Connochaetes mearnsi (Heller, 1913)

Don E. Wilson & Russell A. Mittermeier, 2011, Bovidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 444-779 : 664-665

166.

Serengeti White-bearded Wildebeest

Connochaetes mearnsi

French: Gnou de Mearns / German: Serengeti-WeiRbartgnu / Spanish: Nu barbiblanco del Serengueti

Taxonomy. Gorgon albojubatus mearnsi Heller, 1913 ,

Loita Plains, southwestern Kenya.

Formerly considered a subspecies of C. taurinus . Monotypic.

Distribution. Restricted to the Serengeti— Mara ecosystem in S Kenya and N Tanzania, within which the bulk of the population migrates N and S seasonally.

Descriptive notes. Few measurements available. Shoulder height 100-123 cm (males) and 117 cm (females); weight 171-242 kg (males) and 141-186 kg (females). This is a small and dark species, with darker legs that contrast less with the general body color. Individuals tend to be blackish on the chest and flanks. It has a noticeably longer tail than other species of “Brindled Gnus” (the C. taurinus group). As in the Eastern White-bearded Wildebeest (C. albojubatus), the mane hangs limp. The horns do not have such a wide spread, and the tips do not turn inward as much as in the other species in this group, but they have a more pronounced basal boss. When a skull is placed on a flat surface, the minimum distance of the downward curve of the horns above the surface is 6 cm. The vocalizations, particularly of the territorial males, are different from those of other species of wildebeest, being described as “throatier, more sustained” with “a less metallic timbre” by R. D. Estes, who said that the call “when voiced by thousands of bulls (especially during rut) resounds like a chorus of immense frogs.”

Habitat. Populations of the Serengeti White-bearded Wildebeest inhabit short-grass plains, never too far from water, and migrate when growth stops in the dry season.

Food and Feeding. They are completely grazers, although less selective of leaf than sympatric hartebeest. Stable isotope analysis indicates that this species subsists 100% on grass, whereas the figure for the Blue Wildebeest ( C. taurinus ) is about 90%. A large fraction of the diet is Themeda triandra.

Breeding. Rutting occurs at the end of the rains, when all males and females are in good condition. Conception rate is more than 95%. The rut occurs during migration, and males fight, each trying to collect females into his tiny territory. There is no ritualization of behavior—they simply run at any invaders and ram them, occasionally even breaking a horn while doing so. They may also fight when the populations are sedentary, when the pastures are regrowing after rain. A male will approach a herd with a rocking canter and try to round it up. If a female is in estrus, he makes a lowstretch display and urinates. A cow in estrus holds her tail to one side, and may solicit copulation by rubbing her head on the male’s body and sniffing his penis; the male may rise to his hindlegs to try to mate if a female does not stand still. Curiously, while a male in the vicinity of estrous females is indulging in all this frenzied activity and calling, nearby males simply rest or graze. These behaviors occur at any time, but calling, herding, and fighting increase toward the time of the rut, and males may even begin frothing at the mouth. Even bachelor males call continuously, like the territorial males, as the migrating females pass. The birth period lasts only three weeks, starting up to about a month before the period of the most reliable rains. Gestation is 8-8-5 months. Immediately after giving birth, the mother turns and starts to lick the calf. Calves stand within six minutes and suckle immediately. Mothers with new calves come together in nursery herds, thus offering protection, but a female rejects all calves but her own, which she recognises by scent. The newborn has a tan-colored coat, which is replaced after two months. Sexual maturity can occur at about 16 months if the calf is very well nourished, but usually occurs a year after this. Males more than about a year old live in bachelor herds, having been driven out of their natal herds by territorial males. Males become territorial at 4-5 years of age.

Activity patterns. Territorial bulls are active and vocal. Every day, they interact aggressively with their neighbors, the rituals including tail-swishing, head-shaking, pawing the ground, horning the ground, urinating and urine-testing, and displacement grazing, during which two males move counterparallel to each other. There may also be bluff attacks, with two males dropping to their knees and briefly clashing horns with each other. Territorial males are extraordinarily noisy, calling all the time.

Movements, Home range and Social organization. When the populations are sedentary, they live in small herds averaging eight females and calves, with home ranges of a few hectares, overlapping with 4-5 males’ territories. Herd composition is stable unless their home ranges are too close together. Within a herd, the females have a dominance hierarchy; the dominant female will rub her face on a subordinate’s rump or shoulder, and sometimes chase her, or even jab her with a horn. No appeasement behavior seems to be displayed by either male or female; a subordinate merely moves away. The males’ territories average about 1 ha, and are maintained even outside the three-week rut; only one-third to one-half of the adult males hold territories. When the dry season begins, the usable pastures are reduced to small pockets, and the herds joined together into a huge aggregation. This is when they begin their long-distance movements, seeking new grazing. They head north toward the Mara River, or toward distant thunderstorms that will stimulate new pasture growth. Not all individuals migrate; a few remain on the same pastures year-round. Males join the migrations, but continue to maintain their interindividual spacing, and they interact very little. Each time the migrating herd stops moving, the males set up tiny territories averaging only 0-3 ha.

Status and Conservation. Classified as Least Concern on The IUCN Red List (under C. taurinus ). The number of Serengeti White-bearded Wildebeest on the Serengeti-Mara ecosystem has increased enormously over time, from about 100,000 in the 1950s to an estimated 500,000 in 1970 and 1-3 million in 1977; since then, the population has stabilized at 1-1-5 million, fluctuating across good and bad years.

Bibliography. Estes (1969, 1991a, 1991b), Hillman et al. (1988), Kingdon (1982), Murray (1993), Rodgers & Swai (1988), Roosevelt & Heller (1914).

Figures

162. Black Wildebeest (Connochaetes gnou), 163. Blue Wildebeest (Connochaetes taurinus), 164. Johnston’s Wildebeest (Connochaetes johnstoni), 165. Eastern White-bearded Wildebeest (Connochaetes albojubatus), 166. Serengeti White-bearded Wildebeest (Connochaetes mearnsi)

Distribution. Restricted to the Serengeti— Mara ecosystem in S Kenya and N Tanzania , within which the bulk of the population migrates N and S seasonally.