Assessing the utility of two- and three-dimensional behavioural metrics in habitat usage models

Abstract

For deep-diving, wide-ranging marine predators, foraging behaviour is often inferred from movement data. Various metrics are used to do this, and recently, metrics have been developed that consider both horizontal movement and vertical dive behaviour to better describe the use of the 3-dimensional environment these animals inhabit. However, the efficacy of these different metrics in predicting behavioural state is poorly understood. We used first passage time (2-dimensional) and first bottom time (3-dimensional) analyses on tracks derived from satelliterelayed data loggers to quantify and determine seal behavioural state while foraging at sea. Movement and dive data were collected from 38 southern elephant seals Mirounga leonina from Macquarie and Campbell Islands (in the Pacific sector of the Southern Ocean). Using a suite of environmental variables, linear mixed-effect models were derived for the 2 broad habitats visited by the seals: shelf and open ocean. The best-fitting models for each foraging metric in each habitat were then compared using a cross validation analysis to identify which foraging metric produced the best predictions of habitat use. In shelf habitats, the 3-dimensional foraging metric provided better predictions than the 2-dimensional metric, while the 2-dimensional foraging metric resulted in the best predictive capacity in the open ocean habitats. These findings highlight the importance of considering the appropriate foraging metrics when modelling foraging behaviour.

Inter‐ and intrasex habitat partitioning in the highly dimorphic southern elephant seal

“…In contrast, subadult males focused their feeding on the Kerguelen Plateau or Antarctic Shelf regions. These differences are not simply due to age differences as adult male southern elephant seals retain this preference for shelf habitats (McIntyre et al., 2011; Pascoe et al., 2016). This has been attributed to the greater absolute energy requirements of adult males, which are five times bigger than adult females (Carrick et al., 1962; Laws, 1953).…”

Climate mediates the success of migration strategies in a marine predator

“…; Pascoe et al . ). Given the spatial error associated with ARGOS tags, we investigated ARS behaviour between 20 and 50 km radii.…”

“…We identified probable foraging areas using First Passage Time (FPT) analysis to detect area-restricted search (ARS; Fauchald & Tveraa 2003). First passage time measures the length of time an animal spends within an circle of a given radius, and is considered to be a reliable predictor of pelagic foraging behaviour in elephant seals Pascoe et al 2016). Given the spatial error associated with ARGOS tags, we investigated ARS behaviour between 20 and 50 km radii.…”

Validation of Dive Foraging Indices Using Archived and Transmitted Acceleration Data: The Case of the Weddell Seal

“…It also appears that hunting indices can provide a value that correlates well with time spent in PrCA behaviors, despite data being highly degraded for satellite transmission. Nonetheless, to ensure rigorous analyses and ecological conclusions, we would recommend using the hunting indices as proxies of foraging effort, alongside overall prey distribution and availability in the water column, rather than prediction of the exact time spent in PrCAs behaviors (Labrousse et al, 2015;Arthur et al, 2016;Carter et al, 2016;Pascoe et al, 2016;Heerah et al, 2017).…”