|
|||||
|
|
A test of two hypotheses explaining the seasonality of reproduction in temperate mammals |
|
| Authors: | F Fournier D W Thomas & T Garland JR |
| Institution: | Groupe de recherche en écologie, nutrition et énergétique, département de biologie, Universitéde Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1,,;Musée du Séminaire de Sherbrooke, Sherbrooke, Québec, Canada J1H 1J9 and,;Department of Zoology, 430 Lincoln Drive, University of Wisconsin, Madison, WI 53706, USA |
| Abstract: | 1. Two proposed hypotheses about energy allocation were tested to explain the patterns of seasonal reproduction found in temperate mammals. The two hypotheses predict either that total demand for energy is greater during reproduction than during winter (when thermoregulatory costs are high) (Increased Demand Hypothesis) or that total costs during winter are greater than or equal to total costs during reproduction (Reallocation Hypothesis). 2. Data were compiled from the literature on summer (non-reproducing) and winter metabolic rates of temperate mammals, and were used on litter sizes and a published equation to predict metabolic rates during lactation. 3. All three measures of metabolic rate scaled to body mass with slopes significantly less than one. Metabolic rates during winter averaged ≈ 2 times greater than those of non-reproducing mammals during summer. On average, predicted metabolic rates during lactation were not significantly greater than during winter, but for some individual species they clearly were. 4. It is suggested that neither the Reallocation nor the Increased Demand Hypothesis can fully explain seasonal reproductive patterns in temperate mammals. |
| Keywords: | Comparative method mammals reallocation of energy seasonal reproduction |