Measuring The Effects Of Early Life Adversity—In Marmots

IRA FLATOW: It’s well established in psychology that if you experience trauma as a child, chances are it’ll impact your physical and mental health as an adult, and could even affect your economic status. In academic terms, this is called early adversity. And psychologists have developed a scoring system for measuring the cumulative effect of early adversity in childhood, which can include abuse and household dysfunction. And it can help predict health risks later in life.

So we can specifically measure that in humans, but what about in other animals? For example, if you’ve adopted a dog that’s had a turbulent past, you know that that can result in reclusive or skittish behavior as an adult. But there hasn’t been a good way to measure it in nonprimate animals.

Well, a new study from UCLA, published in the journal Ecology Letters, establishes a similar index for nonprimate animals for the first time. And it uses decades of findings from a mammal, the yellow bellied marmot, sometimes known as the giant ground squirrel.

So how could it help conservation efforts for other mammals? Here to tell us more about the study is one of its authors, Xochitl Ortiz Ross. She’s a doctoral student in Ecology and Evolutionary Biology at UCLA. Welcome to Science Friday.

XOCHITL ORTIZ ROSS: Thank you, Ira. Nice to be here.

IRA FLATOW: Nice to have you. We know that negative childhood experiences can have an impact on human adults. Why is it important to develop a similar score or index for nonhumans?

XOCHITL ORTIZ ROSS: Yeah, so it’s important for many of the same reasons. We’re interested in how cumulative adversity affects humans because we’re interested in their well-being– and be able to prevent the consequences of an accumulation of stressors later in life. And so with animals, we also care about their well-being. And we’re particularly interested in that when we talk about conservation, but also when we just want to have questions about their ecology and their evolution.

IRA FLATOW: All right. So tell me why, of all the animals you’d choose, why did you choose to focus on yellow bellied marmots? I think they’re a pretty big rodent that most people have never seen.

XOCHITL ORTIZ ROSS: Well, they’re certainly adorable, but one of the major reasons why we chose yellow bellied marmots is because they’re the longest continuously running study of mammals in the world. The data has been collected for over 60 years. And so we have a lot of knowledge about these individuals and their ecology and life history. But also, we’re able to use a lot of data to quantify the cumulative impact of multiple stressors. So we had a lot of data available is the short answer.

IRA FLATOW: And speaking of stress, tell us what kind of stressors they go through in the wild.

XOCHITL ORTIZ ROSS: Yeah. So they experience a number of different stressors. The ones that we selected can be things like the timing of spring. So arrival of spring is great because it brings in food. Grass starts to grow again after the winter. And so that’s an important determinant of fitness in this population. So late spring is an adversity.

Similarly, summer drought can also be adverse, as well as predation pressure, and other things, like parental effects. Did you have a stressed-out mother, or did your mother not have a lot of mass going into the pregnancy? And even losing your mother can have important consequences.

IRA FLATOW: And they have to deal with us humans, too, right?

XOCHITL ORTIZ ROSS: Absolutely.

IRA FLATOW: Yeah. Were there any results that were surprising to you?

XOCHITL ORTIZ ROSS: Overall, we were hoping that we would find this decrease in survival probability with increasing adversity, which is what we found. So it was a pleasant surprise, but it was also what we were expecting or hoping to see. We also found that not all of the adversity measures had a significant impact on survival, but our index shows that the accumulation of them, experiencing multiple ones of them, did. So that’s the main thing.

IRA FLATOW: Yeah so how, now that you have this index, this cumulative adversity index– how do you use it?

XOCHITL ORTIZ ROSS: You use it in analyses. So a big reason why at least the impact of multiple stressors hasn’t really been studied in wild populations before is because we didn’t really have a good way of measuring it. And so this is just a way that you can ask those questions regarding cumulative impacts that you may not have been able to answer before. But now, you can use this one number as a substitute for a list of many different stressors.

IRA FLATOW: Yeah, it sounds like it could help local governments focus on specific strategies to protect these populations, especially all the stressors that people give them– light, sound, pollution, stuff like that.

XOCHITL ORTIZ ROSS: Absolutely. One of my biggest concerns and reasons why I started this study was because animals around the world are experiencing these increasing stressors, especially with humans in the picture. And so my hope is that people will start to use it and consider more of the cumulative impact of multiple stressors when thinking about conservation.

Most of the way we think about conservation action is to identify the stressor that has the highest impact and then work on trying to minimize that, while we’re suggesting that it might be equally helpful, if not perhaps even more helpful, to consider maybe some of those– let’s call them– lower stressors, but trying to tackle multiple ones that we might have control over– things like exposure to humans, so reducing ecotourism in a particular area, especially during the rearing of the younger individuals.

We could provide greater food access during times when there is a food shortage, either due to drought or due to habitat loss. I guess my perspective is to think about them less hierarchically and more by paying attention to this cumulative impact, so considering even those stressors that you might not think have a greater effect.

Small things can accumulate really quickly. And so thinking about what can we actually have an impact on, what can we actually reduce, and focusing on those instead of trying to reduce something that may be really hard or impossible to do.

IRA FLATOW: Well, good luck to you. I want to thank you for taking time to be with us today.

XOCHITL ORTIZ ROSS: Thank you so much.

IRA FLATOW: Xochitl Ortiz Ross, a doctoral student in Ecology and Evolutionary Biology at UCLA.

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