An efficient and inexpensive method for measuring long-term thermoregulatory behavior

Abstract

Thermoregulatory ability and behavior influence organismal responses to their environment. By measuring thermal preferences, researchers can better understand the effects that temperature tolerances have on ecological and physiological responses to both biotic and abiotic stressors. However, because of funding limitations and confounders, measuring thermoregulation can often be difficult. Here, we provide an effective, affordable (∼$50 USD per unit), easy to construct, and validated apparatus for measuring the long-term thermal preferences of animals. In tests, the apparatus spanned temperatures from 9.29 to 33.94 °C, and we provide methods to further increase this range. Additionally, we provide simple methods to non-invasively measure animal and substrate temperatures and to prevent temperature preferences of the focal organisms from being confounded with temperature preferences of its prey and its humidity preferences. To validate the apparatus, we show that it was capable of detecting individual-level consistency and among individual-level variation in the preferred body temperatures of Southern toads (Anaxyrus terrestris) and Cuban tree frogs (Osteopilus septentrionalis) over three-weeks. Nearly every aspect of our design is adaptable to meet the needs of a multitude of study systems, including various terrestrial amphibious, and aquatic organisms. The apparatus and methods described here can be used to quantify behavioral thermal preferences, which can be critical for determining temperature tolerances across species and thus the resiliency of species to current and impending climate change.

The thermal mismatch hypothesis explains host susceptibility to an emerging infectious disease

“…zeteki , we maintained uninfected animals individually in thermal gradient apparatuses (Sauer et al . ; n = 24, 25 and 9 animals, respectively). Detailed methods describing the construction and application of the apparatuses for temperature preference trials are described in Sauer et al .…”

Behavioural fever reduces ranaviral infection in toads

“…In each experiment, we first measured baseline non‐infected temperature preference (baseline T pref ) in thermal gradient apparatuses (see next paragraph for the frequency of these measurements). These apparatuses were previously shown to provide variation in temperature that is independent of humidity and which does not confound amphibian and prey temperature preferences (see Figure S1 and supplemental methods, and Sauer, Sperry, and Rohr () for thermal gradient construction and validation details). The apparatuses provided an ecologically relevant ambient temperature range of 12–33°C (Fritts et al, ; Sauer et al, , ).…”

“…These apparatuses were previously shown to provide variation in temperature that is independent of humidity and which does not confound amphibian and prey temperature preferences (see Figure S1 and supplemental methods, and Sauer, Sperry, and Rohr () for thermal gradient construction and validation details). The apparatuses provided an ecologically relevant ambient temperature range of 12–33°C (Fritts et al, ; Sauer et al, , ). After measuring baseline T pref , individuals were split into two groups of similar mean body masses and baseline T pref ( N = 53), (a) a sham‐exposed control group (metamorph: n = 12; adult n = 14) and (b) a ranavirus‐exposed treatment group (metamorph: n = 13; adult n = 14).…”

“…Throughout the experiment, temperature measurements were taken each day, every four hours, between 10:00 hr and 22:00 hr (two during the lighted part of the photoperiod and two during the dark) at the centre of each animal's dorsum (Rowley & Alford, ) (Extech ® High Temperature IR Thermometer; accuracy: ±2% < 932°F). The only exception is that these measurements were not taken during feeding periods, during which all individuals were fed 10 live crickets in containment bags to prevent crickets from moving freely within the thermal gradient (see Sauer et al () and Figure S4 for more details). Temperature measurements were taken for 4 days before ranaviral or sham exposure.…”

A simple, band-mounted device to measure behaviorally modified thermal microclimates experienced by birds

“…), and laboratory‐based studies of thermal tolerance (e.g., Sauer et al. ). Such indirect approaches are not necessarily suitable for mobile organisms, such as birds, especially when important demographic processes (e.g., mortality and fecundity) can depend on relatively short‐duration exposure to extreme temperatures (McKechnie and Wolf , Cunningham et al.…”