Acute Heat Exposure Upregulates Zebra Finch Physiology While Avoiding DNA Damage Across Both Sexes.

A recent increase in the frequency of extreme heat events has urged researchers to examine physiological responses to hot temperatures. Across species, there is variation in whether the sexes respond the same or differently to extreme temperatures. Accordingly, our study investigated the sex-specific responses to an acute heat exposure. We assigned adult male and female zebra finches to a 5-h control (22°C; female: n = 20, male: n = 19) or a heat treatment (43°C; female: n = 23, male: n = 22). We collected blood samples 2 weeks pre-treatment and immediately post-treatment to measure blood concentrations of corticosterone, glucose, ketones (beta-hydroxybutyrate), and DNA damage. Additionally, we measured the core body temperatures of the birds via PIT tags. Heat exposure significantly increased body temperature, blood glucose, blood ketone, and plasma corticosterone levels. In contrast, we found no significant difference in DNA damage levels in the red blood cells. Finally, we found no sex differences in these physiological measures. To explore systematic interactions, we utilized Gaussian Graphical Models, which indicated that heat stress results in more coupled interactions between variables. Notably, ketones and glucose were positively correlated in the control group but negatively correlated in the heated group, suggesting a shift in metabolic fuel utilization. Our findings suggest that physiological and cellular responses to acute heat stress are consistent across sexes in adult zebra finches. These findings are an important step to better understand the physiological underpinnings of how birds respond to acute heat stress.