ABSTRACT Endotherms balance high and stable body temperatures against significant energetic costs and food demands. Heterothermy, including torpor, helps individuals balance energy budgets under challenging conditions. Small flying endotherms face considerable challenges when balancing energy budgets during periods of inclement weather with low food availability. Although there is a wealth of knowledge about heterothermic responses of temperate insectivorous bats, considerably less is known about its occurrence and the factors that promote it in nectar‐feeding bats from tropical regions. Here, we experimentally tested whether Merriam's long‐tongued bat ( Glossophaga mutica ), a Neotropical nectarivorous species, uses heterothermy in response to reduced energy intake. Using temperature sensitive PIT‐tags, we monitored subcutaneous temperature in wild‐caught males fed either the full (100%) or restricted (25%) amount of predicted daily energy expenditure. Compared to bats that were fed a full energy diet, energetically challenged bats maintained subcutaneous temperatures significantly closer to roost temperature during the daytime inactive period, indicating a greater heterothermic response. Our results provide further evidence that G. mutica can flexibly modulate body temperature in response to short‐term energy deficits. This is similar to patterns observed in other nectarivorous bats, insectivorous bats, and nectar‐feeding birds like hummingbirds. This study contributes to a growing understanding of heterothermy in tropical mammals and suggests that nectarivorous bats use heterothermy as an adaptive response to unpredictable food availability likely driven in part by climate change.
Czenze et al. (Wed,) studied this question.