Raymond D. Dueser

Interspecific territoriality in two sympatric species of Peromyscus (Rodentia: Cricetidae)

SummaryAggressive behavior of two morphologically and ecologically similar sympatric congeners, Peromyscus leucopus noveboracensis and P. maniculatus nubiterrae, was studied in the field to determine whether coexistence between these two species could be mediated by interspecific territoriality.In intra- and interspecific paired behavioral trials conducted in the home range of one of the animals, resident animals won between 53 and 93% of paried encounters against opponents of either species. Thus, dominance was site-specific and not species-specific.Strong defense in centers of home ranges and lower levels of aggression on the periphery suggest that both species have defended core areas (territories) with peripheral areas of home range overlapping with neighbors of either species. Social organization of these two species is apparently based on mutual recognition of neighbors and intoleance and aggression toward strangers.

Of mice and habitats: tests for density-dependent habitat selection

Stable URL:http://links.jstor.org/sici?sici=0030-1299%28199402%2969%3A1%3C107%3AOMAHTF%3E2.0.CO%3B2-2Oikos is currently published by Nordic Society Oikos.Your use of the JSTOR archive indicates your acceptance of JSTORs Terms and Conditions of Use, available athttp://www.jstor.org/about/terms.html. JSTORs Terms and Conditions of Use provides, in part, that unless you have obtainedprior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content inthe JSTOR archive only for your personal, non-commercial use.Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained athttp://www.jstor.org/journals/oikos.html.Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printedpage of such transmission.The JSTOR Archive is a trusted digital repository providing for long-term preservation and access to leading academicjournals and scholarly literature from around the world. The Archive is supported by libraries, scholarly societies, publishers,and foundations. It is an initiative of JSTOR, a not-for-profit organization with a mission to help the scholarly community takeadvantage of advances in technology. For more information regarding JSTOR, please contact support@jstor.org.http://www.jstor.orgTue Jul 17 16:34:31 2007

Overwater Movement of Raccoons (Procyon lotor) in a Naturally Fragmented Coastal Landscape

Abstract Procyon lotor (Raccoon) is a major predator of beach-nesting and colonial waterbirds on the Virginia barrier islands. An understanding of water as a barrier to inter-island movement by Raccoons will be essential to effective management of these predators in this naturally fragmented coastal environment. We examined 4 independent lines of direct evidence for Raccoon movement between 1999 and 2007: 1) locations of recaptured, ear-tagged Raccoons on both the islands and the adjacent mainland, 2) overland movements of radio-collared Raccoons, 3) inter-island movements of radio-collared resident Raccoons, and 4) movements of translocated Raccoons. We recaptured 78 of 177 ear-tagged island Raccoons, all on the same island as the initial capture. We also tagged and released 65 mainland Raccoons, none of which was ever recaptured on an island. We often observed overland movements >1 km per day by radio-collared animals on both the islands and the mainland. Nevertheless, only 3 of 51 (6%) collared animals (2 males and 1 female) moved overwater from the location where they were captured. None of the 4 Raccoons radio-collared on the mainland moved to an island. Although Raccoons in this system are highly mobile, overwater movements seem to be infrequent events; only 3 of 234 tagged/ collared island individuals moved between islands, and none of the 69 tagged/collared mainland individuals moved to an island. Finally, we observed return movements by 22 of the 32 (69%) animals (11 males and 11 females) that were translocated either from the mainland to a nearby island or between adjacent islands. Translocated animals exhibited a much greater tendency than resident animals to make overwater crossings. In all cases of overwater movement, the water channels were relatively shallow and relatively slow moving. None of the 335 marked animals in this study crossed a tidal inlet. The mobility observed here is consistent with the idea that the distribution of Raccoons on the islands has expanded in recent decades. Predation management on these islands will require a strategic approach that takes into account both island isolation and Raccoon mobility.

A Comparison of Methods for Measuring Small-Mammal Dispersal by Use of a Monte-Carlo Simulation Model

A principal obstacle to study of dispersal movements by small mammals has been the difficulty with which dispersal is observed. A simple, discrete-time, Monte-Carlo simulation model was used to make quantitative comparisons of three methods of estimating dispersal rates in a situation in which, unlike nature, the true amount of dispersal was known. Simulations were used to explore the effects of grid size, probability of capture, spacing behavior, and intertrapping-time interval on estimates of dispersal based on the body-mass, removal-grid, and distance-criterion methods. Results from all methods differed among grid sizes, and results from all but the distance method varied with probability of capture. Intertrapping interval affected the body-mass method and distance method, but not the removal-grid method. None of the methods were sensitive to changes in interindividual spacing. On a 5.0-ha grid, distance and body-mass methods were more accurate in classifying both residents and dispersers than was the removal-grid method. On a 1.0-ha grid, the distance method misclassified a smaller proportion of residents as dispersers than either of the other methods, but misclassified most dispersers, and the body-mass method was superior to the removal-grid method in classifying both residents and dispersers.

A Test for Suppression of Body Growth and Sexual Maturity in Small Male Meadow Voles (Microtus pennsylvanicus) in Field Enclosures

To test predictions that young males should grow more slowly in populations with many large adult males and that young males should attain sexual maturity at a lower weight in populations with few or no large males, 12 enclosed populations of meadow voles (Microtus pennsylvanicus) were manipulated in three treatments: (1) all males equal to or exceeding 38 g (the median weight at sexual maturity in unmanipulated populations) were removed; (2) large males (238 g) were added; (3) a control in which no large males were added or removed. Each treatment consisted of four replicate grids, each in a 30 by 50 m field enclosure. Body growth rates for small males did not differ between treatments, nor were there differences in weight at sexual maturity or survival. There was no evidence that small males were significantly affected by the density of large males. The enclosed populations were at densities comparable to those of unenclosed populations, suggesting that suppression of small males occurs infrequently or not at all in natural populations. The implications of these results for current theories on the evolution of suppression are discussed.

Allozymic Variation in the Endangered Delmarva Fox Squirrel (Sciurus niger cinereus): Genetics of a Translocated Population

Abstract We examined allozymic variation at 42 loci in a translocated population of the endangered Delmarva fox squirrel, Sciurus niger cinereus, as well as the naturally occurring (source) population from which individuals were obtained to establish it. The translocated population was founded more than 20 y ago by a total of 30 animals introduced directly from the source population and by descendants from a previous translocation from the same source population. Genetic variation, as measured by mean heterozygosity, did not differ significantly between the source and translocated populations. The mean number of alleles per locus was significantly lower in the translocated population relative to the source population. Genetic variation in both S. n. cinereus populations is within the range of values found in other populations of S. niger. Nevertheless, we suggest that the Chincoteague population and other translocated populations of S. n. cinereus be examined periodically (using larger samples sizes, if possible) for losses of genetic variation. Also, additional methods (e.g., analysis of mitochondrial and/or nuclear DNA) should be used to document genetic variation within and among translocated and naturally occurring populations of S. n. cinereus.

Method for Casting Large Numbers of Clay Eggs for Use in Studies of Artificial Nests

Abstract We describe a method for making clay mimics of bird eggs. These eggs can be used in experiments that require many uniform, accurate artificial eggs. We developed methods and made about 1,000 clay eggs at a cost of

Food Habits of Sympatric Peromyscus leucopus and Peromyscus maniculatus

0.55 each.