Animals are stressed during eclipses. But not for the reason you think

JUANA SUMMERS, HOST:

This month's total solar eclipse is behind us, but researchers in various fields are just beginning to make sense of the data they collected during totality, including biologist Adam Hartstone-Rose. He led a study of animal behavior during the eclipse at the Fort Worth Zoo in Texas, and he set out to answer one big question. Why are animals so stressed out during an eclipse? Adam Hartstone-Rose is here with us now. He is a biology professor at North Carolina State University. Welcome, Adam.

ADAM HARTSTONE-ROSE: Thanks for having me.

SUMMERS: So Adam, before we get into the results of your study, I'm hoping you can just set the scene for us. What species did you watch, who was involved and how did you gather data?

HARTSTONE-ROSE: We watched a few dozen species at the zoo this past eclipse, and I set students all over the zoo. We watched mostly mammals, but we also watched some amazing birds and also some reptiles. And we watched those animals the day before the eclipse and the many hours leading up to the eclipse and then during those very exciting minutes surrounding the eclipse. And also, we watched after the eclipse to see if and when the animals returned to normal.

SUMMERS: I'm hoping you can just walk us through a few examples of how different species reacted as the sky grew darker and we were approaching totality. What was that like?

HARTSTONE-ROSE: The amazing thing is - and what we really confirmed this last time - is that animals essentially all universally have the same reaction, which is they behave as if it becomes evening. The majority of the animals at the zoo in Fort Worth, they get let in in the evening. They go into an indoor enclosure. A lot of them get an evening meal. And what we saw - like, the most dramatic example of that - well, there were a few, but one of them, the entire troop of gorillas all, in unison, got up and went to where their door is to be let in for the evening.

SUMMERS: Wow.

HARTSTONE-ROSE: And when that door wasn't open, they got kind of stressed out, and they were looking around wondering, you know, maybe were we left out when we shouldn't have been, or did they forget to give us our evening meal?

The most extreme reaction we saw was actually with the Aldabra tortoises. They wanted to get into their evening barn so badly that they reared up on their hind legs, which I didn't even know tortoises can do, and they pushed so hard against the door that they actually bent the door frame.

SUMMERS: Wow. That's incredible. I want to go back to something you mentioned a minute ago, and it's the idea about the gorillas experiencing stress, being stressed out. Is stress something that's bad for animals?

HARTSTONE-ROSE: It's a great question. Obviously, we don't want our animals to be stressed out. And so we do a lot of things to try to mitigate that stress. We try to give them activities to try to enrich their experience and hopefully calm them down. But the truth is that animals are stressed out most of the time, especially in the wild. Zoo animals actually have it pretty good compared to their wild brethren. We should be aware of, like, trying to reduce the stress in zoo animals, especially if they are habitually stressed. But allowing animals to become stressed on occasion is actually a very natural state for them.

SUMMERS: One more question for you about the stress that you observed among these animals. Where did that stress come from? What was the origin of it, to the degree that you know?

HARTSTONE-ROSE: That's, I think, the most interesting thing that we figured out during this last eclipse. It turns out that animals get a little bit stressed out if they are in a space that maybe they feel like they shouldn't be in. So those species that are supposed to be let in for the evening or if they feel like they've missed a meal, then the way that we interpret it is it kind of is like turning the stress dial up to, like, a level one or two.

However, we have witnessed many animals really get very stressed out during eclipses. For instance, in 2017, we saw giraffes starting to gallop, and that was reported at several zoos. And in fact, just across Texas, not so far from us in Dallas, the giraffes started galloping close to totality. But it turns out, we think, that the reason that some animals go from that very mild level of stress to a more excessive level of stress is because people do crazy things during eclipses. And we think that the animals are just much more perceptive of our own emotionality during an eclipse than we previously sort of gave them credit for.

SUMMERS: Adam Hartstone-Rose is a biology professor at North Carolina State University. Adam, thank you.

HARTSTONE-ROSE: Thank you. It's an exciting event, and I hope everybody gets to experience it. Transcript provided by NPR, Copyright NPR.