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Counting frogs and toads, one croak at a time

This article first appeared in the St. Louis Beacon, Jan. 23, 2013 - The frogs are all right. Across the state of Missouri, frog and toad populations have remained stable for at least six years.

This less-than-startling report is actually very good news, in view of a worldwide decline in frog and toad numbers, with about 500 of the approximately 6,000 known species considered critically endangered.

Fungus deadly, habitat destruction deadlier

Some of the amphibian decline can be traced to the deadly chytrid fungus that is decimating frog and toad populations in Central and South America. This fungus has been traced to the South African clawed frog, used in pregnancy testing in the mid-1900s. That species was resistant to the fungus but was a ‘Typhoid Mary’ type of carrier. The fungus is spread by contact and in the water. It does not do well in very warm temperatures.

The chytrid fungus came to Missouri in the 1960s, so the 24 species of frogs and toads in the state are either naturally resistant, like the American bullfrog, or have survived the crisis, according to Missouri Department of Conservation’s herpetologist Jeff Briggler.

According to Briggler and St. Louis Zoo naturalist instructor Mike Dawson, by far the greater danger to amphibians is habitat destruction. Since amphibians breed in water, wetland destruction is the destroyer of populations. Weather may play a role. Introduction of a new fungus or bacterium may cause a frog or toad pandemic.

Citizen scientist projects

Preserving biological diversity works best when scientists know what species are out there and can see trends in populations. Birdwatchers have been keeping track of populations for years. Amphibian-watchers have only recently begun.

Two fairly new programs have enrolled citizen scientists to establish amphibian databases. Both rely on sound rather than sight. Frogs and toads are most active in breeding and feeding at night. Most of them are quite small and well camouflaged when hiding during the day. And though many species are difficult for the novice to identify visually, the mating calls are amazingly varied. (To hear the peeper and many other frogs, go to www.pwrc.usgs.gov/Frogquiz/index.cfm?fuseaction=main.lookup)

When male frogs start calling to attract mates, the decibel level can be immense. (A great example is the spring peeper.) In both programs, volunteers learn to identify frogs and toads by their calls and to estimate populations by the sound volume. A good frog watcher will be able to separate the sounds of two or more species in the same chorus.

Both programs are internet-based. As volunteers record time, location, weather conditions and frog/toad quantities -- the latter basically as none, one, a few, or a lot -- they enter their data into an online national database. The databases can be examined not only for species distribution, but for variables such as correlation of rainfall and intense breeding.

FrogWatch to begin training volunteers

FrogWatch USA from the Association of Zoos and Aquariums asks citizen scientists to monitor a single wet site of their own choosing for three minutes two times a week for the entire breeding season, approximately February through August. The St. Louis Zoo will hold threetraining sessions Saturdays, Jan. 26, Feb. 23 and March 9.“In just a couple of hours, we will train you to distinguish the croaks, peeps and various calls of the 10 most common frog and toad species around the St. Louis area,” says Dawson. While FrogWatchers are not required to be tested or certified, they are encouraged to pursue certification. Data from certified and non-certified participants are coded separately.

Dawson emphasizes that families can be a reporting unit. They can do a useful project together while getting out to observe the world around them.

The North American Amphibian Monitoring Program (NAAMP) uses a different protocol for collecting the same type of data. Administered locally through the Missouri Department of Conservation, its volunteers must be certified by passing a frog call test. These volunteers go out on a pre-specified route three times a year during the three breeding seasons. NAAMP volunteer routes are spread fairly evenly across the state, while FrogWatchers tend to be urban.

Amphibian trends slow to establish

Why have such programs? These databases establish a baseline from which to discern trends. Briggler emphasizes that it takes up to 10 years to define a trend because climate and other conditions vary from year to year. For example, last year’s early warm spell found all frogs breeding 1-1 ½ months early. Then in the extreme heat of summer, many normally wet areas dried up completely and NAAMP observers found almost no breeding sites.

A low level of breeding activity during a particular summer’s heat wave is not necessarily a trend, says Briggler. Frogs are relatively long-lived and can stay underground during extreme temperature and live to breed another season. In fact, since fish are the natural predators of frogs, dried ponds that have lost their fish might allow the frogs to increase during the next breeding season.

Because frogs and toads must breed in water, the databases will also reflect wetland distributions. A frog or toad can travel up to half a mile to get to a good breeding spot — explaining why their calls carry so well. Dawson describes a species of autumn-breeding toad that lives near Alton and can be seen crossing roads by the hundreds in October.

Traveling frogs will also make it to backyard ponds that have no fish. According to Briggler, “You build it and they will come.” They will be primarily the Southern leopard frog, the gray tree frog, and the American toad. In larger natural areas like Forest Park, Babler, or Columbia Bottoms, unstocked ponds and lakes eventually draw a diversity of amphibians.

“Since I began participating in the Forest Park bioblitz I have seen a marked increase in the amphibian diversity and populations. The changes that were implemented in Forest Park in the last 10 years to improve the quality of its habitats have had profound impact,” Dawson said.

Prospective FrogWatchers are asked to sign up for one of the three training session by calling the zoo at 314-646-4551 or go online to register. Anyone interested in the NAAMP survey should email kate.kelly@mdc.mo.gov or go to the NAMMP website.

How to tell a frog from a toad

Frogs have smooth wet skin.

Toads have dry warty skin.

Frogs have tiny teeth on upper & lower jaws.

Toads do not have teeth.

Frogs jump or leap.

Toads hop or crawl.

Frogs lay eggs singly or in masses

Toads lay eggs in long strings.

Information from Missouri’s Toads and Frogs

Jo Seltzer is a freelance writer.

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