Graduation Date

Fall 2017

Document Type

Thesis

Program

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

Committee Chair Name

Dr. Daniel Barton

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Brian Hudgens

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. Matthew Johnson

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Wildlife

Abstract

Many amphibian species are in decline due to habitat loss and changing climates. Understanding how habitat characteristics and climate influence vital rates, and if they act in concert or in opposition can inform management decisions. This study investigated the potential interaction of canopy cover and climate on early stage vital rates of northern red-legged frogs. Demographic data were collected from sample populations in experimental canopy cover treatments across a latitudinal distribution. Rearing cages were used to estimate hatch success, and mark-recapture surveys to estimate tadpole survival. Ambient air temperature was used as an index of climate because it is easily relatable to the effects of climate change and collected at fine scales without specialized equipment. Estimates from field data, along with published accounts were used in a matrix modeling analysis to evaluate if tadpole survival impacted population growth rates.

Egg hatch success did not differ between canopy treatments or among sites. Canopy cover did affect tadpole survival rates, but not tadpole development time. The effect of canopy over on tadpole survival varied depending on which population was being evaluated. There was no evidence that the effect of canopy cover on tadpole survival was dependent on air temperature. Tadpole survival rates did impact population growth rates.

This research shows that the effect of canopy cover on early stage vital rates for this species is variable between populations, but not due to differences in average air temperatures. For some populations the effect of canopy cover on tadpole survival was large enough to change projected population growth rates from stable to decreases of 30%. These results demonstrate that manipulating canopy cover can influence tadpole survival sufficiently enough to alter population trajectories. However, the variable effects of canopy cover on vital rates suggest a universal management strategy through canopy cover manipulation will not have equal impacts across populations.

Citation Style

Journal of Wildlife Managment

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