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How Are The Frogs?

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Published on: Feb. 2, 1996

Last revision: Oct. 20, 2010

Several years ago there were a remarkable number of stories in the popular press concerning the decline of some amphibian populations. Biologists and amphibian specialists (known as herpetologists) in many parts of the world reported that toads or frogs they had been studying were becoming scarce or had disappeared.

An international meeting of herpetologists was convened in California. From that meeting a new organization was formed, the Declining Amphibian Population Task Force, of which I am an active member.

Where does Missouri fit into this story? How are the amphibians doing in the Show-Me State? Luckily, I had been searching for, observing, photographing and studying Missouri's 41 amphibian species (salamanders, toads and frogs) for the past 20 years - 18 as an employee with the Missouri Department of Conservation.

My work has given me a good idea as to the distribution of these interesting, but seldom-seen creatures. I've been able to learn about their habitat requirements and reproductive biology (how big frogs make little frogs). But, knowing the exact population status of most of the frogs, toads or salamanders is another matter.

When the decline alarm rang out, I, like most herpetologists, lacked the scientific data to evaluate population changes. Sad to say, there are few places in the U.S. where such data exists. A few Midwestern states have long-term surveys of breeding toads and frogs. Of note is Wisconsin's survey which began in 1981.

This type of survey relies mostly on amateur volunteers. They select a number of wetlands and visit them three times each season on nights when toads and frogs are sure to be breeding. They learn the breeding calls and learn to estimate the number of male toads or frogs "croaking."

They complete field data forms and send them to the survey coordinator where the data are tabulated. After a number of years, rough population trends can be determined.

This type of survey is under way in Missouri using volunteer professional biologists. We hope to expand the toad and frog breeding survey statewide so that most of the 21 species are covered.

Of equal value in determining the long-term population status of our amphibians is a forest habitat evaluation project in Missouri's southern Ozarks. This extensive research is a combined effort of the Conservation Department's research staff and many temporary employees. It involves the gathering of data on forest plants, birds and small animals.

Included in this 30-plus year effort is the study of amphibian and reptile populations as they react to changes in the forest. This large project, known as the Missouri Ozark Forest Ecosystem Project (MOFEP), was begun just before the amphibian "decline alarm" sounded and has already provided some valuable data. For example, a rare species of woodland salamander, the four-toed salamander, has been found to be more abundant than expected.

As information accumulates over the years, we will have a much better idea of the status of many species in the lower Missouri Ozarks.

Missouri's toad and frog populations generally seem to be doing well. They've had to live through several droughts during the last 20 years and amphibians are especially vulnerable in such dry conditions.

The Blanchard's cricket frog, a cousin of treefrogs and one of our smallest species, is easily seen because it lives along the edges of swamps, marshes, along creek banks and on the flat, muddy banks of farm ponds. It's found in every Missouri county. This one-inch frog has had rather drastic population declines due to drought, but, at least in Missouri, the species has rebounded when normal rainfall returns.

This has not been the case in other states (that's why I've been keeping track of them here). Cricket frogs have nearly disappeared in the northern half of Illinois and throughout their range in Wisconsin. Why this has happened is not known.

Bullfrogs, on the other hand, drop in numbers during a drought, but are able to repopulate quickly when normal rainfall returns. Missouri is blessed with incredible bullfrog habitat. The construction of small and medium sized, deep (over five feet) ponds on public and private lands has caused the bullfrog to be abundant. This, of course, is wonderful news to those who enjoy catching and eating bullfrogs.

During 1992 and 1993, increased rainfall resulted in many more small puddles. Puddles prove an ideal breeding habitat for toads. As the floodwaters began to recede in 1993, I received numerous complaints from home owners and city managers that there were "...too [blank] many toads!" Even the Missouri State Capitol in Jefferson City had toads on the steps and in the basement parking garage. Toads are now back to "normal" numbers.

These examples help to illustrate that, so far, the majority of Missouri's toads and frogs seem to be holding their own. As it turned out, that amphibian population decline alarm of the late 1980s and early 1990s may have been premature for some species. Several amphibian experts are now saying that normal climatic fluctuations have been the cause of several temporary declines and simply show the natural ups-and-downs of animal populations.

However, the plight of amphibians on a worldwide scale is still in question. In many western states the introduction of trout into high elevation lakes (which had been fishless for hundreds of years) has hurt frog and toad populations. Most amphibians cannot coexist with fish, even here in Missouri.

In addition the eggs of high elevation amphibians that breed in shallow water are being killed by increased ultraviolet rays caused by a reduction in the Earth's protective ozone layer. The loss of breeding habitat, the introduction of bullfrogs outside their historic range (bullfrogs will eat other frogs), chronic amphibian diseases and excessive use of insecticides have also caused some amphibian populations to decline.

Although I was alarmed about the loss of toads and frogs, I was also pleased with the huge, never-seen-before public interest in the plight of these little animals with protruding eyes and wet skin. It shows that people are still interested in what is happening to the environment.

The Conservation Department is committed to do its part to monitor amphibian populations and provide adequate habitat for such things as pickerel frogs or narrowmouth toads.

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