Abstract
Predicting how climatic variations will affect marine predator populations relies on our ability to assess foraging success, but evaluating foraging success in a marine predator at sea is particularly difficult. Dive metrics are commonly available for marine mammals, diving birds and some species of fish. Bottom duration or dive duration are usually used as proxies for foraging success. However, few studies have tried to validate these assumptions and identify the set of behavioral variables that best predict foraging success at a given time scale. The objective of this study was to assess if foraging success in Antarctic fur seals could be accurately predicted from dive parameters only, at different temporal scales. For this study, 11 individuals were equipped with either Hall sensors or accelerometers to record dive profiles and detect mouth-opening events, which were considered prey capture attempts. The number of prey capture attempts was best predicted by descent and ascent rates at the dive scale; bottom duration and descent rates at 30-min, 1-h, and 2-h scales; and ascent rates and maximum dive depths at the all-night scale. Model performances increased with temporal scales, but rank and sign of the factors varied according to the time scale considered, suggesting that behavioral adjustment in response to prey distribution could occur at certain scales only. The models predicted the foraging intensity of new individuals with good accuracy despite high inter-individual differences. Dive metrics that predict foraging success depend on the species and the scale considered, as verified by the literature and this study. The methodology used in our study is easy to implement, enables an assessment of model performance, and could be applied to any other marine predator.
Highlights
Predicting the effect of oceanographic and climatic variation on top marine predator populations and/or establishing management decisions are often based on resource selection analyses and habitat modeling output [1,2,3,4,5]
We assumed in this study that the number of prey capture attempts was representative of foraging success
Our study shows that several diving parameters can be used at different temporal scales to predict with reasonable accuracy foraging success in Antarctic fur seal females breeding on Kerguelen Islands
Summary
Predicting the effect of oceanographic and climatic variation on top marine predator populations and/or establishing management decisions (i.e., marine protected areas) are often based on resource selection analyses and habitat modeling output [1,2,3,4,5]. A growing number of studies are focused on characterizing foraging habitats for numerous marine species [2,3,4,6] This task is challenging in the marine environment because of the high spatial and temporal dynamics of oceanic systems and the difficulty of observing these predators at sea. Residence time (estimated as time spent per unit area), first passage time, or state–space modeling approaches are commonly used to infer foraging behavior from tracking data [6,7,8,9,10] These indices are based on the assumption that animals will increase the time spent searching for food in more profitable prey patches [11], reducing their speed and increasing their turning angles [12]. Depending on the species and environmental conditions, inferring foraging success from tracking data is not always possible [13,14,15] and could result in misleading assessments of habitat selection [16]
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