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This thesis presents the results of a 3 year field study on the behavioural ecology of the mara on the Valdés Peninsula in Argentina. The main goal was to investigate why the mara's social system incorporates both monogamy and communal denning, a combination unknown in other mammals. The research techniques used were behavioural observations and radio-tracking. Radio-tracking of 9 maras revealed that pairs were continually moving into new areas, suggesting that their ranging behaviour is adapted to an irregular pattern of resource distribution. Two maras had prevailing ranges of 35 ha and moved yearly over about 200 ha. Ranges floated around a geographic centre. One constraint on the animals' movements may be the need to stay near a den site for pupping. Maras were diurnal, and spent on average 46% of the day grazing. Ranges may overlap up to 33%, but range use between neighbouring pairs were negatively correlated suggesting that animals were avoiding each other--pairs may be occupying floating territories. Evidence that maras are monogamous in the wild is presented. The factors leading to monogamy are argued to be: (i) females are irregularly dispersed because of the distribution of food; and (ii) the brevity of the female's oestrus (1-2 hrs). A male attempting to mate polygynously would have difficulties in finding and securing a female; thus males may do best by staying with one female to ensure a successful mating. Males may enhance their reproductive success by watching for predators so that their females can spend more time feeding to meet the energetic demands of lactation and gestation. During the pupping season, August to January, groups of 1 to 22 pairs gather at single dens. Several dens may be located near each other to form denning communities. Most pairs produce only one litter a year and there is a peak of births in September and October. Pairs visit the den once a day for a period of 5-6 weeks to nurse their young. Den sites are not limited; and the reason maras den communally appears to be the increased protection from predators accruing to pups and adults in larger groups. Two possible routes are suggested in the evolution of the mara's social system: (i) from a monogamous starting point it has become advantageous to creche pups; or (ii) ancestral maras were more colonial and probably polygynous, but have been forced to space out because of changes in the distribution of food, which has led to monogamy. Finally, maras were compared with other caviomorph rodents, lagomorphs, and monogamous ruminants and were shown to be most similar to the latter in their adaptations to the environment a remarkable example of convergent evolution.

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This thesis examined the odiferous nature of rodent saliva for the male Mongolian gerbil, male and diestrous female golden hamsters, and male and female degus. Within each species,like-sexed pairs were dichotomized as to dominance or submissiveness and individual animals were presented with salivary samples from dominant pairings, an opposing gender, and a saline control; in an open field arena. Both degus and gerbils did not show any discriminative responding, via sniffs, time spent in proximity of and approaches to allstimuli. Degus discriminated salivary stimuli over the control when allowed to contact the stimuli. Degus preferred, via approaches, female samples. Male hamsters discriminated amongst all stimuli for the three behavioral measures. Dominant males preferred other male cues over diestrous female and saline samples via sniff. For approaches, dominant males preferred other dominant cues over submissive or female cues. Submissives preferred all salivary cues over the control via sniffs, but showed no individual preferences amongst the salivary cues. Female hamsters discriminated amongst all stimuli via sniffs. Dominant females preferred other submissive samples over those of a male and preferred dominant and submissive samples over the control, submissive females preferred all three salivary cues over the control; no other preferences were found. The importance of salivary cues and the odiferous nature of chemical cues of all secretory by-products of rodents are discussed.

Communities of granivorous desert rodents are structured by habitat selection and may be influenced by either predatory risk or resources. To examine these hypotheses, I manipulated illumination using lanterns, parachute canopies, or natural moonlight and resources using seeds. Foraging behavior is risk-sensitive; increased illumination reduces foraging in open areas while adding shadows to open areas using parachutes increases foraging there. Foraging behavior is also affected by resource enrichments. Differences among species in habitat selection were determined by specific abilities to detect and avoid predators. The least vulnerable species, Dipodomys deserti, foraged heavily in the open and was largely unaffected by treatments; other species of kangaroo rats and kangaroo mice also prefer the open, but responded to both risk and resource manipulations; highly vulnerable Peromyscus maniculatus was always restricted to bushes even under the most favorable circumstances; Perognathus longimembris was restricted to bushes in the absence of P. maniculatus in 1980 and was displaced from preferred microhabitats by the presence of kangaroo rats in 1981. A correlation between auditory bullar volume and use of open habitat by the various species in this community suggests that predatory risk provides an axis along which habitat segregation occurs. Predation can shape community structure by influencing foraging decisions of individuals. Desert rodents from North America and the Middle East have converged morphologically and perhaps in behavior and in community structure. Using desert rodent communities in the Great Basin Desert of U.S.A. and in the Negev Desert of Israel, I manipulated predatory risk in both communities and noted that foraging activity declines with increased predatory risk. Additional evidence suggests that predation also affects habitat selection behavior in both communities. Furthermore, differences in habitat utilization among species which promotes coexistence are related to morphological anti-predator specialization of the species. Predation appears to have shaped behavior and contributed to community structure in similar ways in both communities.

Indiana University-Purdue University Indianapolis (IUPUI) / Assessments of delay discounting in rodent lines bidirectionally selected for home cage intake and preference of alcohol have had mixed findings. The current study sought to examine if delay discounting related differentially to alcohol seeking versus and alcohol drinking, two processes underlying alcohol intake and preference. Three strains of rats were utilized to answer this question Long Evans (LE), high alcohol drinking rats (HAD2), and alcohol preferring P rats. All strains were compared in an adjusting amount delay discounting task. Operant self-administration of alcohol was then assessed in the sipper tube model, and finally home cage drinking was assessed in a 24 hour 2 bottle choice paradigm. In the delay discounting it was found that the P rats were steeper discounters than both the LE and HAD2. In the sipper tube model, P rats displayed higher levels of seeking than both the HAD2s and the LE, but both the P rats and the HAD2s had higher intakes than the LE. During 24 hour home cage access, the P rats and the HAD2s had higher intake and preference for alcohol than the LE, but were not different from each other. These results show that increased discounting of delayed rewards tracks with appetitive processes versus consummatory factors and home cage intake of alcohol. This builds on prior findings using selected line pairs by providing an explanation for discordant results, and supports the hypotheses that increased delay discounting is an intermediate phenotype that predisposes individuals to alcohol use disorders.