Observations of aggregating behaviour in adult male polar bears (Ursus maritimus)

1990 ◽  
Vol 68 (7) ◽  
pp. 1390-1394 ◽  
Author(s):  
Andrew E. Derocher ◽  
Ian Stirling
Keyword(s):  
Adult Male ◽  
Ursus Maritimus ◽  
Hudson Bay ◽  
Polar Bears ◽  
Adult Males ◽  
Mean Size ◽  
The Mean ◽  
Competition For Food ◽  
Competition For Resources ◽  
Solitary Species

Polar bears (Ursus maritimus) are usually considered a solitary species, but between 50 and 60% of the adult male polar bears captured on land during the ice-free period in western Hudson Bay were sighted in aggregations with a mean size of 4 and a range of 2–14 individuals. The mean weight of aggregating adult males was significantly greater (approximately 60 kg) than the mean weight of nonaggregating adult males, but there were no significant differences in the mean age. Aggregations occurred throughout the ice-free period (August–October) and were most common at prominent points along the coast or nearby islands. Some locations were used over several years. The lack of competition for food and the absence of breeding activity during the ice-free period produce conditions that may facilitate aggregating. Familiarity with conspecifics may yield benefits by reducing the severity and frequency of competition for resources on the sea ice.

Spatial relationships and behavior of polar bears (Ursus maritimus Phipps) concentrated on land during the ice-free season of Hudson Bay

1981 ◽  
Vol 59 (9) ◽  
pp. 1763-1774 ◽  
Author(s):  
Paul B. Latour
Keyword(s):  
Social Behavior ◽  
Sea Ice ◽  
Social Systems ◽  
Ursus Maritimus ◽  
Hudson Bay ◽  
Polar Bears ◽  
Adult Males ◽  
Single Population ◽  
A Site ◽  
And Behavior

I observed polar bears (Ursus maritimus Phipps) at Cape Churchill, Manitoba, a site where polar bears congregate during the autumn when Hudson Bay is ice free. Adult males, subadult males, and subadult females were spatially segregated to a degree that depended primarily on density. The higher the density, the greater the degree of segregation. Adult males showed the closest intraclass association. Subadult females spent more time in activity than did either adult or subadult males; this may be due to subadult females being approached more by other subadults. Much of an individual's social behavior occurred with members of its own age–sex class, perhaps as a result of spatial segregation. In the noncompetitive situation of this study, polar bears aggregated and were more social than when hunting on the sea ice. This study provides further evidence for the flexibility of carnivore social systems, not only between populations of the same species, but also within a single population.

Distribution of polar bears (Ursus maritimus) during the ice-free period in western Hudson Bay

1990 ◽  
Vol 68 (7) ◽  
pp. 1395-1403 ◽  
Author(s):  
Andrew E. Derocher ◽  
Ian Stirling
Keyword(s):  
Energy Conservation ◽  
Sea Ice ◽  
Ursus Maritimus ◽  
North Coast ◽  
Hudson Bay ◽  
Polar Bears ◽  
Adult Males ◽  
The North ◽  
Western Hudson Bay ◽  
Age And Sex

The distribution and movements of polar bears (Ursus maritimus) during the ice-free period in western Hudson Bay were studied using mark and recapture and radiotelemetry locating of animals of known age and sex collected between 1966 and 1987. Polar bears segregated themselves by age, sex, and reproductive status. Adult males occupied coastal areas. Family groups and pregnant females occupied areas farther inland. Subadult females and males occupied similar habitats which overlapped with those of adult males. Avoidance of conspecifics, energy conservation, philopatry, denning habitat, and habitat selection appeared to influence observed patterns. A southward shift in the population was evident early in the ice-free period and was followed by a return movement northward during October and November. This may be due to ice-formation patterns which permit earlier access to the sea ice along the north coast and hunting habitat to the northeast. All bears moved less than bears on the sea ice, and movements were consistent with a strategy of energy conservation. Most bears appear to have travelled directly from the sea ice to the study area and remained until the sea ice reformed. Little exchange with adjacent populations and a high degree of philopatry were evident for all age and sex groups; this may be a function of the distribution of denning habitat, the winter distribution of sea ice habitat and seals, and the noncompetitive conditions that prevail during the ice-free period which make dispersal of limited benefit.

HAPTEN-RADIOIMMUNOASSAY OF PLASMA OESTRADIOL

1973 ◽  
Vol 72 (2) ◽  
pp. 330-344 ◽  
Author(s):  
Peter Doerr
Keyword(s):  
Adult Male ◽  
Normal Values ◽  
Normal Adult ◽  
Adult Males ◽  
Reagent Blank ◽  
Keyhole Limpet Haemocyanin ◽  
Ether Extraction ◽  
The Mean ◽  
Assay Precision ◽  
Plasma Oestradiol

