transport oxygen
across the allantoic membrane of the embryo. common ostrich 73 common ostrich
This can be attributed to the high metabolic need of the developing embryo, thus
high oxygen affinity serves to satisfy this demand. When the chick hatches
hemoglobin E diminishes while hemoglobin A and D increase in concentration.
common ostrich 73 common ostrich This shift in hemoglobin concentration results
in both decreased oxygen affinity and increased P50 value. common ostrich 73
common ostrich
Furthermore, the P50 value is influenced by differing organic modulators. common
ostrich 73 common ostrich In the typical mammalian RBC 2,3 – DPG causes a lower
affinity for oxygen. 2,3- DPG constitutes approximately 42–47%, of the cells
phosphate of the embryonic ostrich. common ostrich 73 common ostrich However,
the adult ostrich have no traceable 2,3- DPG.In place of 2,3-DPG the ostrich
uses inositol polyphosphates (IPP), which vary from 1–6 phosphates per molecule.
common ostrich 73 common ostrich In relation to the IPP, the ostrich also uses
ATP to lower oxygen affinity. common ostrich 73 common ostrich ATP has a
consistent concentration of phosphate in the cell. common ostrich 73 common
ostrich Around 31% at incubation periods, and dropping to 16–20% in 36-day-old
chicks. common ostrich 73 common ostrich However, IPP has low concentrations,
around 4%, of total phosphate concentration in embryonic stages; However, the
IPP concentration jumps to 60% of total phosphate of the cell. common ostrich 73
common ostrich The majority of phosphate concentration switches from 2,3- DPG to
IPP, suggesting the result of the overall low oxygen affinity is due to these
varying polyphosphates. common ostrich 73 common ostrich
Concerning immunological adaptation, it was discovered that wild common
ostriches have a pronounced non specific immunity defense, with blood content
reflecting high values of lysosome, and phagocyte cells in medium. This is in
contrast to domesticated ostriches, who in captivity develop high concentration
of immunoglobulin antibodies in their circulation, indicating an acquired
immunological response. It is suggested that this immunological adaptability may
allow this species to have a high success rate of survival in variable
environmental settings. common ostrich 74 common ostrich
Osmoregulation
Physiological challenges
The common ostrich is a xeric animal, due to the fact that it lives in habitats
that are both dry and hot. common ostrich 64 common ostrich Water is scarce in
dry and hot environment, and this poses a challenge to the ostrich's water
consumption. Also the ostrich is a ground bird and cannot fly to find water
sources, which poses a further challenge. Because of their size, common
ostriches cannot easily escape the heat of their environment; however, they
dehydrate less than their small bird counterparts because of their small surface
area to volume ratio. common ostrich 75 common ostrich Hot, arid habitats pose
osmotic stress, such as dehydration, which triggers the common ostrich’s
homeostatic response to osmoregulate.
System overview
The common ostrich is well adapted to hot, arid environments through
specialization of excretory organs. The common ostrich has an extremely long and
developed colon the length of approximately 11–13 m (36–43 ft) between the
coprodeum and the paired caeca, which are around 80 cm (31 in) long. common
ostrich 75 common ostrich A well developed caeca is also found and in
combination with the rectum forms the microbial fermentation chambers used for
carbohydrate breakdown. common ostrich 75 common ostrich The catabolism of
carbohydrates produces around 0.56 g (0.020 oz) of water that can be used
internally. common ostrich 64 common ostrich The majority of their urine is
stored in the coprodeum, and the faeces are separately stored in the terminal
colon. common ostrich 75 common ostrich The coprodeum is located ventral to the
terminal rectum and urodeum (where the ureters open). common ostrich 61 common
ostrich Found between the terminal rectum and coprodeum is a strong sphincter.
