The frogs are alright.
Locally, and across the state of Missouri, frogs and toad populations have remained stable for at least 6 years.
This less-than-startling news is actually very good news, in view of a worldwide decline in frog and toad numbers, with about 500 of the approximately 6000 known species considered critically endangered.
Chitrid fungus deadly, habitat destruction deadlier
Some of the amphibian decline can be traced to the deadly chytrid fungus that is currently 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 1900’s. 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.
Photo courtesy of Missouri Department of Conservation
The chytrid fungus came to Missouri in the 1960’s, 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 for frog/toad databases
Of course, 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.
Photo courtesy of Missouri Department of Conservation
When male frogs start calling to attract mates, the decibel level can be immense (think spring peepers). 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 also for variables such as correlation of rainfall and intense breeding.
The Zoo’s FrogWatch Program to begin training volunteers
How to tell a frog from a toad should you happen to see one.
Frogs have smooth wet skin.
Toads have dry warty skin.
Frogs have tiny teeth on both upper and 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.
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-August. The Saint Louis Zoo will hold three training 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 is 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 approximately 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 corresponding to 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 ten 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 1-1½ 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 temperatures—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 “have a field day” during the next breeding season.
Photo by John P. Clare
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.
Travelling 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 will eventually draw a diversity of amphibians. Dawson remarks “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.”
Prospective FrogWatchers are asked to register for one of the three training session at www.stlzoo.org/frogwatch, or call (314) 646-4551. Anyone interested in the NAAMP survey should email kate.kelly@mdc.mo.gov or go to the NAAMP website.
This article was originally published in the St. Louis Beacon.