Available at: https://digitalcommons.calpoly.edu/theses/3351
Date of Award
6-2026
Degree Name
MS in Biological Sciences
Department/Program
Biological Sciences
College
College of Science and Mathematics
Advisor
Heather Liwanag
Advisor Department
Biological Sciences
Advisor College
College of Science and Mathematics
Abstract
The northern elephant seal (Mirounga angustirostris) is a marine mammal known for engaging in long foraging migrations at sea. Adult male northern elephant seals follow pathways along the western coast of North America towards Alaska and adult female northern elephant seals follow pathways to open ocean in the North Pacific. However, there is little information on weaned northern elephant seal pup foraging behavior during their first foraging migration. This lack of knowledge is significant because northern elephant seals have a mortality rate of >50% in the first year. This project aimed to better understand the at-sea migratory movement and space use of northern elephant seals during this critical life stage by deploying satellite tags on 25 weaned northern elephant seal pups across three seasons (Spring of 2022, 2023, and 2024).
In this thesis, I investigated directional movement, track metrics, foraging behavior, and timeframe for migratory events between sexes, between natal breeding sites, among foraging trips, and across years. I found that weaned pups displayed consistent north-south trajectories during their foraging trips, typically staying close to the coast, ranging from southern Alaska to Baja California, and some individuals engaged in multiple foraging trips within their first year. I found evidence that the second foraging trip had a shorter duration, fewer focal foraging areas (FFAs), and decreased time spent in foraging areas compared to the first trip. Additionally, I found evidence of increased time spent in foraging areas in 2023 when compared to other years, which is likely due to the 2023 El Niño event. In contrast, there was no strong evidence that the remaining track metrics (i.e., daily transit speed, total distance, and maximum distance), migratory event dates, or space use (i.e., Kernel density areas) differed between sexes, natal breeding sites, foraging trips, or years.
The decrease in trip duration, number of points in FFAs, and time spent in FFAs in the second trip when compared to the first trip, as well as the lack of trends in the timing of migratory events, suggest that this first year is an information-gathering migration, with weaned pups significantly adjusting their migratory strategies between just the first and second foraging trip. Future work exploring the influence of environmental variables (e.g., ocean current directions, sea surface temperature, bathymetry, etc.), large-scale weather events (e.g., El Niño events), and prey concentration and distribution, as well as incorporating diving behavior and third foraging trips, may provide further insights into why and how weaned northern elephant seal pups made the directional and space use decisions outlined in this thesis.