common ostrich 61 common ostrich The coprodeum and cloaca are the main
osmoregulatory mechanisms used for the regulation and reabsorption of ions and
water, or net water conservation. common ostrich 61 common ostrich As expected
in a species inhabiting arid regions, dehydration causes a reduction in faecal
water, or dry feces. common ostrich 61 common ostrich This reduction is believed
to be caused by high levels of plasma aldosterone, which leads to rectal
absorption of sodium and water. common ostrich 61 common ostrich Also expected
is the production of hyperosmotic urine; cloacal urine has been found to be 800
mosmol/L. common ostrich 61 common ostrich The U:P (urine:plasma) ratio of the
common ostrich is therefore greater than one. Diffusion of water to the
coprodeum (where urine is stored) from plasma across the epithelium is voided.
common ostrich 61 common ostrich This void is believed to be caused by the thick
mucosal layering of the coprodeum. common ostrich 61 common ostrich
Common ostriches have two kidneys, which are chocolate brown in color, granular
in texture, and lie in a depression in the pelvic cavity of the dorsal wall.
common ostrich 76 common ostrich They are covered by peritoneum and a layer of
fat. common ostrich 61 common ostrich Each kidney is about 300 mm (12 in) long,
70 mm (2.8 in) wide, and divided into a cranial, middle, and caudal sections by
large veins. common ostrich 61 common ostrich The caudal section is the largest,
extends into the middle of the pelvis. common ostrich 61 common ostrich The
ureters leave the ventral caudomedial surface and continue caudally, near the
midline into the opening of the urodeum of the cloaca. common ostrich 61 common
ostrich Although there is no bladder, a dilated pouch of ureter stores the urine
until it is secreted continuously down from the ureters to the urodeum until
discharged. common ostrich 76 common ostrich
Kidney function
Common ostrich kidneys are fairly large, and so are able to hold significant
amounts of solutes. Hence, common ostriches drink relatively large volumes of
water daily, and excrete generous quantities of highly concentrated urine. It is
when drinking water is unavailable or withdrawn, that the urine becomes highly
concentrated with uric acid and urates. common ostrich 61 common ostrich It
seems that common ostriches who normally drink relatively large amounts of water
tend to rely on renal conservation of water when drinking water is scarce within
the kidney system. Though there have been no official detailed renal studies
conducted common ostrich 77 common ostrich on the flow rate (Poiseuille's Law)
and composition of the ureteral urine in the ostrich, knowledge of renal
function has been based on samples of cloacal urine, and samples or quantitative
collections of voided urine. common ostrich 61 common ostrich Studies have shown
that the amount of water intake, and dehydration impacts the plasma osmolality
and urine osmolality within various sized ostriches. During a normal hydration
state of the kidneys, young ostriches tend to have a measured plasma osmolality
of 284 mOsm, and urine osmolality of 62 mOsm. Adults have higher rates with a
plasma osmolality of 330 mOsm, and a urine osmolality of 163 mOsm. The
osmolality of both plasma and urine can alter in regards to whether there is an
excess or depleted amount of water present within the kidneys. An interesting
fact of common ostriches is that when water is freely available, the urine
osmolality can reduce to 60–70 mOsm, not losing any necessary solutes from the
kidneys when excess water is excreted. common ostrich 61 common ostrich
Dehydrated or salt-loaded ostriches can reach a maximal urine osmolality of
approximately 800 mOsm. When the plasma osmolality has been measured
simultaneously with the maximal osmotic urine, it is seen that the urine:plasma
ratio is 2.6:1, the highest encountered among avian species. common ostrich 61
common ostrich Along with dehydration, there is also a reduction in flow rate
from 20 L·d−1 to only 0.3–0.5 L·d−1.
