View From Below: Inferring Behavior and Physiology of Southern Ocean Marine Predators From Dive Telemetry

Abstract

Air-breathing marine animals, such as seals and seabirds, undertake a special form of central-place foraging as they must obtain their food at depth yet return to the surface to breathe. While telemetry technologies have advanced our understanding of the foraging behavior and physiology of these marine predators, the proximate and ultimate influences controlling the diving behavior of individuals are still poorly understood. Over time, a wide variety of analytical approaches have been developed for dive data obtained via telemetry, making comparative studies and syntheses difficult even amongst closely-related species. Here we review publications using dive telemetry for 24 species (marine mammals and seabirds) in the Southern Ocean in the last decade (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016). We determine the key questions asked, and examine how through the deployment of data loggers these questions are able to be answered. As part of this process we describe the measured and derived dive variables that have been used to make inferences about diving behavior, foraging, and physiology. Adopting a question-driven orientation highlights the benefits of a standardized approach for comparative analyses and the development of models. Ultimately, this should promote robust treatment of increasingly complex data streams, improved alignment across diverse research groups, and also pave the way for more integrative multi-species meta-analyses. Finally, we discuss key emergent areas in which dive telemetry data are being upscaled and more quantitatively integrated with movement and demographic information to link to population level consequences.

Diel and lunar variation in diving behavior of rough‐toothed dolphins (Steno bredanensis) off Kauaʻi, Hawaiʻi

“…Without adequate gut content analyses, we cannot confidently say whether rough‐toothed dolphins are switching prey across temporal cycles and what the drivers for this would be if they were. Since the species of the mesopelagic boundary community are fairly well documented (Clark, 1980; Reid et al, 1991), assessing their presence in future rough‐toothed dolphin diet studies, possibly through genetic analyses of fecal samples (e.g., Ford et al, 2016), may provide further data on whether they are feeding on mesopelagic prey in the deep scattering layer at dusk and night (Reid et al, 1991; Roncon et al, 2018). Identifying prey could also help determine if the abundance, caloric differences, or catchability of different prey may make the investment in diving deeper worthwhile.…”

“…Understanding factors that influence species' spatial ecology, particularly movement patterns, can provide insight into habitat use and foraging patterns (Jonsen et al, 2019; Roncon et al, 2018). Predators often track their prey's behavior to maximize foraging opportunities while expending as little energy as possible.…”

Track and dive-based movement metrics do not predict the number of prey encountered by a marine predator

“…In addition, high-resolution data requires physical recovery as the data is generally too large to be transferred through satellite communications [ 12 – 14 ]. Consequently, researchers often rely on lower-resolution data, such as summarized dive profiles [ 15 ], from which they use movement proxies to infer feeding behavior [reviewed in 7 , 16 ].…”

Clustering and classification of vertical movement profiles for ecological inference of behavior

“…Movement in the vertical dimension, which more rapidly exposes animals to changes in trophic and physical conditions (particularly in marine ecosystems; Shepard et al, 2013; Steele, 1989), has received less attention. The causes and consequences of various classes of vertical movements are often less understood than horizontal movement categories, especially for remote portions of the migratory path (Hochscheid, 2014; Roncon et al, 2018). For air‐breathing marine animals that utilize both vertical and horizontal dimensions for signature behaviors such as foraging and transiting, ecological trade‐offs have important implications, where dive duration and depth balance respiratory demands against energy gains (Hochscheid, 2014; Thomson et al, 2011).…”