In 2017 and 2018, satellite transmitters were deployed (n2017 = 13, n2018 = 14) on Aleutian Terns Onychoprion aleuticus in two areas of Alaska, USA, to investigate breeding season movements and temporal patterns of colony activity. The effort was intended to aid in the development of a large-scale population-assessment framework. Across the two years, we observed dispersal to seven confirmed or potential (putative) colonies, none of which were previously documented, ranging in distance from 0.4 to 64.2 km from tag deployment sites. Although most terns did not associate with any known colonies during the breeding season, several individuals from the study area in western Alaska were sequentially associated with multiple colonies. Breeding season movements were usually within tens of kilometers of the capture location, but movements of several hundred kilometers were recorded occasionally. These results should be interpreted cautiously because we do not know the post-tagging nesting status of marked terns, nor were we able to determine whether there were tern behavioral changes related to capture and tagging. With this caution in mind and based on our findings, we recommend that future efforts to estimate total Aleutian Tern population sizes or trends consider the following: (1) estimates should not rely solely upon surveys of previously documented colonies; (2) estimation procedures should account for the potential movement of individual terns among colonies, the possible lack of association of a tern with any colony, the possible association of a tern with multiple colonies, and/or the possibility that adults do not attempt to breed each year; and (3) if necessary, studies should survey subsets of the Alaska breeding range in successive years to reduce the uncertainty around the size of the statewide tern population.

For longer-lived species, individuals hedge their bets by skipping breeding when conditions are poor to preserve the opportunity for future breeding attempts. Thus, understanding the ecological drivers behind the 'choice' to reproduce or not is a key step in identifying and diagnosing causes of population change. We investigated both marine and terrestrial factors that might influence whether Kittlitz's Murrelets Brachyramphus brevirostris-a long-lived seabird of conservation concern that is often associated with glacially-influenced habitats-choose to breed in a given year. We used a suite of proxies to explain variation in reproductive metrics of radio-tagged Kittlitz's Murrelets, exploring three hypotheses related to prey availability, nest depredation risk, and energetic costs of nesting in Icy Bay, Alaska, 2007-2012. In two of the years, we compared results with the locally co-occurring, closely-related Marbled Murrelet B. marmoraus. Across the six-year period of our study, the posterior mean breeding propensity of Kittlitz's Murrelets was 0.21 (95% credible interval [CrI] = 0.15-0.27), nesting success was 0.41 (CrI = 0.25-0.57), and fecundity was 0.04 (CrI = 0.02-0.06). Although none of our three hypotheses were strongly supported by the data, our results collectively suggest that successful nesters expended greater effort than failed nesters and non-nesters to acquire sufficient prey-they stayed longer in the study area, had larger marine core use areas, spent slightly less time diving, and had shorter commuting distances and longer incubation shifts. Also, in years when fecundity was highest, overlap of individual marine core use areas was greatest, suggesting predictable foraging hotspots for murrelets in those years. Importantly, when comparing Brachyramphus species, we found that Marbled Murrelets outperformed Kittlitz's Murrelets reproductively by three to four times in overlapping years, suggesting different drivers of reproduction. From our collective results, we posit that the limitation to reproduction of Kittlitz's Murrelets may not be prey abundance or quality, but instead efficient access to prey. While our associations with indices of prey availability, depredation risk, and energetic costs to nesting did not explain much of the variation in fitness metrics, our study demonstrates the value of using a comparative approach and multiple metrics to diagnose factors limiting a population, especially when data are sparse. For bet-hedging species with complex life histories, we recommend using a combination of integrated modeling and a monitoring framework designed to accumulate evidence across studies to estimate population dynamics and improve inferences about ecological drivers.