In mammals and common ostriches, the increase of the glomerular filtration rate
(GFR) and urine flow rate (UFR) is due to a high protein diets. As seen in
various studies, scientists have measured clearance of creatinine, a fairly
reliable marker of glomerular filtration rate (GFR). common ostrich 61 common
ostrich It has been seen that during normal hydration within the kidneys, the
glomerular filtration rate is approximately 92 ml/min. However, when an ostrich
experiences dehydration for at least 48 hours (2 days), this value diminishes to
only 25% of the hydrated GFR rate. Thus in response to the dehydration, ostrich
kidneys secrete small amounts of very viscous glomerular filtrates that have not
been broken down, and return them to the circulatory system through blood
vessels. The reduction of GFR during dehydration is extremely high, and so the
fractional excretion of water (urine flow rate as a percentage of GFR) drops
down from 15% at normal hydration to 1% during dehydration. common ostrich 61
common ostrich
Water intake and turnover
Common ostriches employ adaptive features to manage the dry heat and solar
radiation in their habitat. Ostriches will drink available water; however, they
are limited in accessing water by being flightless. They are also able to
harvest water through dietary means, consuming plants such as the Euphorbia
heterochroma that hold up to 87% water. common ostrich 61 common ostrich
Water mass accounts for 68% of body mass in adult common ostriches; this is down
from 84% water mass in 35-day-old chicks. The differing degrees of water
retention are thought to be a result of varying body fat mass. common ostrich 61
common ostrich In comparison to smaller birds ostriches have a lower evaporative
water loss resulting from their small body surface area per unit weight. common
ostrich 64 common ostrich
When heat stress is at its maximum, common ostriches are able to recover
evaporative loss by using a metabolic water mechanism to counter the loss by
urine, feces, and respiratory evaporation. An experiment to determine the
primary source of water intake in the ostrich indicated that while the ostrich
does employ a metabolic water production mechanism as a source of hydration, the
most important source of water is food. When ostriches were restricted to the no
food or water condition, the metabolic water production was only 0.5 L·d−1,
while total water lost to urine, feces and evaporation was 2.3 L·d−1. When the
birds were given both water and food, total water gain was 8.5 L·d−1. In the
food only condition total water gain was 10.1 L·d−1. These results show that the
metabolic water mechanism is not able to sustain water loss independently, and
that food intake, specifically of plants with a high water content such as
Euphorbia heterochroma, is necessary to overcome water loss challenges in the
common ostrich's arid habitat. common ostrich 61 common ostrich
In times of water deprivation, urine electrolyte and osmotic concentration
increases while urination rate decreases. Under these conditions urine
solute:plasma ratio is approximately 2.5, or hyperosmotic; that is to say that
the ratio of solutes to water in the plasma is shifted down whereby reducing
osmotic pressure in the plasma. Water is then able to be held back from
excretion, keeping the ostrich hydrated, while the passed urine contains higher
concentrations of solute. This mechanism exemplifies how renal function
facilitates water retention during periods of dehydration stress. common ostrich
64 common ostrich common ostrich 78 common ostrich
Nasal glands
A number of avian species use nasal salt glands, alongside their kidneys, to
control hypertonicity in their blood plasma. common ostrich 79 common ostrich
However, the common ostrich shows no nasal glandular function in regard to this
homeostatic process. common ostrich 79 common ostrich Even in a state of
dehydration, which increases the osmolality of the blood, nasal salt glands show
no sizeable contribution of salt elimination. common ostrich 79 common ostrich
Also, the overall mass of the glands was less than that of the duck’s nasal
gland. common ostrich 79 common ostrich The common ostrich, having a heavier
body weight, should have larger, heavier nasal glands to more effectively
excrete salt from a larger volume of blood, but this is not the case. These
unequal proportions contribute to the assumption that the common ostrich’s nasal
glands do not play any role in salt excretion. The nasal glands may be the
result of an ancestral trait, which is no longer needed by the common ostrich,
but has not been bred out of their gene pool. common ostrich citation needed
common ostrich
Biochemistry
The majority of the common ostrich’s internal solutes are made up of sodium ions
(Na+), potassium ions (K+), chloride ions (Cl-), total short-chain fatty acids
(SCFA), and acetate. common ostrich 75 common ostrich The caecum contains a high
water concentration with reduced levels nearing the terminal colon, and exhibits
a rapid fall in Na+ concentrations and small changes in K+ and Cl-. common
ostrich 75 common ostrich The colon is divided into three sections and take part
in solute absorption. The upper colon largely absorbs Na+ and SCFA, and
partially absorbs KCl. common ostrich 75 common ostrich The middle colon absorbs
Na+, SCFA, with little net transfer of K+ and Cl-. common ostrich 75 common
ostrich The lower colon then slightly absorbs Na+ and water, and secretes K+.
