Information

Mammals: Giraffe

Mammals: Giraffe

Systematic classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
suborder: Ruminantia
Family: Giraffidae
Kind: Giraffe
Species: G. camelopardalis - Linnaeus, 1758

The Giraffe (Giraffa camelopardalis - Linnaeus, 1758) is a ruminant Artiodactyla (Artiodactyla) belonging to the Okapia (Okapia johnstoni), to the Giraffidae family (Giraffidae).
The name of the genus, would derive from the Bantu dialect "Zahraf", which means "docile animal", while that of the species from a text by Cicero, which speaks of a strange animal, with the characteristics of a camel and a leopard.
Biologists agree today in believing that there are 9 subspecies or breeds of giraffes, distinguishable by the coat's phenotype-color-morphology, and that they would be:
- Giraffa camelopardalis reticulata (Somali Giraffe)
- Giraffa camelopardalis angolensis (Angolan Giraffe)
- Giraffa camelopardalis antiquorom (Kordofan Giraffe)
- Giraffa camelopardalis tippelskirchi (Masai Giraffe)
- Giraffa camelopardalis camelopardalis (Nubian Giraffe)
- Giraffa camelopardalis rothschildi (Baringo Giraffe)
- Giraffa camelopardalis giraffa (South African Giraffe)
- Giraffa camelopardalis thornicrofti (Thornicroft Giraffe)
- Giraffe camelopardalis peralta (Nigerian giraffe)
The neck of the giraffe (which can reach from individual to individual and from race to race) even the length of 2 meters, may suggest to anyone who is not a biologist, that it is made up of a much larger number of the seven cervical vertebrae that they make up the human and all other placental mammals, in reality the number of cervical vertebrae is identical (always equal to 7), what changes is the length of each individual vertebra, which is greater.
In giraffes there is also an evident problem of physiology of the circulation caused by the fact that in an upright position, the brain is about three meters higher from the heart and when the animal bends its head, it comes to be at a height difference of 2 meters from the heart.
This undeniably determines considerable efforts, to ensure that the blood always reaches one of the organs that electively require a constant physiological contribution of it, for its regular nutrition and oxygenation.
To this end, evolution has led to the creation of a triple control system, which maintains systemic blood pressure safely and constantly at physiological values, as well as having modeled the size of the heart they reach, from the pointed apex at the base of the myocardium the length of 60 cm!
Thanks to a particular adaptation (anatomo-histological) of the internal carotid artery, the presence of valves in the jugular veins and a vascular system called the Mirabile Network that stabilizes the pressure in the cerebral vessels (dilating and constricting the small arteries of which it is made ), the homeostasis of blood pressure is guaranteed, so that the animal will not lose its senses (due to changes in blood pressure) when it quickly raises its head and when it quickly lowers it.

Giraffe from Somalia - Giraffa camelopardalis reticulata (photo H. Zell)

Zoogeography

Endemic to sub-Saharan Africa (from Somalia, Angola to South Africa).

Habitat-Ecology

Savannah.

Nutrition

Of both nocturnal and diurnal habits for nutrition, it feeds on buds, fruits, pods and leaves (in particular Acacia), which it rips with its prominent lips, after grasping the branch with a long, prehensile tongue.

