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Feral pigs facilitate hyperpredation by golden eagles and indirectly cause the decline of the island fox
- Gary W. Roemer, Timothy J. Coonan, David K. Garcelon, Jordi Bascompte, Lyndal Laughrin
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- Journal:
- Animal Conservation forum / Volume 4 / Issue 4 / November 2001
- Published online by Cambridge University Press:
- 26 November 2001, pp. 307-318
- Print publication:
- November 2001
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Introduced species can compete with, prey upon or transmit disease to native forms, resulting in devastation of indigenous communities. A more subtle but equally severe effect of exotic species is as a supplemental food source for predators that allows them to increase in abundance and then overexploit native prey species. Here we show that the introduction of feral pigs (Sus scrofa) to the California Channel Islands has sustained an unnaturally large breeding population of golden eagles (Aquila chrysaetos), a native predator. The resulting increase in predation on the island fox (Urocyon littoralis) has caused the near extirpation of three subspecies of this endemic carnivore. Foxes evolved on the islands over the past 20,000 years, pigs were introduced in the 1850s and golden eagles, historically, were only transient visitors. Although these three species have been sympatric for the past 150 years, this predator-prey interaction is a recent phenomenon, occurring within the last decade. We hypothesize that this interaction ultimately stems from human-induced perturbations to the island, mainland and surrounding marine environments.
The behavioural ecology of the island fox (Urocyon littoralis)
- Gary W. Roemer, Deborah A. Smith, David K. Garcelon, Robert K. Wayne
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- Journal:
- Journal of Zoology / Volume 255 / Issue 1 / September 2001
- Published online by Cambridge University Press:
- 29 August 2001, pp. 1-14
- Print publication:
- September 2001
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Insular populations typically occur at higher densities, have higher survivorship, reduced fecundity, decreased dispersal, and reduced aggression compared to their mainland counterparts. Insularity may also affect mating system and genetic population structure. However, these factors have not been examined simultaneously in any island vertebrate. Here we report on the ecological, behavioural and genetic characteristics of a small carnivore, the island fox Urocyon littoralis, from Fraser Point, Santa Cruz Island, California. Dispersal distances in island foxes are very low (mean 1.39 km, SD 1.26, range 0.16–3.58 km, n=8). Home-range size is one of the smallest (mean annual home range=0.55 km2, sd 0.2, n =14) and density is nearly the highest recorded for any canid species (2.4–15.9 foxes/km2). Similar to other fox species, island foxes are distributed as mated pairs that maintain discrete territories. Overlap among mated pairs was always high (mean 0.85, sd 0.05), while overlap among neighbours (mean 0.11, sd 0.13), regardless of sex, was low. Despite this high degree of territoriality, island foxes are not strictly monogamous. Four of 16 offspring whose parents were identified by paternity analysis were a result of extra-pair fertilizations. Mated pairs were unrelated, however, suggesting inbreeding avoidance. Substantial population differentiation was found between the Fraser Point subpopulation and one only 13 km away (Fst=0.11). We suggest that the primary effect of finite island area is to limit dispersal, which then influences the demography, behaviour and genetic structure of island fox populations.
