Pomerleau C.,University of Quebec at Rimouski |
Pomerleau C.,Canadian Department of Fisheries and Oceans |
Lesage V.,Maurice Lamontagne Institute |
Ferguson S.H.,Canadian Department of Fisheries and Oceans |
And 3 more authors.
Marine Ecology Progress Series | Year: 2012
The eastern Canada-West Greenland (EC-WG) bowhead whale Balaena mysticetus population is slowly recovering from the intensive commercial whaling of the 18th and 20th centuries. However, climate change, through effects on ice conditions and prey availability, is one of several threats that might affect bowhead whale recovery. In this study, we exploited the variability observed in isotopic signatures of prey assemblages across the eastern Arctic to examine variability in diet among bowhead whales (n = 202) and identify their potential foraging areas. We compared δ13C and δ15N isotope ratios of biopsied skin samples with those of potential zooplankton prey species collected across the Canadian eastern Arctic, and calculated the proportional contributions of various sources (zooplankton) to the diet of bowhead whales using a Bayesian stable isotope mixing model. A cluster analysis indicated some variability in isotopic composition among groups of individuals, but not between males and females or age classes. The isotopic model discounted Davis Strait and Disko Bay as potential foraging areas for bowhead whales, at least in spring and summer. Lancaster Sound, Baffin Bay and the Gulf of Boothia were the 3 main areas likely used for summer feeding, where bowhead whales fed primarily on large Arctic calanoid copepods (Calanus hyperboreus, C. glacialis, Metridia longa, and Paraeuchaeta spp.), mysids and euphausiids. While some inter-individual variability in diet was observed, the strong dependence of this endemic Arctic species on Arctic zooplankton may make them vulnerable to the predicted latitudinal shift in prey species composition caused by ongoing warming. © Inter-Research and Fisheries and Oceans Canada 2012.
Waterman J.M.,University of Manitoba |
Macklin G.F.,University of Manitoba |
Enright C.,Assiniboine Park Zoo
Canadian Journal of Zoology | Year: 2014
Sex-biased parasitism is found in many species, but the skew to one sex or the other varies and is most likely due to differences in host and parasite behaviour and the intensity of sexual selection. We examined sex-biased parasitism in Richardson's ground squirrels (Urocitellus richardsonii (Sabine, 1822)) and hypothesized that males would be more heavily parasitized than females, as they are larger, have larger home ranges, and display high aggression and fighting during the short mating season, suggesting that they may trade off investment in immunity for higher investment in reproduction. Squirrels were caught during the mating season and examined for endoparasites and ectoparasites. Body mass, condition, and immune measures were recorded. Males had higher nematode prevalence and abundance, whereas females had higher flea prevalence. Males also had lower lymphocytes than females, as well as higher neutrophil to lymphocyte ratios. Females had higher eosinophils and they were in poorer body condition than males. The higher endoparasite loads in males suggests that they may be trading off immunity, whereas higher flea prevalence in females may be due to differences in sociality between the sexes. Our study demonstrates the importance of examining multiple parasite types to understand the factors influencing sex-biased parasitism.
Ryan C.P.,University of Manitoba |
Ryan C.P.,Northwestern University |
Anderson W.G.,University of Manitoba |
Berkvens C.N.,Assiniboine Park Zoo |
Hare J.F.,University of Manitoba
PLoS ONE | Year: 2014
The adaptive manipulation of offspring sex and number has been of considerable interest to ecologists and evolutionary biologists. The physiological mechanisms that translate maternal condition and environmental cues into adaptive responses in offspring sex and number, however, remain obscure. In mammals, research into the mechanisms responsible for adaptive sex allocation has focused on two major endocrine axes: the hypothalamic pituitary adrenal (HPA) axis and glucocorticoids, and the hypothalamic pituitary gonadal (HPG) axis and sex steroids, particularly testosterone. While stress-induced activation of the HPA axis provides an intuitive model for sex ratio and litter size adjustment, plasma glucocorticoids exist in both bound and free fractions, and may be acting indirectly, for example by affecting plasma glucose levels. Furthermore, in female mammals, activation of the HPA axis stimulates the secretion of adrenal testosterone in addition to glucocorticoids (GCs). To begin to untangle these physiological mechanisms influencing offspring sex and number, we simultaneously examined fecal glucocorticoid metabolites, free and bound plasma cortisol, free testosterone, and plasma glucose concentration during both gestation and lactation in a free-living rodent (Urocitellus richardsonii). We also collected data on offspring sex and litter size from focal females and from a larger study population. Consistent with previous work in this population, we found evidence for a trade-off between offspring sex and number, as well as positive and negative correlations between glucocorticoids and sex ratio and litter size, respectively, during gestation (but not lactation). We also observed a negative relationship between testosterone and litter size during gestation (but not lactation), but no effect of glucose on either sex ratio or litter size. Our findings highlight the importance of binding proteins, cross-talk between endocrine systems, and temporal windows in the regulation of trade-offs in offspring sex and number. Copyright: © 2014 Varanda et al.
Watt C.A.,University of Manitoba |
Petersen S.D.,Assiniboine Park Zoo |
Ferguson S.H.,University of Manitoba |
Ferguson S.H.,University of Winnipeg
Polar Biology | Year: 2015
Narwhals (Monodon monoceros) are an entirely arctic odontocete, living in upwards of 95 % pack ice and complete darkness over the winter. As a result of the harsh conditions in which they live, there are few studies of their social structure; however, it has been hypothesized that narwhals display a matrilineal social structure where pods are centered on the mother. A fortuitous opportunity arose to study social structure when an ice entrapment event near the community of Pond Inlet, Nunavut, Canada captured many females and their offspring. Using genetic analyses and fatty acids as a dietary marker, we investigated whether individuals that are closely related forage together, which would support a matrilineally driven social structure where females teach their young foraging strategies, and/or travel and forage together. We found no evidence that genetic relatedness was correlated with the fatty acid biomarkers, which provides some evidence against a matrilineal social structure. The possibility of narwhals displaying a fission–fusion societal structure is discussed, but further observational and experimental techniques are needed to support or refute this hypothesis. © 2015, Springer-Verlag Berlin Heidelberg.
Klondike, a female polar bear, was euthanized after weeks of worsening medical conditions that included mobility problems and infections, officials said. "There was no significant improvement in her condition, and given her advanced age and poor prognosis, zoo staff decided that the best decision would be to humanely euthanize her," Philadelphia Zoo said in a statement posted on Facebook. Klondike exceeded the typical lifespan for her species, which in captivity lives to about 30 years and generally no longer than 20 years in the wild, according to the Pittsburgh Zoo. The zoo's Coldilocks, also 34, has become the country's new oldest polar bear. Both bears arrived at the zoo in October 1981, the year after they were born in different parts of New York state. The world record-holding oldest polar bear, named Debby, died at age 42 seven years ago at Canada's Assiniboine Park Zoo. Polar bears, which can stand as high as 11 feet (3.35 meters) tall and weigh as much as 1,400 pounds (635 kg), use floating sea ice as platforms for hunting, mating and traveling vast distances in the Arctic. They were listed as threatened under the U.S. Endangered Species Act in 2008 due to disappearing sea ice, becoming the first animals granted such protection because of conditions tied to global climate change.