Stability in the Proportion of Harbor Seals Hauled Out Under Locally Ideal Conditions

Simpkins, Michael A.; Withrow, David E.; Cesarone, Jack C.; Boveng, Peter L.

doi:10.1111/j.1748-7692.2003.tb01130.x

Cited by 44 publications

(74 citation statements)

References 26 publications

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“…For estimation of population trends, this issue has usually been addressed by either standardizing survey conditions to minimize differences in haul-out proportions (Jacobs and Terhune 2000; Simpkins et al 2003b) or adjusting for differences in conditions by incorporating appropriate covariates in models of the counts (Calkins et al 1999;Mathews and Pendleton 2006). Estimation of population size generally requires explicit estimates of the proportion of the population hauled out during the survey.…”

Section: Discussionmentioning

confidence: 99%

“…Factors such as time of day, weather, and other environmental conditions have been related to haul-out behavior of various pinnipeds (Simpkins et al 2003b;Bengtson and Cameron 2004;Frost et al 2004;Reder et al 2004;Hayward et al 2005). Walruses using terrestrial haul-out sites spend about 65%-85% of their time in the water (Born and Knutsen 1997;Gjertz et al 2001;Jay et al 2001;Born et al 2005;Acquarone et al 2006;Lydersen et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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Modeling haul-out behavior of walruses in Bering Sea ice

et al. 2009

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Understanding haul-out behavior of ice-associated pinnipeds is essential for designing and interpreting population surveys and for assessing effects of potential changes in their ice environments. We used satellite-linked transmitters to obtain sequential information about location and haul-out state for Pacific walruses, Odobenus rosmarus divergens (Illiger, 1815), in the Bering Sea during April of 2004April of , 2005April of , and 2006. We used these data in a generalized mixed model of haul-out bout durations and a hierarchical Bayesian model of haul-out probabilities to assess factors related to walrus haulout behavior, and provide the first predictive model of walrus haul-out behavior in sea ice habitat. Average haul-out bout duration was 9 h, but durations of haul-out bouts tended to increase with durations of preceding in-water bouts. On average, tagged walruses spent only about 17% of their time hauled out on sea ice. Probability of being hauled out decreased with wind speed, increased with temperature, and followed a diurnal cycle with the highest values in the evening. Our haul-out probability model can be used to estimate the proportion of the population that is unavailable for detection in spring surveys of Pacific walruses on sea ice.Résumé : Il est essentiel de comprendre le comportement d'échouerie chez les pinnipèdes associés aux glaces pour planifier et interpréter les inventaires démographiques et pour évaluer les effets des changements potentiels dans leurs environnements glacials. Nous avons utilisé des émetteurs reliés aux satellites pour obtenir des informations séquentielles sur la position et l'état d'échouerie de morses du Pacifique (Odobenus rosmarus divergens (Illiger, 1815)) dans la mer de Béring en avril 2004de Béring en avril , 2005de Béring en avril et 2006. Ces données utilisées dans un modèle de mélange généralisé de durée des épisodes d'échouerie et un modèle hiérarchique bayésien des probabilités d'échouerie nous servent à évaluer les facteurs reliés aux comportement d'échouerie chez les morses et à mettre au point le premier modèle prédictif sur le comportement d'échouerie chez les morses dans un habitat de glace de mer. Les morses marqués passent en moyenne 9 h par épisode d'échouerie, mais les durées des périodes d'échouerie ont tendance à s'allonger en fonction de la durée des périodes précé-dentes passées en mer. Globalement, les morses marqués passent en moyenne seulement 17 % de leur temps en échouerie sur la glace de mer. La probabilité d'échouerie diminue en fonction de la vitesse du vent, augmente avec la température et suit un cycle journalier avec un maximum en soirée. Notre modèle de probabilité des échoueries peut servir à estimer la proportion de la population qui est à l'abri de la détection lors des inventaires printaniers des morses du Pacifique sur la glace de mer.[Traduit par la Rédaction]

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling haul-out behavior of walruses in Bering Sea ice

et al. 2009

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“…Thus alternative attachment methods that collect information during this period must be considered, e.g. attaching telemetry devices to the flipper (Huber et al, 2001;Simpkins et al, 2003) or by means of an implantable tag (Horning and Hill, 2005;Lander et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

“…Harbour seals show a degree of site fidelity (Yochem et al, 1987;Thompson, 1989;, while marking studies have shown that seals use different haul-out sites throughout the year (Brown and Mate, 1983;Thompson, 1989;Thompson et al, 1996;Simpkins et al, 2003). High levels of site fidelity would support the designation of protected areas for harbour seals at haul-out sites.…”

