Beatragus hunteri Sclater, 1889a

Ruso, Gabrielle E, 2017, Beatragus hunteri (Artiodactyla: Bovidae), Mammalian Species 49 (955), pp. 119-127 : 119-123

Beatragus hunteri Sclater, 1889a

Herola

Damalis hunteri Sclater, 1889a:58 . Type locality “north side of the river Tana.” Restricted by Sclater 1889c:376 to “about 150 miles up the Tana River …only found for certain on the north bank of the river.”

Cobus hunteri: Sclater, 1889b:260 . Name combination vide Lydekker (1914:46). Nomen nudum vide Allen (1939:480).

Alcelaphus hunteri: Lydekker, 1891:980 . Name combination.

Alcelaphus (Damalis) hunteri: Flower and Lydekker, 1891:336 . Name combination.

Damaliscus hunteri: Sclater and Thomas, 1894:53 . Name combination.

Beatragus hunteri: Heller, 1912:8 . First use of current name combination.

CONTEXT AND CONTENT. Context same as for genus. Beatragus hunteri is monotypic.

NOMENCLATURE NOTES. Although the genus Beatragus is accepted today, it has a long history of debate and confusion. The distinction of B. hunteri from Damaliscus has been suggested and acknowledged for some time (Roosevelt and Heller 1914), and others have affirmed the genus but could not offer validation ( Kumamoto et al. 1996; Pitra et al. 1998). Estes (1999) asserted that if B. hunteri exhibit flehmen tasting, then that alone, without additional DNA evidence, supported the separation of B. hunteri from species of Damaliscus and Alcelaphus . The urine-testing behavior exhibited by males suggests that B. hunteri is a relic alcelaphine that retains the flehmen behavior like wildebeest and all bovids other than Damaliscus and Alcelaphus ( Butynski 2000) . Additionally, fossil records indicate that B. hunteri is a remnant species from a lineage older than both damaliscine and alcelaphine antelopes and that considering it a subspecies of D. lunatus is “unacceptable” ( Kingdon 1982:477). In compiling the views of several authorities on the classification of B. hunteri, Butynski (2000:12) summarized it with the statement “there is a growing body of evidence, and a general consensus, that B. hunteri is a monotypic species in the genus Beatragus . ”

Beatragus hunteri was first described and named by Sclater specimen, H. C. V. Hunter ( Butynski 2000; Evans 2011). Sclater also published an article in The Field magazine referring to it as Cobus hunteri (1889b) . I have been unable to view this article (1889b) but included it because it has been referenced in previously constructed synonymies ( Lydekker 1914; Allen 1939). Probably owing to miscommunications and multiple tribal spellings and interpretations, B. hunteri has also been referred to as aroli, arawale, arrola, hirola, arawla, and carowla, all of which refer to the tawny coat color ( Butynski 2000; Evans 2011). Various interpretations have been offered as to the origin and spelling of the common name used for B. hunteri ; for example, Sclater (1889c) was the first to use the Galla (= Orma) word “herola.” Other authorities believe that “hirola” is Somali, not Orma ( Butynski 2000). Kingdon (1982) noted that the Galla name for B. hunteri is actually “blanketta.” Complicating the situation further is the fact that the Swahili also use the term “arrola” for impala ( Dracopoli 1914). Sclater’s (1889c) original herola is retained here.

DIAGNOSIS

Although Beatragus hunteri resembles species of Damaliscus and Alcelaphus , it can be distinguished by its horn shape, body shape, and coloration. B. hunteri has unique lyre-like horns ( Fig. 1 ), with prominent annulations from their bases to the 1st one-half to two-thirds of their lengths ( Sclater 1889c; Roosevelt and Heller 1914; Kingdon 1997; Butynski 2000). B. hunteri is lighter in build than species of Alcelaphus and Damaliscus , its face length is less extreme than Alcelaphus ( Butynski 2000) , and the occipital region of the skull is rounder thus more closely resembling species of Damaliscus (Roosevelt and Heller 1914) . The withers are less elevated in relation to the hindquarters than those of species of Damaliscus and Alcelaphus (Roosevelt and Heller 1914; Butynski 2000). Coloration of B. hunteri is also distinctive, and it has an inverted, white chevron bar located between its eyes ( Fig. 1 ) that connects the white spectacles that surround the eyes (Roosevelt and Heller 1914; Butynski 2000). Most antelopes, including many species of Damaliscus and Alcelaphus , have dark spectacles ( Kingdon 1997). The coat is described as uniformly yellow-brown and tawny ( Butynski 2000) compared with the darker themes of species of Damaliscus and Alcelaphus . Occasionally given the nickname of the “four-eyed antelope” ( Bain 2010), B. hunteri has large preorbital glands ( Butynski 2000; Bain 2010) that also serve as an identifying feature.

