The comparative energetics of 'caviomorph' rodents

The energetics of It species of New World hystricognath ('caviomorph') rode nts are presented and compared with data from the literature on 19 addition al species. Log(10) body mass alone accounts for 94% of the variation in th e log(10) basal rate of metabolism in caviomorphs. The residual variation i n basal rate is correlated with the stratum on which species live: arboreal species have low basal rates; terrestrial and fossorial species have inter mediate basal rates; and aquatic species have high basal rates. When stratu m is not included in the analysis, folivores, especially those that are arb oreal, have lower basal rates than species with other food habits when comb ined with log(10) body mass. Small island endemics, all of which are folivo res, have basal rates that are 61% of continental species. Log(10) basal ra te correlates with family affiliation when combined with log(10) mass, but only if no other factor is included. Therefore, caviomorphs with low basal rates are arboreal, folivorous, live on small islands and belong to the Cap romyidae, whereas other character combinations are associated with higher b asal rates. These observations demonstrate that the basal rates of caviomor phs reflect many factor interactions. No differences in basal rate were fou nd to reflect climate. Log(10) mass, the only factor to correlate with cond uctance, accounts for 82% of the variation in log(10) minimal thermal condu ctance. Mean interspecific body temperature was 36.9 degreesC; it was lowes t in aquatic and fossorial species. (C) 2001 Elsevier Science Inc. All righ ts reserved.