Elephant Seal Movements: Some Frequency Based Studies

We studied dive patterns of northern elephant seals, that consisted of measurements of time vs. depth, by applying several time series based techniques. A primary feature of these patterns is diel variation in dive duration and maximal dive depth. Time series analysis of this variation over a two month period of continuous diving revealed an apparent cir-cadian rhythm. The consistency of this rhythm despite large scale geographic movement during migration may suggest that the pattern is endogenous or that environmental (biotic and abiotic) factors are sufficiently similar over large ocean areas in the eastern North Pacific to-2-result in these consistent circadian foraging behaviors. A model involving stochastically elicited impulse responses is proposed.