Three months journeying of a Hawaiian monk seal

TL;DR

This study models the movement of a Hawaiian monk seal over three months using a stochastic differential equation, revealing insights into its foraging behavior and habitat preferences in the Northwestern Hawaiian Islands.

Contribution

The paper introduces a stochastic differential equation model with a time-varying potential function to analyze seal movement data, a novel approach for studying marine mammal foraging behavior.

Findings

Seal mainly stays southwest of Molokai

Estimated lengths and locations of foraging trips

Model fits the movement data reasonably well

Abstract

Hawaiian monk seals (Monachus schauinslandi) are endemic to the Hawaiian Islands and are the most endangered species of marine mammal that lives entirely within the jurisdiction of the United States. The species numbers around 1300 and has been declining owing, among other things, to poor juvenile survival which is evidently related to poor foraging success. Consequently, data have been collected recently on the foraging habitats, movements, and behaviors of monk seals throughout the Northwestern and main Hawaiian Islands. Our work here is directed to exploring a data set located in a relatively shallow offshore submerged bank (Penguin Bank) in our search of a model for a seal's journey. The work ends by fitting a stochastic differential equation (SDE) that mimics some aspects of the behavior of seals by working with location data collected for one seal. The SDE is found by developing a time varying potential function with two points of attraction. The times of location are irregularly spaced and not close together geographically, leading to some difficulties of interpretation. Synthetic plots generated using the model are employed to assess its reasonableness spatially and temporally. One aspect is that the animal stays mainly southwest of Molokai. The work led to the estimation of the lengths and locations of the seal's foraging trips.