Stress Resilience: How Animals Learn to Cope Better with Severe Challenges

Stress is, first and foremost, a necessary adaptive response. In the short term, stress responses help animals cope with food scarcity, social conflict, predators or extreme weather conditions, for example. However, a stress response that is activated repeatedly or over a prolonged period can have adverse effects on health and fitness. Animals do not respond uniformly, though. Even within a single species, the consequences of chronic stress can vary considerably. Broadly, resilience often involves either maintaining important functions during a challenge or recovering them afterwards. Under certain conditions, repeated challenges may even promote adaptive processes. Key factors include the type, intensity, frequency and duration of a stressor, as well as genetic, developmental and life-history factors.

Valeria Marasco of the FIWI, the study’s senior author, therefore stresses: “There is unlikely to be a single marker that tells us whether an animal is resilient to a stressor. We need to look at different dimensions of the stress response and recovery – including glucocorticoid regulation, oxidative status, neural processes and behaviour. This is because some functions may remain stable or recover quickly, while others may remain altered”.

Natural Habitats as a Research Laboratory

According to the study´s authors, research on wild animals under realistic environmental conditions are particularly important. In the wild, animals are often exposed to several stressors at the same time and over long periods: rising temperatures may coincide with noise, artificial light at night, pollutants or changes in food availability and quality, including increased access to human-derived food resources.

For example, studies in birds and reptiles show that animals living in cities may exhibit altered glucocorticoid hormone levels or attenuated stress responses without any apparent impairment of their performance. According to the researchers, such changes might reflect adjustments to local living conditions and do not necessarily indicate physiological dysregulation.

Can Exposure to Environmental Stressors Increase Resilience?

One of the study’s central questions concerns so-called stress inoculation and hormetic-like effects. These refer to the possibility that mild or moderate challenges may, under certain conditions, strengthen an organism’s ability to cope with future stressors. Early-life conditions and parental influences play an important role in shaping these effects. However, such forms of physiological “memory” may also develop during adulthood, beyond the sensitive developmental windows when physiological plasticity is thought to be greatest.

“Resilience can develop over the course of an individual’s lifetime and may possibly also be influenced across generations,” says Marasco. “Understanding the underlying mechanisms, and determining whether such effects are actually transmitted in vertebrates, remains one of the major open questions for future research.”

Wild Animals Are Key to Understanding Stress Resilience

According to the study´s authors, a major challenge is now to determine how different physiological and behavioural measures of resilience relate to each other and ultimately to health and fitness. If responses across these different dimensions show consistent patterns, they could potentially be combined into an individual “resilience score”. Alternatively, resilience may be better represented as a multidimensional “resilience mosaic”, in which some traits resist disturbance, others recover, while still others remain persistently affected.

The consequences of such individual responses for populations, species and ecosystems remain largely unknown. “Studies of wildlife can provide crucial insights in this area. The diversity of natural life histories offers an opportunity to identify the mechanisms, and which traits, or combinations of traits, enable vertebrates to cope with the rapid changes occurring in their environment,” Marasco concludes.

Because many mechanisms involved in stress responses are conserved across vertebrates, insights from wildlife provide key information to achieve a broader understanding of stress resilience across species, including humans.

The article „When does stress build strength? Linking stress physiology to resilience in the age of rapid environmental change“ by Frederic Angelier, David Costantini, Cecilia Houdelier and Valeria Marasco was published in  „BioEssays“.
 

Scientific article



Scientific contact:
Ass.-Prof. Valeria Marasco PhD
Forschungsinstitut für Wildtierkunde und Ökologie (FIWI)        
Veterinärmedizinische Universität Wien (Vetmeduni)   
Valeria.Marasco@vetmeduni.ac.at