A re-examination of the timing of pupping for Steller sea lions Eumetopias jubatus breeding on two islands in Alaska

Kuhn, Carey E.; Chumbley, Kathryn; Johnson, Devin S.; Fritz, Lowell W.

doi:10.3354/esr00796

Cited by 9 publications

(11 citation statements)

References 31 publications

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“…Adult males establish breeding territories on rookeries beginning in mid-to late May, followed shortly by the arrival of adult females. Parturition usually occurs within days of arrival at the rookery (between late May and mid-July), with the mean birth dates varying between 9 and 11 June within the Aleutian and Commander islands that "bookend" the longitudinal range of this study (170°W-172°E; Pitcher et al 2001;Kuhn et al 2017). We defined the breeding season as May-August, and the non-breeding season as September-April.…”

Section: Methodsmentioning

confidence: 99%

A re-examination of the relationship between Steller sea lion (Eumetopias jubatus) diet and population trend using data from the Aleutian Islands

et al. 2019

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Prey diversity and energy density have been linked to each other and to population trends in many studies of bird and mammal diets. We re-examined these relationships in Steller sea lions (Eumetopias jubatus (Schreber, 1776)) using data collected from the Aleutian Islands, where there has been a strong longitudinal gradient in population trend. Diet diversity and energy density metrics were similar in the western Aleutians, where sea lion counts declined consistently, and in the easternmost Aleutian area, where population trends improved significantly. We compared traditional deterministic diet diversity metrics with diversity scores based on an occupancy model that accounts for differences in sample size and uncertainty in prey group detection. This analysis indicated that there was no significant change in diet diversity over the 23-year study period or any significant differences across the Aleutian Islands. These results are consistent with prey abundance data from nine groundfish bottom trawl surveys conducted over the same period. While diet studies detail what Steller sea lions eat and provide an estimate of their energy intake, they provide only limited information on the energy expended to obtain their food or the consequences of their diet and foraging ecology on individual or population fitness.

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Section: Methodsmentioning

confidence: 99%

A re-examination of the relationship between Steller sea lion (Eumetopias jubatus) diet and population trend using data from the Aleutian Islands

et al. 2019

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“…For each sighting of a marked animal, observers recorded the brand with a level of confidence, the sea lions’ age and sex, and the behavior of the individual. A detailed description of the data collection procedures can be found in [ 12 , 24 , 30 ]. For this analysis, only marked females associated with a pup (e.g.…”

Section: Methodsmentioning

confidence: 99%

“…Since 2005, pup counts have been conducted during annual aerial surveys, with some supplemental land- or boat-based counts [ 4 , 10 , 11 ]. The aerial pup count surveys occur between late June and mid-July when pups are approximately 1 month old [ 4 , 12 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

“…The dates of aerial surveys are constrained by a number of factors, including the timing of pupping, weather, flight logistics, and the travel distance to cover the sea lions’ range. Sea lion behavior is also considered because surveys must be conducted after the majority of pups are born, yet before pups begin to spend significant time in the water [ 12 – 15 ]. Mean pupping date for Steller sea lions in Alaska generally occurs between 8 and 12 June, with the first births occurring in mid- to late May [ 12 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

“…Sea lion behavior is also considered because surveys must be conducted after the majority of pups are born, yet before pups begin to spend significant time in the water [ 12 – 15 ]. Mean pupping date for Steller sea lions in Alaska generally occurs between 8 and 12 June, with the first births occurring in mid- to late May [ 12 , 13 ]. Steller sea lion pups begin swimming at 2 to 4 weeks of age and can leave the rookeries with their mothers when 2 to 3 months of age [ 15 – 18 ].…”

Section: Introductionmentioning

confidence: 99%

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Estimating dispersal rates of Steller sea lion (Eumetopias jubatus) mother-pup pairs from a natal rookery using mark-resight data

et al. 2017

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To monitor population trends of Steller sea lions (Eumetopias jubatus) in Alaska, newborn pups are counted during aerial surveys. These surveys are scheduled to occur after the majority of pups are born, but before pups begin to spend significant time in the water. Some studies have reported dispersal of mother-pup pairs away from breeding beaches during the pupping season (July), which may influence survey results. Using a multistate mark-recapture model with state uncertainty, we estimated the amount of dispersal during the pupping season based on observations of permanently marked sea lions. Research was conducted at land-based observation sites on Marmot Island, Alaska, between 2000 and 2013. Both marked adult females with dependent pups and marked pups were observed at two rookery beaches from May to July. Cumulative dispersal rates were minimal (< 1%) prior to the planned start of the aerial survey (23 June) and increased to 11.2% by the planned survey completion date (10 July). The increased cumulative dispersal rate during the remainder of the observation period (end of July) suggests potential bias in surveys that occur beyond 10 July, however surveys past this date are rare (< 10% between 1973 and 2016). As a result, movements of mother-pup pairs during the pupping season are not likely to influence aerial survey estimates.

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Age‐specific reproduction in female Steller sea lions in Southeast Alaska

Hastings,

Jemison,

Pendleton

et al. 2023

Ecology and Evolution

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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.

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A re-examination of the timing of pupping for Steller sea lions Eumetopias jubatus breeding on two islands in Alaska

Cited by 9 publications

References 31 publications

A re-examination of the relationship between Steller sea lion (Eumetopias jubatus) diet and population trend using data from the Aleutian Islands

A re-examination of the relationship between Steller sea lion (Eumetopias jubatus) diet and population trend using data from the Aleutian Islands

Estimating dispersal rates of Steller sea lion (Eumetopias jubatus) mother-pup pairs from a natal rookery using mark-resight data

Age‐specific reproduction in female Steller sea lions in Southeast Alaska

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