Climate-scale hydrographic features related to foraging success in a capital breeder, the northern elephant seal Mirounga angustirostris

Abstract

In marine ecosystems, physical and biological processes act at multiple temporal and spatial scales to influence the distribution of prey species and subsequently habitat selection of foraging apex predators. Understanding how apex predators may respond to climate changes requires knowledge of habitat selection in relation to measures of foraging success at spatio-temporal scales relevant to the question and analytical approach. In this study, we used satellite telemetry from 75 adult female northern elephant seals Mirounga angustirostris, coupled with point measures of foraging success (energy gain), to examine habitat selection at large temporal and spatial scales. The main hydrographic ecoregion used on the post-moult (PM) migration was the Transition Zone, while on the post-breeding (PB) migration, females focused on the Subarctic Gyre. Characteristics of arearestricted search (ARS) behaviours, as determined by the fractal landscape method (such as time spent in ARS, total distance travelled in ARS and number of ARS) also differed significantly between the PM and PB migrations. Underlying differences in prey composition and/or distribution may drive the differences seen in searching behaviour and foraging success of elephant seals at large scales. Despite these differences, seals showed comparable levels of foraging success across both migrations and in all ecoregions. Foraging success was notably greater than measured in previous studies. These results highlight the benefits of a capital breeding strategy to a relatively slow-moving, large vertebrate predator allowing individuals to exploit large areas of the heterogeneous North Pacific.

Large-scale movements and high-use areas of western Pacific leatherback turtles,Dermochelys coriacea

“…), tunas (Thunnus spp. ), swordfish (Xiphias gladius), and elephant seals (Mirounga angustirostris) (Polovina et al 2000, Hyrenbach et al 2002, Seki et al 2002, Simmons et al 2010. Four of the six leatherback turtles from PBI that moved towards the KE engaged in ARS behavior, and only one of the four tracks was more than 12 months duration, so inference for this region is limited.…”

“…Telemetry studies have provided insight into the movements of diverse marine predators including sharks, tunas, pinnipeds, whales, seabirds, and turtles (Shaffer et al 2006, Bailey et al 2009, Walli et al 2009, Jorgensen et al 2010, Simmons et al 2010, Witt et al 2011. In some cases, the results of such studies have contributed to the development of conservation strategies (e.g., Howell et al 2008).…”

Development of an animal-borne “sonar tag” for quantifying prey availability: test deployments on northern elephant seals

“…In the case of northern and southern elephant seals (Mirounga angustirostris and Mirounga leonina), for instance, small-scale changes in movement and diving behaviors have been related to changes in oceanographic variables and, presumably, changes in prey availability and perhaps prey type. Indirect metrics of foraging have included measurements of surface movements (e.g., transit rate, indices of arearestricted search) and dive characteristics (e.g., frequency of "drift dives" thought to be postprandial), often coupled to estimates of energy gain based on pre-and post-trip measurements of body composition [3,9,10,14,[17][18][19][20]. Jaw motion events recorded by accelerometers have also been used as an index of feeding, with initial deployments on adult female northern elephant seals suggesting that feeding occurred during the majority of dives, including during dive types and movement patterns believed previously not to be associated with feeding [21].…”

“…Recent developments in electronic tagging technologies have provided unprecedented insight into the movements and behavior of a variety of large marine predators at spatial and temporal scales previously inaccessible via traditional sampling techniques [1][2][3][4][5][6]. Examining the relationships of movements and behavioral decisions revealed by such technologies with the animal's physical and biological environment is an active area of investigation [7,8].…”

Biologging technologies: new tools for conservation. Introduction

“…Four examples in this Theme Section, from pinnipeds, a reptile, and a fish, demonstrate the utility of biologging to characterize ocean habitat and obtain critical subsurface ocean data. Simmons et al (2010) …”