We all know that childhood trauma can have a profound and lasting impact on human health and well-being. But what about our animal companions, both domesticated and wild? Just like humans, animals can experience adversity, and its consequences can be just as severe.
While the effects of early life stress on pets are often noticeable, it’s easy to dismiss the hardships faced by wild animals as simply part of the natural world. However, these negative experiences, from food scarcity to predator encounters, have lasting repercussions for their survival and behavior.
As behavioral ecologists, we delve into the intricate ways early adversity shapes an animal’s decisions, interactions, and overall well-being. We’re particularly interested in understanding how multiple stressors accumulate over time and how they ultimately affect an animal’s ability to survive in the wild.
Numerous studies across species have emphasized the crucial role of early life experiences in shaping an individual’s development. But researchers have limited knowledge about how the cumulative impact of multiple stressors affects an animal’s well-being.
Wild populations face a constant barrage of challenges: competition for resources, the ever-present threat of predators, illness, and extreme weather conditions. And in a rapidly changing world, human activities add another layer of stress, including pollution, habitat destruction, and climate change.
With biodiversity facing unprecedented losses, understanding how animals cope with these stressors is paramount for effective conservation efforts. But measuring the cumulative impact of such a diverse range of stressors is no easy task.
To tackle this challenge, our research team drew inspiration from psychological research on human childhood trauma. Inspired by the Adverse Childhood Experiences (ACE) score, we developed a Cumulative Adversity Index specifically designed for wild animals.
The ACE score, a groundbreaking tool in human health, measures the total number of adverse experiences a person endures during childhood, including abuse, neglect, and household dysfunction. This single score serves as a powerful predictor of later-life health risks, such as chronic diseases, mental illness, and even socioeconomic status.
Motivated by the success of the ACE score, we wondered if a similar approach could be applied to wild animal populations to predict survival outcomes and identify individuals at risk.
Our research focused on yellow-bellied marmots, a large ground squirrel closely related to groundhogs. These charismatic creatures offer a unique study system, as they are active during the day and inhabit defined colonies, making them readily observable.
We collected extensive data on marmot populations over several generations, recording a range of adverse events they might experience. These included ecological factors like late springs, summer droughts, and high predator presence.
We also considered parental influences, such as an underweight or stressed mother, delayed birth or weaning, and maternal loss. Additionally, we accounted for demographic factors like litter size and the number of male siblings.
Interestingly, our analysis focused exclusively on females, as they are the ones that typically remain within their natal colony. This allowed us to examine specific stressors affecting females, such as the masculinizing effect of large litters with many male siblings.
Our findings revealed a stark correlation between the number of adverse events a marmot experienced early in life and its chances of survival. Even a single adverse event before the age of two nearly halved an adult marmot’s odds of survival.
This research marks the first evidence of lasting negative consequences from maternal loss in this species.
Our study is not an isolated case. Similar findings have emerged from research using an index analogous to the ACE score in wild primates and hyenas.
We envision this framework as a valuable tool for researchers across diverse species. By understanding how animals cope with multiple stressors, we can tailor conservation and management strategies more effectively.
This approach could help identify populations at high risk, allowing for targeted interventions and preventative measures. Instead of focusing solely on the single most impactful stressor, we can strive to reduce the overall burden of adversity experienced by these species.
For instance, in the face of climate change, we can investigate ways to mitigate the impact of extreme weather events by closing trails or providing supplemental food during critical periods.
The Cumulative Adversity Index is still in its early stages, but it holds immense potential to revolutionize our understanding of animal adaptation to stress in the wild. This innovative tool opens up new avenues for research, empowering us to create a more resilient future for wildlife.