Looking Backward, Looking Forward: MLA Members Speak
- April Alliston, Elizabeth Ammons, Jean Arnold, Nina Baym, Sandra L. Beckett, Peter G. Beidler, Roger A. Berger, Sandra Bermann, J.J. Wilson, Troy Boone, Alison Booth, Wayne C. Booth, James Phelan, Marie Borroff, Ihab Hassan, Ulrich Weisstein, Zack Bowen, Jill Campbell, Dan Campion, Jay Caplan, Maurice Charney, Beverly Lyon Clark, Robert A. Colby, Thomas C. Coleman III, Nicole Cooley, Richard Dellamora, Morris Dickstein, Terrell Dixon, Emory Elliott, Caryl Emerson, Ann W. Engar, Lars Engle, Kai Hammermeister, N. N. Feltes, Mary Anne Ferguson, Annie Finch, Shelley Fisher Fishkin, Jerry Aline Flieger, Norman Friedman, Rosemarie Garland-Thomson, Sandra M. Gilbert, Laurie Grobman, George Guida, Liselotte Gumpel, R. K. Gupta, Florence Howe, Cathy L. Jrade, Richard A. Kaye, Calhoun Winton, Murray Krieger, Robert Langbaum, Richard A. Lanham, Marilee Lindemann, Paul Michael Lützeler, Thomas J. Lynn, Juliet Flower MacCannell, Michelle A. Massé, Irving Massey, Georges May, Christian W. Hallstein, Gita May, Lucy McDiarmid, Ellen Messer-Davidow, Koritha Mitchell, Robin Smiles, Kenyatta Albeny, George Monteiro, Joel Myerson, Alan Nadel, Ashton Nichols, Jeffrey Nishimura, Neal Oxenhandler, David Palumbo-Liu, Vincent P. Pecora, David Porter, Nancy Potter, Ronald C. Rosbottom, Elias L. Rivers, Gerhard F. Strasser, J. L. Styan, Marianna De Marco Torgovnick, Gary Totten, David van Leer, Asha Varadharajan, Orrin N. C. Wang, Sharon Willis, Louise E. Wright, Donald A. Yates, Takayuki Yokota-Murakami, Richard E. Zeikowitz, Angelika Bammer, Dale Bauer, Karl Beckson, Betsy A. Bowen, Stacey Donohue, Sheila Emerson, Gwendolyn Audrey Foster, Jay L. Halio, Karl Kroeber, Terence Hawkes, William B. Hunter, Mary Jambus, Willard F. King, Nancy K. Miller, Jody Norton, Ann Pellegrini, S. P. Rosenbaum, Lorie Roth, Robert Scholes, Joanne Shattock, Rosemary T. VanArsdel, Alfred Bendixen, Alarma Kathleen Brown, Michael J. Kiskis, Debra A. Castillo, Rey Chow, John F. Crossen, Robert F. Fleissner, Regenia Gagnier, Nicholas Howe, M. Thomas Inge, Frank Mehring, Hyungji Park, Jahan Ramazani, Kenneth M. Roemer, Deborah D. Rogers, A. LaVonne Brown Ruoff, Regina M. Schwartz, John T. Shawcross, Brenda R. Silver, Andrew von Hendy, Virginia Wright Wexman, Britta Zangen, A. Owen Aldridge, Paula R. Backscheider, Roland Bartel, E. M. Forster, Milton Birnbaum, Jonathan Bishop, Crystal Downing, Frank H. Ellis, Roberto Forns-Broggi, James R. Giles, Mary E. Giles, Susan Blair Green, Madelyn Gutwirth, Constance B. Hieatt, Titi Adepitan, Edgar C. Knowlton, Jr., Emanuel Mussman, Sally Todd Nelson, Robert O. Preyer, David Diego Rodriguez, Guy Stern, James Thorpe, Robert J. Wilson, Rebecca S. Beal, Joyce Simutis, Betsy Bowden, Sara Cooper, Wheeler Winston Dixon, Tarek el Ariss, Richard Jewell, John W. Kronik, Wendy Martin, Stuart Y. McDougal, Hugo Méndez-Ramírez, Ivy Schweitzer, Armand E. Singer, G. Thomas Tanselle, Tom Bishop, Mary Ann Caws, Marcel Gutwirth, Christophe Ippolito, Lawrence D. Kritzman, James Longenbach, Tim McCracken, Wolfe S. Molitor, Diane Quantic, Gregory Rabassa, Ellen M. Tsagaris, Anthony C. Yu, Betty Jean Craige, Wendell V. Harris, J. Hillis Miller, Jesse G. Swan, Helene Zimmer-Loew, Peter Berek, James Chandler, Hanna K. Charney, Philip Cohen, Judith Fetterley, Herbert Lindenberger, Julia Reinhard Lupton, Maximillian E. Novak, Richard Ohmann, Marjorie Perloff, Mark Reynolds, James Sledd, Harriet Turner, Marie Umeh, Flavia Aloya, Regina Barreca, Konrad Bieber, Ellis Hanson, William J. Hyde, Holly A. Laird, David Leverenz, Allen Michie, J. Wesley Miller, Marvin Rosenberg, Daniel R. Schwarz, Elizabeth Welt Trahan, Jean Fagan Yellin
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- Journal:
- PMLA / Publications of the Modern Language Association of America / Volume 115 / Issue 7 / December 2000
- Published online by Cambridge University Press:
- 23 October 2020, pp. 1986-2078
- Print publication:
- December 2000
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