Habitat preferences of polar bears in the western Canadian Arctic in late winter and spring

Polar Record ◽  
1993 ◽  
Vol 29 (168) ◽  
pp. 13-24 ◽  
Author(s):  
Ian Stirling ◽  
Dennis Andriashek ◽  
Wendy Calvert
Keyword(s):  
Sea Ice ◽  
Habitat Preferences ◽  
Canadian Arctic ◽  
Late Winter ◽  
Polar Bears ◽  
Adult Males ◽  
Age Classes ◽  
Habitat Types ◽  
Adult Females ◽  
Fast Ice

ABSTRACTBetween late March and May, from 1971 through 1979, we surveyed 74,332 km2 of sea-ice habitatin the eastern Beaufort Sea and Amundsen Gulf in the western Canadian Arctic. We defined seven sea-ice habitat types and recorded sightings of polar bears and their tracks in each to determine their habitat preferences. 791 bears (including cubs) and 6454 sets of tracks were recorded. 42.3%, 39.7%, and 15.6% of the bears were seen on floe-edge, moving ice, and drifted fast-ice habitats, respectively. Significant differences in habitat preferences were shown by bears of different sexes and age classes. Adult females accompanied by cubs of the year were the only group that showed a strong preference for fast ice with drifts, probably because they could feed adequately there while avoiding adult males that might prey upon their cubs. The highest densities of seals are found in floe-edge and moving ice habitats and this likely explains the predominance of bears there. Lone adult females and females with two-year-old cubs, adult males, and subadult males were found two and one-half to four times more frequently than predicted in floe-edge habitat. Since there are no data to suggest seals are more abundant along the floe edge than in moving ice habitat, the preference of these groups of adult polar bears for the floe edge in spring may be related to reproductive behavior.

On the mating system of polar bears

1986 ◽  
Vol 64 (10) ◽  
pp. 2142-2151 ◽  
Author(s):  
Malcolm A. Ramsay ◽  
Ian Stirling
Keyword(s):  
Sex Ratio ◽  
Sea Ice ◽  
Mating System ◽  
Breeding Season ◽  
Large Body ◽  
Arctic Sea Ice ◽  
Polar Bears ◽  
Adult Males ◽  
Terrestrial Mammals ◽  
Adult Females

Polar bears are intimately associated with arctic sea ice and their distribution is approximated by its winter extent. They are the only terrestrial mammals, other than humans, to have adapted so completely to sea ice, a quite different habitat, spatially and temporally, from that occupied by other terrestrial mammals. We propose that the dynamics of sea ice and the associated variability in access to food have played a major role in the evolution of the social structure and mating system of polar bears. Adult females and males move to areas of the sea ice where the greatest success in hunting is realized. Such regions are unpredictable in location, however, both seasonally and annually. Because female distributions are unpredictable, adult males are unable to defend stable territories that will encompass the home ranges of one or more females and may instead distribute themselves among different sea-ice habitats at the same relative densities as solitary adult females. Females keep nursing cubs with them for more than 1 year; hence the mean interbirth interval is 2 or more years. This results in a functionally skewed sex ratio, with fewer females available to breed in any one year than males, and in intrasexual competition among males for access to breeding females. Consequently, established dominance hierarchies among males are unstable, and wounding, scarring, and breakage of canine teeth are common; these are evidence of direct physical confrontations during the breeding season. Large body size is advantageous in these fights and this has resulted in one of the highest degrees of sexual dimorphism among terrestrial mammals. Because of the funtionally skewed sex ratio and the shifting distribution of both females and males, however, even the largest male probably cannot be certain of locating a larger than average number of receptive females in any one breeding season.

Aggregating Behavior of Ovigerous Female Red King Crab, Paralithodes camtschaticus, in Auke Bay, Alaska

1993 ◽  
Vol 50 (4) ◽  
pp. 750-758 ◽  
Author(s):  
Robert P. Stone ◽  
Charles E. O'Clair ◽  
Thomas C. Shirley
Keyword(s):  
Shallow Water ◽  
Nearest Neighbor ◽  
Ovigerous Female ◽  
Early Spring ◽  
Late Winter ◽  
Red King Crab ◽  
Paralithodes Camtschaticus ◽  
Adult Males ◽  
Age Classes ◽  
King Crab

