Doctoral Dissertations

Date of Award

12-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Life Sciences

Major Professor

Michael R. Pelton

Abstract

Among mammals, some of the most common types of cohesive social groupings originate form natal philopatry through the extended mother family. The recognition that females among some solitary mammals demonstrate natal philopatry suggests that an important part of understanding the evolution of social groupings in mammals is through establishing the conditions that lead to natal philopatry in solitary species. The North American raccoon, Procyon lotor, is a relatively solitary carnivore of the Procyonidae, a family that demonstrates both variability and flexibility in the nature and degree of sociality. This dissertation examines the conditions surrounding natal philopatry in a raccoon population in east Tennessee with the goals of identifying 1) the population correlates and individual consequences of female philopatry, and 2) the influence of philopatry and kinship on female spatial organization.

I gathered over three years of radio telemetry and mark-recapture data to obtain information on raccoon population ecology and female spatial relationships on the Oak Ridge Reservation. Most female offspring persisted on the natal area beyond dependence and beyond their mother’s next breeding episode. Most dispersal was in the early Spring (Jan — Mar) when mortality was highest among philopatric females. Population density of raccoons on the study area was high relative to other raccoon populations in east Tennessee, as was the proportion of females in older age classes. Individual and population characteristics of young females at White Oak Lake indicated that philopatry under these demographic conditions was costly. Although female raccoons are physiologically capable of reproduction at one year, lower body weight, delated reproduction and higher mortality in younger females relative to older females suggested that competition from older females limited free access to food and breeding opportunities. The presence of a yearling daughter within the home range did not seem to incur reproductive costs to mothers. At least 50% of mothers who shared space with yearling daughters became pregnant the following year. No philopatric daughters became pregnant when their mothers were alive on the natal area.

DNA amplification employing primers of arbitrary sequence (RAPDs) indicated that female philopatry in raccoons led to a greater likelihood that neighbors were more related than expected by chance. Genetic distance based on RAPD band frequency was positively associated with spatial distance among females. Genetic similarity was positively associated with the extent of home range overlap. Genetic similarity was positively associated with the extent of home range overlap. Philopatry seemed biased toward females; average female-female similarities at White Oak Lake were greater than average male-male similarities or average male-female similarities. High home range overlap among females with low and moderate levels of band sharing suggested that maternal inheritance of space was not a prerequisite for home range sharing. High home range overlap was less common among parous females. Spatial and temporal interaction among females was independent of the percentage of band sharing with most responses to shared areas being random. Individual spacing among most females was high relative to the distances between their activity centers, reflecting the predominantly solitary nature of female raccoons.

Hypotheses explaining the formation of cooperative social groups in carnivores invoke ecological, demographic and behavioral factors that influence an individual’s reproductive opportunities and the probability of philopatry. Certain aspects of female philopatry in raccoons bear a closer resemblance to circumstances hypothesized to promote natal philopatry in some social carnivores.

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