The lithalsas in the Hudson Bay region of northern Québec, Canada, are the closest modern analogs of ancient features that collapsed to form conspicuous circular depressions (“viviers”) common in the Hautes-Fagnes, a region in Belgium. Observations made in both regions are complementary and suggest that these mounds formed by frost heaving displacing soil not only upward, as previously assumed, but also laterally. This lateral displacement is consistent with diverse observations and inferences, which include (1) the simple rounded outline, either circular or oval, typical of both active and relic lithalsas; (2) evidence of local lateral extension inferred from exposures of the relic forms; (3) the relative inefficiency of solifluction in accumulating surface material to form the peripheral ramparts of remnant lithalsas due to the very gentle slopes of the mounds; and (4) the dip of ice lenses within a lithalsa in the Hudson Bay region, perhaps indicating that the freezing front dipped outward along its periphery. The growth of segregation ice is the primary driver for the vertical growth and lateral enlargement of a lithalsa.

Radiocarbon ages from Southampton Island (Canada) provide new chronological control on the deglaciation of Foxe Channel and northern Hudson Bay, a strategic area for understanding the demise of a marine-based portion of the Laurentide Ice Sheet. A regional marine reservoir age of 630 ± 45 yr and a reservoir offset (ΔR) of 263 ± 48 yr were calculated from two early to mid-Holocene terrestrial/marine radiocarbon age pairs. These values are consistent with corrections based on early 20th century mollusks suggesting that following deglaciation the oceanic conditions controlling the regional reservoir effect rapidly became similar to those of modern times. However, our ΔR value is 352 ± 52 yr less than another correction from eastern Foxe Basin, which may be affected by 14 C dilution from carbonate rocks. Our ΔR value is used to calibrate new marine radiocarbon ages which help further develop the deglaciation history of Southampton Island, especially along the north coast where deglaciation of Foxe Channel appears to have been completed by 8100–7800 cal yr BP (2σ). This provides key chronological constraints on the development of a long marine ice margin in southern Foxe Basin prior to the final breakup of the Foxe ice dome.

We examined data on live-captured polar bears (Ursus maritimus) from western Hudson Bay relative to differential maternal investment and facultative sex ratio theory. In spring, shortly after den emergence, we found no differences in mass or body length of cubs in litters of one or two. In triplet litters captured in spring, male cubs were larger than females in both mass and body length, possibly due to sibling competition for limited maternal resources. In cubs captured during autumn, sex-based differences in mass and body length were found only in litters of one with males larger than females. Yearling males captured in autumn were heavier and longer than females in litters of one and two. In twin litters of one male and one female cub in spring and autumn, we found no differences in mass or body length. Except singleton female cubs in spring and female and male triplets in spring, cub and yearling mass were correlated with maternal mass. Mothers with singletons in spring were more likely to have male cubs but, in general, there was little evidence to suggest that mass or age of mothers influenced offspring sex. Litter size, maternal mass, and maternal age all influenced cub and yearling size, but offspring sex was less important. Results suggest that female polar bears do not normally invest differentially between offspring of different sexes except in triplet litters in spring.

The growth patterns of body length and head size in female and male polar bears (Ursus maritimus) in western Hudson Bay were compared with those of five other populations using the von Bertalanffy equation. Our objective was to determine if differences in growth patterns could account for higher reproductive rates reported in female polar bears from western Hudson Bay compared to the other populations. Significant differences in asymptotic size and growth rate were found in body length and head size. At age of first breeding in western Hudson Bay (4.1 years old), females reached 97% of asymptotic body length, while females in other populations took between 4.5 and 5.5 years to attain the same proportion. Body length of three- and four-year-old females in western Hudson Bay declined between the 1960s and 1990s and temporal variation in growth rates makes cross-population studies uncertain. Zygomatic breadth and head length may provide the most useful measures to compare populations because they are simple to measure, non-varying, and growth in head length is almost complete (97–98%) by the age of first breeding in females. We conclude that higher reproductive rates in western Hudson Bay were associated with higher growth rates. However, the reason for the higher growth rates remain unknown.