Re-estimating the Size of the Polar Bear Population in Western Hudson Bay

A mark-recapture study of polar bears (Ursus maritimus) ashore during the ice-free period of Hudson Bay was undertaken in 1994 and 1995 to re-estimate the size of the western Hudson Bay population. Previous estimates were based on animals caught between the Churchill and Nelson Rivers; consequently, bears in the southern part of the geographic range of this population were not sampled. We used Jolly-Seber models to re-estimate population size from two data sets: bears handled between the Churchill and Nelson Rivers from 1984 to 1995 and bears handled between Churchill and the Manitoba-Ontario border from 1984 to 1986 and by us in 1994 and 1995. Both data sets gave similar estimates. Thus, our best estimate of the size of the western Hudson Bay polar bear population is 1200 ±250 animals in autumn 1995.En 1994 et 1995, on a entrepris une étude sur la reprise d'ours polaires (Ursus maritimus) étiquetés sur la terre ferme durant la période libre de glace dans la baie d'Hudson, en vue d'établir une nouvelle estimation de la taille de la population dans la partie ouest de cette baie. Les estimations précédentes s'appuyaient sur le nombre d'animaux pris entre les fleuves Churchill et Nelson; par conséquent, les ours situés dans la partie méridionale de l'étendue géographique de cette population n'ont pas fait l'objet d'un échantillonnage. On s'est servi de modèles Jolly-Seber pour établir une nouvelle estimation de la taille de la population à partir de deux ensembles de données: des ours marqués entre le Churchill et le Nelson de 1984 à 1995, et des ours marqués entre le Churchill et la frontière Manitoba-Ontario de 1984 à 1995. Ces derniers prélèvements renfermaient des données sur la reprise d'ours étiquetés effectuée de 1984 à 1996 par le ministre ontarien des Ressources naturelles le long de la côte est du Manitoba, et par nous-mêmes en 1994 et 1995. Les deux ensembles de données fournissaient des estimations similaires. Ainsi, pour l'automne 1995, notre estimation la plus précise de la taille de la population de l'ours polaire dans l'ouest de la baie d'Hudson est de 1200 ± 250 individus

Polar Bear Distribution and Abundance on the Southwestern Hudson Bay Coast During Open Water Season, in Relation to Population Trends and Annual Ice Patterns

In Hudson Bay, all the ice melts in summer, and the last areas to be ice-free (around mid-to-late July) are usually off the coasts of Manitoba and Ontario. Thus, all polar bears are forced ashore to fast until freeze-up in November (ca. four months). Pregnant females remain ashore for eight months. In most years from 1963 through 1997, aerial surveys to monitor polar bear populations were conducted along all or part of the coastline between Cape Churchill, Manitoba, and Cape Henrietta Maria, Ontario, in late August and early September. Satellite data, from which breakup and ice absence times could be estimated, first became available in 1971. The numbers of animals counted were tallied in two subareas within Manitoba and three within Ontario. We evaluated the coastal counts, along with independent data on the movements of tagged bears and annual patterns of ice breakup from 1971 through 1996. We concluded that 1) the coastal survey data reliably indicated the population trends in Manitoba and Ontario; 2) little exchange occurred between the Western Hudson Bay (Manitoba) and Southern Hudson Bay (Ontario) populations; 3) between 1971 and 2001, there was a statistically significant trend toward earlier breakup of sea ice off the Manitoba coast, but not off the Ontario coast; 4) the onset of ice absence along the coast had no significant relationship to the number of bears present in each sub-sampling area within either the Manitoba or the Ontario population, but did significantly influence the distribution of bears on the coastline of each province independently of the other; 5) timing of the surveys can influence the results; and 6) adult male and female bears both showed a high degree of fidelity to specific areas during summer, independent of the pattern of ice breakup.Dans la baie d'Hudson, toute la glace fond en été, et les dernières zones à être non englacées (du milieu à la fin de juillet environ) se trouvent généralement au large des côtes du Manitoba et de l'Ontario. Ainsi, tous les ours polaires sont forcés de rester sur la terre ferme et de jeûner jusqu'à l'engel en novembre (soit environ quatre mois). Les femelles gravides, elles, restent sur la terre ferme pendant huit mois. Presque chaque année entre 1963 et 1997, à la fin août et au début de septembre, on a effectué des relevés aériens pour surveiller les populations d'ours polaires le long du littoral entre Cape Churchill, au Manitoba, et Cape Henrietta-Maria, en Ontario. Les données satellitaires, qui ont permis d'estimer la période de la débâcle et celle de l'absence de glace, sont devenues disponibles à partir de 1971. Le nombre d'animaux repérés a été inventorié comme provenant de deux sous-zones à l'intérieur du Manitoba et de trois à l'intérieur de l'Ontario. On a évalué le dénombrement des relevés côtiers ainsi que des données indépendantes sur les déplacements d'ours marqués et les schémas annuels de débâcle de 1971 à la fin de 1996. On en a conclu que: 1) les données des relevés côtiers révélaient de façon fiable les tendances démographiques au Manitoba et en Ontario; 2) il n'y avait que peu d'échanges entre les populations de la baie d'Hudson occidentale (Manitoba) et de la baie d'Hudson méridionale (Ontario); 3) entre 1971 et 2001, il y a eu une tendance statistiquement significative à une débâcle précoce au large du littoral manitobain, mais pas au large du littoral ontarien; 4) le début de l'absence de glace le long de la côte n'avait pas de lien marqué avec le nombre d'ours présents dans chaque secteur de sous-échantillonnage, au sein de la population du Manitoba ou de celle de l'Ontario, mais cette absence de glace avait une forte incidence sur la distribution des ours le long de la côte de chaque province indépendamment l'une de l'autre; 5) le choix de l'époque des relevés peut influencer les résultats; et 6), durant l'été, les ours mâles comme femelles manifestaient une grande fidélité pour des secteurs spécifiques, indépendamment de l'évolution de la débâcle

