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Thomson's gazelle

  (tŏm'sənz)

A small gazelle (Gazella thomsoni) of eastern Africa, having a broad black stripe on each side of the body.

[After Joseph Thomson (1858–1895), Scottish geologist and explorer.]

Gazella thomsonii

TAXONOMY

Gazella thomsonii Günther, 1884, Kilimanjaro, Kenya.

OTHER COMMON NAMES

English: Tommies.

PHYSICAL CHARACTERISTICS

Thomson's gazelles have a head and body length of 3–4 ft (91–122 cm), tail length of 6–8 in (15–20 cm), and weight of 29–66 lb (13–30 kg). Males have a shoulder height of 23–28 in (58–70 cm), and a weight of 37–66 lb (17–30 kg), while females have a shoulder height of 23–35 in (58–64 cm), and a weight of 29–53 lb (13–24 kg). They have a light reddish brown coat on top, a white belly, a fawn colored stripe underneath, a distinctive black stripe running from the foreleg to the hindquarters, and a white rump patch that extends to the entirely black tail. The uniquely dark side stripes may serve as visual signals to keep the herd together. They have pronounced facial markings. The eyes are rimmed with a white line, which then extends to the nose along the muzzle and above black cheek stripes. A dark finger-like pattern occurs on the inside of the ears. Their sight and sense of hearing are well developed, which lets them scout out a large area. Their dark parallel horns are long and only slightly curved. Males have robust, curved horns with large ridges (rings) encircling them. They can reach 11.5–12.0 in (29.2–30.5 cm) in length and are used exclusively for intra-species fighting. Female horns are shorter and more slender; and are used in order to defend their feeding area, especially when food resources are limited. Because of this excess use of their horns, females often end up with broken or deformed horns, or without horns. They have facial and leg glands for territorial marking and species recognition. This species is the least drought tolerant of all the gazelles.

DISTRIBUTION

Southern and central Kenya, southwestern Ethiopia, northern Tanzania, and southeast Sudan.

HABITAT

They stay primarily in the short grassy plains and savannas where food is most abundant and where the landscape is open enough to allow for the gathering of large herds. They feed and reproduce on the short-grass plains during the rainy season and in the taller grasslands in the drier season.

BEHAVIOR

Thomson's gazelles are both nocturnal and diurnal, but are most active early and late in the day, preferring to rest during the hottest part of the day. They are primarily silent animals. Their primary defense against predators is to run, which they can do very effectively at speeds of 40–50 mph (65–80 kph). They can gracefully leap 10 ft (3 m) into the air, jump 30 ft (9 m) in a single leap, and make turns much faster than can a cheetah, one of its main predators. Thomson's gazelles engage in gaits called "stotting" or "pronking" when playing or alarmed. This action entails bouncing stiff-legged so that all four legs land on the ground together. It is believed that this activity helps them to communicate alarm to each other, to give them a better view of approaching predators, and even to confuse or intimidate predators. They have elongated foot bones and anklebones that gives them their speed. They live in herds up to 200 members but normally associate in groups of 2–20. These groups are loosely based, and can change by the hour. They often migrate in groups numbering in the thousands. Multiple groups are often seen interacting with each other. Territories can range from 6 to 495 acres (2–200 ha) but normally are 25–75 acres (10–30 ha). They are very water-dependent but can become water-independent when necessary. During dry periods, they need to be near a water source, sometimes travelling as much as 100 mi (160 km) to find one. During the breeding season males establish territories in order to secure mating rights with females. Males mark their territories with urine and dung piles, and also with secretions from their pre-orbital glands. Territorial males will tolerate familiar subordinate males in their territories as long as they remain subordinate and do not approach the females. Nonbreeding males form bachelor herds.

FEEDING ECOLOGY AND DIET

Thomson's gazelles graze on short grasses, alfalfa hay, and leaves. They avoid tall grass areas. Almost all of their diet consists of grasses. They get most of the water they need from the grasses they eat.

REPRODUCTIVE BIOLOGY

Polygamous. Thomson's gazelles generally breeds twice a year in parallel with the coming rainy season in late December/early February (short rains) and late June/July (long rains), but reproduction is also dependent on the health of the female and environmental conditions. Females give birth to one baby after a gestation period of 5–6 months. The young coat is mottled darker than the mother's coat, but lightens within 1–2 weeks. Females isolate themselves during the birth of their young in order to strength the fawn, and will remain separated from the herd for the first few weeks of life. Once the offspring can run well enough (within 3–4 weeks), mother and fawn will rejoin the group. The weaning period lasts about four months. Females can become impregnated 2–4 weeks after giving birth. Lifespan in the wild is 10–20 years.

