John D. Skinner

On the origin, evolution and phylogeny of giraffes Giraffa camelopardalis

The origin, phylogeny, and evolution of modem giraffes (Giraffa camelopardalis) is obscure. We review here the literature and conclude that the proximate ancestors of modern giraffes probably evolved in southern central Europe about 8 million years ago (Mya). These ancestors appear to have arisen from the gelocid ancestral assemblage of 20–25 Mya via the family Palaeomerycidae. From the palaeomerycids arose the Antilocaprinae (Pronghorns) via the subfamily Dromomerycinae, and two subfamilies of giraffids, the Climacoceratidae and Canthumerycidae. The terminal genus of the Climacoceratid line was the now extinct massive giraffid Sivatherium sp. The Canthumerycids gave rise to the okapi and giraffes via the intermediate forms of Giraffokeryx, Palaeotragus sp. (of which the okapi is the extant form), Samotherium sp. and Bohlinia sp. All of which are extinct. Stimulated by climate change, progeny of Bohlinia entered China and north India, evolved into typical Giraffa species and became extinct there about 4 Mya. Similarly, following their preferred habitat, African Giraffa entered Africa via Ethiopia about 7 Mya. Here, seemingly unaffected by the climate changes occurring to the east and causing extinction of its Asian counterparts, Giraffa radiated into several sequential and coeval species culminating with the evolution of G. camelopardalis in East Africa from where it dispersed to its modern range. Fossils of G. camelopardalis appear about 1 Mya in East Africa. The underlying stimulus for Giraffa evolution seems to have been the vegetation change that began about 8 Mya, from the prevalent forest (C3) biome to a savannah/woodland/shrub (C4) biome. Giraffas success as a genus is attributed to its great height and unique coat markings. Its height is a consequence of elongation of all seven cervical vertebrae and of the lower more than the upper limb bones. Advantages conferred by its height include protection from predation, increased vigilance, and in males sexual dominance and access to nutrients. Its coat colourings are highly hereditable and provide protection from predation by camouflage, especially in the young. As giraffe are unable to sweat and pant, the patches may also act as thermal windows and may have an important thermoregulatory function.

From fetus to adult--an allometric analysis of the giraffe vertebral column.

As mammalian cervical vertebral count is almost always limited to seven, the vertebral column of the giraffe (Giraffa camelopardalis) provides an interesting study on scaling and adaptation to shape in light of these constraints. We have defined and described the growth rates of the lengths, widths, and heights of the vertebrae from fetal through neonatal life to maturity. We found that the disproportionate elongation of the cervical vertebrae is not a fetal process but occurs after birth, and that each cervical (C2-C7) vertebrae elongates at the same rate. C7 is able to specialize toward elongation as its function has been shifted to T1. We concluded that T1 is a transitional vertebra whose scaling exponent and length is between that of the cervical and thoracic series. Despite its transitional nature, T1 is still regarded as thoracic, as it possesses an articulating rib that attaches to the sternum. The other dimensions taken (width, height, and spinous process length) show that giraffe vertebral morphology exhibit adaptations to biomechanical strain, and we have underlined the importance of the thoracic spinous processes in supporting the head and neck.

Inherent seasonality in the breeding seasons of African mammals: evidence from captive breeding

Breeding records from zoos provide a virtually untapped source of information for determining reproductive patterns of species unconstrained by nutritional variables and may be important in planning conservation strategies for rare species for which little “wild” data exist. In this study, we have analysed records of births in the National Zoological Gardens, Pretoria, from 1917 to 2001 for two species of zebras, 20 species of bovids, seven species of carnivores, the white rhinoceros and the hippopotamus. The zebras and pachyderms are aseasonal breeders, whilst the bovids show some variation. The African buffalo breeds throughout the year as do sable antelope in captivity, mountain reedbuck and all the arid-adapted species. The grazers tend to be seasonal, while browsers, with the exception of the kudu, tend to be aseasonal. Four species of felids and the spotted hyaena have an aseasonal breeding pattern but the African wild cat and wild dog are more seasonal. Possible reasons for the different patterns are discussed, with particular reference to the role of environmental cues.

Diet of brown hyaenas (Parahyaena brunnea) on the Namibian coast

The diet of brown hyaenas on the southern Namibian coast was determined via direct observation, scat analysis and by examining the faunal remains at nine dens consisting of 16 135 bones and bone fragments. All remains were identified to species and element where possible. Movements of four individual hyaenas from three different coastal clans were tracked via satellite collar. Range use was higher in coastal areas than in inland areas of the range. However, seasonal range use differences were detected. Seals formed the major proportion of the diet determined by scat analysis. In addition, the number of seal remains found at dens decreased with increasing distance to a coastal food source, scat analysis and direct observations indicated that the local population of hyaenas utilises a much broader food source than just seals. Behavioural differences between the current study population and previously reported populations of Parahyaen a brunnea are noted.

