Thomson's gazelles form small herds but are socially very flexible (2) (3). Herds of females overlap with other herds, and movement between herds is common. Within their shared home range the females rest, move between pastures and visit waters (2). Males are a little less flexible and mature males fight to obtain and defend territories within the female's favourite pastures (2). They denote the boundaries of their territory with dung and by marking grass stems and twigs with secretion from the scent glands beneath their eyes (2). Territoriality in males' peaks during mating periods when frequent fights and stand-offs occur between neighbouring males, and males attempt to mate with any receptive female that enters their area (2) (3). Lambs may be born at any time of the year, but birthing often occurs towards the end of the rainy season (3). Females are pregnant for 188 days, after which a single lamb weighing two to three kilograms is born (3). Thomson's gazelles feed on fresh green grass whenever possible, but during the dry season, feeding on seeds and the foliage of shrubs is necessary (2). Thomson's gazelles need to drink water every day or two, and in its dry grassland habitat this sometimes requires making round trips of ten miles or more (4).

Despite its limited distribution this is by far Africa's most abundant gazelle (3). The 'tommy', as it is locally known (3), has a distinct black band running along the side of the body that divides the yellowish-fawn to reddish-fawn upperparts from the clean white underparts (2). The white buttocks are edged with black (2), extending to the short, black tail which is constantly flicking (3). Both sexes of the Thomson's gazelle have long, strongly ringed horns that grow fairly close together, although those of the ewe are generally shorter, thinner, and frequently deformed (3). The face is boldly marked with white, fawn, dark brown and black, and varies between individuals (2).

Thomson?s Gazelle occurs widely within its historical range in the grasslands of southern and central Kenya. The largest populations occur in the Mara ranches, Masai Mara National Reserve and the Laikipia and Kajiado rangelands. In Tanzania, the species occupies about half of its former range in Acacia savannas and grasslands in the north (East 1999).

Thomson's gazelles are found in eastern Africa, in Kenya, Tanzania, and southern Sudan.

Biogeographic Regions: ethiopian (Native )

Thomson's gazelle occurs in Kenya and Tanzania, whilst subspecies G. t. albonotata inhabits south-eastern Sudan and possibly south-western Ethiopia (3).

Thomson's gazelles are small gazelles, the typical weight range is 15 to 35 kg. Males are larger overall, ranging in weight from 20 to 35 kg, females are from 15 to 25 kg. They have white bellies and reddish-brown backs, divided by a bold, black stripe laterally. Their rumps are white and their tails are black. Thomson's gazelles have reddish-brown fur on their faces, with a broad white stripe that extends from the eye to the nose and is bordered below by a black stripe. Males and some females have horns that curve backwards and are curved forwards distally in males. Females have smaller horns, if any, both lengthwise and in circumference. The horns are arrayed with a series of marked annulations. Thomson's gazelles resemble Grant's gazelles (Nanger granti) somewhat, although Grant's gazelles are larger overall, have horns that curve outwards, and the white of their rump extends to above the tail. Thomson's gazelles have a head and body length of 80 to 120 cm, a tail length of 15 to 27 cm, and height at the shoulder of 55 to 82 cm. They have prominent pre-orbital glands.

Thomson's gazelles are exceptionally fast runners, able to run at speeds up to 70 km/hour. They can outrun cheetahs if they can evade them for long enough because cheetahs can maintain high speeds for shorter times.

Range mass: 15 to 35 kg.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger; ornamentation

Habitat and Ecology

Systems

• Terrestrial

Thomson's gazelles live in dry, short grasslands and shrubby savannas. They are an arid-adapted species and are able to stay in dry grasslands for longer than other plains ungulates in the same region, which migrate towards more moist habitats. They follow a similar sort of seasonal migratory pattern as other ungulates in their range, but they stay for longer on the wet season range and don't migrate as far north in the dry season.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: savanna or grassland

Other Habitat Features: agricultural

Thomson's gazelle inhabits dry grasslands and shrubby steppes. It prefers heavily grazed, trampled or burnt grasslands, or naturally open steppe, and can stay on pastures long after large herbivores have deserted it (2).

Thomson’s gazelles graze mainly on short grasses. They eat twigs, seeds, and leaves from trees as well, especially during the dry season. Their smaller body size and drought tolerance make it possible for them to persist on arid grasslands that cannot support larger ungulates. Preferred grasses include Themeda, Cynodon, and Harpachne species. Foliage and seeds taken are from Acacia, Balanites, Boscia, Sida, and Solanum species.

Plant Foods: leaves; wood, bark, or stems; seeds, grains, and nuts

Primary Diet: herbivore (Folivore )

Thomson's gazelles are eaten by large predators such as lions, hyenas, and jackals. They modify plant communities through their grazing.

Mutualist Species:

• impalas (Aepyceros melampus)
• Grant's gazelles (Nanger granti)

Predators of Thomson's gazelles include lions, spotted hyenas, wild dogs, cheetahs, leopards, and jackals. During the calving season, the young are easy prey for all of these predators, as well as yellow baboons and pythons. Thomson's gazelles travel in small herds, which helps to protect individuals from predation. They are alert and can run quickly.

