Reticulated giraffe

Reticulated giraffe
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Giraffidae
Genus: Giraffa
Species: G. camelopardalis
Subspecies: G. c. reticulata
Trinomial name
Giraffa camelopardalis reticulata
De Winton, 1899
Range map in turquoise blue

The reticulated giraffe (Giraffa camelopardalis reticulata), also known as the Somali giraffe, is a subspecies of giraffe native to Somalia, southern Ethiopia, and northern Kenya. Reticulated giraffes can interbreed with other giraffe subspecies in captivity or if they come into contact with populations of other subspecies in the wild.

The reticulated giraffe is among the most well-known of the nine giraffe subspecies. Together with the Rothschild giraffe, it is by far the giraffe most commonly seen in zoos.[1] Its coat consists of large, polygonal, liver-colored spots outlined by a network of bright-white lines. The blocks may sometimes appear deep red and may also cover the legs. The extraordinary height of giraffes is attributed to a ritual known as "necking", where two males fight for reproduction rights by slamming their necks into one another. The giraffes with the tallest and strongest necks are victorious and allowed to reproduce, thus passing these genes on to future generations.[2]

Habitat

Giraffes historically occurred widely throughout Africa. Their favoured habitats are savannas, woodlands, seasonal floodplains, and rainforests.

Diet

Reticulated giraffes are herbivorous and have been recorded to feed on more than 100 species of plants, with a staple of Acacia, Commiphora, and Terminalia leaves. Giraffe have been seen eating the carcass of an antelope and chewing on dried bones for their calcium content.[3] While leaves are preferred, a giraffe will browse on many other kinds of vegetation, especially in the dry season. Giraffe food preferences change according to seasons: in the dry season, they seem to be fine with pine-like needles.[3] Giraffes feed by browsing, which typically means they eat continuously throughout the day. A male is able to eat 75 pounds of food in a single day.[4] Giraffes use their sense of smell to locate the leaves they want. They ingest everything on the branch when eating, including insects, bark, and thorns. The giraffe uses its massive tongue (up to 18 in long) to scrape off the leaves.[3] Giraffes have very tough lips to guard against scratching. While the acacia tree is their favorite, giraffes have also been known to eat mareola berries and other fruits.[4] Reticulated giraffes are ruminants, just like cattle and other ungulates, and their stomachs have four parts, with food passing through the first and water going directly to the second. The first stomach partially digests the twigs, leaves, and whatever else the giraffe has ingested whole. During the day, when the animal is not feeding, parts of this fermented mixture are brought back up from the stomach in hard lumps (eructation). Giraffes chew on these lumps, called cud, throughout the day, helping to further break the food down. Once they are done chewing on the piece of cud, it is sent to the third stomach, and finally the fourth stomach to be digested fully.[4]

Giraffes are very good at conserving water in the hot African climate. They are able to conserve and maintain their body temperature in part because of their shape; their long thin legs allow heat to release quickly.[4] The leaves they eat are actually a good source of water, and can allow them to go days without a drink.[5] Giraffes have a difficult time lowering their massive heads to the ground to drink, and this also leaves them vulnerable to predators. They are able to reach water by spreading their front legs and stretching their necks down.

Evolution of the neck

In order for giraffes to have developed into having long necks, it would have had to take several life generations. There is no possible way for an animal to form an adaptation in one lifetime. Though this huge adaptation looks very complex, it really isn't. There are only seven vertebrae in a giraffe’s neck. Millions of years before, the trait of a long neck was just a genetic mutation that eventually created a new species. At this time though; these animals were just plain old antelopes.

It is thought that their necks have grown this long for eating at the very top of trees. Through many studies, this thought was proven wrong. Research was conducted and proves that giraffes eat from shoulder height. They eat the leaves of the Acacia tree. These trees are really tall; therefore, the giraffe is really only able to reach the branches at shoulder height.[6] Giraffe's also use this elongated body part to attract mates through a process called necking.[7] Another advantage of a long neck, though not the primary reason for the adaptation, is that they are able to see predators from far across the savanna where the shorter grazers will not be able to see over the tall brush.[8]

Being extraordinarily tall makes drinking water a much harder activity than it should be. Because of them not being able to drink water without having to spread their front legs far apart, they have adapted another way in order to not need to consume near as much water as smaller animals.

Since the long neck of a giraffe was an evolutionary adaptation, it can be concluded that the advantages outweighed the disadvantages. There will always be negative affects to adaptations, but if they will overall benefit the species, those animals with the mutation have a higher chance of living longer in order to pass on the genes to their offspring.

Necking

The commonly accepted reason that giraffes have such long necks was proposed by Charles Darwin in 1871. Darwin got his idea from many African locals, who said the giraffe evolved its long neck to reach the tops of the trees, where the best leaves reside.[2] This presents a possible advantage of giraffe being the only mammal able to feed on prime leaves.