Taenia solium porcine cysticercosis in Madagascar: Comparison of immuno-diagnostic techniques and estimation of the prevalence in pork carcasses traded in Antananarivo city

Taenia solium cysticercosis was reported in official veterinary and medical statistics to be highly prevalent in pigs and humans in Madagascar, but few estimates are available for pigs. This study aimed to estimate the seroprevalence of porcine cysticercosis among pigs slaughtered in Antananarivo abattoirs. Firstly, the diagnostic performance of two antigen-ELISA techniques (B158B60 Ag-ELISA and HP10 Ag-ELISA) and an immunoblotting method were compared with meat inspection procedures on a sample of pigs suspected to be infected with (group 1; n = 250) or free of (group 2; n = 250) T. solium based on direct veterinary inspection in Madagascar. Sensitivity and specificity of the antigen ELISAs were then estimated using a Bayesian approach for detection of porcine cysticercosis in the absence of a gold standard. Then, a third set of pig sera (group 3, n = 250) was randomly collected in Antananarivo slaughterhouses and tested to estimate the overall prevalence of T. solium contamination in pork meat traded in Antananarivo. The antigen ELISAs showed a high sensitivity (>84%), but the B158B60 Ag-ELISA appeared to be more specific than the HP10 Ag-ELISA (model 1: 95% vs 74%; model 2: 87% vs 71%). The overall prevalence of porcine cysticercosis in Antananarivo slaughterhouses was estimated at 2.3% (95% credibility interval [95%CrI]: 0.09–9.1%) to 2.6% (95%CrI: 0.1–10.3%) depending on the model and priors used. Since the sample used in this study is not representative of the national pig population, village-based surveys and longitudinal monitoring at slaughter are needed to better estimate the overall prevalence, geographical patterns and main risk factors for T. solium contamination, in order to improve control policies. (Résumé d'auteur

Fostering behaviour and milk stealing in Antarctic fur seals

During the lactation period, female otariid seals alternate trips at sea to feed with visits ashore to nurse their pups. A female returning ashore must be able to recognize her own pup, and it is generally agreed that this is facilitated by auditory and olfactory cues. Instances of fostering behaviour (females nursing nonfilial pups) and milk stealing are reportedly rare among the otariids. In the austral summer of 1989, I observed eight and two instances of fostering behaviour and milk stealing, respectively, by Antarctic fur seals at Bird Island, South Georgia. The following summer, 26 cases of fostering behaviour and 71 cases of milk stealing were documented. In 1990, females appeared to have difficulty acquiring sufficient resources to feed their pups, so nutritional stress was probably responsible for the increase in milk stealing. The occurrence of fostering behaviour suggests that mothers were unable to recognize their own pups, although in the above cases the cause was not clear; neither human disturbance nor density appeared to be the primary factor. Maternal experience may have been a factor in 1990, as 10 of 14 females fostering pups were 5 years of age or less and had given birth to either their first or second pup

