Population increase in the Amsterdam Island fur seal Arctocephaius tropicalis at Gough Island

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

Time budgets and activity patterns of sub-Antarctic fur seals at Gough Island

The diurnal activity patterns of sub-Antarctic fur seals, Arctocephalus tropicalis, were observed at a non- breeding colony site at Gough Island (40°20′S, 9°54′W) during summer. Time budgets of adult males were also studied at idle and breeding colony sites, Levels of activity were highest during the early morning and late afternoon. High ambient temperatures depressed the interaction rate on the dry hauling ground, but activity increased as a result of the movement of heat-stressed seals to and from the sea where favourable conditions for heat loss exist. The fur seals were largely inactive, in particular adult males which spent 93,2% of the time inactive in breeding colonies and 97,9% of Ihe time inactive at idle colony beaches. The daily change in numbers ashore, the relative contribution of the different age and sex classes, their location and distribution on site, and the prevailing weather conditions influence the pattern of interaction and allocation of time to the various activities in A. tropicalis. The predominance of inactivity is considered to be a behavioural thermoregulatory response to limit endogenous heat production as is energy conservation. Both views translate into improved tenure for territorial males, in particular those without access to water for cooling during the breeding season

Seasonal and age-related changes in the micro-anatomy of the prostate gland of the Subantarctic fur seal, Arctocephalus tropicalis

The prostate glands of male Subantarctic fur seals Arctocephalus tropicalis, taken at Gough Island (40°20'S, 09°54'W) between November 1977 and October 1978, were examined. Significant changes in the mass of the prostate, the diameter of the alveoli and height of the secretory epithelium precede the breeding season and support the fact that A. tropicalis is a seasonal breeder. Peak activity of the prostate is reached during November-January. We propose that seasonal changes in the prostate gland, and in male reproductive activity in general, may be cued by changing photoperiod. Micro-anatomical features of the prostate of the male Subantarctic fur seal differ between different age groups. Peak prostate mass, alveoli diameter and secretory cell height indicate that Subantarctic fur seal males reach full adulthood at 10–11 years of age

An assessment of spatial and temporal variation in the diet of Cape clawless otters (Aonyx capensis) in marine environments

We studied the diet of Cape clawless otters (Aonyx capensis) at three sites along the eastern and southern coast of South Africa to assess possible spatial variation along a community species richness and biomass gradient associated with rocky shores.A total of 309 spraints representing two seasons (summer 2013/2014 and winter 2014) were collected and subsequently analysed. The percentage occurrence and percentage dry mass of numerous prey categories were compared between sites and seasons. Variation in the importance of prey items was found between sites, whilst no variation was found between seasons within the same site. Crab was the most important prey item in the southernmost study area (Tsitsikamma National Park) and at the northernmost study site (KwaZulu-Natal Coast), whilst lobster was the most important prey item in the central area (Mkambati Nature Reserve). Fish was the second most important prey item at all three sites. Our results suggest that otters are opportunistic feeders that are likely able to adapt to potential prey species and abundance changes associated with current and future anthropogenically driven changes. Furthermore, long-term, site-specific stability in diet suggests that monitoring the diet of otters could provide some useful information on the status of shoreline communities

A global cline in a colour polymorphism suggests a limited contribution of gene flow towards the recovery of a heavily exploited marine mammal

Evaluating how populations are connected by migration is important for understanding species resilience because gene flow can facilitate recovery from demographic declines. We therefore investigated the extent to which migration may have contributed to the global recovery of the Antarctic fur seal (Arctocephalus gazella), a circumpolar distributed marine mammal that was brought to the brink of extinction by the sealing industry in the eighteenth and nineteenth centuries. It is widely believed that animals emigrating from South Georgia, where a relict population escaped sealing, contributed to the re-establishment of formerly occupied breeding colonies across the geographical range of the species. To investigate this, we interrogated a genetic polymorphism (S291F) in the melanocortin 1 receptor gene, which is responsible for a cream-coloured phenotype that is relatively abundant at South Georgia and which appears to have recently spread to localities as far afield as Marion Island in the sub-Antarctic Indian Ocean. By sequencing a short region of this gene in 1492 pups from eight breeding colonies, we showed that S291F frequency rapidly declines with increasing geographical distance from South Georgia, consistent with locally restricted gene flow from South Georgia mainly to the South Shetland Islands and Bouvetøya. The S291F allele was not detected farther afield, suggesting that although emigrants from South Georgia may have been locally important, they are unlikely to have played a major role in the recovery of geographically more distant populations

Endoparasites of the subantarctic fur seal Arctocephalus tropicalis from Gough Island

Two hundred and fourteen subantarctic fur seals Arctocephalus tropicalis, culled at Gough Island, South Atlantic Ocean, were examined grossly for endoparasites. Respiratory and alimentary tracts were searched in particular. Unweaned individuals only harboured tracheal mites Orthohalarachne diminuata, whilst larval cestodes Phyllobothrium delphini were found in subcutaneous blubber of the majority of older animals. In addition, pseudophyllidean cestodes Diphyllo-bothrium sp. predominated in the caecal area, and anisakine nematodes Anisakis simplex and Contracaecum osculatum in stomachs. A. tropicalis is a new host record for the tetraphyllidean cestode Monorygma grimaldii, an incidental parasite in this case

Juvenile survival and population regulation in southern elephant seals at Marion Island

We examined annual juvenile survival in southern elephant seals (Mirounga leonina) at Marion Island for the period 1994–1999 during which time the population was stable. Using mark–recapture models, we tested for age- and sex-specific differences in survival rates over the first three years of life. We found that survival was age- but not sex-related and compared our estimates to similar estimates from a previous study on the same population while in a state of decline. This was done to determine whether changes in juvenile survival were instrumental in terminating the population decline at Marion Island. On average, the probability of survival was 59.5 %, 81.4 % and 78.1 % for the first, second and third year respectively. These estimates were remarkably similar to those previously calculated for the population while in a state of decline, and we dismiss juvenile survival as a major population regulating component in southern elephant seals at Marion Island.Keywords: southern elephant seals, juvenile survival, mark–recapture, population regulation