Abstract Age‐, region‐, and year‐specific estimates of reproduction are needed for monitoring wildlife populations during periods of ecosystem change. Population dynamics of Steller sea lions (Eumetopias jubatus) in Southeast Alaska varied regionally (with high population growth and survival in the north vs. the south) and annually (with reduced adult female survival observed following a severe marine heatwave event), but reproductive performance is currently unknown. We used mark‐resighting data from 1006 Steller sea lion females marked as pups at ~3 weeks of age from 1994 to 1995 and from 2001 to 2005 and resighted from 2002 to 2019 (to a maximum age of 25) to examine age‐, region‐, and year‐specific reproduction. In the north versus the south, age of first reproduction was earlier (beginning at age 4 vs. age 5, respectively) but annual birth probabilities of parous females were reduced by 0.05. In an average year pre‐heatwave, the proportion of females with pup at the end of the pupping season peaked at ages 12–13 with ~0.60/0.65 (north/south) with pup, ~0.30/0.25 with juvenile, and ~0.10 (both regions) without a dependent. In both regions, reproductive senescence was gradual after age 12: ~0.40, 0.40, and 0.20 of females were in these reproductive states, respectively, by age 20. Correcting for neonatal mortality, true birth probabilities at peak ages were 0.66/0.72 (north/south). No cost of reproduction on female survival was detected, but pup production remained lower (−0.06) after the heatwave event, which if sustained could result in population decline in the south. Reduced pup production and greater retention of juveniles during periods of poor prey conditions may be an important strategy for Steller sea lions in Southeast Alaska, where fine‐tuning reproduction based on nutritional status may improve the lifetime probability of producing pups under good conditions in a variable and less productive environment.

The North Pacific marine heatwave of 2014–2016 (PMH), one of the most geographically-extensive and severe marine heatwaves on record, resulted in widespread and persistent perturbation of the Gulf of Alaska and California Current ecosystems. Negative effects of the PMH on marine mammals have been observed, but are not yet well understood. The endangered Steller sea lion Eumetopias jubatus is an important top predator in the Gulf of Alaska that is also particularly vulnerable to sudden or severe ecosystem shifts. We examined survival of 4,178 known-aged Steller sea lions marked from 2000 to 2016 from Kodiak Island through Southeast Alaska, using mark-recapture models and 12,811 resightings collected from 2001 to 2021. Survival of adult females aged 3–15 was reduced -0.05 to -0.23 during the PMH in the areas east, but not west, of Cook Inlet. Survival of Kodiak females was unaffected by the PMH, but survival of Sugarloaf females aged 5–8 was reduced -0.13 from summer 2015 to summer 2016. Lowest survival in Southeast Alaska occurred from summer 2016 to summer 2017, but was also reduced from summer 2014 to summer 2016. Reduced survival continued post-PMH in Kenai Peninsula/Prince William Sound, but not in Southeast Alaska. Survival of adult males was insensitive to the PMH, except in Southeast Alaska where male survival was reduced -0.25 from summer 2016 to summer 2017. Prolonged or intermittent high adult female mortality may reduce population growth and initiate regional declines. Survival response of Steller sea lions to the PMH varied regionally despite similar patterns of ocean warming throughout our study area, suggesting areas east versus west of Cook Inlet were affected differently by the PMH, perhaps due to habitat and oceanographic differences.

Most research that has been done regarding Steller sea lions (SSLs; Eumetopias jubatus) has been during the breeding season. Adult SSLs are known to have high among-year breeding-season site fidelity, typically with movement away from breeding-season locations during non-breeding seasons. Using non-breeding-season sighting data of permanently marked SSLs from four areas in Alaska and broad-scale breeding-season sightings, we estimated among-year non-breeding-season site fidelity (i.e., the probability a SSL moves from its breeding-season location to a specific non-breeding-season area). Some SSLs, especially females, have high site fidelity to non-breeding-season areas; fidelity is markedly lower for males. We found no evidence that site fidelity varied among natal rookeries, but our sample sizes were relatively small, possibly limiting our ability to determine such effects. With our estimates of non-breeding-season site fidelity, coupled with previously demonstrated breeding-season site fidelity, we concluded that SSLs should be considered partial migrants (i.e., migratory behavior exhibited by only some individuals in a population) with at least some individual SSLs, particularly females, exhibiting migratory behavior.

