This study dealt with the life history and population dynamics of the pine vole, Microtus pinetorum. In the past there has been a void of ecological material concerning this small mammal in the southwestern region of its range. From November, 1969, through February, 1970, a survey was conducted in Marion County and Harrison County, Texas, to determine the most suitable habitat for an ecological study of Microtus pinetorum. A study was then initiated in March, 1970, and continued through March, 1971, on an undisturbed marsh five miles south of Marshall, Harrison County, Texas.

Bioenergetic measurements were made on adult, lactating females, and growing juvenile pine voles. Adult pine voles showed a seasonal cycle in daily maintenance energy requirements. Winter was energetically the most expensive season. Requirements during the summer season were the lowest of all seasons. There was no significant difference in the daily energy requirements between adult male or female voles except during the summer season. Nesting material was found to be an important insulator asset which significantly depressed total daily energy requirements of adults. The period of lactation among female pine voles was energetically very demanding. The average lactating female and her litter required 47.5 percent more metabolizable energy than nonbreeding adult females of equivalent bodyweight. The net conversion of metabolized energy into tissue production during the period of lactation was extremely high among lactating female pine voles. Production efficiency was estimated to be 26.0 percent over 21 days of lactation. Production efficiency of lactating female pine voles was considerably higher than estimates derived for other vole species. Juvenile pine voles between the ages of 22-46 days had metabolizable energy requirements which were similar to those of an adult. Over the 24 days of postnatal development, the average juvenile pine vole metabolized 282 kcal of energy of which 25.8 kcal was deposited as tissue. The overall efficiency of production in juvenile voles was 9.2 percent which was considerably higher than estimates derived for other species of voles. A lignin analysis of stomach contents showed a distinct seasonal cycle in the digestibility of foods consumed by voles from the maintained and abandoned apple orchard. The highest digestibilities coincided with the maturation of the apple crop. The quantity of primary production available during the winter was lowest of all seasons. It was estimated that the amount of primary production available to pine voles during the winter season could support 994 nonreproducing adult voles per hectare in the maintained orchard and 147 nonreproducing adult voles per hectare in the abandoned apple orchard. / Master of Science

A mechanistic model was developed. to simulate apple orchard populations of the pine vole (Microtus pinetorum) in southwest Virginia. Population. size and demographic parameters were modeled on a weekly basis as functions of bioenerqetic status. Forage gross energy availability, digestibility, palatability, and preference were functions of Julian day. Daily energy budget (DEB) was a function of age, reproductive status, body weight, ambient temperature, and daily activity level. Energy acquisition was simulated assuming that consumption exceeded neither dietary energy demand nor a known maximum ingestion rate, and using linear programming to allocate forage class gross energy among competing vole classes. The 5 forage classes were queued by preference and consumed until all voles had fed maximally or forage was exhausted. Body weight and fat change were functions of age and energy restriction. Survivorship was a function of body fat balance, and probabilities of reproduction were functions of body fat balance and photoperiod. Animals were graduated between age and reproductive classes in a modified. Leslie algorithm by independent Bernoulli trial to avoid simulating fractional animals. Validation simulations suggested that dietary energy availability may limit pine vole populations in abandoned apple orchards, but not in maintained orchards. Simulation experiments suggested that pest populations of the pine vole in commercially maintained orchards may be controlled by a single control application in the fall achieving 80% mortality, or by 2 applications in the fall and spring achieving 50% mortality each. / Master of Science

Many lipophilic pesticides are known to be transferred to offspring via the mother's milk. The present study was conducted to determine how much endrin was transferred from endrin resistant and susceptible dams to their suckling pups and to further characterize the effects that endrin may have on the hepatic mixed function oxidase (MFO) system in the pups. Dosing of the dams with endrin began one day after birth with either (l) oral doses of endrin in corn oil or (2) a mixture of endrin in ground feed. The total amount of endrin in the pup was determined by gas chromatography. MFO activity was determined in 2-1/2 week old pups and for adult animals using maximal activities for the demethylation of ethylmorphine and hydroxylation of aniline. No difference in the amount of endrin present in the pups was observed between strains provided both received equal amounts of endrin. MFO activity for endrin dosed mature animals and for 2-1/2 week old pups from endrin dosed dams exhibited a significant decrease from control activities. There was no difference in MFO activities between age groups. A significantly higher ethylmorphine demethylase activity was observed in comparing the resistant to the susceptible strain but there was no significant difference in aniline hydroxylase activity. / Master of Science