Finding frogs in the field using new technology

One of the most important stages of any conservation reintroduction program is post-release monitoring. While the reintroduction itself is an exciting aspect of our work – it is gratifying to watch captive-born, endangered animals explore their natural, wild habitats for the first time –it is very transient: the animals are in one place, then they’re in another.

Preparing the animals for release and finding out what they’re up to once they’re back out in the wild—that’s often where the real work comes in. Without tracking and monitoring animals after releasing them, it’s hard to say whether or not these conservation initiatives are effective.

Post-release monitoring and surveying can take many forms. Some scientists use traps, either physical traps or motion-triggered camera traps. Others use visual surveys or auditory surveys, listening for bird or amphibian calls. When funds are available and animals are sufficiently large, radio- or GPS transmitters attached to collars or backpacks can be used to track individual movement.

For the mountain yellow-legged frog, an endangered species native to Southern California, many of these methods don’t work well. Physical traps would make frogs too vulnerable to predators. Camera traps depend on movement and heat signatures, so are not well-suited for tiny, ectothermic (“cold-blooded”) animals. Mountain yellow-legged frogs do not call and are difficult to see in the wild, as they camouflage and hide in their habitat. These frogs seem to be made to make post-release monitoring difficult.  

This year, the mountain yellow-legged frog program at ICR is trying something new. Every released frog is given a tiny microchip (about the size of a grain of rice), similar to the microchips used in pet dogs and cats. A grant from the Schwemm Family Foundation allowed us to purchase a new long-range microchip reader, which looks like a metal detector. Instead of beeping when it finds metal, though, it beeps when it finds a microchipped frog.

The first time we took the reader out in the field we were worried. It’s hard to climb waterfalls while managing something that looks like a metal detector. There are boulders, plants, and logs everywhere, and we wondered if the reader would even be able to detect frogs amongst these obstacles.

Minutes after beginning our first survey, the reader loudly beeped over a small rock in the stream. We put gloves on and gently lifted the rock. Crouched beneath it and looking up at us was one of our juvenile frogs (individual 181692, according to the reader). Since finding 181692 we have identified and located hundreds of hiding frogs using the reader. It’s only been a month since the release, but this essential tool is now allowing us to reidentify frog individuals without having to rely upon vision, and without even having to capture and bother the frogs at all.

Conservation biology increasingly depends upon new technology like this and we’re excited to learn from all the data this reader will allow us to collect on the 231 frogs we’ve released this year. Stay tuned!

Photos by Talisin Hammond.