However, this theory has been challenged by Simmons. In his research, Simmons found giraffes feed mostly at shoulder level, not reaching the tops of trees at all. They only reach for the top of the tree during the rainy season. He found, in all the giraffes studied, only those in South Africa fed on leaves out of the reach of other animals. This presents a problem to the theory of long necks serving as an advantage in feeding.

An alternate theory has to do with mating rituals and sexual selection. Giraffes often find mates through a technique known as “necking”. The males stand next to each other and swing their necks wildly at the other. Whichever giraffe uses his neck and head most effectively and remains standing the longest is declared the winner and is allowed to mate with the female. Robert Simmons's hypothesis is that giraffes with the longest and strongest necks would be the most likely to win the "necking" contest.[2]

To help win over the female, the males use their ossicones on the top of their head, like a ram, and they are quite capable of breaking their opponents bones.[9]

Reproduction

Reticulated giraffes at Samburu National Reserve, Kenya

Once pregnant, a female giraffe has a gestation period of about 15 months and usually only has one young at a time, but can have up to eight in her lifetime.[5] Females return to the same spot each year to give birth to their young.[5] Giraffes have babies at all times during the year, but most of the births occur during the dry season.[10] When born, baby giraffes fall seven feet to the ground, since mother giraffes birth standing up.[11] Giraffe calves can weigh up to 200 pounds when they are born, and stand as tall as six feet.[11] Baby giraffes can stand up less than half an hour after being born, and are able to feed from mother’s milk. Baby giraffes will continue to feed from the milk until they are about a year old.[11] Calves can grow 9 inches during the first month, and continue to grow at an enormous rate during the first year.[3] After that, growth slows to less than an inch per year. Giraffes are very herd-oriented animals, and will even entrust the care of their young to the crowd.[10] Females begin to breed at about four years old, and males at about 10 years.[11]

Predators and threats

Due to their formidable size and ability to spot danger, giraffes have very few predators, but are regularly preyed upon by lions and less so by crocodiles and spotted hyenas.[3] Humans are one very real threat to giraffes, although efforts are being made to help conserve them. Giraffes are killed by poachers for their hair and skin. Their very thick, sturdy hair is highly sought after for bracelets and rope. Some villages in Sudan legally serve giraffe meat.[11] Currently, about 100,000 giraffes roam Africa, although some subspecies are almost completely gone, with fewer than 100 individuals.[12] Giraffes must deal with the tsetse fly, which lands on them and sucks blood. Tsetse flies are also carriers of sleeping sickness, a dangerous disease to humans.[11] Giraffes can use their powerful tails to swat the flies and get some relief from the pest. Giraffes have a symbiotic relationship with a few types of birds, most notably the oxpecker. These birds perch on the backs of giraffes, and alert them to possible predators. Oxpeckers also eat mites and dirt off the giraffes, keeping them clean.[3] However, the oxpecker can irritate other wounds by pecking at them, too. Epidemics have also affected giraffes. The worst one, according to scientist Anne Dagg, was rinderpest, which killed hundreds of giraffes in the 1880s (see 1890s African rinderpest epizootic). The epidemic continues to arise in small bursts; one in the 1960s wiped out half of the giraffe population of Kenya.[3]

References

  1. ↑ ISIS (2010). Giraffa. Version 1 October 2010
  2. 1 2 3 Simmons, Robert E., Scheepers, Lee (1996). "Winning by a neck: sexual selection in the evolution of giraffe" (PDF). The American Naturalist 148 (5): 771–86. doi:10.1086/285955. JSTOR 2463405.
  3. 1 2 3 4 5 6 7 Dagg, Anne Innis (1976). The Giraffe: its biology, behavior, and ecology. New York: Van Nostrand Reinhold Company ISBN 0442224311.
  4. 1 2 3 4 Sattler, Helen Roney (1989). Giraffes: the sentinels of the savannas. New York: Lothrop, Lee & Shepard Books ISBN 068808284X.
  5. 1 2 3 Markert, Jenny (2001). Giraffes. Chanhassen, MN: The Child’s World, Inc. ISBN 0895657236
  6. ↑ http://www.giraffeconservation.org/giraffe_facts.php?pgid=2
  7. ↑ http://www.londolozi.com/cubsden/why-do-giraffes-have-long-necks/
  8. ↑ http://animals.nationalgeographic.com/animals/mammals/giraffe/
  9. ↑ http://www.newscientist.com/article/dn19135-zoologger-how-did-the-giraffe-get-its-long-neck.html#.VCwoKvldXC8
  10. 1 2 Sinclair, A.R.E., Simon, A., Mduma, R., and Arcese, Peter (2000). "What determines phenology and synchrony of ungulate breeding in Serengeti?". Ecology 81 (8): 2100. doi:10.1890/0012-9658(2000)081[2100:WDPASO]2.0.CO;2. JSTOR 177099.
  11. 1 2 3 4 5 6 Leach, Michael (2001). Giraffe. Austin, Texas: Raintree Steck-Vaughn Company ISBN 0750234199.
  12. ↑ African giraffes highly endangered: study. AFP (2007-12-22)

External links

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