Known Predators:

• lions (Panthera leo)
• spotted hyenas (Crocuta crocuta)
• cheetahs (Acinonyx jubatus)
• leopards (Panthera pardus)
• African wild dogs (Lycaon pictus)
• black backed jackals (Canis mesomelas)
• golden jackals (Canis aureus)
• yellow baboons (Papio cynocephalus)
• pythons (Python)

Thomson’s gazelles are fairly silent animals that communicate more visually. When alarmed they will communicate to conspecifics by stotting, which is a stereotyped series of high jumps with the head held high and the legs stiff. Males communicate to other males and females by marking territories with their scent glands, including preorbital glands that they use to mark grasses and stems. Males also drop dung at spots in their territory to advertise ownership.

Communication Channels: visual ; chemical

Perception Channels: visual ; acoustic

Thomson's gazelles typically have a lifespan of 10.5 years in the wild. Approximately half of calves will die within their first year.

Average lifespan

Status: wild: 10.5 years.

Maximum longevity: 20 years (captivity)

Thomson's gazelle males defend small territories and attempt to mate with females in that area. Females prefer rich foraging grounds, so preferred territories are those in areas with good grazing. Males use markings from preorbital glands and dung to advertise their territories and actively defend them against other males. They sometimes attempt to "herd" females in order to keep them in their territory for longer.

Mating System: polygynous

There is little available information on breeding in Thomson's gazelles. Thomson's gazelles mate twice yearly. Gestation is for 6 months and the majority of births occur right after the rainy season, with a single calf being born at 2 to 3 kg.

Breeding interval: Thomson's gazelles can breed twice a year.

Breeding season: Most breeding is timed so that most births occur right after the rainy season, although births can occur throughout the year.

Range number of offspring: 1 (low) .

Average number of offspring: 1.

Average gestation period: 6 months.

Range birth mass: 2 to 3 kg.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Thomson's gazelle calves are precocial at birth, able to stand and walk soon after, although they spend their first days hidden and motionless in the grass. The mother will leave the young in high grass and frequently come back a few times during the day to nurse. After this hiding period, the young follow and accompany their mother with the herd.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

Carotid rete cools brain: Thomson's gazelle
 

The carotid rete of the Thomson's gazelle cools its brain via counter-current heat exchange.

     
  The Thomson’s gazelle lives in the East African savannah where is it  exposed to high temperatures and predation by big cats, like the  cheetah, lion, or leopard. These gazelles have been recorded to run at  up to 43-50 miles per hour. Such a burst of speed may raise the  metabolic rate, and thus heat production, by as much as 40 fold.  Dissipating such heat loads is difficult, especially in arid  environments where water is scarce and an animal needs to avoid losing  too much.  

The brain is a part of the body that is particularly sensitive  to high temperature. Hence some ungulates, like the Thomson’s gazelle,  have evolved a counter-current heat exchanging structure known as the  carotid rete, a configuration of blood vessels in the brain that can  keep its temperature lower than body temperature. The blood flowing to  the brain moves from the carotid artery into a network of small arteries  within a large venous sinus or cavity filled with cooled blood  returning from the nasal passages. The warm arterial blood gives up some  of its heat to the cool venous blood and this lowers the temperature of  the blood on its way to the brain. In the running Thomson’s gazelle,  body temperature rises more than brain temperature such that a  difference between brain and body temperature has been measured at 2.7°  C. A predator like the cheetah must stop running when its body and brain  temperature reaches 40.5° C but the gazelle can keep running as its  body temperature rises above 43° without its brain temperature exceeding  40.5°. The ability to keep a cool head can thus give the gazelle a  survival edge in these predatory pursuits as he can outlast the cheetah  who cannot maintain a cooler brain. 

Counter-current heat exchangers can be found in many organisms  in many configurations. While such mechanisms are well known to  engineers, a close look at the design of those used by nature may be  useful in designing thermal control systems of human habitations. (Courtesy of The Biomimicry Institute)

  Learn more about this functional adaptation.

According to the IUCN Red List, Thomson's gazelles are listed as near threatened. Although populations are stable in some areas and widespread, some populations have experienced severe declines since the 1970's. If E. thomsonii and E. mongalla (southern Sudan populations) are considered separate species, then E. thomsonii has a small and restricted distribution, which further threatens this species. In Kenya, the largest populations are found in the lands of the Masai Mara, the Masai Mara National Reserve, and the Laikipia and Kajiado rangelands. They occupy about half of their former range in Tanzania. In some areas population declines can be partially attributed to human impacts such as roads, habitat changes, and the impacts of tourism. Large parts of their range are already in protected areas, including the Serengeti National Park and Masai Mara National Reserve.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: near threatened

Classified as Lower Risk / Conservation Dependent (LR/cd) by the IUCN Red List 2007. Subspecies: Gazella thomsonii albonotata, the Mongalla gazelle, classified as Lower Risk / Near Threatened (LR/nt) (1). The status of Thomson's gazelle is currently under review for the IUCN Red List 2008.

Population

Population Trend

Major Threats

The Thomson's gazelle was once widespread throughout its range, but now occurs in fragmented populations, in ever-declining areas (2). This is likely to be due to the encroachment of man onto their habitat (5), and hunting (1).

Conservation Actions

Whilst in many areas Thomson's gazelles have declined, in some areas the species remains common, particularly in protected areas (2), such as the Serengeti National Park. The continued protection and management of such areas is likely to be vital for the conservation of Thomson's gazelle.

Thomson's gazelles may be killed by farmers who think that they compete with domestic livestock. However, their impact is likely to be negligible.

Thomson's gazelles may be hunted for skin and meat. They are also part of the charismatic African ungulate fauna that supports a huge ecotourism industry in eastern Africa.

Positive Impacts: food ; body parts are source of valuable material; ecotourism