Morphophysiology

The characteristic is a neck that can reach two meters in length, overall the male animal can reach 5-5.7 m in height and weigh between 800-2000 kg. The females are smaller and can reach 4 -4.5 m, with a weight of 500-1200 Kg.
The coat has a varied morphology, or brown spots on a yellow background as in the Giraffa camelopardalis camelopardalis, or with darker spots (brown) surrounded by a white line to form a lattice on a yellow background as in the Giraffa camelopardalis reticulata, further small diversifications in other breeds.
With excellent eyesight, it is one of the few mammals (like pongid primates and humans) able to distinguish colors, even hearing and smell are well developed.
The eyes have robust eyelashes that defend it during nutrition from thorns and twigs. Finally, there are two not excessively large auricles (spear-shaped) well developed on a thin and elegant head with an elongated muzzle.
On the head there is a variable number (from race and race) of horns, very different from those of the bovids (which are cavicorns) since supported by a bony protuberance, covered by skin (always) with the presence of irregular tufts of hair.
Well developed limbs, very long, massive trunk short compared to the neck and inclined in the rear direction, presence of a long tail (it can reach 1 meter in length) ending in a compact tuft of hair.
In the 1960s, the zoological biologists Dag Innis and C. A. Spinage thoroughly studied the structure of the giraffe's skull.
The horns, which always remain covered with hair, develop from ossification centers under the skin and merge with the underlying bone.
The two larger horns are inserted on the parietals; the median horn, uneven, on the front and on the nasal bones.
There are often other smaller, even horns on the occipital region and above the eyes; there are also extensions of the median horn.
As the animals age, more bone is deposited, which includes the blood vessels in tubular cavities, unlike in deer, where the blood vessels are located externally to the bone, under the velvet of the antlers.
In old males the "exostoses" (bony protuberances) are very extensive and give the skull a gnarled appearance.
C.A. Spinage made the hypothesis that this conformation is to be correlated with the habit of the giraffes to rub each other's long neck, and that the secondary ossification serves to protect the blood vessels from possible damage, during the most intense phase of this behavior.
He observed that a male with a skull weighing 11 kg has a considerable advantage in fighting, compared to a male who has a 7 kg skull.
Exostoses are not a consequence of mechanical trauma, but a "secondary sexual character", of genetic origin, and therefore not a response to an injury or stimulation resulting from the fight.
In many, but not all ruminants, the liver lacks the gallbladder.
Many giraffes were dissected in the past by biologists, but the doubt still remained as to whether or not they had a gallbladder.
Until the biologist A. J. I. Cave, solved the question in 1950.
For a strange combination, the giraffe examined by the zoologist biologist Owen in 1838, the first to be dissected in Europe by a zoologist biologist (before it was only a curious work of hunters, who made no contribution to Comparative Anatomy), had a large gallbladder , while later zoological biologists had been unable to find one in their specimens examined.
A. J .I. Cave found that a rudimentary gallbladder is normally present in the fetus, but that it usually undergoes physiological regression and involution, so that it is absent at birth; as had not happened in the abnormal specimen of Owen which, for more than a century, was the cause of so much confusion.

