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Luanne Johnson, Ph.D., is a 2016 graduate of the PhD Program in Environmental Studies at Antioch University, New England

Dissertation Committee:

  • Jonathan Atwood, Ph.D., Committee Chair
  • Stephen DeStefano, Ph.D., Committee Co-Chair
  • Rachel Thiet, Ph.D., Committee Member

Document Type

Dissertation

Publication Date

2016

Abstract

We studied coastal striped skunks (Mephitis mephitis) on the island of Martha’s Vineyard, Massachusetts, USA to gather information on the population characteristics of this mesopredator on Atlantic coast beaches with nesting piping plovers (Charadrius melodus). From 2004 – 2008, we captured and marked 138 skunks and fitted 51 adults with VHF radio-collars. Capture rates ranged from 1 – 7 individuals/100 trap nights (TN) in the spring and 4 – 21 individuals/100 TN in the fall. Spring capture rates were highest at Dogfish Bar (DB), a beach with abundant wrack in the intertidal zone in close proximity to low-density housing, where we estimated a spring density of 8-10 skunks/km2. All adult skunks were residents at this site, and most were initially captured in April/May (100% of males and 67% of females). Spring capture rates were too low for a density estimate at Norton Point/Wasque (NPW), a beach with sparse wrack and farther from development. We initially captured 80% of adult males in April/May but only 1 adult female. Most adult females (88%) were captured in June/July, which coincided with the arrival of anthropogenic food on the beach. While all adult females captured at NPW were residents, 50% of males were non-residents. Half (50%) of all radio-collared skunks died from human-related causes while disease killed another 29%. Female site fidelity was high at both sites, with 40% recurring in subsequent years. While male recurrence at DB was high at 36%, no males recurred at NPW. Similarly, no juveniles recurred in subsequent years at the NPW, but 26% of juveniles recurred at DB. The Martha’s Vineyard skunk population does not exhibit any distinguishing characteristics from mainland striped skunk populations at this time. Skunks captured exhibited all stripe patterns known for the species, but narrow (45%) and short-striped (37%) patterns were most abundant. Adult skunks weighed a mean of 1.47 ± 0.05 kg between April and July and 2.08 ± 0.09 kg between August and November. At beaches where exclusion fencing is not an option for protecting eggs of rare and threatened birds, spring trapping could be effective in reducing skunk densities for most of the nesting season because our data indicates that female territories would remain vacant until late summer. Future research tracking the temporal and spatial variation in wrack line fauna availability on beaches with sparse vs. dense wrack lines will increase our understanding of the factors influencing interactions between piping plovers and predators that share foraging habitat with them, such as skunks and crows. On beaches that are seasonally urban habitats (SUH), research using experimental designs to investigate the influence of predictable anthropogenic food subsidies (PAFS) on the activity and density of generalist predator species during the summer could provide valuable data for management efforts and public outreach aimed at reducing predation on rare and threatened beach species.

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Luanne Johnson

ORCID Scholar ID# 0000-0001-8002-4675

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