Keeping your cool: thermoregulatory performance and plasticity in desert cricetid rodents

Author

Richard W. Ramirez, University of New Mexico - Main CampusFollow
Eric A. Riddell, Iowa State UniversityFollow
Steven R. Beissinger, University of California - BerkeleyFollow
Blair W. Wolf, University of New Mexico - Main CampusFollow

Publication Date

Winter 2-2022

Abstract

Small mammals in hot deserts often avoid heat via nocturnality and fossoriality and are thought to have a limited capacity to dissipate heat using evaporative cooling. Research to date has focused on thermoregulatory responses to air temperatures (T_a) below body temperature (T_b). Consequently, the thermoregulatory performance of small mammals exposed to high air temperatures is poorly understood, particularly responses across geographic and seasonal scales. We quantified the seasonal thermoregulatory performance of four cricetid rodents (Neotoma albigula, N. lepida, Peromyscus eremicus, P. crinitus) exposed to high T_a, at four sites in the Mojave Desert. We measured metabolism, evaporative water loss and T_b using flow-through respirometry. When exposed to T_a ≥ T_b, rodents showed steep increases in T_b, copious salivation and limited evaporative heat dissipation. Most individuals were only capable of maintaining T_a-T_b gradients of ~1 °C resulting in heat tolerance limits (HTL) ranging from T_a = 43-45°C. All species exhibited a thermoneutral T_b of ~35-36 °C, and T_b increased to maximal levels of ~ 43°C. Metabolic rates and rates of evaporative water loss increased steeply in all species as T_a approached T_b. We also observed significant increases in resting metabolism and evaporative water loss from summer to winter at T_as within and above the thermoneutral zone. In contrast, we found few differences in the thermoregulatory performance within species across sites. Our results suggest that cricetid rodents have a limited physiological capacity to cope with environmental temperatures that exceed T_b and that a rapidly warming environment may increasingly constrain their nocturnal activity.

Language

English

Keywords

Cricetid, high air temperatures, water balance, hyperthermia, metabolism

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Blair Wolf

Second Committee Member

Christopher Witt

Third Committee Member

Joseph Cook

Recommended Citation

Ramirez, Richard W.; Eric A. Riddell; Steven R. Beissinger; and Blair W. Wolf. "Keeping your cool: thermoregulatory performance and plasticity in desert cricetid rodents." (2022). https://digitalrepository.unm.edu/biol_etds/347