Graduation Date

Summer 2018

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Wildlife

Committee Chair Name

William Bean

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Joseph Szewczak

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Micaela Szykman Gunther

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

William Zielinski

Fourth Committee Member Affiliation

Community Member or Outside Professional

Subject Categories

Wildlife

Abstract

Climate change models and analyses predict a disproportionate impact on climatically sensitive species such as the mountain beaver (Aplodontia rufa). Mountain beavers have physiological constraints that limit their distribution to cool, moist climates. While mountain beavers have persisted through past periods of climate change, increasing temperature since the last glacial maximum is believed to have had a strong influence in reducing their range. This is particularly true for the Point Arena subspecies (A. r. nigra, “PAMB”), found towards the southwestern edge of their range on the coast of California. Here, I examined the climatic niche of mountain beavers at four scales: range-wide; by clade; PAMB rangewide; and PAMB microclimates to test whether PAMB exhibit different climatic requirements than other subspecies.

I examined the climatic space occupied by mountain beavers at four scales using the machine learning method MaxEnt and occurrence points from museum records, previous surveys conducted by USFS, and personal survey data. First, I modeled the distribution of mountain beaver range-wide and the distributions of the five individual genetic clades (Coastal, Californica, Olympica, Pacifica, and Rufa). To examine the microclimate use of PAMB, I developed fine-scale climate surfaces using temperatures recorded from dataloggers and topographic variables calculated from LiDAR data. These layers were incorporated with PAMB occurrence data to model distribution. Finally, I examined pairwise differences in microhabitat use between burrows and available space.

At all scales high temperatures were a limiting factor in distribution. Despite a low level of niche overlap at broad scales, mountain beavers appear to display some level of niche conservatism. PAMB does seem to exist in a warmer climate than other mountain beavers; however, they apparently persist by selecting the coolest places within that range. This suggests that niche overlap between the Coastal clade and all other clades may be higher than what is detected at the coarser scale. Further research is needed to understand the mechanisms limiting this distribution, but it may be that mountain beavers in marginal habitat are more adaptable to changes in climate.

Citation Style

Journal of Wildlife Management

Share

Thesis/Project Location

 
COinS