ABSTRACT A hapten-radioimmunoassay for plasma oestradiol is described and information about the reliability of the method is given in detail. Oestradiol-3-hemisuccinate coupled to keyhole limpet haemocyanin is used for immunization of rabbits. The antiserum utilized for the assay is characterized by its titer, affinity and specificity. Following ether extraction and NaOH-light petroleum partition oestradiol is separated from crossreacting oestrogens by TLC. Oxidation of oestradiol on the plate is prevented by mercaptoethanol. To separate free and antibody bound ligand 250 μg dextran-coated charcoal per tube is used in the presence of bovine serum gammaglobulin (1 mg/ml). The between-assay precision based on 15 different determinations of control samples from normal adult male plasma was 9.4% (C. V.). The mean reagent blank value of 31 determinations was equivalent to 0.3 pg oestradiol and the detection limit in terms of the 99% confidence limit for a single blank value, was equivalent to 4.3 pg oestradiol. A procedure for detecting plasma blanks is described. Plasma oestradiol is separated from approximately all concomitant substances originally present in the sample by enzymatic conversion into oestrone and a second TLC. No plasma blanks could be detected with respect to normal adult male plasma. Normal values for adult males based on 51 subjects were characterized by a median of 17.2 pg/ml and the 95 percentiles of 9.5–27.6.

An observation of possible cannibalism by polar bears (Ursus maritimus)

1985 ◽  
Vol 63 (6) ◽  
pp. 1516-1517 ◽  
Author(s):  
N. J. Lunn ◽  
G. B. Stenhouse
Keyword(s):  
Adult Female ◽  
Adult Male ◽  
Physical Condition ◽  
Polar Bear ◽  
Ursus Maritimus ◽  
Polar Bears ◽  
Ecological Significance ◽  
Natural Conditions ◽  
Old Adult

We observed a case of cannibalism by a 23-year-old adult male polar bear in very poor physical condition on Southampton Island, N.W.T. It had apparently killed an adult female and was feeding on the carcass. Cannibalism among polar bears does occur under natural conditions. It is difficult to document how often this occurs and of what ecological significance it might be.

Crayfish Growth in Lake Tahoe: Effects of Habitat Variation

1977 ◽  
Vol 34 (1) ◽  
pp. 155-159 ◽  
Author(s):  
R. Warren Flint ◽  
Charles R. Goldman
Keyword(s):  
Food Availability ◽  
Lake Tahoe ◽  
Benthic Habitat ◽  
Freshwater Crayfish ◽  
Regression Analyses ◽  
Habitat Variation ◽  
Lake Bottom ◽  
Mean Size ◽  
The Mean ◽  
Competition For Food

The natural history and ecology of the freshwater crayfish Pacifastacus leniusculus was investigated in Lake Tahoe for 1 yr. Growth of individual groups varied between three different transects (I, II, and III). The mean size of carapace of adult crayfish trapped on Transects II and III was greater than those trapped at Transect 1. Linear regression analyses of premolt–postmolt carapace length revealed similar differences. At the onset of sexual maturity females from Transect I were smaller than those from either Transect II or III.Examination of physical and biological parameters in the benthic habitat revealed that food availability, amount of shallow water, and size and area of stone cover influenced the number and size of adult crayfish on each transect. Greater food availability and more extensive stone cover on the lake bottom attracted higher numbers of crayfish to Transect I. The result was overcrowding and competition for food and larger stone cover for larger adults. The effect was a slower growth rate of crayfish on Transect I compared with animals on either of the other transects.

Midsummer observations on the behavior of wild polar bears (Ursus maritimus)

1974 ◽  
Vol 52 (9) ◽  
pp. 1191-1198 ◽  
Author(s):  
Ian Stirling
Keyword(s):  
Diurnal Rhythm ◽  
Intraspecific Competition ◽  
Ursus Maritimus ◽  
Polar Bears ◽  
Phoca Hispida ◽  
Devon Island ◽  
Adult Females ◽  
Ringed Seals ◽  
Single Animal ◽  
The Mean

Wild polar bears (Ursus maritimus) were observed from Caswall Tower, Devon Island (74°43′ N; 91°10′ W), from 24 July to 8 August 1973. A total of 602.7 bear hours of observations was recorded. Two types of hunting were observed, stalking and still-hunting. Of 288 hunts observed, 65 (22.6%) were stalks and 233 (77.4%) were still-hunts. All cubs observed hunted, but they exhibited great variety in patience and apparent skill. Scavenging and intraspecific competition for possession of kills were observed. When threatened, adult females with cubs were not subordinate to tears of any other age or sex classes. A diurnal rhythm was recorded in which bears slept most during the latter third of the 24-h cycle and least in the first third. The average of 17 sleeps longer than 60 min was 465 ± 301.3 min.Basking ringed seals (Phoca hispida) alternated between lying flat and raising their heads to look about for predators. The mean duration of the lying and looking phases was 26.3 and 7.0 s respectively (n = 591 and 580). The variation between individual seals was greater than within individuals. If a group of seals hauled out together, all individuals maintained watchful behavior; no single animal acted as a "sentry" for the others.

scholarly journals Incorporating climate change in a harvest risk assessment for polar bears Ursus maritimus in Southern Hudson Bay

2021 ◽  
Vol 258 ◽  
pp. 109128
Author(s):  
Eric V. Regehr ◽  
Markus Dyck ◽  
Samuel Iverson ◽  
David S. Lee ◽  
Nicholas J. Lunn ◽  
...  
Keyword(s):  
Climate Change ◽  
Risk Assessment ◽  
Ursus Maritimus ◽  
Hudson Bay ◽  
Polar Bears
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