2020/09/08 by Blair O. Wolf, Andrew E. McKechnie, Charlotte Schmitt +3 · 1 citation
Agricultural and Biological Sciences · Environmental Science · #Bat Biology and Ecology Studies #Physiological and biochemical adaptations #Climate variability and models #Torpor #Hummingbird #Biology #Ecology #Mammal #Zoology #Thermoregulation
paper · pdf · doi:10.1098/rsbl.2020.0428
openalex publication_date 2020/09/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Abstract Torpor is thought to be particularly important for small endotherms occupying cold environments and with limited fat reserves to fuel metabolism, yet among birds deep torpor is both rare and variable in extent. We investigated torpor in hummingbirds at approximately 3800 m.a.s.l. in the tropical Andes by monitoring body temperature (Tb) in 26 individuals of six species held captive overnight and experiencing natural air temperature (Ta) patterns. All species used pronounced torpor, with one Metallura phoebe reaching a minimum Tb of 3.26°C, the lowest yet reported for any bird or non-hibernating mammal. The extent and duration of torpor varied among species, with overnight body mass (Mb) loss negatively correlated with both minimum Tb and bout duration. We found a significant phylogenetic signal for minimum Tb and overnight Mb loss, consistent with evolutionarily conserved thermoregulatory traits. Our findings suggest deep torpor is routine for high Andean hummingbirds, but evolved species differences affect its depth.