Date Approved

12-2019

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

First Advisor

Paul Keenlance

Second Advisor

Joseph Jaquot

Third Advisor

Jennifer Moore

Academic Year

2019/2020

Abstract

Snowshoe hares (Lepus americanus) are a climate sensitive species that have a southern range boundary moving northward. Snowshoe hares are found on the Apostle Islands, Wisconsin which are near their southern boundary and differ by island in vegetative and carnivore communities. The archipelago serves as a natural laboratory to assess how top-down and bottomup forces interact and impact snowshoe hare populations. The objectives of this study were to determine the influence of vegetative characteristics, specifically visual obstruction, and the presence of predators on snowshoe hare abundances across the Apostle Islands. We conducted fecal pellet surveys to estimate hare abundance, measured visual obstruction to assess vegetative cover, and quantified predators using camera trap data on seven islands and the nearby mainland. Hares were found at 10 of our 18 sampling grids, which included 6 of the 7 islands sampled, along with on the mainland, all primarily at low densities. Grids where snowshoe hares were found provided higher levels of visual obstruction than those that without hares. Hare abundance was positively correlated with visual obstruction, along with several carnivore abundances including total carnivore relative abundance, raccoon (Procyon lotor), gray wolf (Canis lupus), and most strongly with coyote (Canis latrans) and was negatively correlated with marten (Martes americana) and gray fox (Urocyon cinereoargenteus). At their current low densities, hares were found in areas with high levels of visual obstruction. The positive correlation between hares and multiple predator abundances suggest predators are cuing to the presence of hares as potential prey. Hare abundance was nearly 10 times higher on Devils island, which has limited potential predation pressure, which highlights the release from top-down forces. However, its high abundance was coupled with lower habitat quality than other locations where snowshoe hares were found, which may be a result of hares overgrazing and preventing regeneration. Both top-down and bottom-up forces are interacting to determine snowshoe hare abundance across the Apostle Islands.

Download

Share

COinS