We outline a computer model of heat and mass transfer through flesh, fat and porous fur for endotherms of any dimensions. We then validate it with a series of laboratory studies. Finally, we explore applications of the model to Bergmann's rule, predicting the mouse-to-elephant curve, climatedisease-toxicant interactions, animal 'design' via genetic engineering and energetic constraints on community structure.As a first test of the model we present calculations and metabolic chamber measurements for mammals ranging in size from mice to Holstein calves. We then compare simultaneous measurements on deer mice, Peromyscus maniculatus, of oxygen consumption, doubly labelled water turnover and food consumption with calculations of metabolic rate using body temperature radio-telemetry as input to the endotherm model. The endotherm model derived in the Appendix requires data on allometry (body dimensions, surface area), fur properties, core temperature, air and radiant temperatures and wind speed. The model is useful for calculating energetic expenditure in different microclimates without the need for extensive physiological measurements in the laboratory. Model predictions of metabolic rate at 12°C and at 22°C were well correlated with each of the three empirical estimates. The model shows that the posture an animal assumes can influence measurements of metabolic rate. Model calculations of metabolic rate using postures ranging from a curled-up ball-like geometry to a sprawled-out, cylinder or ellipsoid geometry bracket all three sets of simultaneous empirical data taken on the same animals.Applications of the model show that it can be applied in a wide variety of circumstances to gain insight into physiological and ecological problems.

We investigated the developmental toxicity in mice of a common commercial formulation of herbicide containing a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D), mecoprop, dicamba, and inactive ingredients. Pregnant mice were exposed to one of four different doses of the herbicide mixture diluted in their drinking water, either during preimplantation and organogenesis or only during organogenesis. Litter size, birth weight, and crown-rump length were determined at birth, and pups were allowed to lactate and grow without additional herbicide exposure so that they could be subjected to additional immune, endocrine, and behavioral studies, the results of which will be reported in a separate article. At weaning, dams were sacrificed, and the number of implantation sites was determined. The data, although apparently influenced by season, showed an inverted or U-shaped dose-response pattern for reduced litter size, with the low end of the dose range producing the greatest decrease in the number of live pups born. The decrease in litter size was associated with a decrease in the number of implantation sites, but only at very low and low environmentally relevant doses. Fetotoxicity, as evidenced by a decrease in weight and crown-rump length of the newborn pups or embryo resorption, was not significantly different in the herbicide-treated litters.

The effects of marginal malnourishment , infections, and environmental chemicals on growth and reproductive success in Swiss-Webster white mice and wild deer mice were studied with fractional factorial designs. Interaction effects were discovered. For example, malnourished mice were more sensitive to virus exposure and environmental chemicals (a plant growth regulator or polychlorinated biphenyls). Since several commercial plant growth regulators also appear to suppress the immune system, these results cast doubt on the adequacy of current toxicity testing procedures in which factors are studied individually and not in combination.

This paper describes the results of 5 years of research on interactive effects of mixtures of aldicarb, atrazine, and nitrate on endocrine, immune, and nervous system function. The concentrations of chemicals used were the same order of magnitude as current maximum contaminant levels (MCLs) for all three compounds. Such levels occur in groundwater across the United States. Dosing was through voluntary consumption of drinking water. We used fractional and full factorial designs with center replicates to determine multifactor effects. We used chronic doses in experiments that varied in duration from 22 to 103 days. We tested for changes in thyroid hormone levels, ability to make antibodies to foreign proteins, and aggression in wild deer mice, Peromyscus maniculatus, and white outbred Swiss Webster mice, Mus musculus, ND4 strain. Endocrine, immune, and behavior changes occurred due to doses of mixtures, but rarely due to single compounds at the same concentrations. Immune assay data suggest the possibility of seasonal effects at low doses. We present a multiple-level model to help interpret the data in the context of human health and biological conservation concerns. We discuss six testing deficiencies of currently registered pesticides, and suggest areas of human health concerns if present trends in pesticide use continue.

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