GENERAL CHARACTERS

Beatragus hunteri is a tawny antelope of medium build that runs with a heavy gallop like species of Alcelaphus ( Sclater 1889c) . Butynski (2000) acknowledged the white spectacles and inverted chevron between the eyes; the white underside, ears, and tail; the large preorbital glands; lyrate, sharp horns; tawny coat; and long tail, but he also noted the previously unpublished characteristics that follow. The forehead, back, withers, and fronts of the legs from knees to hooves are darker in color than the rest of the body; the base and dorsal side of the tail is tan and the tip has white and black hairs; the horns, nostrils, ear-tips, eyes, udder, and hooves are black; the sides of the belly are a lighter tawny color and become whitish tawny on the center of the belly and inner sides of the legs; and the coats of young are paler and less glossy than those of adults ( Butynski 2000).

The horns of B. hunteri are unique in formation and appearance ( Fig. 2 ). The horns lack a basal pedicle ( Butynski 2000), are very upright, lyrate-shaped, and very sharp, resembling the common impala, Aepyceros melampus melampus ( Andanje 2002) . They begin by curving outward then slanting up and back. When viewed from the front, they create a U-shape.

Ranges of typical measurements (kg or cm) of B. hunteri , as summarized from various sources, were: body mass 73–118, head–body length 120–200, shoulder height 95–125, girth behind shoulders 121–122, ear length 18–19, tail length 30–45, and The bases of the horns in males also tend to be thicker and more strongly annulated ( Kingdon 1982). Two sets of female horns collected by the Nairobi Club in the late 1800s averaged 54 cm long with an 28 cm spread, and 6 sets of male horns averaged 61 cm long with a 33 cm spread ( Ward 1892). Mean horn length is 55.4 cm for males and 42.4 cm for females ( Andanje 2002).

horn length 55–72 ( Dracopoli 1914; Dorst and Dandelot 1970; Kingdon 1982, 1997; Butynski 2000, 2013). Additional, unpublished body measurements taken by R. Kock during the translocation of B. hunteri to Tsavo East National Park were referenced in Butynski (2000), all of which are within the aforementioned measurement ranges.

Dimorphism between male and female B. hunteri is present but slight. Males are more of a café au lait color than the rufous females (W. T. Bunderson, in litt.) and are slightly larger ( Sclater 1889c; Butynski 2000; Andanje 2002). For example, mean total body length is 178.7 cm for males and 166.7 cm for females ( Andanje 2002). The horns of females are shorter and more slender than in males but are “proportionately larger,” and the tips appear to diverge rather than converge ( Sclater 1889c:376).

DISTRIBUTION

Because Beatragus hunteri has been the subject of relatively few studies, the geographical history of the species is scant. Roosevelt and Heller (1914) generalized Hunter’s account of the distribution of B. hunteri ( Sclater 1889c) as the north side of the Tana River from Durani to Massa in Kenya and then spreading parallel to the coast at Port Durnford in Somalia. Due to concerns about extinction, more recent studies have been conducted dealing with the shrinking populations and geographical distributions of the original and introduced populations of B. hunteri (Andanje and Ottichilo 1999; Muthoni 2007). Butynski (2000) investigated and clarified historical accounts of the distribution of B. hunteri and declared that Hunter’s account of its distribution ( Sclater 1889c) was either inflated or misinterpreted. Butynski (2000:14) concluded that the historical distribution of B. hunteri was approximately “ 30–50 km inland from, and parallel to, the Indian Ocean, from near Garsen on the Tana River to north of Kismayu on the Juba River ” and that the northern extent was probably “ from about half-way between Bura and Garissa (i.e., at Massa Bubu) on the Tana River, northeast to about 0°35’N in the Lack Dere (= Lag Dera = Lake Dera) region, and then southeast to near the Juba River.” In contrast, W. T. Bunderson (in litt.), after having spent 3 years just outside of the Arawale National Reserve in Kenya, deduced that H. C. V. Hunter ( Sclater 1889c) and Dracopoli (1914) were correct in stating that the western extent of B. hunteri was 40°E and the northern extent was 0°35′S. B. hunteri is now found only in a small pocket of Kenya on the Somalia border ( Fig. 3 ). Until the 1960s and 1970s, the distribution encompassed about 17,900 km 2, but by 1996, it had been constricted to the center and was 42% of its original size ( Butynski 2000). As the distribution has shrunk over time, virtually all extant B. hunteri live in the Garissa District of Kenya, and it remains questionable whether Somalia or the Lamu District of Kenya support any individuals at all ( Butynski 2000).

