No abstract

Among pinnipeds, harbor seals Phoca vitulina have the broadest distribution (a 34° to 50° range in latitudes in the Pacific and Atlantic regions, respectively) and are found in a diversity of habitats. Harbor seals in Alaska, USA, similar to Arctic pinnipeds in many respects, rely upon glacial ice for pupping, mating, and molting. Just as climate change affects Arctic sea ice, tidewater glaciers are rapidly retreating in Alaska, reducing ice availability for harbor seals. An increased understanding of glacial vs. terrestrial harbor seals may reveal information important to conservation of harbor seals and Arctic pinnipeds, as effects of climate change continue. We compared foraging distances, activity budgets, diet, and body condition for seals captured at glacial and terrestrial sites in Glacier Bay, Alaska. Foraging strategies and activity budgets of seals using glacial ice differed substantially from seals using terrestrial sites. Glacial seals traveled significantly farther to forage (≥40 vs. < 5 km) and spent more time hauled out than terrestrial seals (26 vs. 11 to 16%). Diets of glacial seals were higher in pelagic fishes compared to diets of terrestrial seals that foraged primarily on intertidal/demersal fishes. Body condition of seals was similar between habitats (p ≥ 0.09) and suggests that costs of longer foraging trips for glacial seals may be offset by obtaining higher quality diets of pelagic fishes, which may allow seals to spend more time hauled out. During the brief lactation period, more time hauled out could result in more time available for the transfer of energy from adult females to dependent offspring. KEY WORDS: Foraging behaviour · Activity budget · Body condition · Habitat use · Stable isotopes · Time-depth recorder · Phocid · Pinniped Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 429: [277][278][279][280][281][282][283][284][285][286][287][288][289][290] 2011 numbers of pupping harbor seals (Calambokidis et al. 1987), suggesting that these sites provide important pupping and breeding habitats. Steep declines in harbor seal numbers have occurred at several glacial ice sites in Alaska (Hoover-Miller 1994, 2011, Mathews & Pendleton 2006, Womble et al. 2010, highlighting the need for a better understanding of the basic ecology of seals using glacial habitat and the potential benefits and costs of using glacial ice to pup, breed, or molt.Glacier Bay National Park seasonally hosts one of the largest aggregates of harbor seals in Alaska. Seals use both terrestrial substrate and glacial ice within the Bay, which provides a unique opportunity to understand the role of different habitats in influencing seal behavior within a relatively small geographic region. Also of interest is whether a comparison of seals in ice and terrestrial habitats can be used as a corollary to the situation in the Arctic as it relates to diminishing sea ice (Rodrigues 2009, Polyak et al. 2010 and Arctic phocids that rely upon ice substrate for resting, fora...

Continued Arctic warming and sea‐ice loss will have important implications for the conservation of ringed seals, a highly ice‐dependent species. A better understanding of their spatial ecology will help characterize emerging ecological trends and inform management decisions. We deployed satellite transmitters on ringed seals in the summers of 2011, 2014, and 2016 near Utqiaġvik (formerly Barrow), Alaska, to monitor their movements, diving, and haul‐out behavior. We present analyses of tracking and dive data provided by 17 seals that were tracked until at least January of the following year. Seals mostly ranged north of Utqiaġvik in the Beaufort and Chukchi Seas during summer before moving into the southern Chukchi and Bering Seas during winter. In all seasons, ringed seals occupied a diversity of habitats and spatial distributions, from near shore and localized, to far offshore and wide‐ranging in drifting sea ice. Continental shelf waters were occupied for >96% of tracking days, during which repetitive diving (suggestive of foraging) primarily to the seafloor was the most frequent activity. From mid‐summer to early fall, 12 seals made ~1‐week forays off‐shelf to the deep Arctic Basin, most reaching the retreating pack‐ice, where they spent most of their time hauled out. Diel activity patterns suggested greater allocation of foraging efforts to midday hours. Haul‐out patterns were complementary, occurring mostly at night until April‐May when midday hours were preferred. Ringed seals captured in 2011—concurrent with an unusual mortality event that affected all ice‐seal species—differed morphologically and behaviorally from seals captured in other years. Speculations about the physiology of molting and its role in energetics, habitat use, and behavior are discussed; along with possible evidence of purported ringed seal ecotypes.

Harbor seals ( Phoca vitulina richardii (Gray, 1864)) in Alaska are currently treated as three distinct management stocks. Previous genetic analyses using mitochondrial DNA suggested that these stocks are differentiated genetically. We studied populations in Glacier Bay (GB; Southeast Alaska Stock), where harbor seals are declining, and Prince William Sound (PWS; Gulf of Alaska Stock), where the population has recently stabilized. Using six pairs of hypervariable microsatellite primers, we determined that these populations are a single panmictic unit with estimated migration rates of 22 animals/generation (PWS to GB) and 63 animals/generation (GB to PWS). The asymmetrical gene flow between GB and PWS is likely driven in part by a recent increase in competitors and predators of seals in GB. In contrast with males, emigration of females from PWS to GB (8.3 seals/generation) is higher than emigration of females from GB to PWS (3.3 seals/generation), likely because females use glacial ice as pupping habitat. Despite the high gene flow, the number of migrants per year (0.02% of the Gulf of Alaska population) is likely too low to influence the demographics of harbor seals in PWS, and the two populations may best be managed as separate stocks.