There is no net movements of Cl- and SCFA found in the lower colon. common
ostrich 75 common ostrich
When the common ostrich is in a dehydrated state plasma osmolality, Na+, K+, and
Cl- ions all increase, however, K+ ions returned to controlled concentration.
common ostrich 80 common ostrich The common ostrich also experiences an increase
in haematocrit, resulting in a hypovolemic state. common ostrich 80 common
ostrich Two antidiuretic hormones, Arginine vasotocin (AVT) and angiotensin
(AII) are increased in blood plasma as a response to hyperosmolality and
hypovolemia. common ostrich 80 common ostrich AVT triggers antidiuretic hormone
(ADH) which targets the nephrons of the kidney. common ostrich 64 common ostrich
ADH causes a reabsorption of water from the lumen of the nephron to the
extracellular fluid osmotically. common ostrich 64 common ostrich These
extracellular fluids then drain into blood vessels, causing a rehydrating
effect. common ostrich 64 common ostrich This drainage prevents loss of water by
both lowering volume and increasing concentration of the urine. common ostrich
64 common ostrich Angiotensin, on the other hand, causes vasoconstriction on the
systemic arterioles, and acts as a dipsogen for ostriches. common ostrich 64
common ostrich Both of these antidiuretic hormones work together to maintain
water levels in the body that would normally be lost due to the osmotic stress
of the arid environment.
The end-product of catabolism of protein metabolism in animals is nitrogen.
common ostrich 64 common ostrich Animals must excrete this in the form of
nitrogenous compounds. common ostrich 64 common ostrich Ostriches are
uricotelic. They excrete nitrogen as the complex nitrogenous waste compound uric
acid, and related derivatives. common ostrich 64 common ostrich Uric acid's low
solubility in water gives a semi-solid paste consistency to the ostrich's
nitrogenous waste. common ostrich 64 common ostrich
Thermoregulation
Common ostriches are homeothermic endotherms; they regulate a constant body
temperature via regulating their metabolic heat rate. common ostrich 64 common
ostrich They closely regulate their core body temperature, but their appendages
may be cooler in comparison as found with regulating species. common ostrich 64
common ostrich The temperature of their beak, neck surfaces, lower legs, feet
and toes are regulated through heat exchange with the environment. common
ostrich 81 common ostrich Up to 40% of their produced metabolic heat is
dissipated across these structures, which account for about 12% of their total
surface area. common ostrich 81 common ostrich Total evaporative water loss
(TEWL) is statistically lower in the common ostrich than in membering ratites.
common ostrich 82 common ostrich
As ambient temperature increases, dry heat loss decreases, but evaporative heat
loss increases because of increased respiration. common ostrich 81 common
ostrich As ostriches experience high ambient temperatures, circa 50 °C (122 °F),
they become slightly hyperthermic; however, they can maintain a stable body
temperature, around 40 °C (104 °F), for up to 8 hours in these conditions.