Accurate and precise estimates of the timing of whisker growth and shedding are necessary to interpret biochemical information stored in whiskers. This fine-scale examination of harbor seal ( Phoca vitulina Linnaeus, 1758) whisker growth and shedding identified an asymptotic growth pattern with initial rapid growth that decays over time that can be defined with the von Bertalanffy curve. Initial growth rates were similar among whiskers, but estimated growth coefficients ( K) and asymptotic lengths ( L ∞ ) differed by follicle positions suggesting that differences in total whisker lengths result from dissimilarly shaped growth curves. In other words, longer whisker length is attained by delaying the growth rate decay. There was substantial intra- and interseal variation in shedding dates; whisker shedding began at the caudal margin of the whisker bed and progressed toward the nose. Shedding of marked whiskers from the three study seals took from 78 to 133 days; however, selecting whiskers only from the most caudal follicle of the bottom three rows constrained the period of whisker shedding to 7–43 days. These differences in growth and shedding of harbor seal whiskers emphasize the importance of considering follicle position to select whiskers that are the most similar for analyses of information stored in whiskers.

Abstract In this study, we investigated how Little Brown Myotis (Myotis lucifugus), North America's northernmost bat species, adjusted to variable spring and autumn conditions and very little darkness during the boreal summer. We recorded bat activity around Anchorage and the lower Matanuska-Susitna Valley, Alaska. Initiation of bat activity in the spring varied among years and was affected by minimum nightly temperatures in late April and, to a lesser extent, precipitation. Cessation of bat activity in the autumn was consistent among years, with a weak association with early-October minimum temperature. During summer, bat activity was highest on warm, clear nights, but was reduced by wind or rain. Bat activity was positively related to open water and forest cover and negatively related to human development. Most bat activity occurred between sunset and sunrise, even during very short nights in mid-summer. Although there was some activity prior to sunset, bat activity after sunrise was very rare. Pre-sunset bat activity was almost exclusively at sites with high forest cover. After sunset, moderately forested sites were also used, but sites with little forest cover were rarely used before or after sunset.

Recent studies have revealed that western populations of little brown bats (Myotis lucifugus) in North America exhibit different hibernation behavior than their eastern counterparts. Understanding these differences is essential for assessing the risk white-nose syndrome (WNS) poses to western bat populations. We used acoustic monitoring and radiotelemetry to study the overwintering behavior of little brown bats near Juneau, Alaska during 2011-2014. Our objectives were to identify the structures they use for hibernation, measure the microclimates within those structures, and determine the timing of immergence and emergence and the length of the hibernation season. We radiotracked 10 little brown bats to underground hibernacula dispersed along two ridge systems. All hibernacula were <= 24.2 km from where the bats were captured. Eight bats hibernated in the "Milieu Souterrain Superficiel" (MSS), a network of air-filled underground voids between the rock fragments found in scree (talus) deposits. Two bats hibernated in holes in the soil beneath the root system of a tree or stump (rootball). At least two hibernacula in the MSS were reused in subsequent years. Average MSS and rootball temperatures were warmer and more stable than ambient temperature and were well below the optimal growth range of the fungus that causes WNS. Temperatures in the MSS dropped below freezing, but MSS temperatures increased with depth, indicating bats could avoid subfreezing temperatures by moving deeper into the MSS. Relative humidity (RH) approached 100% in the MSS and under rootballs and was more stable than ambient RH, which also was high, but dropped substantially during periods of extreme cold. Acoustic monitoring revealed that bats hibernated by late October and began emerging by the second week of April; estimates of minimum length of the hibernation season ranged from 156 to 190 days. The cold temperatures, dispersed nature of the hibernacula, and close proximity of hibernacula to summering areas may slow the spread and reduce the impacts of WNS on local populations of little brown bats.

