Malformed Frogs: The Collapse of Aquatic Ecosystems

3. Hotspots

three HOTSPOTS If you don’t know the ground you are probably wrong about nearly everything else. NORMAN MACLEAN1 In amphibian conservation biology, the term “hotspot” is used in two contrasting ways. One way, with a good implication, is to denote a site or a region with high amphibian richness. These places are usually located in tropical or subtropical ecosystems and are often the focus of intense conservation efforts. The second use of the term “hotspot,” and the way I use it here, is much less desirable and indicates a site with a large number or percentage of malformed animals. The Minnesota Pollution Control Agency, for example, defined a wetland as a hotspot if, at any time when it was sampled, it exhibited five percent or more animals with malformations. In designating places as malformed frog hotspots, it is important to understand that this can be an arbitrary designation (see “The Nature of the Malformed Frog Data” in Chapter 5). Further, there are likely many more hotspots in existence than have been identified. And finally, it is important to know that some malformed frog hotspots wink on and off; specific sites can be hotspots during some years but not others. Understanding the nature of these hotspots is instructive, because when terms such as “grotesque” and “monstrosity” are used to describe malformed frogs, we envision toxic waste dumps, and what comes to mind is a wetland oozing bubbling green gunk and dead fish with Xs for eyes scattered along the shore. In reality, most hotspots appear at first glance to be perfectly normal wetlands, given their placement on a highly altered landscape. 85 In this chapter I describe some of the best-known hotspot wetlands from Minnesota; I also show a Minnesota control site. These Minnesota sites were considered from an ecoregion perspective.2 I illustrate a staterun aquacultural site from northwestern Iowa that produces malformed frogs. To make comparisons, I show four sets of radiographs of animals from malformation sites in other parts of the country, including: (1) northern leopard frogs from Dan Sutherland’s Trempealeau County, Wisconsin, site; and sets of bullfrog radiographs from (2) the Ripley Pond site in Ohio,3 (3) a Santa Clara County, California, site identified by Pieter Johnson,4 and (4) a Switzerland County, Indiana site.4 Finally, I briefly describe the U.S.F.W.S. National Wildlife Refuge sampling program. Some generalizations about these sites will apply broadly, some will not. MINNESOTA STUDY SITES In 2001, the University of Wisconsin parasitologist Dr. Daniel Sutherland5 and I were asked to visit and re-assess the hottest of the Minnesota malformed frog hotspots. Dan brought along his graduate student, Josh Kapfer, and together we sampled 17 sites (Figure 3.1).4 The majority (11) of these sites were considered hotspots. Four Minnesota and two Iowa wetlands were used as reference sites. During the early days of the malformed frog investigation not enough attention was paid to the characteristics of hotspot sites. No wetland ecologists were brought on board to provide descriptions and search for signs of problems. Instead, field teams would arrive, record the time and perhaps the ambient temperature, collect frogs and/or water samples, and leave for the next site. Our group sampled malformed frogs much in the way that other teams had done; at each site we collected all malformed frogs encountered and a subsample of normal frogs, brought them into the lab, dissected them to determine their parasite loads, then radiographed them. We also collected water samples and shipped them to U.S.G.S. hydrologist Don Rosenberry for analysis. In addition, and beyond what had been done previously, Sutherland, Kapfer, and I described sites in terms of origin (natural, human created, and restored) and malformed frog history (hotspot or reference site; below). We took a close look at each site and considered environmental influences that might be important. For example, we 86 hotspots found sites in close association with high-end housing developments, lowend trailer courts, and agricultural fields (at least one site hosted cattle). Some sites were manmade, most were natural. Some sites were true potholes (with warm standing water), others were spring fed (and cold). Most sites looked fine at first glance; a couple truly looked skanky, and at these hotspots 87 HYD CBA DOR SUN IWPA BLO TRD TRD MHL HIB ROI CTG NEY BUR OKB1 OKB2 GEL CWB HYD CBA DOR SUN IWPA...