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Energetics, Temperature and Water Relations in Winter Aggregated Sceloporus Jarrovi (Sauria: Iguanidae)

1979; Wiley; Volume: 60; Issue: 1 Linguagem: Inglês

10.2307/1936464

1939-9170

Justin D. Congdon, Royce Ε. Ballinger, Kenneth A. Nagy,

Species Distribution and Climate Change

Metabolic rates and water fluxes in winter—aggregated Yarrow's spiny lizards (Sceloporus jarrovi) were measured in the field using doubly—labeled water. Resting metabolic rates were estimated from measurements of microhabitat and lizard body temperatures. During the month (November) following aggregation at the hibernaculum and the month (April) before dispersal, lizards were relatively active and their metabolic rates averaged 0.071 ml CO 2 °g — 1 °h — 1 , °40% of their warm season rates. From December through March, lizards basked but were relatively inactive with metabolic rates averaging 0.031 ml CO 2 °g — 1 °h — 1 , °15% of warm season rates. Water influx rates averaged 10.3 ml°kg — 1 °day — 1 during the 120—day inactive period. Water loss was slightly higher than gain and lizards lost weight slowly while hibernating, having ended the 6—mo aggregation period with a 22% decline in body mass. Total energy expenditures during the aggregation period averaged °7.53 kJ, <2 of which could have been supplied by stored body fat. This, together with other direct and indirect evidence, suggests that lizards fed during the cold season. As a result of basking and displaying some activity, S. jarrovi spent >3 times as much energy during the aggregation period as would a lizard remaining inactive in a crevice at 10°C for the entire 6 mo. Possible benefits of winter basking are discussed.