ABSTRACT Timber interests target coastal temperate rainforests, and within them stands composed of large trees potentially selected by American black bears ( Ursus americanus ) for denning. We identified the location of 75 black bear dens (used ≥14 days) in an intensively logged area on Prince of Wales Island, Alaska, USA. We ground‐visited a subset ( n = 43) of these sites to measure the diameter of living trees and woody structures used by black bears for denning. We contrasted dens with random trees available in the study area in a series of models to characterize black bear den selection. All but 1 of 43 ground‐visited dens were located within woody structures, and all but 2 of these structures were >1 m diameter at breast height (dbh). We built resource selection functions (RSFs) to investigate black bear den selection across a range of spatial scales, though estimated selection was generally scale invariant. Black bears strongly selected large‐diameter woody structures (dead or alive) as dens at the home‐range scale, with the estimated relative strength of selection (RSS) for a 2‐m‐diameter tree approximately 166 times that of a 1‐m‐diameter tree. The estimated RSS of logged forest was unexpectedly greater (2.75 times) than that of the remaining commercially valuable old‐growth forest. Selection for den structures within stumps in previously logged stands suggests features of the woody structure may be of greater importance to black bears selecting dens than attributes of the surrounding forest. There was no observed correlation between bear den selection and second‐growth age, indicating that stumps may persist as suitable dens well after logging. Because denning is an important part of their life history and the denning structures used by black bears on Prince of Wales Island will eventually decay, retaining habitat value for bears in areas intensively managed for timber harvest requires strategies to recruit very large, old trees throughout the landscape. © 2021 The Wildlife Society.

Abstract The duration of offspring care is critical to female fitness and population resilience by allowing flexibility in life‐history strategies in a variable environment. Yet, for many mammals capable of extended periods of maternal care, estimates of the duration of offspring dependency are not available and the relative importance of flexibility of this trait on fitness and population viability has rarely been examined. We used data from 4,447 Steller sea lions Eumetopias jubatus from the Gulf of Alaska and multistate hidden Markov mark–recapture models to estimate age‐specific weaning probabilities. Maternal care beyond age 1 was common: Weaning was later for animals from Southeast Alaska (SEAK) and Prince William Sound (PWS, weaning probabilities: 0.536–0.648/0.784–0.873 by age 1/2) compared with animals born to the west (0.714–0.855/0.798–0.938). SEAK/PWS animals were also smaller than those born farther west, suggesting a possible link. Females weaned slightly earlier (+0.080 at age 1 and 2) compared with males in SEAK only. Poor survival for weaned versus unweaned yearlings occurred in southern SEAK (female survival probabilities: 0.609 vs. 0.792) and the central Gulf (0.667 vs. 0.901), suggesting poor conditions for juveniles in these areas. First‐year survival increased with neonatal body mass (NBM) linearly in the Gulf and nonlinearly in SEAK. The probability of weaning at age 1 increased linearly with NBM for SEAK animals only. Rookeries where juveniles weaned at earlier ages had lower adult female survival, but age at weaning was unrelated to population trends. Our results suggest the time to weaning may be optimized for different habitats based on long‐term average conditions (e.g., prey dynamics), that may also shape body size, with limited short‐term plasticity. An apparent trade‐off of adult survival in favor of juvenile survival and large offspring size in the endangered Gulf of Alaska population requires further study.

Steller sea lions (Eumetopias jubatus) are composed of two genetically distinct metapopulations (an increasing "eastern" and a reduced and endangered "western" population, or stock for management purposes in U.S. waters) that are only recently mixing at new rookeries in northern Southeast Alaska, east of the current stock boundary. We used mark-recapture models and 18 years of resighting data of over 3,500 individuals marked at the new rookeries and at neighboring long-established rookeries in both populations to examine morphology, survival, and movement patterns of pups born at new rookeries based on whether they had mitochondrial DNA haplotypes from the western or eastern population (mtW or mtE); examine survival effects of dispersal to the Eastern Stock region for animals born in the Western Stock region; and estimate minimum proportions of animals with western genetic material in regions within Southeast Alaska. Pups born at new rookeries with mtW had similar mass, but reduced body condition and first-year survival (approximately -10%) compared to pups with mtE. mtE pups ranged more widely than mtW pups, including more to the sheltered waters of Southeast Alaska's Inside Passage. Fitness benefits for western-born females that dispersed to Southeast Alaska were observed as higher female survival (+0.127, +0.099, and +0.032 at ages 1, 2, and 3+) and higher survival of their female offspring to breeding age (+0.15) compared to females that remained west of the boundary. We estimated that a minimum of 38% and 13% of animals in the North Outer Coast-Glacier Bay and Lynn Canal-Frederick Sound regions in Southeast Alaska, respectively, carry genetic information unique to the western population. Despite fitness benefits to western females that dispersed east, asymmetric dispersal costs or other genetic or maternal effects may limit the growth of the western genetic lineage at the new rookeries, and these factors require further study.

