Arctic seabirds exposed to acute stress display state- and environment-dependent patterns of surface temperature change, independent of mercury contamination

Abstract

Animals mount a suite of physiological reactions when confronted with acute stressors, including changes in body temperature (T_b). Such thermal stress responses (TSRs) are important to survival, but may also generate heat stress, making regulation critical. Poor body condition and exposure to chemical contaminants, such as mercury (Hg), a neurotoxin and endocrine disruptor, may have physiological effects that disrupt modulation of TSRs. Implications of such effects could be magnified by climate change. We used infrared thermography (IRT) imagery to measure stress-induced changes in body surface temperature (maximum temperature of the eye region; T_EYE) of an Arctic seabird, the little auk (Alle alle). We evaluated how changes were correlated with Hg contamination, body condition, blood chemistry parameters and ambient temperature (T_a). As Arctic animals, little auks are cold-adapted and face warming rates nearly four times the global average, making them vulnerable to heat stress. Little auks displayed a robust TSR with T_EYE at sample point 1–3 (mean ± SD) of 28.9 ± 6.86 °C, 33.7 ± 5.48 °C, and 35.4 ± 5.76 °C, respectively. Mercury load was unrelated to changes in T_EYE. However, T_EYE was elevated at higher T_a (β ± SE =3.214 ± 0.733) across sampling time points, suggesting upregulation of heat dissipation. Furthermore, little auks in poor condition displayed lower magnitude changes in T_EYE (β ± SE = 0.688 ± 0.232), and several blood chemistry parameters were correlated to changes in T_EYE. Results suggest that thermoregulatory dynamics in the face of acute stress depend on environmental and physiological state.