Limited heat tolerance in a cold-adapted seabird: implications of a warming Arctic

Abstract

The Arctic is warming at approximately twice the global rate, with well-documented indirect effects on wildlife. However, few studies have examined the direct effects of warming temperatures on Arctic wildlife, leaving the importance of heat stress unclear. Here, we assessed the direct effects of increasing air temperatures on the physiology of thick-billed murres (Uria lomvia), an Arctic seabird with reported mortalities due to heat stress while nesting on sun-exposed cliffs. We used flow-through respirometry to measure the response of body temperature, resting metabolic rate, evaporative water loss and evaporative cooling efficiency (the ratio of evaporative heat loss to metabolic heat production) in murres while experimentally increasing air temperature. Murres had limited heat tolerance, exhibiting: (1) a low maximum body temperature (43.3°C); (2) a moderate increase in resting metabolic rate relative that within their thermoneutral zone (1.57 times); (3) a small increase in evaporative water loss rate relative that within their thermoneutral zone (1.26 times); and (4) a low maximum evaporative cooling efficiency (0.33). Moreover, evaporative cooling efficiency decreased with increasing air temperature, suggesting murres were producing heat at a faster rate than they were dissipating it. Larger murres also had a higher rate of increase in resting metabolic rate and a lower rate of increase in evaporative water loss than smaller murres; therefore, evaporative cooling efficiency declined with increasing body mass. As a cold-adapted bird, murres' limited heat tolerance likely explains their mortality on warm days. Direct effects of overheating on Arctic wildlife may be an important but under-reported impact of climate change.

Breeding failures and reduced nest attendance in response to heat stress in a high-latitude seabird

“…High-latitude seabird species may be particularly vulnerable to the direct effects of global warming, as they are adapted to conserve rather than lose heat and therefore show limited heat tolerance (Choy et al 2021). One such high-latitude species is the common guillemot Uria aalge.…”

Warming in the land of the midnight sun: breeding birds may suffer greater heat stress at high- versus low-Arctic sites

“…Many Arctic animals are cold specialists and have evolved physiological adaptations for minimizing heat loss [24,25]. Consequently, high-latitude breeding species are probably vulnerable to even moderate increases in ambient temperature [26][27][28][29]; an alarming fact given that the Arctic has warmed faster than the global average and is expected to continue outpacing the global average over the twenty-first century [4]. Additionally, O'Connor et al [26] recently showed that buntings become heat-stressed at moderate air temperatures and have an extremely limited evaporative cooling capacity.…”

Exposure to cumulative stressors affects the laying phenology and incubation behaviour of an Arctic-breeding marine bird

“…Our prediction was that higher THg levels would result in greater movements due to reductions in PRL that may negatively impact incubation consistency (Tartu et al 2015(Tartu et al , 2016. However, in our study, the combination of THg and heat stressors resulted in less incubation interruptions, potentially due a more complex system than anticipated that includes the reaction of females to acute heat stress, as well as the supressing effect of THg on CORT, which in-turn may interact with PRL levels (Provencher et al 2016;Tartu et al 2015;Choy et al 2021). Females with lower THg levels may have a heightened acute stress response to heat exposure outside of their thermal limits, releasing CORT that supresses PRL and results in greater incubation interruptions (Tartu et al 2015;Choy et al 2021).…”

“…However, in our study, the combination of THg and heat stressors resulted in less incubation interruptions, potentially due a more complex system than anticipated that includes the reaction of females to acute heat stress, as well as the supressing effect of THg on CORT, which in-turn may interact with PRL levels (Provencher et al 2016;Tartu et al 2015;Choy et al 2021). Females with lower THg levels may have a heightened acute stress response to heat exposure outside of their thermal limits, releasing CORT that supresses PRL and results in greater incubation interruptions (Tartu et al 2015;Choy et al 2021). While this action is a potential self-preservation method to obtain water and prevent dehydration, the female risks egg overheating and greater predation risk due to female absence and movements attracting predators (Smith et al 2012;Geldart 2021;Ridley et al 2021).…”

“…These climatic alterations have the potential to affect Arctic species, with effects ranging from changes in primary productivity abundance and phenology, to alterations in prey availability for top marine and terrestrial predators in a complex, connected system (Frederiksen et al 2006;Renaut et al 2018;Pratte et al 2019;Lewis et al 2020). Marine birds in particular are known to be highly sensitive to environmental change and elevated thermal environments (Piatt et al 2007;Le Bohec et al 2013;Choy et al 2021). Environmental shifts can alter avian migratory and reproductive phenology, especially in the Arctic which offers a short favorable window for those breeding, notably via spatio-temporal constraints in prey availability at extreme latitudes (Martin and Wiebe 2004).…”