Does the unusual life history of the precocial cavy (Cavia magna) translate into an exceptional field metabolic rate?
An association between metabolic rate and life history has been predicted but not demonstrated yet. To test this prediction, we measured the field metabolic rate (FMR) of a rodent, Cavia magna, which has an unusual combination of life-history traits. Cavies live aboveground, feed on energy-poor diets, and take relatively long to produce a few highly precocial young. This "slow-living" life history might predict a relatively low metabolic rate. We recorded FMR of 29 individuals of C. magna in Uruguay using doubly labeled water. This represents the first FMR record for a hystricomorph rodent. Besides body mass, season best explained variation in recorded FMR, with higher daily energy expenditures during winter. Surprisingly, the reproductive state of females did not affect FMR. Comparison with allometric prediction did not support the hypothesis that the slow-living life history of precocial grazing cavies translates into relatively low FMR. However, the clear effect of season on FMR as well as the fact that cavies appear able to compensate for the energy cost of reproduction might be associated with the nonburrowing precocial life history of this species.
Kunkele
Joachim
J
Lehrstuhl fur Verhaltensforschung, Universitat Bielefeld, Postfach 100131, 33501 Bielefeld, Germany. joachim.kuenkele@uni-bielefeld.de
Kraus
Cornelia
C
Trillmich
Fritz
F
D000704:Analysis of Variance; D000818:Animals; D001481:Basal Metabolism; D001834:Body Water; D001835:Body Weight; D002245:Carbon Dioxide / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006168:Guinea Pigs / Q000502:physiology*; D008297:Male; D010103:Oxygen Isotopes; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D013696:Temperature; D014316:Tritium; D014583:Uruguay; D014867:Water
D010103:Oxygen Isotopes; D014867:Water; D014316:Tritium; D002245:Carbon Dioxide; C033961:tritium oxide