Ovigerous female red king crab, Paralithodes camtschaticus, monitored with ultrasonic biotelemetry, displayed distinct seasonal shifts in habitat use and bathymetric distribution. Crab occupied deep water between June and mid-November, relatively shallow water between mid-November and early March, and returned to deeper water prior to molting and mating in spring. Females were nonrandomly distributed within both depth ranges but seasonally changed their behavior and degree of association with conspecifics. Tagged crab were more aggregated (lower mean nearest neighbor distances) in winter than in summer and fall (F-test, P < 0.01). Winter SCUBA observations supported these results; females of mixed age-classes formed dense aggregations in shallow water, and crab exhibited "podding" behavior similar to that reported for younger age-classes. Adult males were associated with aggregations during late winter and early spring. Observations from the manned submersible Delta indicated that females were nonrandomly distributed in the deepwater habitat as well and probably formed loosely knit feeding aggregations there. Seasonal changes in aggregation densities and benthic areas used were the same during the two consecutive years of this study.

scholarly journals Turbulent heat transfer as a control of platelet ice growth in supercooled under-ice ocean boundary layers

Ocean Science ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 507-515 ◽  
Author(s):  
Miles G. McPhee ◽  
Craig L. Stevens ◽  
Inga J. Smith ◽  
Natalie J. Robinson
Keyword(s):  
Heat Transfer ◽  
Sea Ice ◽  
Turbulent Heat Transfer ◽  
Late Winter ◽  
Turbulent Heat ◽  
Ice Shelves ◽  
Ice Growth ◽  
Turbulent Heat Exchange ◽  
Fast Ice ◽  
Platelet Ice

Abstract. Late winter measurements of turbulent quantities in tidally modulated flow under land-fast sea ice near the Erebus Glacier Tongue, McMurdo Sound, Antarctica, identified processes that influence growth at the interface of an ice surface in contact with supercooled seawater. The data show that turbulent heat exchange at the ocean–ice boundary is characterized by the product of friction velocity and (negative) water temperature departure from freezing, analogous to similar results for moderate melting rates in seawater above freezing. Platelet ice growth appears to increase the hydraulic roughness (drag) of fast ice compared with undeformed fast ice without platelets. Platelet growth in supercooled water under thick ice appears to be rate-limited by turbulent heat transfer and that this is a significant factor to be considered in mass transfer at the underside of ice shelves and sea ice in the vicinity of ice shelves.

Sex and age differences in distribution, abundance, and habitat preferences of wintering Harlequin Ducks: implications for conservation and estimating recruitment rates

2003 ◽  
Vol 81 (3) ◽  
pp. 492-503 ◽  
Author(s):  
Michael S Rodway ◽  
Heidi M Regehr ◽  
Fred Cooke
Keyword(s):  
Habitat Preferences ◽  
Adult Survival ◽  
Survey Method ◽  
Adult Males ◽  
Intertidal Habitat ◽  
Age Classes ◽  
Specific Distribution ◽  
Age Ratio ◽  
Harlequin Ducks ◽  
Sex And Age Differences

We determined the sex- and age-specific distribution, abundance, and habitat preferences of wintering Harlequin Ducks (Histrionicus histrionicus) and evaluated potential biases in measuring ratios of immature males to adult males to estimate recruitment rates. A comparison of the occurrence of birds with habitat availability at the 1-km scale indicated a preference for wide intertidal habitat with cobble–gravel or bedrock–boulder substrate, small offshore islets and shoreline with attached or nearby reefs and islets, areas without streams, and areas with a greater historical abundance of herring spawn. Where the substrate was bedrock–boulder, birds preferred areas with tidal rapids. Densities of birds were highest along linear and complex shorelines with reefs or islets where intertidal habitat was >100 m wide and substrate was cobble–gravel or bedrock–boulder. Patterns of habitat use among sex and age classes were the same at the 1-km scale but differed at smaller scales, with adult and immature males occurring farther offshore than females. Age ratios varied among areas and were biased by survey method and misidentification of distant birds. Correcting for detected biases gave an estimated male age ratio of 9.8%. Calculated estimates of female recruitment suggest a declining population, but it is necessary to incorporate emigration in estimates of adult survival before demographic trends can be confidently inferred.