Time budgets and foraging characteristics of lactating Antarctic fur seals

(1) We investigated time allocation to parental care ashore and foraging at sea by lactating Antarctic fur seals at Bird Island, South Georgia, during 1988-89 and 1989-90 and related this to foraging behaviour measured in terms of diving performance at sea and growth of pups. (2) The mean duration of foraging trips was 121 h and 100 h in 1988-89 and 1989-90, respectively, while periods ashore were 55 h and 45 h, respectively in the two years. There was a significant difference between these variables in the two years but there was no significant difference in the percentage of time spent at sea. In both years, there was significant variation between individuals in the foraging-attendance time budget. (3) There was a positive correlation between mean time spent ashore and mean time spent at sea for individual seals. The foraging-attendance patterns of seals changed significantly with time through lactation in one year of the study but not in the other. There was no effect of maternal age or size on foraging-attendance time budget. Duration of foraging trips or the period spent ashore had no effect on pup growth rate. (4) During short foraging trips (1-2 d) seals dived for a greater proportion of the time available for foraging than during longer foraging trips (>3 d). Seals fed predominantly on krill during both years. Most foraging occurred at night and this was reflected in diel variation in times of arrival and departure of seals from the pupping colony. Based on estimated swimming speed and travel times to and from Bird Island, it was estimated that seals were normally feeding between 60 and 90 km from Bird Island

Population Demography of Antarctic Fur Seals: The Costs of Reproduction and Implications for Life-Histories

1. This study examined the costs of reproduction in terms of future survival and reproduction in female Antarctic fur seals from Bird Island, South Georgia. It used mark-recapture data from 11 consecutive years, including 3 years when several indices showed that food availability was well below average. 2. Population age structures were used, in conjunction with the measured age-specific survival rates, to estimate the rate of increase of the population as 10.7% per annum. 3. The average annual survival rate was 0.83 (SD = 0.10) with a range from 0.65 to 0.93. Survival rate showed no trend through time but was weakly correlated with pup growth rate, suggesting that it may be influenced by availability of food. Survival rate was unrelated to any other environmental or demographic parameter including population size. 4. There was no evidence of senescence. Survival rate was not related to year of birth or age, after accounting for variation due to pregnancy and calendar year. Survival was reduced as a result of pregnancy which accounted for 40-50% of adult female mortality. This effect was greatest in the age classes with the highest reproductive output (ages 5-8 years). 5. Mean pregnancy rate was 0.70 (SD = 0.11) with an interannual range of 0.59-0.88. Although females normally produced their first pups at age 3-4 years, pregnancy rate peaked at age 8 years and declined thereafter. Otherwise pregnancy rate was unrelated to the environmental or demographic variables we tested. Food availability during the pup-rearing period had no effect on pregnancy rate. 40-50% of failures to become pregnant related to animals having been pregnant in the previous year. 6. Reproduction incurs costs to females, in terms of reduced survival and future fecundity, and consequently, on average, females which survive longest tend to do so because they have lower fecundity

Response of Antarctic fur seals to immobilization with ketamine, a ketamine-diazepam or ketamine-xylazine mixture, and zoletil

Adult Antarctic fur seals (Arctocephalus gazella) were immobilized with Zoletil® (n= 172), ketamine (n= 30), ketamine mixed with diazepam (n= 23) and with ketamine mixed with xylazine (n= 45). Response to all drugs was highly variable. There was a relationship between dose rate and level of immobilization in females given Zoletil®. Males were slightly more sensitive to Zoletil® than females but this could have been due to the greater body mass and lower mass‐specific metabolic rate of males. The dose required to achieve a level of immobilization declined with greater body mass for Zoletil® and ketamine but not for ketamine‐diatepam. Ketamine and ketamine‐sedative mixtures commonly caused mild tremoring and occasionally caused convulsions. Neither reaction was seen with Zoletil®. Mean doses were, Zoletil® 1.5 mg/ kg, ketamine 6.9 mg/kg, ketamine‐diazepam 6.3 mg/kg ketamine and 6.3 μg/kg diazepam, and ketamine‐xylazine 7.3 mg/kg ketamine and 0.62 mg/ kg xylazine. Zoletil® performs at least as well on Antarctic fur seals as ketamine but it may cause respiratory depression. The dose of ketamine required for Antarctic fur seals was greater than for most other species of seals

Age distribution of breeding female Antarctic fur seals in relation to changes in population growth rate

The age distribution of breeding female Antarctic fur seals at Bird Island, South Georgia, in 1988 was compared with the age distribution of a sample obtained in 1971–1973. The mean age in 1971–1973 was 7.41 (SE = 0.26) years and in 1988 it was 6.93 (SE = 0.20) years. After correction for age-dependent arrival time at the pupping beach in 1988, the mean age was 6.22 (SE = 0.14 years), which was significantly lower than in 1971–1973. Indicators of population size suggested that population growth at Bird Island had declined to below 3% annually by 1988 compared with rapid growth (17%) in 1958–1972. Exponential models fitted to the frequency distribution of age-classes greater than age 5 years and corrected for the rate of increase of the population gave adult survival rates of 0.66 (SE = 0.03) and 0.88 (SE = 0.02) for the 1988 and 1971–1973 samples, respectively. The reduced apparent adult survival rate in the 1988 sample was probably caused by emigration brought about by high densities of females on the pupping beaches. There are few signs from this analysis that the fur seal population at South Georgia is close to carrying capacit