Variation of annual apparent survival and detection rates with age, year and individual identity in male Weddell seals (<scp><i>Leptonychotes weddellii</i></scp>) from long‐term mark‐recapture data

Brusa, Jamie L.; Rotella, Jay J.; Garrott, Robert A.; Paterson, J. Terrill; Link, William A.

doi:10.1002/1438-390x.12036

Cited by 5 publications

(8 citation statements)

References 123 publications

(182 reference statements)

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“…Part of the success of our innovative approach to study WESE populations was due to several unique aspects of their life history and because ground validation in Erebus Bay was possible [e.g., (47)(48)(49)(50)]. WESE females raise pups on annually predicable fast ice during austral spring (30,51) and are mixed-capital breeders, meaning they remain visible on the ice for long periods (31,52) and so do not stray away from their haul-out locations (53,54) during November.…”

Section: Discussionmentioning

confidence: 99%

Insights from the first global population estimate of Weddell seals in Antarctica

et al. 2021

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The Weddell seal is one of the best-studied marine mammals in the world, owing to a multidecadal demographic effort in the southernmost part of its range. Despite their occurrence around the Antarctic coastline, we know little about larger scale patterns in distribution, population size, or structure. We combined high-resolution satellite imagery from 2011, crowd-sourcing, and habitat modeling to report the first global population estimate for the species and environmental factors that influence its distribution. We estimated ~202,000 (95% confidence interval: 85,345 to 523,140) sub-adult and adult female seals, with proximate ocean depth and fast-ice variables as factors explaining spatial prevalence. Distances to penguin colonies were associated with seal presence, but only emperor penguin population size had a strong negative relationship. The small, estimated population size relative to previous estimates and the seals' nexus with trophic competitors indicates that a community ecology approach is required in efforts to monitor the Southern Ocean ecosystem.

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Section: Discussionmentioning

confidence: 99%

Insights from the first global population estimate of Weddell seals in Antarctica

et al. 2021

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“…For example, generalised linear mixed models and capture–mark–recapture analyses typically impose restrictions on the sequences of vital rates that individuals can take throughout their life (e.g. Badger et al, 2020; Brusa et al, 2020; Moyes et al, 2011). Even under dynamic condition, individuals are constrained in their future vital rate paths because the heterogeneity is incorporated using covariates that depend on the individual's vital rate history.…”

Section: Discussionmentioning

confidence: 99%

Demystifying individual heterogeneity

2021

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Among‐individual variation in vital rates, such as mortality and birth rates, exists in nearly all populations. Recent studies suggest that this individual heterogeneity produces substantial life‐history and fitness differences among individuals, which in turn scale up to influence population dynamics. However, our ability to understand the consequences of individual heterogeneity is limited by inconsistencies across conceptual frameworks in the field. Studies of individual heterogeneity remain filled with contradicting and ambiguous terminology that introduces risks of misunderstandings, conflicting models and unreliable conclusions. Here, we synthesise the existing literature into a single and comparatively straightforward framework with explicit terminology and definitions. This work introduces a distinction between potential vital rates and realised vital rates to develop a coherent framework that maps directly onto mathematical models of individual heterogeneity. We suggest the terms “fixed condition” and “dynamic condition” be used to distinguish potential vital rates that are permanent from those that can change throughout an individual's life. To illustrate, we connect the framework to quantitative genetics models and to common classes of statistical models used to infer individual heterogeneity. We also develop a population projection matrix model that provides an example of how our definitions are translated into precise quantitative terms.

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“…The uncertainty associated with our model selection results provides unclear information regarding the spatial behavior of the males >20 years of age. Additional spatial data for these older males are necessary to better explain spatial patterns of this age group, but few males survive to reach 20 years of age or older (Brusa et al, 2020). Our results suggest that the variation in the number of reproductive‐age female neighbors surrounding a male in Erebus Bay during the breeding season was greater across individuals than across ages.…”

Section: Discussionmentioning

confidence: 99%

Influence of age and individual identity in the use of breeding colony habitat by male Weddell seals in Erebus Bay, Antarctica

Brusa

Rotella

Garrott

2021

Marine Mammal Science

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Male–male contest behavior can contribute to spatial distributions of male pinnipeds during breeding seasons. To maximize breeding opportunities, the most competitive males would be expected to be surrounded by the highest numbers of reproductive‐age females. As information regarding fine‐scale spatial ecology of Weddell seals is lacking, we performed an exploratory study using kernel density analyses to evaluate age‐specific habitat use of male Weddell seals in Erebus Bay, Antarctica. Additionally, we investigated the relationship between age and number of surrounding reproductive‐age females using a competing set of regression models in a Bayesian framework that considered different functional forms of age while incorporating individual heterogeneity. As male adult Weddell seals aged, to at least 20 years, they were more likely to be found in areas associated with the greatest densities of reproductive‐age females, but individual heterogeneity also influenced the number of reproductive‐age female neighbors. The youngest males tended to haul out in offshore areas associated with better hunting, and older males tended to settle in more nearshore areas associated with more pup production. Our findings from this preliminary investigation indicate that male Weddell seal spatial behavior during the breeding season varies with age and individual and might be related to reproductive activity.

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Variation of annual apparent survival and detection rates with age, year and individual identity in male Weddell seals (Leptonychotes weddellii) from long‐term mark‐recapture data

Cited by 5 publications

References 123 publications

Insights from the first global population estimate of Weddell seals in Antarctica

Insights from the first global population estimate of Weddell seals in Antarctica

Demystifying individual heterogeneity

Influence of age and individual identity in the use of breeding colony habitat by male Weddell seals in Erebus Bay, Antarctica

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