DOI: 10.5061/dryad.47d7wm39k
title: Data from: Body mass affects short term heterothermy in Neotropical bats

description: Recent work in Australia and Africa has shown that heterothermy is
 widespread among phylogenetically diverse tropical and subtropical
 mammalian taxa. However, data on the use of heterothermy by Neotropical
 mammals are relatively scant, and those studies that exist focus on
 insect-eating bats. We investigated the capacity of fruit-eating
 Neotropical bats to use heterothermy when exposed to acute cold
 temperatures, and compared this to previous data focused on insect-eating
 bats sampled from the same region and time of year. We measured rectal
 temperatures prior to acute cold exposure (1 hour at an air temperature of
 6, 7, or 10°C), and again after exposure. Our data show considerable
 variation in the thermoregulatory patterns of Neotropical bats and
 generally, our results show that smaller bats cool quicker and to a
 greater extent than larger bats. Our results highlight the importance of
 energy conservation even in environments in which resources are relatively
 abundant.
description: Bats were captured in mist nets or harp traps set across known
 flight paths. Each bat was identified to species, and we recorded the
 individual’s age, sex and reproductive condition, and measured body mass
 and forearm length. Each bat was placed into a small, one-time-use cloth
 drawstring bag for up to 8 hours. Using cloth bags for bat containment is
 a common practice because they greatly reduce the risk of injury, isolate
 the bat from disturbances, and allow bats to hang in a natural position.
 All bat bags were hung in a sheltered space at our field site where bats
 were allowed to rest for up to 8 hours in
 <em>T<sub>a</sub></em> (26 – 32 ºC). This
 acclamatory period ensured bats would be post-absorptive and in the
 diurnal rest phase of their circadian cycle prior to experimental trials.
 After the 8 hour acclimation, we manipulated the bat bag so that only the
 genital area was exposed and used a sterilized, lubricated thermocouple
 probe to measure resting rectal
 <em>T<sub>b</sub></em> as a proxy of core
 <em>T<sub>b</sub></em> (Britzke, Sewell, Hohmann,
 Smith, & Darling, 2010).  Special care was taken to do this
 quickly so as not to prolong bats’ exposure to stimulus. Similar to Czenze
 & Dunbar (2017), immediately after, we closed the bag and placed
 it into an environmental chamber maintained at either 6, 7, or 10 ± 0.2
 °C, which are within the range of historic low
 <em>T<sub>a</sub></em>s of the area (Belize
 National Meteorological Service; available from
 http://www.hydromet.gov.bz/). After being exposed to a temperature
 treatment for 1 hour, we removed bats and measured rectal<em>
 T<sub>b</sub></em> again using the same manner as
 outlined above. In the wild, a normothermic bat exposed to 5 °C for 1 hour
 may reduce its <em>T<sub>b</sub></em> by ~30 °C
 (Czenze, Jonasson, & Willis, 2017); this exposure time also
 allowed us to operate within the confines of our permits and animal care
 protocols. We sampled individuals once at one of our three temperature
 treatments and repeated with new captures until each species had multiple
 representative individuals across all temperature treatments.  Upon
 conclusion of experimental trails, bats were allowed to rewarm in
 <em>T<sub>a</sub></em> and we used a disposable
 pipette to give bats water or diluted fruit juice to drink before
 releasing them at their site of capture.