Alligators Along The Coast May Just Be Returning Home

May 14, 2018

Every so often you hear about animals appearing in places you’d never expect them. River otters have been showing up in salt water environments off North Carolina’s coast. Occasionally, alligators too. 

It was a run in like that that led Duke University scientist Brian Silliman to take on his latest research. 

He was studying snails in Florida salt marshes, when he looked up and saw a large alligator stalking him.   

"There was a cage between us. I shook the cage and the alligator lunged at me. Luckily, it hit this cage and I saw this big white belly and it doubled back on a flip into the water. And within a few seconds I found myself 50 feet away sort of hyperventilating," said Silliman.

Once the fear wore off, he started asking himself why that alligator was there. After all, everyone knows they like fresh water. What he found seems to indicate we may have misunderstood what many animals consider home.   

Silliman spoke with WFAE's Marshall Terry. Here are some of the highlights of that interview:

Editor's note: This interview has been edited for brevity.  (You can listen to the full interview above)

Q: Why are we seeing these animals show up more frequently in unexpected places?

A: These animals are likely re-colonizing habitats that they formerly forged in, reproduced in, were very successful in living in. It told us that many of the classic and most familiar stories to all of us, scientists and citizens, about large animals being habitat specialists is likely wrong. It's more likely that they're generalists and they can live in a variety of different habitats.

Q: When you said these are areas where they used to be, you mean before, essentially, humans kicked them out?

A: That's what we think and we have evidence for that. In this paper that just came out, we looked at how general was this phenomena that animals after they've been conserved and their populations have increased, do new individuals start to colonize these new habitats. In the case of the alligators and sea otters going into seagrasses from kelp forests on the west coast, we looked at archaeological middens of former human populations and we found the bones of alligators and sea otters there. And what this told us is that thousands of years ago alligators and sea otters were on the coast and it's likely the case that humans over-hunted them in those areas and pushed them back in the refuge habitats in swamps and kelp forest and at the tops of mountains and in small rivers, where we first started studying them.

Q: Could North Carolina ever be like Florida where we see alligators along the coast frequently?

A: I think it will happen more often. I don't think it will get to the level of concentration of alligators that you find in Florida because the alligators are limited here by cold temperatures. The cold temperatures really push them back.

Q: We've mentioned alligators on the coast. Are we going to have to rethink how we interact with animals? I'm thinking of safety measures.

A: That's always important to think about. We can learn from what other people are already doing. Our view about conservation and our paradigms in conservation is that nature should exist sort of segregated and separate from human society. But there's a lot of examples where when conservation has been successful, populations of animals increase, that we coexist with those other animals in a functioning ecosystem and functioning human civilization. It does, however, mean that we do change our behavior and change our tolerance of the animal’s behavior. With that change in behavior, it can lead to decreased potential negative effects. But there's also a lot of positive effects these animals can bring to systems.

Q: Like what?

For example, we've been studying sea otters on the west coast of the United States and they totally surprised us as well. When their populations increased, a lot of individuals started moving tentatively towards the coast - on the beaches, in the salt marshes, in two or three feet of water. They adapted quickly. And, surprisingly to us - in the Monterey Bay, in Elkhorn Slough - with the emergence of sea otters in this environment, also the seagrasses came back and it totally surprised everybody. It’s one of the most polluted estuaries in the United States. It's like pea soup. Through experiments, we realized that the sea otters by eating a lot of crabs were releasing a green sea slug from top-down control. The sea slugs are like little vacuum cleaners that go up and down on seagrass plates and clean them from algae that would otherwise smother them. If we wanted to get to that point with watershed management, it would have cost us tens of millions of dollars.