Ethology and reproductive biology

Giraffes are docile animals, which have a generally non-aggressive character.
The arrangement of the spots is just as individual as the fingerprints in humans and the zoologist biologist Foster, used them during his studies in nature, in the 70s of the last century, to follow the movements and behavior of individual animals; this great biologist was even able to recognize some specimens from photographs taken randomly more than ten years earlier.
Biologists (zoologists, ethologists) often have to use elaborate and difficult marking methods to recognize individuals, but with giraffes this is not necessary.
Among the many African ungulates, the giraffe (together with the black and white rhino, the zebras, the elephant, the hippopotamus and the buffalo buffalo), is one of the few that has been studied in the field completely by zoological biologists with serious academic preparation; as a result, we have a significant amount of data on his life, customs and behavior.
Biologist A. Dagg Innis studied the life of Giraffes in the first half of the 1960s (Giraffa camelopardalis and race Giraffa camelopardalis giraffa), in the lower Veldt of the eastern Transvaal, in a scrubland made up of deciduous broadleaf trees, partly dense and partly more open and similar to a park.
The animals burned the foliage of a large number of different types of trees, but especially those belonging to the order of legumes and were more selective when the trees were completely covered with leaves.
In a subsequent study, Dagg Innis herself, showed that there was no correlation between the preferences of the giraffe and the ashes, the crude extract in ether and the crude protein content of the analyzed foliage.
These preferences are probably mainly based on taste ... it seems only right that giraffes, like us, can be greedy.
When the giraffes eat the foliage, they can reach even 6 m high points, where a marked scuffing line is observed on the crowns of these trees.
In Kenya, biologist Foster showed that trees that exceeded this height were burned in the shape of a "clock glass", while the lower ones in the shape of a "honeycomb". He proposed the hypothesis (still examined today) that the presence of trees of the first type, indicated that in the past the giraffe had been absent for a time from the locality under consideration, since, where it is always present, the trees fail to grow beyond the height of the honeycomb-shaped ones.
D. Innis noted that "it was interesting to see all the taller giraffes feeding on their favorite tree," while the lower giraffes feeding on nearby bushes. An example of a food organization.
Giraffes spend most of the day eating and chewing the bolus, not only when they rest, but also when they walk.
On average, a giraffe chews every bite 44 times, at the rate of one chew per second.
As mentioned, they are the object of the attention of the bufaghe and of the cattle egrets, which feed on the ticks that parasitize them, in particular under the belly and in the areas of the genitals, where the hair is thinner.
And in addition, even giraffes get busy, scratching their stomachs, with movements of coming and going, over bushes and rocks up to 180 cm high.
When, on the other hand, the ticks are installed on the back, they move, to get rid of them, in reverse, in the thick "bush".
Giraffes can live in flocks of even 70 units. However, these are very weak associations, because the individual animals often aggregate and then leave, and there is no specific "leadership", even if in every mixed pack there is always a large male that is usually dominant .
In addition to the mixed ones, there are also herds consisting of only adult and sub-adult males, separated or united. And there is always a certain number of solitary males looking for females in estrus.
The mating period that varies from region to region, but generally turns out to be from July to September
There is no courtship ritual. Usually the male approaches a female and licks its tail, or takes it between its lips.
Apparently pretending nothing, the female in question starts to urinate, and the male collects some of the urine on the lips or on the tongue, to taste it.
Then raise your head, and, with your mouth closed, typically grind your teeth if the female is in estrus, the famous "sign of Flehmen".
From Innis information, it seems that the male, before mating, assumes a characteristic position, with rigid front legs.
The pregnancy of the female is about 14-16 months, the birth occurs with the female standing, which spreads the four legs at the time of the expulsion of the only puppy that is born (rarely you can have a bigemino birth) which on average has a weight of 50-70 kg and is even up to two meters high.
Already after a few hours, the newborn baby is able to walk alongside the mother, breastfeeding frequently. Sexual maturity comes for both sexes towards the third year of life.
In herds of males only, there is a strange manifestation of love games.
The biologist of the fauna M. Coe, who studied this behavior in the giraffes of Kenya from 1966 to 1969 (both the species Giraffa camelopardalis that race Giraffa camelopardalis tippelskirchi), describes it as variable behavior.
Two males can stand face to face and wave their heads so as to rub each other's neck; or they go head-to-tail, and swing their heads giving themselves fairly strong blows with short horns, on the sides and on the loins. This second behavior is often followed by the "sign of Flehmen" and the erection of the penis.
Dagg Innis found similar behavior in Transvaal giraffes and was the first to describe it.
These biologists believe that this homosexuality constitutes an important mechanism of socio-sexual bond, by means of which a hierarchy is created between males, while the exchange between strictly male and mixed groups favors the maintenance of contact between sexes in this polygamous mammal.
In the Transvaal, D. Innis found that males outnumbered females.
In Kenya, on the other hand, Foster noted the opposite, but concluded that these are not noticeable because they tend to live in the forests more than the females and the young, who prefer open areas instead.
Males may also be fewer, because they are more vulnerable to predation in a forest, where the ability to scan the surrounding environment is reduced.
The living space (home-range) of giraffes has not yet been determined, but some biologists believe, from some indications obtained in the field, that females and young people cover an area of ​​50 square km. Neither the males nor the females defend the territory, however.
Not only is the herd structure socio-biologically unstable, but the mother-child bond is also, as was noted by both Foster and Innis.
The babies begin to graze the leaves, from the first week of postnatal life, and moving away from their parents they join groups of other young people; often, shortly thereafter, they return to their mother or move to another group.
And the fact that mothers often see themselves circulating without offspring, made Foster conclude that many infants die in the first days of autonomous life, without leaving a trace, probably victims of predators and their inexperience.
The structure of the adult pack is even more casual than the relationship between parents and children.
Foster noticed that in all the flocks the presence of some different specimens was observed, sooner or later.
Sub-adult males join celibate groups during the third year of life, and do not circulate on their own until they are sexually mature.
None of the zoological biologists mentioned here has ever recorded any communication voice signals.
At most, a warning puff was heard.
It seems that visual communication predominates, that is, a giraffe learns of the presence of a danger, from the behavior of the companions.
In fact, if a giraffe for some reason starts running, all the others immediately do the same, without even knowing why.


Video: Animal Size Comparison 3D (October 2021).