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.

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