Officials of the state of Michigan are looking for volunteers to help with the annual frog and toad survey, which is entering its 20th year.

Scientists have reported a decline in amphibian populations worldwide since the 1980s, caused by pollution, habitat loss, disease and collection.

The annual survey conducted by Michigan is performed along a state-wide route network, with each route containing 10 wetland locations.

Volunteers that have signed up to join the survey visit the locations three times every spring season, which is the time of the year that is the breeding season of frogs and toads. During this time, it is more likely for people to hear the frogs and toads than to see them.

They listen for the calls being made by the frogs, identify from what species the calls are from, and make an estimate on how many of that specific kind of frog species is in the location.

Upper Peninsula volunteers may hear the mink frog's call, which sounds like a horse walking on a stone road. Volunteers in west Michigan, on the other hand, could listen to the Fowler toad's call, which sounds like a bleating lamb. Everywhere else in Michigan, volunteers are likely to hear the green frog's call, which sounds similar to a banjo.

"There are some that sound alike, but if you have a little bit of experience you can usually hear the difference," said Lori Sargent, coordinator for the annual frog and toad survey and a wildlife biologist from the state's Department of Natural Resources.

Sargent is tasked with sending out the volunteers on the routes to survey for the sounds made by any of the 13 different frog and toad species in Michigan, 11 of which are frogs and two are toads.

Biologists from the department then run an analysis on the collected data for monitoring the abundance and distribution of the frog and toad population in the state.

According to Sargent, previous surveys were able to identify the trends concerning amphibian population decline, which guided efforts in slowing down the population decay for certain frog and toad species.

Frogs and toads fall under the amphibian class, meaning that these animals have primitive lungs but are able to breathe through their skin. This makes frogs and toads more susceptible to pollutants and contaminants, with Sargent stating that these animals are the first indicators if an ecosystem is becoming sick.

Photo: Mike Ostrowski | Flickr