Spatial Ecology of Invasive Black Rats (Rattus rattus) On San Clemente Island, California
2015
Higgins, Taylor W. | Bridges, Andrew S. | Sanchez, Jessica N.
Black rats (Rattus rattus) are among the most ecologically destructive invasive vertebrates. On San Clemente Island (SCI) they depredate multiple endemic endangered species. Rat control has been part of the Department of the United States Navy's endangered species conservation programs on SCI since 1987, but no previous research into their ecology had been conducted. To improve understanding and management of black rats on SCI, from September 2011 to January 2012, we conducted a radiotelemetry study to estimate spatial use metrics for 20 rats. We found 95% kernel density estimates ranged from 0.14 to 6.45 ha (mean = 1.75 ha) with an average home-range size of 2.09 ha for males and 1.53 ha for females. We did not detect any effect of habitat type or time of day on spatial-use metrics. Home range overlap among sympatric individuals ranged from 3% to 73%, with 19 of 20 individuals (95%) overlapping two or more other rats wearing transmitters. Better understanding of black rat spatial ecology will allow for improved rat-control efforts to facilitate ESA-listed taxa conservation efforts on SCI.
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