Thomson's Gazelle

The current scientific name of Thomson's gazelle is Eudorcas thomsonii. It is a member of the genus Eudorcas and is classified under the family Bovidae. Thomson's gazelle was first described by British zoologist Albert Günther in 1884. The relationships between Thomson's gazelle and the congeneric Mongalla gazelle (E. albonotata) remain disputed; while some authors such as Alan W. Gentry of the (Natural History Museum, London) consider the Mongalla gazelle to be a subspecies of Thomson's gazelle, others (such as Colin Groves) consider the Mongalla gazelle to be a full species. Zoologist Jonathan Kingdon treated Heuglin's gazelle, sometimes considered a species of Eudorcas (E. tilonura) or a subspecies of the red-fronted gazelle (E. r. tilonura), as a subspecies of Thomson's gazelle. Thomson's gazelle is named after the Scottish explorer Joseph Thomson; the first recorded use of the name dates to 1897. Another common name for the gazelle is "tommy". |2= |label2=Nanger |2= |2=Dama gazelle (N. dama) }} }} }} |2= }} }} Antilope, Eudorcas, Gazella, and Nanger form a clade within their tribe Antilopini. A 1999 phylogenetic analysis showed that Antilope is the closest sister taxon to Gazella, although the earliest phylogeny, proposed in 1976, placed Antilope as sister to Nanger. In a more recent revision of the phylogeny of the Antilopini on the basis of nuclear and mitochondrial data in 2013, Eva Verena Bärmann (of the University of Cambridge) and colleagues constructed a cladogram that clearly depicted the close relationship between Nanger and Eudorcas. Antilope and Gazella were found to have a similar relationship. Two subspecies are identified: *E. t. nasalis (Lönnberg, 1908) – Serengeti Thomson's gazelle ranges from the Serengeti to the Kenya Rift Valley. *E. t. thomsonii (Günther, 1884) – eastern Thomson's gazelle ranges from east of the Rift Valley in Kenya and Tanzania, southward to Arusha District (Tanzania) and then southwestward to Lake Eyasi, Wembere River, and Shinyanga.

Thomson's gazelle lives in East Africa, in the savannas and grassland habitats of Kenya and Tanzania. In the wet seasons, they eat mainly fresh grasses, but during the dry seasons, they eat more browse, ]] Thomson's gazelles are dependent on short grass, preferring Cynodon, Harpachne and Themeda species. Their numbers can be highly concentrated at the beginning of the rains when the grass grows quickly. In the Serengeti, they follow the larger herbivores, such as plains zebras and blue wildebeests as they mow down the taller grasses. This small antelope can run extremely fast, up to , and zigzag, an adaptation which often saves it from predators. Sometimes, they are also taken by leopards, lions, African wild dogs, hyenas, Nile crocodiles and African rock pythons, and their fawns are sometimes the prey of eagles, jackals, and baboons. A noticeable behaviour of Thomson's gazelles is their bounding leap, known as stotting or pronking, used to startle predators and display strength.

]] During the wet season, a time when grass is abundant, adult male gazelles graze extensively. They spread out more and establish breeding territories. Younger males usually spend their time in bachelor groups, and are prevented from entering the territories. Females form migratory groups that enter the males' territories, mostly the ones with the highest-quality resources. As the female groups pass through and forage, the territorial males may try to herd them, and are usually successful in preventing single females from leaving, but not whole groups. Males also mark grass stems with their preorbital glands, which emit a dark secretion. Territories of different males may share a boundary. When territorial males meet at the border of their territories, they engage in mock fights in which they rush towards each other as if they are about to clash, but without touching. After this, they graze in a frontal position, then in parallel and then in reverse, and move away from each other while constantly grazing. These rituals have no victor, but merely maintain the boundaries of the territories. Territorial males usually do not enter another male's territory. If a male is chasing an escaping female, he will stop the chase if she runs into another territory, but the neighboring male will continue the chase.

A male gazelle follows a female and sniffs her urine to find out if she is in estrus, a process known as the Flehmen response. If so, he continues to court and mount her. Breeding takes place year-round, with a peak in births around January/February, and in some populations a second peak around June/July. Newborn fawns weigh . They give birth twice yearly with one or two fawns. When giving birth, a female gazelle crouches as the newborn fawn drops to the ground, tearing the umbilical cord. The mother then licks the fawn clean of amniotic fluid and tissues. In addition, licking possibly also serves to stimulate the fawn's blood circulation, or to "label" it so its mother can recognize it by scent. In the first six hours of the fawn's life, it moves and rests with its mother, but eventually spends more time away from its mother or hides in the grass. The mother stays in the vicinity of the fawn and returns to nurse it daily. Mother and fawn may spend an hour together before the fawn goes and lies back down to wait for the next nursing. Mother gazelles may associate with other gazelle mothers, but the fawns do not gather into "kindergartens". As the fawn approaches two months of age, it spends more time with its mother and less time hiding. Eventually, it stops hiding. Around this time, the fawn starts eating solid food, but continues to nurse from its mother. The pair also joins a herd. Young female gazelles may associate with their mothers as yearlings. Young males may also follow their mothers, but as they reach adolescence, they are noticed by territorial males, so cannot follow their mothers into territories. The mother may follow and stay with him, but eventually stops following him when he is driven away; the male will then join a bachelor group. Thomson's gazelle (Eudorcas thomsoni).jpg|Male gazelle mounting a female Gazella thomsonii, Tanzania - 20100808.jpg|Fawn hiding in the grass Serengeti Thomson's gazelle (Eudorcas thomsonii nasalis) juvenile male Serengeti.jpg|Juvenile male

In an experiment studying the effects of dehydration and heat stress on food intake and dry matter digestibility, Thomson's gazelle exhibited metabolic adaptations for desert environments. When exposed to heat stress alone, neither the food intake nor digestion of Thomson's gazelle was affected. Compared to some other East African ruminant species that did change their food intake and digestion in response to heat stress, Thomson's gazelle appears relatively well-adapted to periodic heat stress. However, Thomson's gazelle is a water-dependent species, and when exposed to dehydration, its food intake decreased. Food intake was further depressed when gazelles were exposed to dehydration in addition to heat stress. Some of this reduction can be attributed to decreased metabolism, which can help the animals conserve water. In another study comparing Thomson's gazelles and Grant's gazelles in foraging and behaviors to avoid predators, it was found that Thomson's gazelle adjusted its diet during drought to eat more trees and shrubs of Acacia species rather than undigestible dried grasses. Acacia species are high in tannins, anti-nutritional factors that can decrease metabolic performance. However, gazelles appear to have the ability to detoxify and metabolize some tannins and moderate levels of condensed tannins may even be beneficial to ruminants by increasing amino acid absorption in the gut.

The population estimate is around 550,000. The population had declined 60% from 1978 to 2005. Threats to Thomson's gazelles are habitat modification, fire management, and road development. Surveys have reported steep declines (60–70%) over periods of about 20 years dating from the late 1970s in several places, including the main strongholds for the species: Serengeti, Masai Mara, and Ngorongoro.