Effects of consumption of juniper (Juniperus monosperma) on cost of thermoregulation in the woodrats Neotoma albigula and Neotoma stephensi at different acclimation temperatures

A study was done to test whether toxic plants that occur naturally in the diet affect thermoregulation in mammalian herbivores. The woodrats Neotoma albigula and Neotoma stephensi both consume juniper (Juniperus monosperma), a plant with high levels of toxic compounds. Body temperature (T_b), basal metabolic rate (BMR), and the minimum cost of thermogenesis (C _min) were measured for both species on control and juniper diets following warm (25°C) and cold (18°C) acclimation. In N. albigula, diet had no uniform effect on T_b, BMR, or C_min, but diet x acclimation-temperature interaction effects on T_b and C_min were highly significant (P < 0.005). For thermoregulation at 15°C, juniper consumption increased the metabolic cost for warm-acclimated N. albigula by 50% but decreased the metabolic cost in cold-acclimated N. albigula by 24%. In N. stephensi, diet significantly affected T_b and C_min (P < 0.05), but there were no significant diet x acclimation-temperature interaction effects. For thermoregulation at 15°C, juniper consumption increased the metabolic cost for warm-acclimated N. stephensi by 33% but had no significant effect on metabolic cost in cold-acclimated N. stephensi.