Age determination of Cape porcupines, Hystrix africaeaustralis

Attempts to determine the absolute age of free-ranging porcupines based on counts of cementum and periosteal lines, age-related changes In eye lens weight, sequential pattern of tooth eruption and replacement, and tooth attrition are described. Variation due to ramification and absorption of cementum and periosteal lines resulted in counts of these lines being unreliable indicators of age. Variation in counts of cementum lines apparently results from continual growth of the hypsodontic open-rooted premolars and molars. Heteroscadasticity resulted in the relationship between age and lens weight being unreliable for predicting age. Consistency In the age at which maxillary molars erupt and premolars are replaced, as well as the wear pattern of the occlusal surfaces, provide a method for distinguishing nine dental age classes. Chronological age, based on observations on captive porcupines could be accurately assigned to six of these

The stimulation of testosterone and LH secretion by synthetic GnRH in the male Cape porcupine

The effects of GnRH stimulation on plasma testosterone and luteinizing hormone (LH) levels in Cape porcupine males were examined by analysing plasma collected before and after an intravenous injection of GnRH. In six mature males and one subadult, which were given an intravenous injection of 0,5 ml saline, levels of plasma testosterone and LH did not increase. Four weeks later an intravenous GnRH challenge (40 μg) caused plasma testosterone to rise three-fold and LH to rise 10-15-fold within 180 min in five of the mature males. Peaks of plasma testosterone and LH occurred 90 and 120 min, respectively, after stimulation, and baseline and peak levels of both hormones were significantly related

Seasonal changes in plasma testosterone levels in the male South African hedgehog (Atelerix frontalis)

Testosterone levels in plasma collected ait monthly intervals from 6 to 15 male South African hedgehogs (Atelerix frontalis) housed in captivity showed a marked seasonal pattern. Values were relatively low (< 0,25 ng/ml) from February to June but increased significantly from July to August. Testosterone levels peaked in August (x̄ = 2,85 ± 1,37 ng/ml; n = 15) and December (x̄ = 2,73 ± 0,36 ng/ml; n = 6) remaining relatively high from August to January. This seasonal pattern is similar to that recorded in the European hedgehog (Erinaceus europaeus)

Aspects of habitat disturbance by Cape porcupines in a savanna ecosystem

Habitat disturbances by Cape porcupines (Hystrix africaeaustralis)in a savanna ecosystem were investigated at Nylsvley Nature Reserve by using transect line surveys for signs of porcupine foraging activities. The density of foraging diggings was significantly higher in Burkea savanna than in Acacia savanna. A significantly higher proportion of trees was debarked in Burkeaand rocky outcrop savanna than in Acacia savanna. The only two species which were preferentially debarked were dominant species in the former two habitat types. Significantly more trees had roots gnawed on by porcupines in Burkea savanna than elsewhere, and the species most affected (Burkea africana) was a dominant species in this habitat type. Concentrated feeding activities in Burkea and rocky outcrop savanna by porcupines may affect the structure of these plant communities

Harem structure of the southern elephant seal Mirounga leonina at Kerguelen island

L'auteur présente des données quantitatives sur les harems de l'Éléphant de mer des Kerguelen (Mirounga leonina) obtenues pendant l'été austral 1977. Le sex-ratio dans les harems était de 1 ♂ pour 29,97 ♀, alors que dans la population adulte générale il était de 1 ♂ pour 15,2 ♀. La structure des harems était en moyenne la suivante : 1 « maître-mâle » ; 2,54 ± 4,03 « assistants » ; 1,29 « challengers » ; 1,89 « célibataires » et 102,3 ± 135,43 femelles adultes (taille de l'échantillon : 375 harems observés sur 79 km de côte). La taille comme la structure des harems sont influencées par la superficie de l'aire de reproduction, les plus grands harems étant observés sur les plages sableuses, et les plus petits sur celles de gros cailloux. Alors que l'énorme augmentation de la population sur une côte modérément accueillante depuis 1952 n'a pas entraîné de changement significatif dans la taille des harems, une faible augmentation de population sur une côte déjà densément peuplée a abouti à une forte augmentation de la taille des harems et à une diminution de leur nombre. Une relation statistiquement significative a été mise en évidence entre la taille des harems et la mortalité des jeunes éléphants de me

Population biology of house mice (Mus musculus L.) on sub-Antarctic Marion Island

Based on mark-recapture models, house mouse densities on sub-Antarctic Marion Island changed seasonally (up to 10-fold) and differed between habitats. Peak densities occurred towards the end of summer (May). On both the hummocky beach and vegetated lava study grids, densities at the end of summer were significantly higher than those recorded during 1979/80. During the rest of the year densities were significantly lower on these study grids than those recorded during 1979/80. Length of the breeding season (6,5 months) and mean litter size (7,24 ± 1,7) were of the same order as those recorded during 1979/80, as were age and sex specific mortality patterns. The incidence of pregnancy (7,27 litters/season) was higher (not significant) than that recorded during 1979/80. Prenatal mortality was positively correlated with ovulation rate. Differences in annual trends may result from yearly changes in environmental conditions and do not support speculation that these may have resulted from medium-term changes in climatic conditions in the sub-Antarctic

Book Reviews

Book Review 1Book Title: The Physiology of ReproductionBook Authors: Editors-in-Chief: E. Knobil, & J.D. KneillRaven Press, 1988. 2633 pagesBook Review 2Book Title: Long-term Studies in Ecology: Approaches and AlternativesBook Author: Gene E. LikensSpringer-Verlag, New York, 1988. 214 pages, 27 figures. ISBN 3-540-96743-5.Book Review 3Book Title: Oceans of Life off Southern AfricaBook Authors: Edited by Andrew I.L. Payne & Robert J.M. Crawford and illustrated by Anthony P. van DalsenVlaeberg Publishers, Cape Town, 1989. 300 pp., numerous figures, tables and photographs.Book Review 4Book Title: Biotic Diversity in Southern Africa: Concepts and ConservationBook Author: Edited by B.J. HuntleyOxford University Press, Cape Town, 1989. 380 pages, hardback edition.Book Review 5Book Title: Ecosystems of the World 14B, Tropical Rain Forest Ecosystems: Biogeographical and Ecological StudiesBook Authors: Edited by H. Leith & M.J.A. WergerElsevier, 1989

Fluctuations in the population of southern elephant seals Mirounga leonina at Kerguelen Island

An analysis of census information published for the years 1952, 1958,1960 and 1970 and that obtained during this study in 1977, indicates that both the breeding bull and cow components of this population fluctuated in numbers during the past 25 years. In spite of these fluctuations, the general trend for the cow component was to increase at a rate of 1,4% per year, while the bull component decreased at a rate of 1,9% per year. An analysis based on subdivisions of the study area into distinct regions indicated that the range of fluctuation increased as mean density increased. The population is regarded as a stable fluctuating population and the influence of environmental and social factors on the observed population trends is discussed

The use of 65Zn for estimating group size of brown hyaenas Hyaena brunnea

The applicability of a method of estimating group size based on the labelling of an individual within a group of hyaenas with the zinc isotope 65Zn is evaluated. This isotope is detectable in faeces and the method is based on the assumption that the proportion of labelled faeces found at latrines, will equal the proportion of labelled hyaenas in the group. Group size estimates increased logarithmically with an increase in the number of stools included in the analysis but remained relatively constant after approximately 140 stools were included. Estimates were in agreement with direct observations