Sunday, February 04, 2007

Calling all frogs


For the past 10 years, the USGS has organized state agencies, non-profit conservation groups and dedicated enthusiasts to monitor breeding frogs to help track population changes. Participants in the North American Amphibian Monitoring Program drive a ten mile route in every corner of the eastern United States three times a year to listen to frogs and record their findings. Several states, including Missouri, previously had their own state agency-specific method of tracking frogs, but the protocol differed from state to state and true population counts were negatively impacted by the differing monitoring protocols: some states would report "stable" populations that would be considered "unstable" by another state. With global amphibian populations currently on the decline and drastic population changes looming in the near future, most states have finally adopted the federal monitoring standard so that now almost every state is on the same proverbial page.

The monitoring protocol is easy to follow: participants drive a pre-determined route, pull over when they approach standing water or when they hear frogs calling, and record what they hear. Individual frogs and choruses are recorded with a series of codes representing population density. It's an easy method that takes about 1 hour to complete. It's hard to hear every calling frog, especially when trucks rumble by, so I intend to make audio recordings at my stops this year. Laughing leopard frogs make these low frequency growls that can't be heard immediately and spring peepers sound a lot like Illinois chorus frogs.

Most states have certain Species of Conservation Concern, animals whose numbers are extremely low or dropping, and they are of particular interest to state and federal organizers. In southeast Missouri we have two SCCs: the Eastern spadefoot (whose call sounds like a baby crying) and the Illinois chorus frog (ICF), a frog who is responsible for keeping boll weevil populations in check. Unfortunately, since the ICF's food source happens to be in and around cotton fields, most of their breeding habitat is so polluted with pesticides that their numbers continue to dwindle. In the Natural Heritage Database, ICFs hold the "threatened" slot just below the state endangered Ozark hellbender, another amphibian whose numbers are abysmally low due to human interactions. In the case of the hellbender, however, it has nothing to do with pesticides, but we dump millions of voracious, grain-fed trout fingerlings into their breeding habitat for our recreational purposes.

The National Wildlife Federation sponsors a similar frog monitoring program, FrogWatch, which is geared towards anyone who is interested in "adopting" a breeding pool for monitoring purposes. Community gardens, landowners with fishless ponds, schools and anyone who might live near a ditch with calling frogs have joined FrogWatch. The program touts thousands of volunteers who monitor thousands of breeding pools throughout the country. There is no driving route associated with FrogWatch and you don't have to take a test before you begin monitoring, though it's encouraged. FrogWatch is a free program and has been invaluable to amphibian researchers at NWF. NAAMP requires that participants pass a frog call test before they can start monitoring and because I haven't heard southeast Missouri's frogs in almost a year, the house has been filled with the dulcet sounds of spring, interrupted by a severe narrator: "Plains leopard frog...Gray treefrog...Northern crawfish frog..."

I drove my NAAMP route a few weeks ago to see where it took me. I don't know the county roads, most of the directive signs have been shot out and it's a lot easier to get around down here if you know exactly where you're going. The route is extremely pauperate, lacking suitable amphibian breeding habitat. My route takes me past a lot of sedimented ditches, some deep water holes that have been carved out to help keep the rainwater off the fields and some old river meanders that held water before the 1930s ditching projects began. I drive through one batture in a conservation area on the Mississippi River that should have high species richness, but I won't know until March.

The NAAMP driving routes are randomly designed based on topographical maps; the organizers in Washington, D.C. chose my route because they saw depressions that should (or at one time did) represent standing water. I don't think they have any clue what kind or quality of water we have down here. Aerial pictures of the area show where the lakes, rivers and sloughs used to be and, if the bottom ever falls out of the farming industry, will be again with help from the USACE.

Neal, the wetlands biologist from the Christmas Bird Count, used to run my NAAMP route. He told me which landowners will yell at you if you park in front of their house. He told me where I could find both state listed threatened animals (a single ditch in a cotton field). He told me not to expect to hear healthy populations of anything but the pollution-tolerant green frogs. While southeast Missouri has the highest rainfall records in the state and a climate that more closely represents the Coastal Plain than anywhere else in the Midwest, this region of the state has the lowest amphibian species diversity in Missouri. The Ozark Highlands harbor 22 frog and toad species. Southeast Missouri has a mere 15 species. Compare this to Louisiana's 42 species, most of whose habitat requirements were here presettlement and it's easy to see that there is a problem down here.

The timber harvest and conversion of land to agriculture wiped out several species that should be thriving here. Just across the border in Arkansas, NAAMP participants will hear pig frogs, bird-voiced treefrogs, squirrel treefrogs and other southeastern United States species. In southeast Missouri, we have healthy populations of green treefrogs (pictured in the banner), lots of Fowler's toads (who resemble dwarf American toads) and plenty green and bullfrogs. I only have to know 15 species for the monitoring program, so I should have no problem taking the frog call test (which is available to the public under the tab "Public Quiz". You can also listen to all the frogs in your state through the same link.) It's a shame I don't have to learn more than what I already know. I won't hear wood frogs or even spring peepers down here, much less bird-voiced treefrogs whose known range is cypress swamps of the embayment. If the cotton farmers aren't careful, the NAAMP participant who takes over my route in the next year will only have to learn 13 calls.

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