For more than 30 y, the Alaska Loon Watch (1985-1999) and the Alaska Loon and Grebe Watch (2000-2015) engaged citizen scientist participants to record more than 10,000 observations of common loons Gavia immer and Pacific loons Gavia pacifia at 346 lakes in five subregions of southcentral Alaska. We used generalized linear mixed models to estimate long-term trends in adult loon counts and chick survival and examined environmental variables associated with loon abundance. Adult common loon counts increased in all five subregions by 0.6-3.6% annually, whereas Pacific loons decreased 3% in the Anchorage subregion, but otherwise had trends not distinguishable from zero. Lake area was positively associated with common loon abundance and negatively associated with Pacific loon abundance. We also noted an inverse relationship between common loon and Pacific loon presence, consistent with the premise of interspecific competition. We did not find strong relationships between loon presence and predictor variables indicative of human disturbance or lakeshore development. Estimates of chick survival over time also revealed no clear pattern, although common loon chicks showed a decline in survival over the study period in one subregion. Citizen science programs provide agencies with a cost-effective tool to collect data over large spatial and temporal extents, which may not be feasible otherwise. However, there are ramifications of common data deficiencies associated with casual or unstructured observations, which can violate the assumptions required for rigorous statistical analysis. The implementation of a carefully predefined sampling protocol can avoid sampling bias, eliminate stringent assumptions, and ensure higher information content of citizen science data.

[This corrects the article DOI: 10.1371/journal.pone.0176840.].

Population dynamics of long-lived vertebrates depend critically on adult survival, yet factors affecting survival and covariation between survival and other vital rates in adults remain poorly examined for many taxonomic groups of long-lived mammals (e.g. actuarial senescence has been examined for only 9 of 34 extant pinniped species using longitudinal data). We used mark–recapture models and data from 2795 Steller sea lion (Eumetopias jubatus) pups individually marked at four of five rookeries in southeastern Alaska (SEAK) and resighted for 21 years to examine senescence, annual variability and covariation among life-history traits in this long-lived, sexually dimorphic pinniped. Sexes differed in age of onset (approx. 16–17 and approx. 8–9 years for females and males, respectively), but not rate (−0.047 and −0.046/year of age for females and males) of senescence. Survival of adult males from northern SEAK had greatest annual variability (approx. ±0.30 among years), whereas survival of adult females ranged approximately ±0.10 annually. Positive covariation between male survival and reproductive success was observed. Survival of territorial males was 0.20 higher than that of non-territorial males, resulting in the majority of males alive at oldest ages being territorial.

The two stocks of Steller sea lions (Eumetopias jubatus) in Alaska include an endangered western stock, recently recovering in parts of its range following decades of decline, and an eastern stock which was removed from the U.S. Endangered Species List in 2013 following increasing numbers since the 1970s. Information on overlapping distributions of eastern and western sea lions is needed for management considerations. We analyzed >30,000 sightings collected from 2000-2014 of 2,385 sea lions that were branded as pups at 10 Alaskan rookeries to examine mesoscale (mostly <500km) spatial distribution, geographic range, and geographic population structure based on natal rookery, sex, and age during breeding and non-breeding seasons. Analyses of summary movement measures (e.g., natal rookery, sex, and age-class differences in spatial distribution and geographic range) indicate wide variation in rookery-specific movement patterns. Correlations between movement measures and population dynamics suggested movement patterns could be a function of density dependence. Animals from larger rookeries, and rookeries with slower population growth and lower survival, had wider dispersion than animals from smaller rookeries, or rookeries with high growth and survival. Sea lions from the largest rookery, Forrester Island, where survival and population trends are lowest, were the most widely distributed. Analysis of geographic population structure indicated that animals born in the eastern Aleutian Islands had the most distinct movements and had little overlap with other western sea lions. Northern Southeast Alaska, within the eastern stock, is the area of greatest overlap between stocks, and is important to western animals, especially those born in Prince William Sound. Detailed knowledge of distribution and movements of western sea lions is useful for defining recovery and population trend analysis regions that better reflect dispersion and population structure and provides valuable information to managers as critical habitat is re-evaluated and the location of the stock boundary reconsidered.

