Date of Award

Spring 4-26-2018

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Aram Calhoun

Second Committee Member

Malcolm Hunter, Jr.

Third Committee Member

Hamish Greig

Additional Committee Members

Rebecca Holberton

Michael Kinnison

Abstract

Vernal pools in the northeastern United States provide essential habitat for pool-breeding amphibians and provide resources for other forest-dwelling wildlife. These pools and pool-breeding amphibians in particular are threatened by land conversion associated with urbanization and urban-associated factors. The responses of these amphibians and of birds and mammals using vernal pools to intermediate levels of urban development are largely unknown. I used field observations and lab experiments to study the amphibians, birds, and mammals associated with vernal pools along an urban development gradient in greater Bangor, Maine.

In Chapter 1, I examined bird and mammal use and assemblage composition at 33 pools, with specific focus on the influence of impervious surface as an indicator of urbanization intensity. I detected 59 bird and mammal species using pools and the adjacent terrestrial areas. Within-pool vegetation and land cover types within 1,000 m of pools likely influenced assemblages with increases in impervious cover linked to shifts towards urban-affiliated species.

Chapters 2 focused on the associations between site characteristics in an urbanizing landscape and wood frog (Lithobates sylvaticus) larval morphology and survival. Differences in morphology were associated with urban land conversion, hydrology, within-pool vegetation, and conspecific density. Urbanization was associated with greater tadpole survival, development rate, and size.

In Chapter 3, I examined the carry-over effects of larval morphology and site characteristics, particularly urban-associated land conversion within 1,000 m, on newly emerged and post-breeding male wood frogs in 15 pools. Egg density had a salient influence with negative effects on larval and froglet responses, and the effects of urban-associated cover near pools at larval and adult stages suggest that the carry-over effects of urbanization from larval to froglet stages may not persist to adulthood.

Chapter 4 addresses the effects of urban-associated land conversion and road salt on breeding effort of wood frog, spotted salamander (Ambystoma maculatum), and the blue-spotted salamander (including the unisexual complex, Ambystoma laterale-jeffersonianum). All three taxa responded negatively to tree cover reduction, but had some positive responses that are indicative of the removal of breeding pools 300-1,000 m from a study pool resulting in displaced adults consolidating breeding in remaining pools.

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