Modelling pinniped abundance and distribution by combining counts at T terrestrial sites and in-water sightings

Pinnipeds are commonly monitored using aerial photographic surveys at land- or ice-based sites, where animals come ashore for resting, pupping, molting, and to avoid predators. Although these counts form the basis for monitoring population change over time, they do not provide information regarding where animals occur in the water, which is often of management and conservation interest. In this study, we developed a hierarchical model that links counts of pinnipeds at terrestrial sites to sightings-at-sea and estimates abundance, spatial distribution, and the proportion of time spent on land (attendance probability). The structure of the model also allows for the inclusion of predictors that may explain variation in ecological and observation processes. We applied the model to Steller sea lions (Eumetopias jubatus) in Glacier Bay, Alaska using counts of sea lions from aerial photographic surveys and opportunistic in-water sightings from vessel surveys. Glacier Bay provided an ideal test and application of the model because data are available on attendance probability based on long-term monitoring. We found that occurrence in the water was positively related to proximity to terrestrial sites, as would be expected for a species that engages in central-place foraging. The proportion of sea lions in attendance at terrestrial sites and overall abundance estimates were consistent with reports from the literature and monitoring programs. The model we describe has benefit and utility for park managers who wish to better understand the overlap between pinnipeds and visitors, and the framework that we present has potential for application across a variety of study systems and taxa

Linking Wolf Diet to Changes in Marine and Terrestrial Prey Abundance

Since most wolf (Canis lupus) diet studies have been conducted in inland ecosystems, comparatively few data are available on diets of wolves in coastal systems. We investigated the diet of wolves in Glacier Bay, Alaska, from 12 May to 28 June in both 2010 and 2011. Although we identified 12 different prey species, including birds and small to medium-sized mammals, in wolf scats, moose (Alces alces) was the most frequent food item, observed in 80% of all scats. In contrast, a study conducted in 1993 in an area 37 km away found harbor seal (Phoca vitulina richardii) in 41% of wolf scats. Although we cannot account for differences in sampling design between the two studies, wolf diets may have changed between the two time periods.Puisque la plupart des études sur le régime alimentaire des loups (Canis lupus) ont été réalisées dans des écosystèmes situés à l’intérieur des terres, relativement peu de données existent sur le régime alimentaire des loups évoluant dans les environnements côtiers. Nous avons étudié l’alimentation des loups de Glacier Bay, en Alaska, du 12 mai au 28 juin 2010 et 2011. Bien que nous ayons retrouvé 12 proies différentes, y compris des espèces aviaires et des mammifères de taille petite ou de taille moyenne dans les déjections de loups, l’aliment le plus fréquemment rencontré, dans une mesure de 80 %, a été l’original, aussi appelé élan (Alces alces). Par contraste, une étude effectuée en 1993 dans une zone située à 37 kilomètres de distance a permis de découvrir du phoque commun (Phoca vitulina richardii) dans 41 % des déjections de loups. Bien que nous ne soyons pas en mesure de prendre en compte les différences d´échantillonnage entre les deux études, il est possible que le régime alimentaire des loups ait changé entre ces deux périodes.Большинство исследований рациона волка (Canis lupus) проводилось на внутриматериковых территориях, в то время как имеется сравнительно небольшое количество данных по рациону волка в прибрежных экосистемах. Ежегодно с 12 мая по 28 июня 2010-2011 гг. нашей группой проводились исследования рациона волков в бухте Глейшер-Бей, Аляска. Несмотря на то, что нами было определено 12 различных видов, используемых волками в качестве добычи, включая птиц, а также мелких и средних млекопитающих, останки лося (Alces alces) встречались в 80% экскрементов волков, указывая на то, что данный вид является наиболее частым пищевым объектом волка.В отличие от данных результатов, эксперимент, проведенный в 1993 г. на участке, удаленном от нашего на 37 км, обнаружил наличие останков тюленя (Phoca vitulina richardii) в 41% экскрементов волков. Несмотря на то, что мы не можем объяснить различия в выборке по каждому из исследований, их результаты указывают на то, что в период между двумя исследованиями в рационе волков могли произойти изменения

Linking marine predator diving behavior to local prey fields in contrasting habitats in a subarctic glacial fjord

