Walrus Vibrissae: Determining Growth Rate, Indication of Niche Variability, and Implications for Climate Resiliency

• Main Author: Blackfield, Danielle
• Other Authors: Steingass, Sheanna, Beechler, Brianna, Jolles, Anna, Ruble, Deborah, Epps, Clinton, College of Veterinary Medicine
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Ocean acidification; Odobenus rosmarus; Sea ice; Alaska; walrus*
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/n009w968w

Pacific walrus (Odobenus rosmarus) are particularly vulnerable to the impacts of climate change due to the high reliance on sea ice for safety, transport, and social behaviors. Additionally, the walrus diet consists of predominantly bivalves, whose populations are in decline as a result of ocean acidification. We first determined the speed at which vibrissae grow using captive walrus, and then utilized vibrissae from wild walrus to evaluate potential changes in diet composition using stable isotope analysis. Whisker measurements were collected weekly from walrus under human care. A linear mixed-effects model demonstrated a strong linear growth rate for walrus whiskers. Stable isotope analysis was conducted on whiskers collected from wild walrus (n = 32) in Alaska to evaluate the applicability of the Niche Variation Hypothesis to walrus. The NVH posits that the expansion of a given population’s niche corresponds with higher variation in diet between individuals. In this study, niche expansion is represented by higher trophic feeding and greater δ15N enrichment, as the traditional walrus diet is fairly homogenous and consists of mainly lower-trophic bivalves. The variance in δ15N enrichment was significantly greater for the higher trophic group than the lower trophic group. This suggests a higher degree of diet specialization among the group with the expanded niche and supports the applicability of the NVH to walrus. This was the first study to evaluate the walrus whisker growth model and test the application of the Niche Variation Hypothesis to walrus.