Processing of acceleration and dive data on‐board satellite relay tags to investigate diving and foraging behaviour in free‐ranging marine predators

Abstract

Biologging technologies are changing the way in which the marine environment is observed and monitored. However, because device retrieval is typically required to access the high‐resolution data they collect, their use is generally restricted to those animals that predictably return to land. Data abstraction and transmission techniques aim to address this, although currently these are limited in scope and do not incorporate, for example, acceleration measurements which can quantify animal behaviours and movement patterns over fine‐scales.In this study, we present a new method for the collection, abstraction and transmission of accelerometer data from free‐ranging marine predators via the Argos satellite system. We test run the technique on 20 juvenile southern elephant seals Mirounga leonina from the Kerguelen Islands during their first months at sea following weaning. Using retrieved archival data from nine individuals that returned to the colony, we compare and validate abstracted transmissions against outputs from established accelerometer processing procedures.Abstracted transmissions included estimates, across five segments of a dive profile, of time spent in prey catch attempt (PrCA) behaviours, swimming effort and pitch. These were then summarised and compared to archival outputs across three dive phases: descent, bottom and ascent. Correlations between the two datasets were variable but generally good (dependent on dive phase, marginal R 2 values of between .45 and .6 to >.9) and consistent between individuals. Transmitted estimates of PrCA behaviours and swimming effort were positively biased to those from archival processing.Data from this study represent some of the first remotely transmitted quantifications from accelerometers. The methods presented and analysed can be used to provide novel insight towards the behaviours and movements of free‐ranging marine predators, such as juvenile southern elephant seals, from whom logger retrieval is challenging. Future applications could however benefit from some adaption, particularly to reduce positive bias in transmitted PrCA behaviours and swimming effort, for which this study provides useful insight.

High mortality rates in a juvenile free‐ranging marine predator and links to dive and forage ability

“…Surface intervals were scaled by dive duration, as were times spent in PrCA behaviors. Descent, bottom, and ascent dive phases were identified following Cox et al (). For each dive performed by each individual, the bottom duration scaled by the total dive duration was taken.…”

“…Recent advances in bio-logging technologies have substantially increased our ability to observe the fine-scale behaviors, movements, and physiology of marine species (Hart & Hyrenbach, 2009;Hazen et al, 2012;Volpov et al, 2015). Moreover, new methods in data abstraction and transmission mean device retrieval is no longer obligatory to obtain the information these instruments record (Cox et al, 2018). For pinniped species, it is now possible to remotely track a suite of dive and foraging metrics such as prey catch attempts (PrCA), swimming effort, dive shape, and surface interval (Cox et al, 2018;Heerah, Cox, Blevin, Guinet, & Charrassin, 2019;Photopoulou, Lovell, Fedak, Thomas, & Matthiopoulos, 2015).…”

“…Moreover, new methods in data abstraction and transmission mean device retrieval is no longer obligatory to obtain the information these instruments record (Cox et al, 2018). For pinniped species, it is now possible to remotely track a suite of dive and foraging metrics such as prey catch attempts (PrCA), swimming effort, dive shape, and surface interval (Cox et al, 2018;Heerah, Cox, Blevin, Guinet, & Charrassin, 2019;Photopoulou, Lovell, Fedak, Thomas, & Matthiopoulos, 2015). As such, the early foraging strategies of free-ranging juveniles that may not return to land can now be observed and, when coupled with double tagging techniques (Drymon & Wells, 2017;Hays, Bradshaw, James, Lovell, & Sims, 2007), examined in relation to survival outcome to gain a more mechanistic understanding of how the two may be related.…”

Body condition influences ontogeny of foraging behavior in juvenile southern elephant seals

“…A full description of DSA tag specifications and on-board processing algorithms can be found in Cox et al (2017). The advantages of this system are that real-time diving data could be transmitted (c. 5 dives daily) negating the need for tag retrieval.…”

Open‐source, low‐cost modular GPS collars for monitoring and tracking wildlife

“…It may be better to send GPS location data via GSM and then supplement it with the accelerometer data once the device can be recovered. There are also post‐processing algorithms that can be part of the device programming which can extract summary statistics or, using pre‐calibrated classifiers, even behavioural classifications which can then be sent over GSM instead of the raw data (Cox et al, ). It is important to note that these algorithms require both memory and processor capacity within the device so must be lightweight and will come with an increase in power draw.…”