Foraging theory predicts that animals will adjust their foraging behavior in order to maximize net energy intake and that trade-offs may exist that can influence their behavior. Although substantial advances have been made with respect to the foraging ecology of large marine predators, there is still a limited understanding of how predators respond to temporal and spatial variability in prey resources, primarily due to a lack of empirical studies that quantify foraging and diving behavior concurrently with characteristics of prey fields. Such information is important because changes in prey availability can influence the foraging success and ultimately fitness of marine predators. We assessed the diving behavior of juvenile female harbor seals (Phoca vitulina richardii) and prey fields near glacial ice and terrestrial haulout sites in Glacier Bay (58°40′N, −136°05′W), Alaska. Harbor seals captured at glacial ice sites dived deeper, had longer dive durations, lower percent bottom time, and generally traveled further to forage. The increased diving effort for seals from the glacial ice site corresponded to lower prey densities and prey at deeper depths at the glacial ice site. In contrast, seals captured at terrestrial sites dived shallower, had shorter dive durations, higher percent bottom time, and traveled shorter distances to access foraging areas with much higher prey densities at shallower depths. The increased diving effort for seals from glacial ice sites suggests that the lower relative availability of prey may be offset by other factors, such as the stability of the glacial ice as a resting platform and as a refuge from predation. We provide evidence of differences in prey accessibility for seals associated with glacial ice and terrestrial habitats and suggest that seals may balance trade-offs between the costs and benefits of using these habitats

Quantification and analysis of icebergs in a tidewater glacier fjord using an object-based approach

Tidewater glaciers are glaciers that terminate in, and calve icebergs into, the ocean. In addition to the influence that tidewater glaciers have on physical and chemical oceanography, floating icebergs serve as habitat for marine animals such as harbor seals (Phoca vitulina richardii). The availability and spatial distribution of glacier ice in the fjords is likely a key environmental variable that influences the abundance and distribution of selected marine mammals; however, the amount of ice and the fine-scale characteristics of ice in fjords have not been systematically quantified. Given the predicted changes in glacier habitat, there is a need for the development of methods that could be broadly applied to quantify changes in available ice habitat in tidewater glacier fjords. We present a case study to describe a novel method that uses object-based image analysis (OBIA) to classify floating glacier ice in a tidewater glacier fjord from high-resolution aerial digital imagery. Our objectives were to (i) develop workflows and rule sets to classify high spatial resolution airborne imagery of floating glacier ice; (ii) quantify the amount and fine-scale characteristics of floating glacier ice; (iii) and develop processes for automating the object-based analysis of floating glacier ice for large number of images from a representative survey day during June 2007 in Johns Hopkins Inlet (JHI), a tidewater glacier fjord in Glacier Bay National Park, southeastern Alaska. On 18 June 2007, JHI was comprised of brash ice ([Formula: see text] = 45.2%, SD = 41.5%), water ([Formula: see text] = 52.7%, SD = 42.3%), and icebergs ([Formula: see text] = 2.1%, SD = 1.4%). Average iceberg size per scene was 5.7 m2 (SD = 2.6 m2). We estimate the total area (± uncertainty) of iceberg habitat in the fjord to be 455,400 ± 123,000 m2. The method works well for classifying icebergs across scenes (classification accuracy of 75.6%); the largest classification errors occur in areas with densely-packed ice, low contrast between neighboring ice cover, or dark or sediment-covered ice, where icebergs may be misclassified as brash ice about 20% of the time. OBIA is a powerful image classification tool, and the method we present could be adapted and applied to other ice habitats, such as sea ice, to assess changes in ice characteristics and availability

Key Questions in Marine Megafauna Movement Ecology

It is a golden age for animal movement studies and so an opportune time to assess priorities for future work. We assembled 40 experts to identify key questions in this field, focussing on marine megafauna, which include a broad range of birds, mammals, reptiles, and fish. Research on these taxa has both underpinned many of the recent technical developments and led to fundamental discoveries in the field. We show that the questions have broad applicability to other taxa, including terrestrial animals, flying insects, and swimming invertebrates, and, as such, this exercise provides a useful roadmap for targeted deployments and data syntheses that should advance the field of movement ecolog

Key Questions in Marine Megafauna Movement Ecology

It is a golden age for animal movement studies and so an opportune time to assess priorities for future work. We assembled 40 experts to identify key questions in this field, focussing on marine megafauna, which include a broad range of birds, mammals, reptiles, and fish. Research on these taxa has both underpinned many of the recent technical developments and led to fundamental discoveries in the field. We show that the questions have broad applicability to other taxa, including terrestrial animals, flying insects, and swimming invertebrates, and, as such, this exercise provides a useful roadmap for targeted deployments and data syntheses that should advance the field of movement ecology