We estimated survival probabilities for Steller sea lion ( Eumetopias jubatus ) pups from 3 wk to 6 wk old and from 6 wk to 1 yr at three rookeries in southeastern Alaska. We also investigated the effect of mass, body condition, health variables, and the genetic origin on 3–6 wk survival. Survival differed substantially among rookeries and between sexes, with survival lowest at Hazy Islands, intermediate at White Sisters, and highest at Graves Rocks and survival lower for males than females. Body mass, body condition, and hematocrit were positively related to survival and blood %H 2 O and haptoglobin level (for females; no relationship for males) were negatively related to survival. Taking predictor variables collectively, sea lion pups at Hazy Islands, which had the lowest survival probability, had the lowest mass, hematocrit, and hemoglobin, and had high levels of blood %H 2 O, and hookworm infection. Values from Graves Rocks, which had the highest survival, were the opposite of those from Hazy Island ( e.g ., high mass, body condition, hematocrit, and hemoglobin), while those from White Sisters (intermediate survival) had varying means ( e.g ., high hematocrit and hemoglobin and low hookworms, but also low body condition); these patterns suggest that physiological factors potentially underlie rookery differences in survival.

Tidewater glacial fjords provide important habitat for breeding harbor seals (Phoca vitulina) that rest, give birth, and nurse pups on icebergs.These fjords also attract tourist vessels that potentially disturb seals.In May and June during 2001-2006, we documented seal abundance, pupping phenology, and seal-vessel interactions in Tracy Arm, a glacial fjord in southeastern Alaska.We used randomized observations to determine the frequency at which seals entered the water in the presence and absence of vessels, and we estimated the reaction distances of seals to approaching vessels.Mean daily vessel counts varied from 10.2 (2001) to 2.0 (2006) (range: 1-33).Tour and power vessels were the most common types of vessels, but seals were most sensitive to cruise ships and kayaks.The odds of a seal entering the water were higher when vessels were present (>2 times) or within 100 m (3.7 times), and when a pup was present (1.3 times).The baseline, undisturbed, rate of seals entering the water was 0.06 (95% CI: 0.05-0.08)per 10 min.Seal births occurred during 30 May-25 June and peaked (4-8 per day) during 7-13 June.The maximum pup count (408) was observed on 24 June.Harbor seal fitness in Tracy Arm may be reduced by vessel disturbances during breeding and pupping.

Full spectrum and zero-crossing recording technologies have been used to record and analyze the echolocation calls of bats for decades. More recent advances in analysis software combine these technologies by extracting zero crossing information from full spectrum recordings using different combinations of signal processing techniques. The purpose of this paper is to explain the physics behind full spectrum and zero crossing technologies and modern hybrid algorithms for bat biologists and ecologists to better understand and appreciate the advantages, disadvantages, and modern capabilities of available technology. We first look at zero crossing and full spectrum recording technologies, how they work, and their relative advantages and disadvantages. We then explore a simple technique for extracting zero crossing data from full spectrum recordings using band-pass filtering and adaptive thresholds. Finally, we explore advanced signal processing techniques including Gaussian noise reduction, echo cancellation, call tracing, adaptive filtering and interpolation to study how they can be used to enhance a full spectrum signal in order to extract richer zero crossing data. We conclude that while zero crossing recordings do have some advantages in limited circumstances, it is far better to record bats in full spectrum and use modern signal processing techniques to enhance the signal before either analyzing the data with full spectrum tools or extracting zero crossing information and then analyzing the data using zero crossing or hybrid tools.