Date of Award

12-2009

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Daniel J. Harrison

Second Committee Member

William B. Krohn

Third Committee Member

William A. Halteman

Abstract

I compared snowshoe hare densities between two locations in northern Maine, 2001-2009, to determine if fluctuations occurred in geographic synchrony, and to compare the magnitude of population change to amplitudes documented for cyclic hare populations within the boreal forest. Changes in winter density occurred synchronously between locations. Hares exhibited a 6-year period of higher density from 2001-2006, followed by a 3-year period of lower density from 2007-2009. Average density during the high period was lower than most peak levels observed in boreal populations, and average density during the low period was higher than the lowest densities observed in cyclic boreal populations. The 2.1-fold change in density was dampened compared to amplitudes of change documented for boreal populations. While hare populations fluctuated synchronously between two locations, they did not exhibit the extreme cyclic dynamics documented in the boreal forest.

I investigated whether forest development can explain the observed hare decline in regenerating conifer stands in northern Maine. I evaluated the strength of relationship between the decline in hare fecal pellet density and a suite of stand development indices, including stand age, site quality, and relative density from a density management diagram. Additionally, I predicted hare pellet density using a model based on measures of vegetation structure and compared observed pellet density during the low hare density period to predicted density based on vegetation structure. Observed pellet density was lower than predicted for all stands. All relationships between the decline in pellet density and stand development indices were non-significant except one, which indicated a negative relationship between the decline in pellet density and relative density. This result was inconsistent with the hypotheses that the hare decline was driven by stand development. Alternatively, broad-scale processes (e.g. community interactions with mobile predators, or spatially-correlated environmental perturbations) may be driving factors behind declines in hare density.

Finally, I evaluated the influence of declines in hares from the period of high density (2001-2006) to the period of low density (2007-2009) on predicted probability of occurrence of Canada lynx across a 1.6 million acre landscape of northern Maine. I estimated the change in landscape-scale densities of hares from the high to low period, and applied an occurrence model to project changes in predicted probability of occurrence of lynx. With habitat composition held static at the 2004 condition, 14.7% of potential lynx home ranges were predicted to have hare density exceeding 0.75 hares/ha during the high period; however, none of the ranges were predicted to have hare density exceeding 0.75 hares/ha during the low period, and 95.1% of the landscape had a predicted density of < 0.50 hares/ha. During the high period, 22.1% of forestland had a probability of lynx occurrence > 80%, but during the low period, only 0.2% had probability > 80%, and 98% had a probability < 50%. On average, lynx would have had to increase their home-range size by 1.9-times during the period of low hare density to have access to an equivalent number of hares as during the period of high density.

Download

Share