Effects of adults on the demography of fox squirrels (Sciurus niger)

1985 ◽  
Vol 63 (4) ◽  
pp. 861-867 ◽  
Author(s):  
Lonnie P. Hansen ◽  
Charles M. Nixon
Keyword(s):  
Home Range Size ◽  
Adult Males ◽  
Sciurus Niger ◽  
Age Classes ◽  
Control Grid ◽  
Local Populations ◽  
Adult Females ◽  
Resource Limited ◽  
Fox Squirrels ◽  
Reproductive Rates

As a test of the hypothesis that adult fox squirrels (Sciurus niger) regulate the number of immature and adult squirrels entering a population, each fall from 1979 to 1981 adult males were removed from two grids (male-removal grids, MRGs), adult females from two grids (female-removal grids, FRGs), all adults from one grid (adult-removal grid, ARG), and one grid was maintained as a control (control grid, CG). The number of previously uncaptured juveniles and subadults (both sexes) and yearling–adult females was greater on FRGs than on the CG and MRGs, especially during the fall. The number of new adult males captured during the fall was higher where adult males had been removed. During spring, reproductive rates (percent lactating) were higher on grids from which females had been removed (FRGs and the ARG), but this was not so during fall. Length of residency was shorter for juvenile–subadult and adult fox squirrels and longer for yearling females where adult females had been removed. Movement patterns in response to removal of adults suggested resident adult females influenced home range size of all sex classes and age-classes. We conclude that the presence of adult females is important in limiting recruitment in local populations of fox squirrels and that this strategy likely evolved in response to resource-limited environments.

Interacting effects of latitude, mass, age, and sex on winter survival of Surf Scoters (Melanitta perspicillata): implications for differential migration

2016 ◽  
Vol 94 (3) ◽  
pp. 233-241 ◽  
Author(s):  
Brian D. Uher-Koch ◽  
Daniel Esler ◽  
Samuel A. Iverson ◽  
David H. Ward ◽  
W. Sean Boyd ◽  
...  
Keyword(s):  
Winter Survival ◽  
Late Winter ◽  
Adult Males ◽  
Differential Migration ◽  
Differential Survival ◽  
Melanitta Perspicillata ◽  
Adult Females ◽  
Study Sites ◽  
Range Core ◽  
Age And Sex

We quantified variation in winter survival of Surf Scoters (Melanitta perspicillata (L., 1758)) across nearly 30° of latitude on the Pacific coast of North America to evaluate potential effects on winter distributions, including observed differential distributions of age and sex classes. We monitored fates of 297 radio-marked Surf Scoters at three study sites: (1) near the northern periphery of their wintering range in southeast Alaska, USA, (2) the range core in British Columbia, Canada, and (3) the southern periphery in Baja California, Mexico. We detected 34 mortalities and determined that survival averaged lower at the range peripheries than in the range core, was lower during mid-winter than during late winter at all sites, and was positively correlated with body mass within locations. Although neither age nor sex class had direct effects, mass effects led to differential survival patterns among classes. When simultaneously incorporating these interacting influences, adult males of mean mass for their location had highest survival at the northern range periphery in Alaska, whereas adult females and juveniles had higher survival at the range core and the southern periphery. Our observations help to explain patterns of differential migration and distribution reported for this species and highlight seasonal periods (mid-winter) and locations (range peripheries) of elevated levels of mortality for demographically important age–sex classes (adult females).

scholarly journals Winter sea ice export from the Laptev Sea preconditions the local summer sea ice cover and fast ice decay

2017 ◽  
Vol 11 (5) ◽  
pp. 2383-2391 ◽  
Author(s):  
Polona Itkin ◽  
Thomas Krumpen
Keyword(s):  
Sea Ice ◽  
Numerical Models ◽  
Ice Cover ◽  
Sensitivity Study ◽  
Arctic Sea Ice ◽  
Late Winter ◽  
Laptev Sea ◽  
Ice Dynamics ◽  
Fast Ice ◽  
The Laptev Sea

Abstract. Ice retreat in the eastern Eurasian Arctic is a consequence of atmospheric and oceanic processes and regional feedback mechanisms acting on the ice cover, both in winter and summer. A correct representation of these processes in numerical models is important, since it will improve predictions of sea ice anomalies along the Northeast Passage and beyond. In this study, we highlight the importance of winter ice dynamics for local summer sea ice anomalies in thickness, volume and extent. By means of airborne sea ice thickness surveys made over pack ice areas in the south-eastern Laptev Sea, we show that years of offshore-directed sea ice transport have a thinning effect on the late-winter sea ice cover. To confirm the preconditioning effect of enhanced offshore advection in late winter on the summer sea ice cover, we perform a sensitivity study using a numerical model. Results verify that the preconditioning effect plays a bigger role for the regional ice extent. Furthermore, they indicate an increase in volume export from the Laptev Sea as a consequence of enhanced offshore advection, which has far-reaching consequences for the entire Arctic sea ice mass balance. Moreover we show that ice dynamics in winter not only preconditions local summer ice extent, but also accelerate fast-ice decay.

scholarly journals Linognathus weisseri n. sp. (Phthiraptera : Linognathidae) of impalas, Aepyceros melampus : description and biology

