Ringed seal (Pusa hispida) breeding habitat on the landfast ice in northwest Alaska during spring 1983 and 1984

Abstract

There has been significant sea ice loss associated with climate change in the Pacific Arctic, with unquantified impacts to the habitat of ice-obligate marine mammals such as ringed seals (Pusa hispida). Ringed seals maintain breathing holes and excavate subnivean lairs on sea ice to provide protection from weather and predators during birthing, nursing, and resting. However, there is limited baseline information on the snow and ice habitat, distribution, density, and configuration of ringed seal structures (breathing holes, simple haul-out lairs, and pup lairs) in Alaska. Here, we describe historic field records from two regions of the eastern Chukchi Sea (Kotzebue Sound and Ledyard Bay) collected during spring 1983 and 1984 to quantify baseline ringed seal breeding habitat and map the distribution of ringed seal structures using modern geospatial tools. Of 490 structures located on pre-established study grids by trained dogs, 29% were pup lairs (25% in Kotzebue Sound and 33% in Ledyard Bay). Grids in Ledyard Bay had greater overall density of seal structures than those in Kotzebue Sound (8.6 structures/km2 and 7.1 structures/km2), but structures were larger in Kotzebue Sound. Pup lairs were located in closer proximity to other structures and characterized by deeper snow and greater ice deformation than haul-out lairs or simple breathing holes. At pup lairs, snow depths averaged 74.9 cm (range 37–132 cm), with ice relief nearby averaging 76 cm (range 31–183 cm), and ice deformation 29.9% (range 5–80%). We compare our results to similar studies conducted in other geographic regions and discuss our findings in the context of recent declines in extent and duration of seasonal cover of landfast sea ice and snow deposition on sea ice. Ultimately, additional research is needed to understand the effects of recent environmental changes on ringed seals, but our study establishes a baseline upon which future research can measure pup habitat in northwest Alaska.

Predation on ringed seals in subnivean lairs in northwest Alaska during spring 1983 and 1984

“…Estimates of predation rates can also vary by the number of replicate surveys conducted at a site during a given study (Hammill & Smith, 1991). Results based on a single survey may overestimate predation success due to greater detectability of carcasses by the search dogs, although each grid in our study was searched at least two or more times until no additional seal structures were found (Hauser et al, 2021).…”

“…Specially trained Labrador retriever dogs were used to search for ringed seal structures on landfast sea ice in two regions of the eastern Chukchi Sea: southern Kotzebue Sound (~66°16′N, 162°32′W) and ~130 nautical miles farther north in Ledyard Bay (~68°53′N, 165°50′W) (Figure 1). Surveyed grids were searched in Kotzebue Sound during April 5–29, 1983 (two study grids) and in Ledyard Bay during April 6 to May 13, 1984 (five study grids), as described elsewhere (Frost & Burns, 1989; Hauser et al, 2021). Ringed seal structures were measured and classified as breathing holes, haul‐out lairs, complex, or pup lairs.…”

“…Our objective is to describe the magnitude of bear and fox predation and kill rates for different types of subnivean structures in two regions of northwest Alaska. These during April 5-29, 1983 (two study grids) and in Ledyard Bay during April 6 to May 13, 1984 (five study grids), as described elsewhere (Frost & Burns, 1989;Hauser et al, 2021). Ringed seal structures were measured and classified as breathing holes, haul-out lairs, complex, or pup lairs.…”

“…Ringed seal structures were measured and classified as breathing holes, haul-out lairs, complex, or pup lairs. Complex and pup lairs were combined for the purposes of this analysis (Hauser et al, 2021), and are hereafter referred to as pup lairs. Modern geospatial tools were also used to locate each structure within a study grid and its proximity to other structures (see Hauser et al, 2021).…”

“…One pup (0.4% of structures) was killed in grid 1983-2. Melt was well underway at the time grid 1983-2 was surveyed and it was difficult to see fox tracks as well as to conduct searches of ringed seal structures (see Hauser et al, 2021).…”