126 



TITANOTHEEES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



divided them into seven subfamilies, each with its 

 distinctive mode of life. During a long period of 

 geologic time the Bovidae have undergone secondary 

 radiations (A-Q, fig. 82), by which certain branches of 

 these subfamilies have become adaptively convergent 

 toward certain branches of other subfamilies through 

 the adoption of similar habits and habitats. Thus, 

 analogous genera and species arise independently in 

 each subfamily. For example, waterless deserts were 

 sought both by the addax, among the Hippotraginae, 

 and by the gazelle, among the Antilopinae; reeds, 

 river borders, and lagoons were sought both by certain 



Figure 82.- 



c 



-Adaptive radiation in the feeding habits of antelopes, as observed by 

 Stevenson-Hamilton in 1912 

 1-7, Primary radiations; A-Q, secondary radiations 



Cervicaprinae, such as the lechwes and kobs, and by 

 certain of the Tragelaphinae, such as the situtungas. 



ADAPTIVE RADIATION IN THE FEEDING HABITS 

 ANTELOPES 



OF 



The habits and habitats of the antelopes, as noted 

 by Stevenson-Hamilton (1912), are as follows: 



1. Antilopinae. — The impalas {Apyceros melampus) eliiig to 

 neighborhoods of dense thorny bush, to which they fly for 

 refuge. More partial to brovv^sing than to grazing. Food con- 

 sists largely of leaves and shoots, but they eat young and tender 

 grass freely after early rains. Staple diet leaves and fruit of 

 certain acacias, also twisted bean pods of the same. In March 



fruit of marula is eaten. Toward the end of the dry season 

 they completely strip the bush of everything edible up to the 

 extreme height which they are able to reach. * * * The 

 springbucks (Antidorcas euchore) are typical of the high veldt 

 fauna of South Africa. The only member of the gazelle group 

 in this region. Love high, open tablelands. * * * Xhe 

 typical African races of gazelles include 14 species. Grant's, 

 Thomson's, Speke's, etc. Inhabitants of wide, open plains or 

 sandy deserts. Largely independent of water. 



2. Bubalidinae. — Antelopes of large size, large, moi.st rhinari- 

 um; including Buhalis (= hartebeest), Damaliscus (= bastard 

 hartebeest), Connochaetes (= gnu, or wildebeest). Buhalis 

 (= hartebeest), eight species, with everywhere same charac- 

 teristics; frequent open or forest countrj' or treeless plains; 

 essentially grass eaters; like to drink 

 regularly. Young carried about eight 

 months. * * * Damaliscus, bonte- 

 buck {D. pycargus), blesbuck, tsessebe 

 (sassaby) (both D. albifrons), grass-eat- 

 ing antelopes, favoring rather open and 

 fairly flat country, never hills or thick 

 jungle, partiality for shady patches of 

 bush or forest for shelter during the hot 

 hours. * * * Connochaetes (gnu, or 

 wildebeest), white-tailed or black (C 

 ()7iu) and brindle or blue (C. tautrinus). 

 Prefer open, rolling country interspersed 

 with thick thorn or other bush. Some- 

 times remain in the open, bare spaces 

 or plains where they can see for long dis- 

 tances. Essentially grass-eating ani- 

 mals. Pasture cropped closely. Socia- 

 l5le, gregarious. 



3. Tragelaphinae. — Elands and bush- 

 bucks, inyalas, kudus, situtungas. Elands 

 {Taurotragus oryx), plains type, graze 

 with horses, donkeys, and cattle but 

 browse by preference, favoring the grass 

 only when fresh and green, sometimes 

 cropping the tops of young river reeds. 

 Gestation period eight and a half months. 



* * * Bongo {Boocercus eurycoros), 

 fond of the most dense forest, leaves and 

 twigs of a certain kind of undergrowth, 

 which grows from 6 to 8 feet in height. 

 Young shoots all nipped off if bongo 

 have been feeding. Also (?) bark eaters. 



* * * Bushbucks {Tragelaphus scrip- 

 txis), forest dwellers, solitarj', nocturnal, 

 prefer densely wooded gullies, or kloofs, 

 of South Africa. Browsers on the leaves 

 of various small shrubs and trees; eat 

 grass sparingly when the latter is fresh 

 and green; roots and tubers form fur- 



* * * Inyalas {Tragelaphus angasi), 

 Exhibit intense localization, probably due 



to the presence of some peculiar foodstuff, limited in quantity 

 but necessary to the health of the individual animal. Probably 

 browse on various leaves, shrubs, and fruits, bean pods and 

 acacias, fruit of the marula; grass eaten when it is young and 

 of good quality. * * * Sitiitnnga.s (Tragelaphus spekei) , semi- 

 aquatic animals, almost amphibious by nature. Great elonga- 

 tion of hoofs. Strong swimmers. Rapid locomotion upon dry 

 land very difficult. Frequent extensive reed and papyrus swamps 

 bordering lakes and large rivers. * * * Kudus {Strepsiceros 

 strepsiceros) , love stony or rather broken ground, covered with 

 thorn scrub. Gregarious, more than most antelopes, a browser, 

 subsisting chiefly on the leaves of thorn acacias and bush shrubs, 

 together with the fruits of the marula and other trees. 



ther articles of diet, 

 very local and rare. 