common ostrich 62 common ostrich When dehydrated, the common ostrich minimises
water loss, causing the body temperature to increase further. common ostrich 62
common ostrich When the body heat is allowed to increase the temperature
gradient between the common ostrich and ambient heat is equilibrated. common
ostrich 64 common ostrich
Physical adaptations
Common ostriches have developed a comprehensive set of behavioural adaptations
for thermoregulation, such as altering their feathers. common ostrich 61 common
ostrich Common ostriches display a feather fluffing behaviour that aids them in
thermoregulation by regulating convective heat loss at high ambient
temperatures. common ostrich 81 common ostrich They may also physically seek out
shade in times of high ambient temperatures. When feather fluffing, they
contract their muscles to raise their feathers to increase the air space next to
their skin. common ostrich 64 common ostrich This air space provides an
insulating thickness of 7 cm (2.8 in). common ostrich 83 common ostrich The
ostrich will also expose the thermal windows of their unfeathered skin to
enhance convective and radiative loss in times of heat stress. common ostrich 82
common ostrich At higher ambient temperatures lower appendage temperature
increases to 5 °C (9.0 °F) difference from ambient temperature. common ostrich
81 common ostrich Neck surfaces are around 6–7 °C (11–13 °F) difference at most
ambient temperatures, except when temperatures are around 25 °C (77 °F) it was
only 4 °C (7 °F) above ambient. common ostrich 81 common ostrich
At low ambient temperatures the common ostrich utilizes feather flattening,
which conserves body heat through insulation. The low conductance coefficient of
air allows less heat to be lost to the environment. common ostrich 64 common
ostrich This flattening behavior compensate for common ostrich's rather poor
cutaneous evaporative water loss (CEWL). common ostrich 84 common ostrich These
feather heavy areas such as the body, thighs and wings do not usually vary much
from ambient temperatures due to this behavioural controls. common ostrich 81
common ostrich This ostrich will also cover its legs to reduce heat loss to the
environment, along with undergoing piloerection and shivering when faced with
low ambient temperatures.
Internal adaptations
The use of countercurrent heat exchange with blood flow allows for regulated
conservation/ elimination of heat of appendages. common ostrich 64 common
ostrich When ambient temperatures are low, heterotherms will constrict their
arterioles to reduce heat loss along skin surfaces. common ostrich 64 common
ostrich The reverse occurs at high ambient temperatures, arterioles dilate to
increase heat loss. common ostrich 64 common ostrich
At ambient temperatures below their body temperatures (thermal neutral zone
(TNZ)), common ostriches decrease body surface temperatures so that heat loss
occurs only across about 10% of total surface area. common ostrich 81 common
ostrich This 10% include critical areas that require blood flow to remain high
to prevent freezing, such as their eyes. common ostrich 81 common ostrich Their
eyes and ears tend to be the warmest regions. common ostrich 81 common ostrich
It has been found that temperatures of lower appendages were no more than 2.5 °C
(4.5 °F) above ambient temperature, which minimizes heat exchange between feet,
toes, wings, and legs. common ostrich 81 common ostrich
Both the Gular and air sacs, being close to body temperature, are the main
contributors to heat and water loss. common ostrich 62 common ostrich Surface
temperature can be affected by the rate of blood flow to a certain area, and
also by the surface area of the surrounding tissue. common ostrich 64 common
ostrich The ostrich reduces blood flow to the trachea to cool itself, and
vasodilates its blood vessels around the gular region to raise the temperature
of the tissue. common ostrich 62 common ostrich The air sacs are poorly
vascularized but show an increased temperature, which aids in heat loss. common
ostrich 62 common ostrich
Common ostriches have evolved a 'selective brain cooling' mechanism as a means
of thermoregulation. This modality allows the common ostrich to manage the
temperature of the blood going to the brain in response to the extreme ambient
temperature of the surroundings. The morphology for heat exchange occurs via
cerebral arteries and the ophthalmic rete, a network of arteries originating
from the ophthalmic artery. The ophthalmic rete is analogous to the carotid rete
found in mammals, as it also facilitates transfer of heat from arterial blood
coming from the core to venous blood returning from the evaporative surfaces at
the head.