Section: Haul-out Patterns and Site Usagementioning

confidence: 93%

“…Harbour seal haul-out behaviour varies according to life history; i.e. the timing of reproduction and moulting according to the sex-and age-class of the population (Thompson and Rothery, 1987;Ha¨rko¨nen et al, 1999;Daniel et al, 2003), and according to environmental states, which include tidal cycles (Schneider and Payne, 1983;Watts, 1996;Simpkins et al, 2003), time of day (Thompson, 1989;Frost et al, 1999;Boveng et al, 2003), season (Thompson, 1989) and weather conditions (Godsell, 1988;Kovacs et al, 1990;Grellier et al, 1996). These factors are therefore also important for assessing the significance of observed changes in counts.…”

Section: Introductionmentioning

confidence: 98%

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Harbour seal movements and haul‐out patterns: implications for monitoring and management

Cunningham¹,

Baxter²,

Boyd³

et al. 2008

Aquatic Conservation

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ABSTRACT1. Compliance with conservation legislation requires knowledge on the behaviour, abundance and distribution of protected species. Seal life history is characterized by a combination of marine foraging and a requirement to haul out on a solid substrate for reproduction and moulting. Thus understanding the use of haul out sites, where seals are counted, as well as their at-sea movements is crucial for designing effective monitoring and management plans.2. This study used satellite transmitters deployed on 24 harbour seals in western Scotland to examine movements and haul-out patterns.3. The proportion of time harbour seals spent hauled out (daily means of between 11 and 27%) varied spatially, temporally and according to sex. The mean haul-out duration was 5 h, with a maximum of over 24 h.4. Patterns of movement were observed at two geographical scales; while some seals travelled over 100 km, 50% of trips were within 25 km of a haul-out site. These patterns are important for the identification of a marine component to designated protected areas for the species.5. On average seals returned to the haul-out sites they last used during 40% of trips, indicating a degree of site fidelity, though there was wide variation between different haul-out sites (range 0% to >75%).6. Low fidelity haul-out sites could form a network of land-based protected areas, while high fidelity sites might form appropriate management units.

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Rescaling of aerial survey data with information from small numbers of telemetry tags to estimate the size of a declining harbour seal population

Lonergan

Duck

Moss

et al. 2012

Aquatic Conservation

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1. Estimates of both absolute abundance and trends in abundance are among the most basic pieces of information required for planning the conservation and management of wildlife populations. They are important for understanding both the current situation of species and potential risks to them.2. This study presents estimates of the size of the harbour seal (Phoca vitulina) population associated with the Orkney Islands, a part of northern Scotland that used to contain one of the largest concentrations of this species in Europe.3. The numbers of animals counted during aerial surveys of this area have decreased substantially over the period 2001-2010. ARGOS transmitters attached to flipper tags were used to rescale the counts into estimates of abundance and to confirm the rate of decline of this population.4. Females hauled out for more of the survey window (0.84; bootstrap 95% CI: 0.63-0.99) than males (0.61; bootstrap 95% CI: 0.34-0.86). The animals hauled out less during weekends (0.57; bootstrap 95% CI: 0.40-0.74) than during the week (0.76; bootstrap 95% CI: 0.58-0.91).5. The sex-ratios of this population is unknown. Assuming it was close to 1:1, then there were around 3586 (bootstrap 95% CI: 2970-4542) harbour seals in Orkney in 2010. A female-skewed sex-ratio would reduce the population estimate, and a changing sex-ratio might mean the counts understate the real decline.6. The mean annual rate of decline in the Orkney population of harbour seals, over the period 2001-2010, is estimated at 13% (95% CI: 10.8-14.8). Similar data for Arisaig, on the west coast of Scotland, shows an increase of around 2% (95% CI: 1.5-2.4) and, assuming an equal sex-ratio, 923 animals (95% CI: 765-1169) in 2007.

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Stability in the Proportion of Harbor Seals Hauled Out Under Locally Ideal Conditions

Cited by 44 publications

References 26 publications

Modeling haul-out behavior of walruses in Bering Sea ice

Modeling haul-out behavior of walruses in Bering Sea ice

Harbour seal movements and haul‐out patterns: implications for monitoring and management

Rescaling of aerial survey data with information from small numbers of telemetry tags to estimate the size of a declining harbour seal population

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