Higher Energy Demands and Lower Body Condition in a Hot Spring: Comparing Relict Leopard Frogs at Two Thermally Contrasting Sites
- 1School of Life Sciences, University of Nevada, Las Vegas Las Vegas Nevada USA
Abstract
Following range‐wide decline, all remnant populations of the relict leopard frog (Rana onca) in the eastern Mojave Desert of the southwestern USA occupied geothermally influenced hot springs. In recent years, however, several large populations have been established at cold‐water sites. There has, however, been little research into the thermal ecology of the species. We monitored body temperature (Tb) of adult frogs at a pair of hot and cold springs using implanted temperature data loggers, and measured body condition across seasons. We determined temperature preference using a thermal gradient, and measured mass‐specific oxygen consumption rates to estimate energy demands in the wild. We found that frogs at the two sites had similar temperature preferences, but the thermal profiles in the wild were seasonally 2.5°C to 5.7°C warmer at the hot site. In summer, frogs at the hot site mostly sought the lowest temperatures available, which were still warmer than measured thermal preferences. Frogs at the cold site maintained cooler temperatures at night, but warmed up during the early part of the day, likely moving in and out of cold water. At both sites, frogs in winter used two overwintering strategies, manifested mostly as differences in Tb variability. Frogs with low Tb variability thermally reflected cold water temperatures throughout most of winter and were interpreted as mostly inactive. Frogs with higher Tb and variability were interpreted as mostly remaining active throughout winter. We estimated that the energy demands at the hot site were 1.27‐fold higher in summer and 1.14‐fold higher in winter than at the cold site. Frogs at the hot site had significantly lower body condition than those at the cold site. We concluded that thermal conditions at the hot site were not favorable to R. onca and required higher energy investment in physiological maintenance, presumably at the expense of growth and reproduction.
Related
- Weaning body condition, preweaning survival, and post-weaning residence under contrasting breeding densities in Baltic grey seals
- Determining Spatial Patterns of Human-Tiger and Human-Leopard Conflict across South Asia through A Multi-Scale Regional Approach
- Identification and characteristics of multiple viruses in snow leopard fecal samples using viral metagenomics
- Seasonal variation in the density of the Persian leopard in the Hyrcanian forests of northern Iran
- Mapping Leopard Conservation Priorities in Southeast Asia
BibTeX
@article{pelletier2026higher,
title = {{Higher Energy Demands and Lower Body Condition in a Hot Spring: Comparing Relict Leopard Frogs at Two Thermally Contrasting Sites}},
author = {Robert P. Pelletier and Michael D. Treat and Frank van Breukelen and Jef R. Jaeger},
journal = {Journal of Experimental Zoology. Part A, Ecological and Integrative Physiology},
year = {2026},
month = sep,
doi = {10.1002/jez.70129},
url = {https://doi.org/10.1002/jez.70129},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Higher Energy Demands and Lower Body Condition in a Hot Spring: Comparing Relict Leopard Frogs at Two Thermally Contrasting Sites
AU - Robert P. Pelletier
AU - Michael D. Treat
AU - Frank van Breukelen
AU - Jef R. Jaeger
PY - 2026
DA - 2026/09/01
JO - Journal of Experimental Zoology. Part A, Ecological and Integrative Physiology
DO - 10.1002/jez.70129
UR - https://doi.org/10.1002/jez.70129
AB - Following range‐wide decline, all remnant populations of the relict leopard frog (Rana onca) in the eastern Mojave Desert of the southwestern USA occupied geothermally influenced hot springs. In recent years, however, several large populations have been established at cold‐water sites. There has, however, been little research into the thermal ecology of the species. We monitored body temperature (Tb) of adult frogs at a pair of hot and cold springs using implanted temperature data loggers, and measured body condition across seasons. We determined temperature preference using a thermal gradient, and measured mass‐specific oxygen consumption rates to estimate energy demands in the wild. We found that frogs at the two sites had similar temperature preferences, but the thermal profiles in the wild were seasonally 2.5°C to 5.7°C warmer at the hot site. In summer, frogs at the hot site mostly sought the lowest temperatures available, which were still warmer than measured thermal preferences. Frogs at the cold site maintained cooler temperatures at night, but warmed up during the early part of the day, likely moving in and out of cold water. At both sites, frogs in winter used two overwintering strategies, manifested mostly as differences in Tb variability. Frogs with low Tb variability thermally reflected cold water temperatures throughout most of winter and were interpreted as mostly inactive. Frogs with higher Tb and variability were interpreted as mostly remaining active throughout winter. We estimated that the energy demands at the hot site were 1.27‐fold higher in summer and 1.14‐fold higher in winter than at the cold site. Frogs at the hot site had significantly lower body condition than those at the cold site. We concluded that thermal conditions at the hot site were not favorable to R. onca and required higher energy investment in physiological maintenance, presumably at the expense of growth and reproduction.
SN - 2471-5638
SN - 2471-5646
ER -