Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Belant, Jerrold

Committee Member

Beasley, James

Committee Member

Rush, Scott

Committee Member

DeVault, Travis

Date of Degree

8-1-2018

Document Type

Dissertation - Open Access

Degree Name

Doctor of Philosophy

Abstract

Roads cause substantial wildlife mortality, but there is currently limited understanding of the relative magnitude of this mortality source. There are also substantial gaps in knowledge concerning the ecological ramifications of carrion introduced to the environment from vehicle collisions and in particular how vertebrate scavengers may consume carrion resulting from vehicle collisions. Although a variety of factors influence scavenger use of carcasses, the mechanisms influencing competition for this resource between obligate and facultative scavengers have not been thoroughly explored. I conducted a global synthesis of mortality of terrestrial vertebrates documenting 42,755 mortalities of known cause from 120,657 individuals representing 305 vertebrate species. Overall, 28% of mortalities were directly caused by humans and 72% were from natural sources. Vehicle collisions accounted for 4% of mortality overall. Larger birds were more likely than smaller birds to die from vehicle collisions and vehicle mortality of mammals increased over time. There was no difference in proportion of rabbit carcasses scavenged or scavenger arrival time between those placed along roads, power line clearings, and forests. No species arrived at roads quicker than other treatments. Turkey vultures (Cathartes aura) and coyotes (Canis latrans) scavenged equally across treatments, whereas gray foxes (Urocyon cinereoargenteus) scavenged along roads and power lines, but not in forests. Scavenger use of carrion near roads likely relates to factors besides carrion availability, such as traffic avoidance and predation risk. Because some scavengers make substantial use of carrion on roads, this resource could be an important mechanism by which human activities impact wildlife. Scavenging by facultative scavengers did not increase in the absence of competition with vultures. I found no difference in scavenger presence between control carcasses and those from which vultures were excluded. Facultative scavengers did not functionally replace vultures during summer in this study. These results suggest that under the conditions of this study, facultative scavengers would not compensate for loss of vultures. Carcasses would persist longer in the environment and consumption of carrion would likely shift from vertebrates to decomposers. Such changes could have substantial implications for disease transmission, nutrient cycling, and ecosystem functioning.

URI

https://hdl.handle.net/11668/20976

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