The age structure, body length distribution, and mortality of eastern Beaufort Sea (EBS) belugas ... more The age structure, body length distribution, and mortality of eastern Beaufort Sea (EBS) belugas was studied and contrasted to four other populations in the eastern Arctic: Baffin Bay (BB), Cumberland Sound (CS), western (WHB) and eastern Hudson (EHB) Bay. Median age of EBS belugas was estimated at 29 and 31 yr for males and females, respectively. These values were significantly higher than those from CS and WHB. Age distributions also differed among populations in their shape. EBS belugas were significantly longer and their growth rate differed, relative to eastern Arctic populations, revealing a geographic gradient in a south, to north, northwest direction, so that EHB belugas were the smallest. Our results suggest that hunting pressure may have played a role in these responses. Mortality was highest amont EBS belugas, but it was not significantly different from other Canadian Arctic populations.
Otariid pinnipeds exhibit large variation in lactation duration, and pups wean at different times... more Otariid pinnipeds exhibit large variation in lactation duration, and pups wean at different times of cycles in marine productivity. Interspecific comparisons to understand the mechanisms driving variation in maternal care strategies and pup development are difficult due to inability to control for confounding effects of differences in environment. Therefore, I investigated interspecific differences in foraging ecology, allocation of maternal resources into pups, and use of maternal resources by pups as they approach weaning, between sympatric Antarctic (AFS) and subantarctic (SFS) fur seals at He de la Possession, lies Crozet, Southern Indian Ocean. Females of both fur seal species fed on the same myctophid fish prey over largely overlapping areas, with minor but important differences in the proportion of prey species consumed. SFS females showed less diel variation in diving behaviour, suggesting that they followed the nycthymeral migrations of their prey to a smaller extent than A...
Journal of Experimental Marine Biology and Ecology, 2014
ABSTRACT Climate change has led to briefer winter ice-cover and reduced snow depth in Hudson Bay.... more ABSTRACT Climate change has led to briefer winter ice-cover and reduced snow depth in Hudson Bay. These conditions have been linked to increased mortality of both polar bear cubs and their ringed seal prey. In ringed seals, increased mortality may be due to changes in foraging and movement patterns around sea ice, and how these animals interact with and move through sea ice may explain why deteriorating ice conditions are affecting survival. To investigate, we analysed the movement and space use of Hudson Bay ringed seals using a switching state-space model to discriminate at-sea behavioural state from satellite-observed movements followed by a series of mixed-effects models to understand how sea ice concentration, age, and sex affect at-sea behaviour. Our analysis revealed a strong annual cycle, whereby the probability of resident movement behaviour increased through the open-water period (summer and fall), reaching its maximum in the fall when sea-ice begins to reform. This tendency then declines through the ice-covered period (winter and spring), reaching a minimum as ice breaks up. Cyclical behaviour was more pronounced in adults, which restricted movements to a greater extent than juveniles during the winter ice-covered period, consistent with predictions of mammalian life history. Consequently, reduced stable fast ice area and less predictable ice conditions associated with climate change should be expected to have a disproportionately larger effect on adults, potentially reducing their ability to accrue resources for reproduction or produce milk for dependant pups. Furthermore, we found large sex-related differences in behaviour in this monomorphic species, suggesting that changing ice conditions may impact one sex more strongly. This finding also implies that similar behavioural differences in sexually size-dimorphic species may be explained by sex-related life history trade-offs associated with the reproductive strategies of each sex and not necessarily body size differences.
Marine mammals are typically poor indicators of point sources of environmental contaminants as a ... more Marine mammals are typically poor indicators of point sources of environmental contaminants as a consequence of their often complex feeding ecologies and extensive movements, all of which mask the contributions of specific inputs. The release of polychlorinated biphenyls (PCBs) by a military radar station into Saglek Bay, Labrador (Canada) has contaminated marine sediments, bottom-feeding fish, seabirds, and some ringed seals, but attributing the PCBs in the latter highly mobile animals to this source is exceedingly difficult. In addition to the application of such tools as stable isotopes (δ(15)N and δ(13)C) and univariate and multivariate statistical exploration of contaminant patterns and ratios, we used satellite telemetry to track the movements of 13 seals in their transient use of different feeding areas. Reduced size of home range and core area (i.e., areas of concentrated use), as well as increased time in coastal inlets, were important determinants of increased PCB concentrations in seals reflecting the contribution of Saglek Bay. Seals were classified into the same feeding groups using both space use and their contaminant burdens 85% of the time, highlighting the link between feeding ecology and exposure to PCBs. While the PCB source at Saglek provided a strong local signal in a remote environment, this first use of satellite telemetry demonstrates the utility of evaluating space-use strategies to better understand contaminant exposure, and more specifically the contribution of contaminant hotspots to mobile predators.
Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict,... more Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict, especially in species where weaning involves a change of habitat. Compared with long lactations, brief lactations are expected to be associated with fast rates of development and attainment of adult traits. We describe allometry and growth for several morphological traits in two closely related fur seal species with large differences in lactation duration at a sympatric site. Longitudinal data were collected from Antarctic ( Arctocephalus gazella (Peters, 1875); 120 d lactation) and subantarctic ( Arctocephalus tropicalis (Gray, 1872); 300 d lactation) fur seals. Body mass was similar in neonates of both species, but A. gazella neonates were longer, less voluminous, and had larger foreflippers. The species were similar in rate of preweaning growth in body mass, but growth rates of linear variables were faster for A. gazella pups. Consequently, neonatal differences in body shape increase...
The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactat... more The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactating female Antarctic (Arctocephalus gazella, AFS) and subantarctic (A. tropicalis, SFS) fur seals were compared at Iles Crozet, where both species coexist. The large disparity in lactation duration (SFS: 10 months, AFS: 4 months), even under local sympatry, has led to the expectation that AFS should exhibit higher foraging effort or efficiency per unit time than SFS to allow them to wean their pups in a shorter period of time. Previous evidence, however, has not supported these expectations. In this study, the distribution of foraging trip durations revealed two types of trips: overnight (OFT, <1 day) and long (LFT, >1 day), in common with other results from Macquarie Island. However, diving behaviour differed significantly between foraging trip types, with greater diving effort in OFTs than in LFTs, and diving behaviour differed between fur seal species. OFTs were more frequent in SFS (48%) than in AFS (28%). SFS performed longer LFTs and maternal attendances than AFS, but spent a smaller proportion of their foraging cycle at sea (66.2 vs. 77.5%, respectively). SFS dove deeper and for longer periods than AFS, in both OFTs and LFTs, although indices of diving effort were similar between species. Diel variation in diving behaviour was lower among SFS, which foraged at greater depths during most of the night time available than AFS. The diving behaviour of AFS suggests they followed the nychthemeral migration of their prey more closely. Concomitant with the differences in diving behaviour, AFS and SFS fed on the same prey species, but in different proportions of three myctophid fish (Gymnoscopelus fraseri, G. piabilis, and G. nicholsi) that represented most of their diet. The estimated size of the most important fish consumed did not vary significantly between fur seal species, suggesting that the difference in dive depth was mostly a result of changes in the relative abundance of these myctophids. The energy content of these fish at Iles Crozet may thus influence the amount and quality of milk delivered to pups of each fur seal species. These results contrast with those found at other sites where both species coexist, and revealed a scale of variation in foraging behaviour which did not affect their effort while at sea, but that may be a major determinant of foraging efficiency and, consequently, maternal investment.
The age structure, body length distribution, and mortality of eastern Beaufort Sea (EBS) belugas ... more The age structure, body length distribution, and mortality of eastern Beaufort Sea (EBS) belugas was studied and contrasted to four other populations in the eastern Arctic: Baffin Bay (BB), Cumberland Sound (CS), western (WHB) and eastern Hudson (EHB) Bay. Median age of EBS belugas was estimated at 29 and 31 yr for males and females, respectively. These values were significantly higher than those from CS and WHB. Age distributions also differed among populations in their shape. EBS belugas were significantly longer and their growth rate differed, relative to eastern Arctic populations, revealing a geographic gradient in a south, to north, northwest direction, so that EHB belugas were the smallest. Our results suggest that hunting pressure may have played a role in these responses. Mortality was highest amont EBS belugas, but it was not significantly different from other Canadian Arctic populations.
Otariid pinnipeds exhibit large variation in lactation duration, and pups wean at different times... more Otariid pinnipeds exhibit large variation in lactation duration, and pups wean at different times of cycles in marine productivity. Interspecific comparisons to understand the mechanisms driving variation in maternal care strategies and pup development are difficult due to inability to control for confounding effects of differences in environment. Therefore, I investigated interspecific differences in foraging ecology, allocation of maternal resources into pups, and use of maternal resources by pups as they approach weaning, between sympatric Antarctic (AFS) and subantarctic (SFS) fur seals at He de la Possession, lies Crozet, Southern Indian Ocean. Females of both fur seal species fed on the same myctophid fish prey over largely overlapping areas, with minor but important differences in the proportion of prey species consumed. SFS females showed less diel variation in diving behaviour, suggesting that they followed the nycthymeral migrations of their prey to a smaller extent than A...