“Operation Hunter’s” was established in 1963 to introduce B. hunteri to Tsavo East National Park, and another introduction was made in 1966 ( Butynski 2000). In 1963, 10–20 B. hunteri were introduced to Tsavo, 79 were there by 1996 when an additional 29 B. hunteri were added, and there were about 105 individuals in 1998 ( Muthoni 2007).

FOSSIL RECORD

The fossil record for Beatragus hunteri is limited, but current evidence suggests that the Beatragus lineage originated 3.1 million years ago ( Gentry 1990; Butynski 2000). B. antiquus differences allow a male B. hunteri to be a precise rammer rather than an agile evader ( Kingdon 1982). Of additional note is the ridge of skin at the nape of the neck of male B. hunteri . This ridge is not a fat reserve or condition indicator; rather, it is just the result of thick skin moving forward when the ears are pricked ( Kingdon 1982).

Leakey, 1965 has been discovered in Olduvai Gorge Beds 1 and 2 ( Tanzania), Shungura member G ( Ethiopia), and Koobi Fora ( Kenya) from the Early Pleistocene ( Gentry 1990; Chaix et al. 2000). B. hunteri is distinguished from the extinct and likely ancestor, B. antiquus , by a smaller overall size, a narrower skull, and less upright horn cores ( Leakey 1965; Gentry 1990; Chaix et al. 2000). B. hunteri fossils were discovered in 1931 in Olduvai Gorge Beds 1, 2, and 4 and were reported as no longer occurring in Olduvai but were part of the Somali –Abyssinian fauna ( Hopwood 1951). Fossils of B. hunteri have also been found in Omo River, Ethiopia ( Gentry 1985); Olduvai, Tanzania ( Leakey 1965); Gobaad, Djibouti ( Thomas et al. 1984); and potentially Elandsfontein, South Africa (Gentry and Gentry 1978; Kingdon 1982; Butynski 2000).

FORM AND FUNCTION

The dental formula is i 0/3, c 0/1, p 3/2, m 3/3, total 30 ( Butynski 2013). Many measurements have been taken of the horns ( Sclater 1889c; Dorst and Dandelot 1970; Kingdon 1982, 1997; Butynski 2000, 2013) and the horn length ranges from 55 to 72 cm. In males, as mentioned previously, the “ramming zone” of the horns is thickened and more annulated, and the horns have a narrower span that the similar-looking impala horns. These

ONTOGENY AND REPRODUCTION

The age and maturation of Beatragus hunteri can be assessed based on horn development ( Andanje 2002; Probert 2011). Calves are identified as individuals that are 0–6 months old without horns or with horns just barely showing; juveniles are 7–12 months old with straight horns about as long as the ears; subadults are 13–18 months old with horns that have grown outward to form an oval shape and whose tips are beginning to converge; and adults are> 18 months old with “fully developed horns who’s tips run parallel to each other” ( Probert 2011:93).

Within their 1st year, most offspring leave their natal group, or original family group, and either stay alone, join a group of Grant’s gazelles ( Nanger granti ), or form or join mixed or single-sex groups of up to 3 subadults ( Andanje 2002). Males leave their family groups at about 6 months of age and may join Grant’s gazelles, mixed-sex groups of other dispersing female B. hunteri , or bachelor groups of older male B. hunteri ( Andanje 2002) . At 32 months of age, males are old enough to begin their own family groups or displace a male already in control of a family group ( Andanje 2002). Most females tend to disperse from their family groups at about 9 months of age and join up with either Grant’s gazelles, young males in mixed-sex yearling groups, adult males with whom they mature and form their own group, or stay solitary ( Andanje 2002). It does not appear common for a new group to be formed by a dispersing female joining up with a lone male or for there to be frequent movement of adults among groups ( Andanje 2002). Nevertheless, in a progress report to the Hirola Management Committee and IUCN/ SSC Antelope Specialist Group, A. H. Ali and J. R. Goheen (in litt.) emphasized the difficulties of individual identification of B. hunteri due to the mixing of individuals among groups, their skittish nature, and their tendency to leave and reoccupy an area during the course of a few weeks.