common ostrich 85 common ostrich
Researchers suggest that common ostriches also employ a ‘selective brain
warming’ mechanism in response to cooler surrounding temperatures in the
evenings. The brain was found to maintain a warmer temperature when compared to
carotid arterial blood supply. Researchers hypothesize three mechanisms for this
finding. They first suggest a possible increase in metabolic heat production
within the brain tissue itself to compensate for the colder arterial blood
arriving from the core. They also speculate that there is an overall decrease in
cerebral blood flow to the brain. Finally, they suggest that warm venous blood
perfusion at the ophthalmic rete facilitates warming of cerebral blood that
supplies the hypothalamus. Further research will need to be done to find how
this occurs. common ostrich 85 common ostrich
Breathing adaptations
The common ostrich has no sweat glands, and under heat stress they rely on
panting to reduce their body temperature. common ostrich 62 common ostrich
Panting increases evaporative heat (and water) loss from its respiratory
surfaces, therefore forcing air and heat removal without the loss of metabolic
salts. common ostrich 82 common ostrich Panting allows the common ostrich to
have a very effective respiratory evaporative water loss (REWL). Heat dissipated
by respiratory evaporation increases linearly with ambient temperature, matching
the rate of heat production. common ostrich 61 common ostrich As a result of
panting the common ostrich should eventually experience alkalosis. common
ostrich 64 common ostrich However, The CO2 concentration in the blood does not
change when hot ambient temperatures are experienced. common ostrich 62 common
ostrich This effect is caused by a lung surface shunt. common ostrich 62 common
ostrich The lung is not completely shunted, allowing enough oxygen to fulfill
the bird’s metabolic needs. common ostrich 62 common ostrich The common ostrich
utilizes gular fluttering, rapid rhythmic contraction and relaxation of throat
muscles, in a similar way to panting. common ostrich 64 common ostrich Both
these behaviors allow the ostrich to actively increase the rate of evaporative
cooling. common ostrich 64 common ostrich
In hot temperatures water is lost via respiration. common ostrich 64 common
ostrich Moreover, varying surface temperatures within the respiratory tract
contribute differently to overall heat and water loss through panting. common
ostrich 62 common ostrich The surface temperature of the gular area is 38 °C
(100 °F); that of the tracheal area, between 34 and 36 °C (93 and 97 °F); and
that of both anterior and posterior air sacs, 38 °C (100 °F). common ostrich 62
common ostrich The long trachea, being cooler than body temperature, is a site
of water evaporation. common ostrich 62 common ostrich
As ambient air becomes hotter, additional evaporation can take place lower in
the trachea making its way to the posterior sacs, shunting the lung surface.
common ostrich 62 common ostrich The trachea acts as a buffer for evaporation
because of the length, and the controlled vascularization. common ostrich 62
common ostrich The Gular is also heavily vascularized; its purpose is for
cooling blood, but also evaporation, as previously stated. Air flowing through
the trachea can be either laminar or turbulent depending on the state of the
bird. common ostrich 64 common ostrich When the common ostrich is breathing
normally, under no heat stress, air flow is laminar. common ostrich 62 common
ostrich When the common ostrich is experiencing heat stress from the environment
the air flow is considered turbulent. common ostrich 62 common ostrich This
suggests that laminar air flow causes little to no heat transfer, while under
heat stress turbulent airflow can cause maximum heat transfer within the
trachea. common ostrich 62 common ostrich
Metabolism
Common ostriches are able to attain their necessary energetic requirements via
the oxidation of absorbed nutrients. Much of the metabolic rate in animals is
dependent upon their allometry, the relationship between body size to shape,
anatomy, physiology and behaviour of an animal. Hence, it is plausible to state
that metabolic rate in animals with larger masses is greater than animals with a
smaller mass.
When a bird is inactive, unfed, and the ambient temperature (i.e. in the
thermo-neutral zone) is high, the energy expended is at its minimum. This level
of expenditure is better known as the basal metabolic rate (BMR), and can be
calculated by measuring the amount of oxygen consumed during various activities.
common ostrich 61 common ostrich Therefore, in common ostriches we see use of
more energy when compared to smaller birds in absolute terms, but less per unit
mass.