Journal of Experimental Marine Biology and Ecology, 2014
ABSTRACT Climate change has led to briefer winter ice-cover and reduced snow depth in Hudson Bay.... more ABSTRACT Climate change has led to briefer winter ice-cover and reduced snow depth in Hudson Bay. These conditions have been linked to increased mortality of both polar bear cubs and their ringed seal prey. In ringed seals, increased mortality may be due to changes in foraging and movement patterns around sea ice, and how these animals interact with and move through sea ice may explain why deteriorating ice conditions are affecting survival. To investigate, we analysed the movement and space use of Hudson Bay ringed seals using a switching state-space model to discriminate at-sea behavioural state from satellite-observed movements followed by a series of mixed-effects models to understand how sea ice concentration, age, and sex affect at-sea behaviour. Our analysis revealed a strong annual cycle, whereby the probability of resident movement behaviour increased through the open-water period (summer and fall), reaching its maximum in the fall when sea-ice begins to reform. This tendency then declines through the ice-covered period (winter and spring), reaching a minimum as ice breaks up. Cyclical behaviour was more pronounced in adults, which restricted movements to a greater extent than juveniles during the winter ice-covered period, consistent with predictions of mammalian life history. Consequently, reduced stable fast ice area and less predictable ice conditions associated with climate change should be expected to have a disproportionately larger effect on adults, potentially reducing their ability to accrue resources for reproduction or produce milk for dependant pups. Furthermore, we found large sex-related differences in behaviour in this monomorphic species, suggesting that changing ice conditions may impact one sex more strongly. This finding also implies that similar behavioural differences in sexually size-dimorphic species may be explained by sex-related life history trade-offs associated with the reproductive strategies of each sex and not necessarily body size differences.
Marine mammals are typically poor indicators of point sources of environmental contaminants as a ... more Marine mammals are typically poor indicators of point sources of environmental contaminants as a consequence of their often complex feeding ecologies and extensive movements, all of which mask the contributions of specific inputs. The release of polychlorinated biphenyls (PCBs) by a military radar station into Saglek Bay, Labrador (Canada) has contaminated marine sediments, bottom-feeding fish, seabirds, and some ringed seals, but attributing the PCBs in the latter highly mobile animals to this source is exceedingly difficult. In addition to the application of such tools as stable isotopes (δ(15)N and δ(13)C) and univariate and multivariate statistical exploration of contaminant patterns and ratios, we used satellite telemetry to track the movements of 13 seals in their transient use of different feeding areas. Reduced size of home range and core area (i.e., areas of concentrated use), as well as increased time in coastal inlets, were important determinants of increased PCB concentrations in seals reflecting the contribution of Saglek Bay. Seals were classified into the same feeding groups using both space use and their contaminant burdens 85% of the time, highlighting the link between feeding ecology and exposure to PCBs. While the PCB source at Saglek provided a strong local signal in a remote environment, this first use of satellite telemetry demonstrates the utility of evaluating space-use strategies to better understand contaminant exposure, and more specifically the contribution of contaminant hotspots to mobile predators.
Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict,... more Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict, especially in species where weaning involves a change of habitat. Compared with long lactations, brief lactations are expected to be associated with fast rates of development and attainment of adult traits. We describe allometry and growth for several morphological traits in two closely related fur seal species with large differences in lactation duration at a sympatric site. Longitudinal data were collected from Antarctic ( Arctocephalus gazella (Peters, 1875); 120 d lactation) and subantarctic ( Arctocephalus tropicalis (Gray, 1872); 300 d lactation) fur seals. Body mass was similar in neonates of both species, but A. gazella neonates were longer, less voluminous, and had larger foreflippers. The species were similar in rate of preweaning growth in body mass, but growth rates of linear variables were faster for A. gazella pups. Consequently, neonatal differences in body shape increase...
The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactat... more The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactating female Antarctic (Arctocephalus gazella, AFS) and subantarctic (A. tropicalis, SFS) fur seals were compared at Iles Crozet, where both species coexist. The large disparity in lactation duration (SFS: 10 months, AFS: 4 months), even under local sympatry, has led to the expectation that AFS should exhibit higher foraging effort or efficiency per unit time than SFS to allow them to wean their pups in a shorter period of time. Previous evidence, however, has not supported these expectations. In this study, the distribution of foraging trip durations revealed two types of trips: overnight (OFT, <1 day) and long (LFT, >1 day), in common with other results from Macquarie Island. However, diving behaviour differed significantly between foraging trip types, with greater diving effort in OFTs than in LFTs, and diving behaviour differed between fur seal species. OFTs were more frequent in SFS (48%) than in AFS (28%). SFS performed longer LFTs and maternal attendances than AFS, but spent a smaller proportion of their foraging cycle at sea (66.2 vs. 77.5%, respectively). SFS dove deeper and for longer periods than AFS, in both OFTs and LFTs, although indices of diving effort were similar between species. Diel variation in diving behaviour was lower among SFS, which foraged at greater depths during most of the night time available than AFS. The diving behaviour of AFS suggests they followed the nychthemeral migration of their prey more closely. Concomitant with the differences in diving behaviour, AFS and SFS fed on the same prey species, but in different proportions of three myctophid fish (Gymnoscopelus fraseri, G. piabilis, and G. nicholsi) that represented most of their diet. The estimated size of the most important fish consumed did not vary significantly between fur seal species, suggesting that the difference in dive depth was mostly a result of changes in the relative abundance of these myctophids. The energy content of these fish at Iles Crozet may thus influence the amount and quality of milk delivered to pups of each fur seal species. These results contrast with those found at other sites where both species coexist, and revealed a scale of variation in foraging behaviour which did not affect their effort while at sea, but that may be a major determinant of foraging efficiency and, consequently, maternal investment.
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