CANCELLED - Linking movement and dive data to prey distribution models: new insights in foraging behaviour and potential pitfalls of movement analyses

Background/Question/Methods

: Animal movement data are often used to infer foraging behaviour and relationships to environmental characteristics, often to help identify critical habitat. To characterize foraging, movement models make a set of theoretical assumptions (e.g., time spent foraging increases with prey density). Our objective was to assess the validity of these assumptions by associating horizontal movement and diving of 53 ringed seals (Pusa hispida) – an opportunistic predator – in Hudson Bay, Canada, to modelled prey data and environmental proxies. Specifically, we modelled seal movement behaviour using a move persistence mixed-effects model which incorporated modelled prey biomass estimates, and compared these models to ones which incorporated proxies of prey (i.e., bathymetry, sea surface temperature). We then compared these movement models to foraging effort (e.g., number of dives).

Results/Conclusions

: Counter to theory, seals appeared to forage more in areas with low prey diversity and biomass, potentially due to reduced foraging efficiency. Modelled prey data performed better than their proxies for explaining seal movement. Specifically, we found the best model to predict seal movement included prey diversity and bathymetry as covariates. Additionally, we did not find the expected relationships between foraging-like movement and diving behaviours, nor those between dive behaviour and modelled prey biomass. Our study highlights the need to validate movement analyses with prey data to effectively estimate foraging behaviour. Further, these nuances of foraging more in areas with low prey diversity and biomass should be considered as statistical methods for animal movement data continue to become more advanced and accessible, and as identifying habitat to protect depends on effective analysis of movement data.