A key point when looking at the common ostrich metabolism is to note that it is
a non-passerine bird. Thus, BMR in ostriches is particularly low with a value of
only 0.113 ml O2 g−1 h−1. This value can further be described using Kleiber's
law, which relates the BMR to the body mass of an animal. common ostrich 86
common ostrich
{\displaystyle \mathrm {Metabolic\ Rate} =70M^{0.75}} \mathrm {Metabolic\ Rate}
=70M^{0.75}
where {\displaystyle M} M is body mass, and metabolic rate is measured in kcal
per day.
In common ostriches, a BMR (ml O2 g−1 h−1) = 389 kg0.73, describing a line
parallel to the intercept with only about 60% in relation to other non-passerine
birds. common ostrich 61 common ostrich
Along with BMR, energy is also needed for a range of other activities. If the
ambient temperature is lower than the thermo-neutral zone, heat is produced to
maintain body temperature. common ostrich 61 common ostrich So, the metabolic
rate in a resting, unfed bird, that is producing heat is known as the standard
metabolic rate (SMR) or resting metabolic rate(RMR). The common ostrich SMR has
been seen to be approximately 0.26 ml O2 g−1 h−1, almost 2.3 times the BMR.
common ostrich 61 common ostrich On another note, animals that engage in
extensive physical activity employ substantial amounts of energy for power. This
is known as the maximum metabolic scope. In an ostrich, it is seen to be at
least 28 times greater than the BMR. Likewise, the daily energy turnover rate
for an ostrich with access to free water is 12,700 kJ·d−1, equivalent to 0.26 ml
O2 g−1 h−1. common ostrich 61 common ostrich
Status and conservation
The wild common ostrich population has declined drastically in the last 200
years, with most surviving birds in reserves or on farms. common ostrich 7
common ostrich However, its range remains very large (9,800,000 square
kilometres (3,800,000 sq mi)), leading the IUCN and BirdLife International to
treat it as a species of Least Concern. common ostrich 1 common ostrich Of its 5
subspecies, the Arabian ostrich (S. c. syriacus) became extinct around 1966, and
the North African ostrich (S. c. camelus) has declined to the point where it now
is included on CITES Appendix I and some treat it as Critically Endangered.
common ostrich 24 common ostrich common ostrich 25 common ostrich common ostrich
26 common ostrich common ostrich 87 common ostrich
Scene with common ostriches, Roman mosaic, 2nd century AD
Ostriches and humans
Common ostriches have inspired cultures and civilizations for 5,000 years in
Mesopotamia and Egypt. A statue of Arsinoe II of Egypt riding a common ostrich
was found in a tomb in Egypt. common ostrich 88 common ostrich Hunter-gatherers
in the Kalahari use ostrich eggshells as water containers, punching a hole in
them. They also produce jewelry from it. common ostrich 7 common ostrich common
ostrich 89 common ostrich common ostrich 90 common ostrich The presence of such
eggshells with engraved hatched symbols dating from the Howiesons Poort period
of the Middle Stone Age at Diepkloof Rock Shelter in South Africa suggests
common ostriches were an important part of human life as early as 60,000 BP.
common ostrich 91 common ostrich
Hunting and farming
Fashion accessories made from common ostrich feathers, Amsterdam, 1919
File:1000 Ostriches on the move.ogv
Domestic common ostriches being moved between camps in preparation for filming a
movie in South Africa.
In Roman times, there was a demand for common ostriches to use in venatio games
or cooking. They have been hunted and farmed for their feathers, which at
various times have been popular for ornamentation in fashionable clothing (such
as hats during the 19th century). Their skins are valued for their leather. In
the 18th century they were almost hunted to extinction; farming for feathers
began in the 19th century. At the start of the 20th century there were over
700,000 birds in captivity. common ostrich 56 common ostrich The market for
feathers collapsed after World War I, but commercial farming for feathers and
later for skins and meat became widespread during the 1970s. Common ostriches
are so adaptable that they can be farmed in climates ranging from South Africa
to Alaska.
Common ostrich eggs on the oil lamps of the Church of Saint Lazarus, Larnaca,
Cyprus.
