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

International audience

إنجليزي. 1. Biologging technologies are changing the way in which the marine environment isobserved and monitored. However, because device retrieval is typically required toaccess the high-resolution data they collect, their use is generally restricted tothose animals that predictably return to land. Data abstraction and transmissiontechniques aim to address this, although currently these are limited in scope and donot incorporate, for example, acceleration measurements which can quantifyanimalbehaviours and movement patterns over fine-scales.2. In this study, we present a new method for the collection, abstraction and transmissionof accelerometer data from free-ranging marine predators via the Argos satellitesystem. We test run the technique on 20 juvenile southern elephant sealsMirounga leonina from the Kerguelen Islands during their first months at sea followingweaning. Using retrieved archival data from nine individuals that returned tothe colony, we compare and validate abstracted transmissions against outputs fromestablished accelerometer processing procedures.3. Abstracted transmissions included estimates, across five segments of a dive profile, oftime spent in prey catch attempt (PrCA) behaviours, swimming effort and pitch. Thesewere then summarised and compared to archival outputs across three dive phases:descent, bottom and ascent. Correlations between the two datasets were variablebut generally good (dependent on dive phase, marginal R2 values of between.45 and.6 to >.9) and consistent between individuals. Transmitted estimates of PrCA behavioursand swimming effort were positively biased to those from archival processing.4. Data from this study represent some of the first remotely transmitted quantificationsfrom accelerometers. The methods presented and analysed can be used toprovide novel insight towards the behaviours and movements of free-ranging marinepredators, such as juvenile southern elephant seals, from whom logger retrievalis challenging. Future applications could however benefit from some adaption,particularlyto reduce positive bias in transmitted PrCA behaviours and swimmingeffort, for which this study provides useful insight.