Michigan is asking for volunteers to help count the state's frogs and toads.

The Michigan Department of Natural Resources and Environment announced plans Tuesday for the state's 15th annual Frog and Toad Survey. Michigan has 13 native species of frogs and toads.

The department says there's been a documented worldwide decline in the population of frog, toads and other amphibians since the 1980s. It says amphibians may be disappearing because of habitat loss, pollution, disease and collection.

The state says it conducts the surveys with volunteer observers along a system of 200 survey routes. They're visited three times during spring when frogs and toads breed. Observers listen for calling frogs and toads at each site.