In Eastern Christianity it is common to hang decorated common ostrich eggs on
the chains holding the oil lamps. common ostrich 92 common ostrich The initial
reason was probably to prevent mice and rats from climbing down the chain to eat
the oil. common ostrich 92 common ostrich Another, symbolical explanation is
based in the fictitious tradition that female common ostriches do not sit on
their eggs, but stare at them incessantly until they hatch out, because if they
stop staring even for a second the egg will addle. common ostrich 92 common
ostrich This is equated to the obligation of the Christian to direct his entire
attention towards God during prayer, lest the prayer be fruitless. common
ostrich 92 common ostrich
Various ostrich leather products. The ostrich leather is used for material of
bag and belt, purse.
Common ostriches have been farmed in South Africa since the beginning of the
19th century. According to Frank G. Carpenter, the English are credited with
first taming common ostriches outside Cape Town. Farmers captured baby common
ostriches and raised them successfully on their property, and were able to
obtain a crop of feathers every seven to eight months instead of killing wild
common ostriches for their feathers. common ostrich 93 common ostrich It is
claimed that common ostriches produce the strongest commercial leather. common
ostrich 94 common ostrich Common ostrich meat tastes similar to lean beef and is
low in fat and cholesterol, as well as high in calcium, protein and iron.
Uncooked, it is dark red or cherry red, a little darker than beef. common
ostrich 95 common ostrich Ostrich stew is a dish prepared using common ostrich
meat.
Some common ostrich farms also cater to agri-tourism, which may produce a
substantial portion of the farm's income. common ostrich 96 common ostrich This
may include tours of the farmlands, souvenirs, or even ostrich rides. common
ostrich 97 common ostrich common ostrich 98 common ostrich
Attacks
Common ostriches typically avoid humans in the wild, since they correctly assess
humans as potential predators. If approached, they often run away, but sometimes
ostriches can be very aggressive when threatened, especially if cornered, and
may also attack if they feel the need to defend their territories or offspring.
Similar behaviors are noted in captive or domesticated common ostriches, which
retain the same natural instincts and can occasionally respond aggressively to
stress. When attacking a person, common ostriches deliver slashing kicks with
their powerful feet, armed with long claws, with which they can disembowel or
kill a person with a single blow. common ostrich 99 common ostrich In one study
of common ostrich attacks, it was estimated that two to three attacks that
result in serious injury or death occur each year in the area of Oudtshoorn,
South Africa, where a large number of common ostrich farms are set next to both
feral and wild common ostrich populations. common ostrich 57 common ostrich
Racing
See also: List of racing forms § Animal racing
Jacksonville, Florida, man with a common ostrich-drawn cart, circa 1911
In some countries, people race each other on the backs of common ostriches. The
practice is common in Africa common ostrich 100 common ostrich and is relatively
unusual elsewhere. common ostrich 101 common ostrich The common ostriches are
ridden in the same way as horses with special saddles, reins, and bits. However,
they are harder to manage than horses. common ostrich 102 common ostrich
File:Struisvogelrennen-514008.ogv
Common ostrich race in 1933 in The Netherlands
The racing is also a part of modern South African culture. common ostrich 103
common ostrich Within the United States, a tourist attraction in Jacksonville,
Florida, called 'The Ostrich Farm' opened up in 1892; it and its races became
one of the most famous early attractions in the history of Florida. common
ostrich 104 common ostrich Likewise, the arts scene in Indio, California,
consists of both ostrich and camel racing. common ostrich 105 common ostrich
Chandler, Arizona, hosts the annual "Ostrich Festival", which features common
ostrich races. common ostrich 106 common ostrich common ostrich 107 common
ostrich Racing has also occurred at many other locations such as Virginia City
in Nevada, Canterbury Park in Minnesota, common ostrich 108 common ostrich
Prairie Meadows in Iowa, Ellis Park in Kentucky, common ostrich 109 common
ostrich and the Fairgrounds in New Orleans,
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