2004 ◽  
Vol 71 (1) ◽  
Author(s):  
L.A. Durden ◽  
I.G. Horak
Keyword(s):  
Adult Male ◽  
Instar Nymph ◽  
Early Summer ◽  
Limpopo Province ◽  
Late Winter ◽  
Age Classes ◽  
Mpumalanga Province ◽  
Adult Females ◽  
First Instar ◽  
Aepyceros Melampus

The adult male and female and first instar nymph of the sucking louse Linognathus weisseri n. sp. are described. This louse was collected from impalas, Aepyceros melampus, at three localities in Limpopo Province, and at three in Mpumalanga Province, South Africa. Although it usually accounted for only a small proportion of the total louse burden, its overall prevalence exceeded 27 %. Its prevalence on adult male impalas (9 %) was significantly lower (P = 0.004) than that on adult females (39 %), but did not differ among age classes. However, the intensity of L. weisseri infestation was higher on lambs than on yearlings and adults, and peaked on impalas in late winter to early summer. Five species of lice are now known to parasitize impalas and a key for distinguishing adults of these species is included.

The population pattern of Miniopterus schrebersii (Chiroptera) in north-eastern New South Wales

1966 ◽  
Vol 14 (6) ◽  
pp. 1073 ◽  
Author(s):  
PD Dwyer
Keyword(s):  
New South ◽  
New South Wales ◽  
Population Characteristics ◽  
Adult Males ◽  
Age Classes ◽  
Adult Females ◽  
South Wales ◽  
Wide Range ◽  
North Eastern ◽  
Population Pattern

In north-eastern New South Wales Miniopterus schreibersii is found at a wide range of cave and mine roosts as colonies that may include up to several thousands of individuals. Between April 1960 and September 1963 a field study of the biology and population characteristics of this species was carried out. Field criteria permitting aging of individuals were developed. Age classes considered were juveniles (< 9 months), yearlings (9-21 months), and adults (> 21 months). Seasonal changes in numbers, and in the sex and age composition of colonies were followed in detail at several roosts and comparative information was obtained at others. Movement patterns were assessed by a marking and recapture programme in which 1365 recoveries were obtained from a marked (toe clips and bands) population of 8775. Conspicuous sex or age biases or both were shown to exist in clusters of M. schreibersii at specific roosts and it was suggested that clustering in this species functions, in part, as a social spacing mechanism. Segregation of different sex or age classes at specific colonies permitted classification of colonies as (1) maternity colonies in which adult females and their young predominate, (2) "adult" colonies which are predominantly adult, or adult and yearling, in composition, and (3) "juvenile" colonies in which juveniles, or juveniles and yearlings, are almost prevalent. The observed social biases of colonies appeared to be related to particular phases of the reproductive cycle. Certain adult colonies were interpreted as important sites of copulatory behaviour. Recovery data for two of these mating colonies showed that adult females were more transient members of the colony than adult males. Juveniles are often well represented at adult colonies in the autumn, and during this season their presence may be correlated with a drop in the abundance of older males.

Comparative hunting abilities of polar bear cubs of different ages

1978 ◽  
Vol 56 (8) ◽  
pp. 1768-1772 ◽  
Author(s):  
Ian Stirling ◽  
Paul B. Latour
Keyword(s):  
Polar Bear ◽  
Canadian Arctic ◽  
Ursus Maritimus ◽  
Adult Males ◽  
Age Classes ◽  
Adult Age ◽  
Probability Of Survival ◽  
Age Class ◽  
Management Concept ◽  
Kill Rate

In most areas of the Canadian Arctic polar bear (Ursus maritimus) cubs apparently remain with their mothers until they are 2.5 years of age. The degree to which cubs of each age-class participate in the hunting of seals while with their mothers is examined in this paper in order to evaluate the degree to which they might be capable of independent hunting, should they be orphaned prior to the completion of the normal weaning period. Cubs of all age-classes did almost no hunting during the spring. The proportions of time spent hunting by yearling and 2-year-old cubs, and the durations of their lying 'still hunts' were not significantly different from each other but they were significantly shorter than their mothers' and than adult males' during the summer. However, the frequency of the lying 'still hunts' of 2-year-old cubs was double that of yearling cubs and the kill rate of 2-year-old cubs was comparable with that of adult age-classes, despite the fact they hunted for a significantly lesser proportion of their time. These results suggest that cubs which remain with their mothers until they are weaned have a higher probability of survival than those that do not and this interpretation lends support lo the management concept of total protection of family groups and the harvesting of independent bears only.

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