Abstract:
A major focus in the study of endothermic thermoregulation
has been the description of thermoregulatory patterns used by
various species and/or populations. Compared with ectotherms,
relatively few attempts have been made to study the thermoregulation
of endotherms in an adaptive framework.We believe
that one of the main factors limiting this area of research has
been the lack of an appropriate metric to directly compare body
temperature (Tb) variation across all endothermic species. Thus,
we present a simple comparative metric, the heterothermy index
(HI), to quantify the expression of heterothermy by endotherms
during a given time frame. Key advantages of HI are
that (1) it represents a new analytical technique that has different
strengths than the metrics commonly used to describe
variation in Tb, (2) it allows for evaluation of nonenergetic
costs and benefits that affect the expression of heterothermy,
and (3) it has the potential to unify research on homeotherms
and heterotherms through quantitative comparative analyses
that examine the entire continuum of thermoregulatory patterns.
In short, we suggest that our metric provides a means
to overcome one of the hurdles presently slowing the advancement
of research on endothermic thermoregulation beyond the
simple description of thermoregulatory patterns.
