Divergent migration routes reveal contrasting energy-minimization strategies to deal with differing resource predictability

Shuert, Courtney R.; Hussey, Nigel E.; Marcoux, Marianne; Heide‐Jørgensen, Mads Peter; Dietz, Runé; Auger‐Méthé, Marie

doi:10.1186/s40462-023-00397-y

Cited by 3 publications

(1 citation statement)

References 117 publications

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“…The evolution of seasonal migration has been hypothesized as primarily driven by maintenance of site fidelity to advantageous breeding locations (Winger et al, 2019). Such behaviour is notable in Arctic marine mammals, who display high seasonal site fidelity, migrating between habitats based on sea ice conditions (Tynan & DeMaster, 1997;Hauser et al, 2017;Shuert et al, 2022). Females can show higher spatial fidelity than males (e.g., Lone et al, 2013), potentially to garner energetic and reproductive benefits for gestation or care of young (Gauthier, 1990).…”

Section: Introductionmentioning

confidence: 99%

Maternal den site fidelity of polar bears in western Hudson Bay

Klappstein,

McGeachy,

Pilfold

et al. 2024

Preprint

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Seasonal migrations allow to access temporally varying resources and individuals may show fidelity to specific locations. Polar bears (Ursus maritimus) are a sea ice dependent species that migrate between marine and terrestrial habitats, the latter being important for parturition and early cub rearing. However, fidelity to maternity den sites is poorly understood. We assessed polar bear maternal den site fidelity of the Western Hudson Bay subpopulation in Manitoba, Canada. Using capture and telemetry data collected between 1979-2018, we examined site fidelity from 188 maternity den locations from 78 individuals. We calculated within-individual inter-year distances between dens, and compared these to between-individual distances via non-parametric bootstrapping. We used generalised additive models to assess how maternal age, years between denning events, and sea ice conditions affected site fidelity. We found some evidence of site fidelity, as within-individual inter-year distances were smaller than between-individual den distances by approximately 18.5 km. As time between captures increased, inter-den distances also increased (ranging from approximately 25 km to 55 km), but no other variables significantly affected fidelity. Our findings suggest that western Hudson Bay polar bears show a moderate amount of fidelity to denning areas, but not necessarily to specific sites.

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Section: Introductionmentioning

confidence: 99%

Maternal den site fidelity of polar bears in western Hudson Bay

Klappstein,

McGeachy,

Pilfold

et al. 2024

Preprint

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Satellite tracking of American Woodcock reveals a gradient of migration strategies

Clements,

Berigan,

Fish

et al. 2024

Ornithology

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Diversity in behavior is important for migratory birds in adapting to dynamic environmental and habitat conditions and responding to global change. Migratory behavior can be described by a variety of factors that comprise migration strategies. We characterized variation in migration strategies in American Woodcock (Scolopax minor), a migratory gamebird experiencing long-term population decline, using GPS data from ~300 individuals tracked throughout eastern North America. We classified woodcock migratory movements using a step-length threshold, and calculated characteristics of migration related to distance, path, and stopping events. We then used principal components analysis (PCA) to ordinate variation in migration characteristics along axes that explained different fundamental aspects of migration, and tested effects of body condition, age-sex class, and starting and ending location on PCA results. The PCA did not show evidence for clustering, suggesting a lack of discrete strategies among groups of individuals; rather, woodcock migration strategies existed along continuous gradients driven most heavily by metrics associated with migration distance and duration, departure timing, and stopping behavior. Body condition did not explain variation in migration strategy during the fall or spring, but during spring adult males and young females differed in some characteristics related to migration distance and duration. Starting and ending latitude and longitude, particularly the northernmost point of migration, explained up to 61% of the variation in any one axis of migration strategy. Our results reveal gradients in migration behavior of woodcock, and this variability should increase the resilience of woodcock to future anthropogenic landscape and climate change.

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Do beluga whales truly migrate? Testing a key trait of the classical migration syndrome

Storrie,

Loseto,

Sutherland

et al. 2023

Mov Ecol

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Background Migration enables organisms to access resources in separate regions that have predictable but asynchronous spatiotemporal variability in habitat quality. The classical migration syndrome is defined by key traits including directionally persistent long-distance movements during which maintenance activities are suppressed. But recently, seasonal round-trip movements have frequently been considered to constitute migration irrespective of the traits required to meet this movement type, conflating common outcomes with common traits required for a mechanistic understanding of long-distance movements. We aimed to test whether a cetacean ceases foraging during so-called migratory movements, conforming to a trait that defines classical migration. Methods We used location and dive data collected by satellite tags deployed on beluga whales (Delphinapterus leucas) from the Eastern Beaufort Sea population, which undertake long-distance directed movements between summer and winter areas. To identify phases of directionally persistent travel, behavioural states (area-restricted search, ARS; or Transit) were decoded using a hidden-Markov model, based on step length and turning angle. Established dive profiles were then used as a proxy for foraging, to test the hypothesis that belugas cease foraging during these long-distance transiting movements, i.e., they suppress maintenance activities. Results Belugas principally made directed horizontal movements when moving between summer and winter residency areas, remaining in a Transit state for an average of 75.4% (range = 58.5–87.2%) of the time. All individuals, however, exhibited persistent foraging during Transit movements (75.8% of hours decoded as the Transit state had ≥ 1 foraging dive). These data indicate that belugas actively search for and/or respond to resources during these long-distance movements that are typically called a migration. Conclusions The long-distance movements of belugas do not conform to the traits defining the classical migration syndrome, but instead have characteristics of both migratory and nomadic behaviour, which may prove adaptive in the face of unpredictable environmental change. Such patterns are likely present in other cetaceans that have been labeled as migratory. Examination of not only horizontal movement state, but also the vertical behaviour of aquatic animals during directed movements is essential for identifying whether a species exhibits traits of the classical migration syndrome or another long-distance movement strategy, enabling improved ecological inference.

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Divergent migration routes reveal contrasting energy-minimization strategies to deal with differing resource predictability

Cited by 3 publications

References 117 publications

Maternal den site fidelity of polar bears in western Hudson Bay

Maternal den site fidelity of polar bears in western Hudson Bay

Satellite tracking of American Woodcock reveals a gradient of migration strategies

Do beluga whales truly migrate? Testing a key trait of the classical migration syndrome

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