Conservation of Biological Diversity

The challenges that face tropical forestry in the 21st century are significant and well known. In the early 1990s, due to unsustainable forestry, illegal logging, overgrazing and agriculture, the total area of deforested and degraded tropical land surpassed the area of mature tropical forests. Tropical forestry is confronted with the task of finding strategies to alleviate pressure on remaining forests and techniques to enhance forest regeneration and restore abandoned lands, using productive alternatives that can be attractive to local communities. In addition, sustainable forestry in tropical countries must be supported by appropriate policies to promote and maintain specific activities at local and regional scales.

Bone collecting by hyaenas: a review

Three species of hyaenas are discussed, comparing their scavenging, feeding and hunting habits in relation to bone collecting. Hyaena hyaena and Parahyaena brunnea can be classified as ineffectual hunters but as solitary scavengers, while Crocuta crocuta, although it does scavenge, subsists largely by hunting medium-sized to large ungulates in packs. These differences have given rise to a great deal of conjecture in the past but it is now unequivocally established that the smaller scavenging hyaenas carry food back to their cubs at maternity dens, thereby contributing to extensive bone assemblages at den sites, which, in turn, reflect the faunal assemblage in adjacent areas to the den. Bones such as mandibles and long bones do not disintegrate at the same rate as smaller bones. On the other hand, spotted hyaenas largely feed where they kill their prey on find their food, carrying predominantly long bones away.

Orbit orientation and eye morphometrics in giraffes (Giraffa camelopardalis)

Giraffe are thought to have excellent vision.We measured eye size, orbit orientation and retina surface area in 27 giraffes of both sexes ranging in age from neonates to mature adults (>10 yrs), to assess how it changes with growth, whether their eye anatomy correlates with their apparently excellent vision and lifestyle, and we have compared our findings with those for other large mammals to assess whether giraffe eye anatomy is unique.We found that giraffe eye volume increases from 33 cm3 at birth to approximately 65 cm3 in adults. The focal (axial) length increases from c. 40 to 48 mm in adults and retina surface area from c. 3000 mm2 at birth to 4320 mm2 in adults. The orbital axis angle at birth is c. 73° and the horizontal visual field mainly monocular and panoramic.With age the axis angle becomes more acute to c. 50° in adults and the visual field more binocular, changes that occur concurrently with increasing neck length. These results show that the giraffe eye and retinal surface area are larger than in all other ungulates, and their visual fields more binocular, attributes which are consistent with the idea that they have excellent vision.

Nematodes of the small intestine of African buffaloes, Syncerus caffer , in the Kruger National Park, South Africa

The abundance and distribution of parasitic helminths in populations of African buffaloes, Syncerus caffer, have not been well documented. A total of 28 buffaloes of different ages and sexeswere sampled in the Kruger National Park, South Africa, for nematodes of the small intestine. Three nematode species were identified, namely Cooperia fuelleborni, Cooperia hungi and Trichostrongylus deflexus, with C. hungi being a new country record for African buffalo in South Africa. The overall prevalence was 71%and the average number of worms was 2346 (range: 0-15 980). This is a small burden for such a large mammal. Sex, age and body condition of the buffaloes had no significant effect on worm occurrence.

Do male cheetahs Acinonyx jubatus commit infanticide

Infanticide, in which males kill unrelated juveniles presumably to advance their genetic contribution has been documented in many felids, a notable exception being the cheetah Acinonyx jubatus. Males apparently always tolerate cubs during encounters between females with litters but indefinite paternity has confused the issue in previous reports. We observed cheetah females with cubs interact with known sire and non-sire males, and infanticide never occurred. Sires and non-sires also did not differ in the frequency of different aggressive behaviours directed towards females and cubs during encounters. We suggest that cheetahs are unusual among wild felids in that males do not kill unrelated cubs and discuss possible reasons why infanticide does not occur in the species.

The Structure and Function of Giraffe Jugular Vein Valves

When a giraffe (Giraffa camelopardalis) lowers its head to drink, blood could enter the Jugular vein from the Inferior vena cava or regurgitate from the Jugular veins into the cranial veins. We investigated the anatomy of Jugular valves in giraffes to establish if they could prevent either of these regurgitations. Jugular vein length and intervalve distances of 396 valves (192 left, 204 right) were measured in 60 veins from 25 adult (11 males and 14 females) and five foetal giraffes. The average number of valves in the left Jugular veins was 6.4 ± 2.7 (mean ± S.D.; range = 2-13) and in the right was 6.8 ± 2.1 (range = 3–12). Male giraffes had 7.3 ± 2.7, females 5.9 ± 2.1, and foetuses 7.0 ± 2.1 valves per vein. None of these differences was statistically significant (t-test; P > 0.05). Most valves (88%) were bicuspid in structure. Their position in the veins was Irregular. Most (36.1 %) were located in the first 500 mm of vein. The relative distribution of foetal valves was not significantly different from that in adult giraffes (&khgr;2 = 0.274, P > 0.05). We concluded that the main function of the Jugular vein valves is to prevent regurgitation of blood from the Inferior vena cava and right atrium Into the Jugular vein and that the number of valves is fixed in utero.