African Zoology - Volume 15, Issue 4, October 1980

The essential features of the chondrocrania of both D. angusticeps and D. polylepis polylepis are very similar and conform closely to the platytrabic ophidian type. Specialized features such as a marked reduction of the solum nasi, as well as of the orbitotemporal region of the chondrocranium are noticeable. The basal plate and the occipital and auditory regions do not differ in important respects from those descriptionbed in other snakes. Taxonomic justification for the separation of these elapids into two distinct species is adequately confirmed by structural differences between their chondrocrania.

The occurrence of vesicular follicles and corpora lutea (CL), without evidence of ovulation, in late fetuses and during prepubertal life was confirmed in the southern giraffe. In this, and other respects, the pattern of ovarian development is similar in the southern giraffe to the northern subspecies. This early ovarian activity recedes during late prepubertal life. Numerous accessory CL were present in pregnant and non-pregnant giraffe but they did not attain the size- of the true CL of pregnancy. The latter undergo an initial phase of rapid enlargement lasting about 100 days, followed by a period of recession till mid�pregnancy and a second growth phase which persists until term (457 days). The CL of pregnancy rapidly regresses after parturition. The accessory CL regress slowly and form normal looking corpora albicantia (CA). These CA are most abundant during early adult life as also are vesicular follicles.

Otoliths and scales were used for age and growth determinations of Sarotherodon mossambicus in the Luphephe-Nwanedzi impoundment, a subtropical man-made reservoir in Venda, northern South Africa. Two rings are deposited annually on the otolith whereas only one ring Is deposited on the scales. The growth of S. mossambicus in the Luphephe-Nwanedzi impoundment is compared to other S. mossambicus populations in South Africa.

Population size of Arctocephalus tropicalis on Gough Island was determined by direct censuses of parts of the coast during the summers of 1974 - 1976 and 1977 - 1978 and correction factors for undercounting and seasonal cycles were applied. Present population size is approximately 200000, giving an intrinsic rate of increase of 15,9% per year since 1955/56, but is now approaching the negative acceleration phase in population growth as a result of optimal breeding space becoming limited. An extension of breeding colony sites has also occurred since 1955.

Southern elephant seals Mirounga leonina selected mainly the gently sloping, smooth-surfaced beaches and vegetated areas of the sheltered north-east coast. Mainly adults hauled out during the spring breeding season, with all pups being born by late October and the majority of the pups dispersing from their birthsites by December. Subadults were most abundant at the onset of the summer moult haul-out, with bulls and some subadult males being most abundant towards the end of the moulting season. Moulting seals preferred vegetated areas to exposed beaches. During the 1977/78 summer, total population was estimated at 163 suggesting a slight decrease since 1955/56. Harems were small and few in number, and pregnant cows showed fidelity to previous pupping sites. Spatial and temporal separation of the breeding populations of elephant and fur seals (Arctocephalus tropicalis) precluded competition for haul-out sites.

The deposition onto grass stalks of two distinct, strongsmelling substances produced in the anal scent pouch, is the most common form of scent marking in the brown hyaena (Hyaena brunnea). It is called pasting. The behaviour associated with pasting is descriptionbed, as is the related functional anatomy of the scent pouch. The dispersion pattern of pastings within a group territory and the rate of marking in different parts of the territory were ascertained by direct observations on radio collared hyaenas. The data were analysed by the computer programs SYMAP and SYMVU which graphically display the data as a three dimensional map. Brown hyaenas leave most pastings in those areas in which they spend most time. This is in the central part of the territory. When they visit the boundaries, however, the frequency of pasting increases. GLC analyses of the pastings from two known individuals show distinct differences in the relative concentrations of the many compounds in the pastings of each. Behavioural observations show that the hyaenas are able to recognize different individuals' pastings. Pasting could function to inform group members of each other's movements as well as to inform outsiders that the territory is occupied.

The volatile properties of the three major components of the chest gland secretion of Galago crassicaudatus were studied. Artificial scents were prepared using these components and were tested under natural conditions at a field site in the Soutpansberg mountains of the Northern Transvaal. In order to establish a natural basis for analysing the communicatory function of the scent mark which results from chest rubbing behaviour, the social structure of the group of G. crassicaudatus at the study site was investigated. The chest gland secretion appears to function as a relatively short�lived cue which facilitates communication between individuals found near each other; and a relatively persistant cue which may be used for territorial marking.

The mammal fauna of the Kammanassie Mountain State Forest Reserve and Mountain Catchment Area was censused in the high-rainfall southeastern sector and low-rainfall northwestern sector from 2 -12 February, 1979. Collecting yielded 287 specimens of 17 species of small mammals, while the presence of a further 16 species of larger mammals was confirmed. Mean trapping success was low (2,0%) which reflects the low density of most species. Of the 10 species of small mammals collected in the southeastern sector Acomys subspinosus and Otomys ;irroratus were abundant, while Rhabdomys pumilio, Praomys verreaux; and Myosorex varius were common; the other five species collected were rare. In the northwestern sector the species composition and relative density of each differed. Here Aethomys namaquensis was abundant, R. pumilio common, and five other species (including A. subspinosus and O. irroratus) rare. Few carnivores occur. Stomach samples of collected specimens yielded information on feeding habits; species vary considerably in their diet. Twenty-four species of both large and small mammals occur in the southeastern part, and 25 in the northwestern sector; 17 species are common to both.

A detailed quantitative investigation of the feeding habits of seven important Natal inshore reef fish (Epinephelus andersoni Boulenger, 1903, Coracinus multifasciatus (Pellegrin, 1914), Pomadasys olivaceum Day, 1875, Diplodus sargus Linnaeus, 1758, Sarpa salpa (Linnaeus, 1766), Acanthurus triostegus Linnaeus, 1758 and Neoscorpis Iithophilus (Gilchrist & Thompson, 1908)) is descriptionbed. Qualitative information on the feeding of 23 other species is also given, and when all species are considered the ratio of carnivores, omnivores and herbivores is 4:1:1.

The very short duration of vigorous movement (1 1/2 to 7 min) in fresh water and physiological solutions make trout spermatozoa difficult subjects for cryopreservation studies. Solutions consisting of 250 to 280 mmol sucrose and 5 to 12% dimethyl sulphoxide (DMSO) (4 parts) did not activate trout spermatozoa (1 part), but after dilution with fresh water vigorous motility could be fully restored. These sucrose-DMSO solutions were employed in cryopreservation studies. Using straws and a fast freezing - fast thawing procedure, post-thaw dilution with fresh water resulted in 25% - 60% of spermatozoa becoming motite, all with vigorous forward progression. Some existing methods for the cryopreservation of other freshwater fish spermatozoa were repeated on trout without success.

At 18?C the eggs of the kelp-fly, Fucellia capensis, hatch in 24 - 32 h and the larval and pupal stages last 10- 12 and 9-14 days respectively. The growth curve is discontinuous, with declining relative growth rates in successive larval instars. Kelp-fly larvae are probably less significant consumers of drift kelp than amphipods or isopods, but they promote the decay of wrack beds and are favoured as food by sea-shore birds.

Ground counts of red billed oxpeckers Buphagus erythrorhynchus and their mammalian symbionts were made during November 1974 and December 1979 in an area of approximately 343 000 ha near Shingwedzi in the Kruger National Park, South Africa. Mean ratios for oxpecker/symbiont were 0,025 and 0,043 for 1974 and 1979 respectively (Table 1); the difference between the two values being statistically significant (dO,05 = � 1,645 < 4,09).