Opportunities for behavioral rescue under rapid environmental change

Abstract

Laboratory measurements of physiological and demographic tolerances are important in understanding the impact of climate change on species diversity; however, it has been recognized that forecasts based solely on these laboratory estimates overestimate risk by omitting the capacity for species to utilize microclimatic variation via behavioral adjustments in activity patterns or habitat choice. The complex, and often context‐dependent nature, of microclimate utilization has been an impediment to the advancement of general predictive models. Here, we overcome this impediment and estimate the potential impact of warming on the fitness of ectotherms using a benefit/cost trade‐off derived from the simple and broadly documented thermal performance curve and a generalized cost function. Our framework reveals that, for certain environments, the cost of behavioral thermoregulation can be reduced as warming occurs, enabling behavioral buffering (e.g., the capacity for behavior to ameliorate detrimental impacts) and “behavioral rescue” from extinction in extreme cases. By applying our framework to operative temperature and physiological data collected at an extremely fine spatial scale in an African lizard, we show that new behavioral opportunities may emerge. Finally, we explore large‐scale geographic differences in the impact of behavior on climate‐impact projections using a global dataset of 38 insect species. These multiple lines of inference indicate that understanding the existing relationship between thermal characteristics (e.g., spatial configuration, spatial heterogeneity, and modal temperature) is essential for improving estimates of extinction risk.

Heat tolerance and thermal preference of the copepod Tigriopus californicus are insensitive to ecologically relevant dissolved oxygen levels

“…Indeed, our behavioral preference test showed that females avoided near-lethal temperatures even if by doing so they had to deal with lower oxygen levels at lower temperatures. This behavioral preference of T. californicus , which remains to be demonstrated in a natural setting, supports a recent prediction that behavioral responses of natural populations may enable them to exploit microclimatic variations in heterogeneous habitats as an important mechanism to rescue species from rapidly changing environments 17 , 18 .…”

“…For example, extreme temperatures decrease the oxygen solubility while simultaneously increasing the organism’s oxygen demand, hence intensifying hypoxic stress on marine species 7 , 13 . To locally survive, organisms may have to adjust their physiology 14 – 16 and/or behaviors 14 , 17 , 18 to cope with or avoid stressful conditions. However, we know relatively little about the prevalence and magnitude of the present-day interactions among stressors and their impacts on marine species 10 – 12 .…”

“…By similar logic, it is also possible that oxygen levels influence organismal temperature preferences. Mobile species can employ behavioral adjustments to avoid stressful conditions by selecting specific microhabitats in spatially heterogeneous environments 14 , 18 . Indeed, spatial heterogeneity is a widespread feature of natural habitats 28 , 29 , even in small splashpools 29 , 30 .…”

“…Indeed, spatial heterogeneity is a widespread feature of natural habitats 28 , 29 , even in small splashpools 29 , 30 . Behavioral adjustments can provide an alternative mechanism to rescue species from stressful conditions 14 , 17 , 18 . Many species can adjust their position to seek preferred thermal and oxygen zones 31 , 32 .…”

“…Fewer studies have examined preference behaviors in a multi-stressor context, and those showed that fish have a lower temperature preference in hypoxic conditions than in normoxia 34 , 35 . Overlooking the potentials of behavioral responses to multiple stressors such as extreme temperatures and low dissolved oxygen (DO) levels may fail to accurately quantify the real risk of environmental changes in natural populations 17 , 18 .…”