The ages at which wild B. hunteri reach sexual maturity are not well known, but based on records from captive individuals, it is estimated that females mature at 1.5–2 years and first give birth at 2–3 years, and males reach adult size at 3 years but do not form territories until 4 years of age ( Butynski 2013).

Beatragus hunteri breeds seasonally. The height of the mating season is in March at the start of the main rainy season ( Kingdon 1997), and after a gestation period of about 7.5 months ( Andanje 2002), young are born in October–November at the beginning of the short rainy season ( Kingdon 1997). In Tsavo East National Park, Andanje (2002) documented births occurring as early as between August and March, but with the majority of them occurring in October and November. This seasonal timing aligns with suggested changes in the nutrition of adults and requirements of abundant and high-quality grass for offspring. Similar to other alcelaphines, neonatal B. hunteri experience a lying-up period before they and their mothers join a family herd and are very vulnerable to predators during this time ( Kingdon 1982).

The most quantitative information regarding reproduction of B. hunteri is based on observations in captivity. Dvůr Králové Zoo in Czechoslovakia is one of the few zoos that have housed B. hunteri ( Šmielowski 1987) . Over the span of 11 years from 1971 to 1981, reproduction of a small group of 2 male and 5 female B. hunteri was recorded ( Šmielowski 1987). Births occurred in April–November, and 80% of those were in June–October ( Šmielowski 1987). The sexual maturity of males and females was reached in their 2nd year, with 1 female mating as early as 15 months and 18 days of age ( Šmielowski 1987). One male sired 15 offspring and lived in the zoo for 10 years, 3 months, and 5 days, setting a record for the longest captive survival period of B. hunteri ( Šmielowski 1987) . Gestation length ranged from 210 to 295 days, but these data appear questionable and may have been attributed to the difficulty associated with recording copulations in captivity ( Šmielowski 1987). Other proposed reasons for the data discrepancy were that estrus in female antelopes, in general, lasts for 36 h/cycle at most (more often for just a few hours per cycle) and that actual mating of antelopes lasts only minutes or seconds ( Dittrich 1972). Of the 11 zoo-born B. hunteri that reached 3 months of age, the average life span was 2 years, 11 months, and 4 days and the longest was 6 years, 5 months, and 10 days ( Šmielowski 1987). In 1979, B. hunteri at Dvůr Králové began contracting the diseases acidosis, tympanie, tuberculosis, and mycobacteriosis and the small herd was completely decimated by 1981 ( Šmielowski 1987). Kock et al. (2010) noted the maximum longevity of B. hunteri in captivity as> 22 years but without a time or place for this record. The oldest known captive B. hunteri , on record, died at 15 years and 2 months of age in 1989 at the Gladys Porter Zoo in Brownsville, Texas ( Weigl 2005; Probert 2011). Disease and lack of management understanding make future captive projects daunting ( Kock et al. 2010).

Figures

Fig. 1.—An adult female Beatragus hunteri from the Ishaqbini Conservancy in Ijara, Kenya, August 2012. Used with permission of photographer A. H. Ali.

Fig. 2.—Dorsal, ventral, and lateral views of skull and lateral view of mandible of an adult male Beatragus hunteri (Powell-Cotton Museum at Quex Park, specimen NH.SOM2.2). Collected 10 miles north of Afmadow, Jubaland, Somalia 0°8′N, 41°55′E by Miss Diana Powell- Cotton on 12 April 1934. Occipitonasal length is 349 mm. Photographs are used with permission of the photographer Mr. H. Basford and are copyrighted under Powell-Cotton Museum, Birchington CT7 0BH, Kent, United Kingdom.

Fig. 3.—Geographic distribution of Beatragus hunteri. The black outline represents estimated historical distribution (ca. 1886–1960s) and the solid black polygon represents known native distribution based on an aerial survey in May 1996. Information on Somalia range is not available for security reasons when the survey was conducted. Map adaptation drawn with information from Butynski (2000).