CONSERVATION STATUS

Lower Risk/Conservation Dependent. Predation on this small gazelle is always high; they are preyed upon primarily by cheetahs, but also by lions, hyenas, wild dogs, jackals, honey badgers, crocodiles, and leopards. Smaller predators such as pythons, serval cats, baboons, and birds of prey (such as eagles) will also eat the young. Despite the large numbers and types of predators, Thomson's gazelles can be found in numbers of up to 500,000 in Africa, the most common of the gazelles in east Africa.

SIGNIFICANCE TO HUMANS

They are hunted for food and skins.

The noun has one meaning:

Meaning #1: E African Gazelle; smallest gazelle
  Synonym: Gazella thomsoni

Thomson's Gazelle
Gazella thomsoni
Conservation status
Conservation Dependent
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Artiodactyla Family: Bovidae Subfamily: Antilopinae Genus: Gazella Species: G. thomsoni
Binomial name
Gazella thomsoni Günther, 1884

Male Thompson's gazelle. Ngorongoro Crater, Tanzania.

Thomson's Gazelle

A Thompson's gazelle running at full speed while being pursued by a cheetah. Ngorongoro Crater, Tanzania.

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Gazella thomsonii

The Thomson's Gazelle (Gazella thomsoni) is one of the best-known gazelles. It is named after explorer Joseph Thomson, and is often referred to as the "tommy". It is considered by some (e.g. Kingdon 1997) to be a subspecies of the Red-fronted Gazelle (G. rufifrons).

Thomson's Gazelles live in Africa's savannas and grassland habitats, particularly the Serengeti region of Kenya and Tanzania, though they can also be found in Ethiopia, Somalia, and Sudan. They eat low vegetation and grass. Most of the water they need comes from what they eat.

Description

Thomson's Gazelles are 60–90 cm (24-35 in) tall and weigh 13–16 kg (29-35 lb). They have light brown coats with white underparts and a distinctive black stripe. Their horns are long and pointed with slight curvature. The white patch on their rump extends to underneath the tail but no further. An error sometimes made is the misidentification of Grant's Gazelles as Thomson's Gazelles. Although some Grant's do have the black stripe running across their sides, the white on their rump always extends above the tail. They can reach a speed of 80 km/h (50 mph)^[1] when chased by their enemy, the cheetah.

A noticeable behaviour of Thomson's Gazelles is their bounding leap, known as stotting or pronking, used to startle predators and display strength. They often congregate with other hoofed mammals, or ungulates, such as wildebeest and zebra and usually live and migrate in herds with hundreds or thousands of other Thomson's Gazelles.

Social structure and behaviour

The social structure of gazelles consists of several types of groups. Male gazelles are territorial throughout their adult lives, though not usually before 2–3 years of age. During the non-territorial periods males usually spend their time in bachelor groups or as part of a mixed herd. Likewise females will form migratory female groups that travel through the males' territory. As the female groups pass through, the territorial males will try to herd them to prevent them from leaving. Adult male bucks with adjoining territories will engage in combat several times a day, fighting with their horns to establish dominance and the boundaries of their territories. In this way, the accepted boundaries of the territory can change on a daily basis. If a lone male, a bachelor group, or in some cases even an adolescent male fawn of a female gazelle should be passing through a territorial male's region, the male will chase the offender out of his territory. Interestingly, this territoriality does not extend to males of other species. The territory of a Thomson's gazelle and several other types of ungulates may overlap with no problem whatsoever. Occasionally, a Thomson's gazelle and a zebra or other ungulate will even appear to enjoy one another's company with great sociability.

Breeding and life expectancy

Female Thomson's Gazelles give birth to single fawns after a 5–6 month gestation period. They are unusual among ungulates in that they can give birth twice yearly, rather than just once.

In the wild, Thomson's Gazelles can live up to 10–15 years, although they are preyed on by most African big cats and hyenas, and are (depending on the location), sometimes the preferred prey of cheetahs. Cheetahs are able to attain higher speeds, but Thomson's Gazelles can outlast cheetahs in long chases and are able to make turns more speedily. Half of all the fawns born will be lost to predators before reaching adulthood, and after a while they farticus on a lamb.^{[citation needed]}

References

1. ^ http://www.infoplease.com/ipa/A0004737.html

• Kingdon, Jonathan (1997) The Kingdon Field Guide to African Mammals. Academic Press, San Diego and London. Pp. 411–413. (ISBN 0-12-408355-2)
• Antelope Specialist Group 1996. Gazella thomsonii. 2006 IUCN Red List of Threatened Species. Downloaded on 30 July 2007.

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