ISU Professor Makes Ribbiting Breakthroughs In Frog Research

A thumb-sized frog lays very tiny eggs, but that didn’t stop an Illinois State University professor at taking a closer look.

Professor Matthew Dugas studies poison dart frogs he keeps in a fish tank in a walk-in cooler in his laboratory. Dugas specifically studies parental care. He spent a lot of time focusing on the begging behavior tadpoles exhibit, similar to that of birds. 

“It makes it's whole body stiff, and then it vibrates really, really fast. Those vibrations seem to be related in whether the mom is going to feed it or not. The offspring are in individual rearing sites, which is really good for studying begging, because if you're imagining a bird nest, everybody's begging, there's all sorts of stuff going on and they're kind of pushing each other around,” said Dugas. “The parents see them all together, and that's very different from the (poison dart frog) parent, who interacts with one tadpole at a time.”

https://www.youtube.com/watch?v=AZpcdg4a9PI

When tadpoles emerge about 10 days after the female lays her eggs, she returns to transport them on her back one at a time. Dugas said in other dart frogs this is not the typical kind of parental care. He said in a lot of dart frog species, the males will transport tadpoles and they transport them as a group.

In the dart frogs he studied, the females carried just one baby at a time.

“Why do these females do one at a time? I don't know...one of the more intriguing things to me is how that happens,” said Dugas. “You would think all the tadpoles would like to be on their mom's back when the mom is there. So how does she manage to get only one at a time? I don't know. The simplest answer would be that they put them in just really small bodies of water, and so those small bodies of water may not be good for more than one.” 

Dugas said it could be that the tadpoles might fight and kill each other if there were to be multiple on the female’s back. The female lays a clutch of about six eggs and then disappears for a while. Then the male cares for those eggs, moistening them and keeping them from drying out.

“In most of the dart frogs, and probably the ancestral of the dart frog, it's the male, who's doing everything. So this female transport has only evolved a couple of times, or maybe it's only evolved in one genus. A female transporting the tadpoles is rare. Normally, it is common for frogs, it is also common in fish to do the defending,” said Dugas.

The brightly colored poison frogs are among the most toxic animals on the planet with chemicals released from the skin of some species capable of killing humans. However, Dugas said this characteristic tends to be over-dramatized.

“There's one genus in South America that can be very, very toxic,” said Dugas. “Most of them, you wouldn't want to eat it. I’ve actually handled hundreds of them and eaten my lunch. It's no problem.”

Dugas has spent nearly a decade observing the tiny poison dart frog. When he studied them in Costa Rica, he would get up at 4 a.m. with a bag packed with cameras, set them up in places he knew had tadpoles, and loop back to change the batteries before picking all of them up at the end of the day and viewing the files to see if the mothers came.

Dugas said his favorite non-work related characteristic of the poison dart frog is their charismatic behavior and their active lifestyle. Their little body adds to the science. 

“We can get them doing natural-ish things, so being in a lab is not the same as being in nature, but we can get them sort of behaving normally in a really small enough space relative to something like, studying birds or if you were studying elephants ... the space you need would be much different,” said Dugas. 

The frogs are difficult to study in the wild, but it helps that you can attract O. pumilio by attaching plastic shot glasses to trees, providing a convenient place for parents to place tadpoles, and more convenient for researchers.