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The North American Reporting Center for Amphibian Malformations

An Example Application


As of September 1998, the Reporting Center contained more than 1300 reports, most (82%) of which represent frogs, with fewer toads (13%) and salamanders (5%). Malformed animals had been reported from 41 states and three Canadian provinces.

Most of the reports submitted to the Center were from opportunistic findings; that is, someone found a malformed amphibian and submitted a report of it. Such reports do not permit an assessment of the true incidence of malformations, for they are obviously biased toward sites with malformed animals, and often normal-appearing amphibians are not noted or recorded. There are at least two exceptions. First, the Minnesota Pollution Control Agency has conducted systematic surveys of anurans at various locations in that state. Second, the U.S. Fish and Wildlife Service conducted surveys at numerous wildlife refuge lands in its Northeast and Great Lakes regions. Refuge managers in those regions were asked to sample two randomly chosen sites on each refuge, attempt to capture 100 or more frogs and toads at each site, and determine how many of them had malformations and what the types were. Refuge staff used protocols developed by FWS and USGS collaborators.

For the analysis presented here, we used only reports that included a substantial number of normal-appearing, as well as any malformed, amphibians. That restriction was made to reduce the effect of the opportunistic reporting of only malformed animals. Only reports of at least ten animals, all species combined, were included. Reports before 1986 were excluded, to better reflect the current situation.

The data base at present (September 1998) contains records of 452 sites that meet the criteria described above (Table 1). Of these, 136 were from the national wildlife refuge survey and 316 were from other sources. Of the states and provinces, Minnesota has by far the most reports, 169 in total. Vermont, with 39 reports, and Wisconsin, with 30, follow (Table 1). Of the types of malformations, missing limbs or digits were reported at more sites (236) than other types, followed by eye abnormalities (69), extra limbs or digits (48), and jaw deformities (27). One hundred and seventy-six (39%) of the sites had no observed malformed animals (Table 1). This rate differed between refuge sites (61% reporting no malformed animals) and non-refuge sites (29%).

Table 1. Number of sites included in analysis, and number with types of malformations reported.
  Number of sites Number of sites with malformation type
State/Province Refuges Other Total Missing Extra Eye Jaw Any None
British Columbia 0 5 5 0 0 0 0 0 5
California 0 9 9 5 6 3 0 6 3
Connecticut 0 1 1 1 0 0 0 1 0
Delaware 2 1 3 1 0 0 0 1 2
Florida 0 1 1 0 1 0 0 1 0
Illinois 8 3 11 2 0 2 0 4 7
Indiana 3 1 4 1 0 0 0 1 3
Iowa 5 0 5 2 1 1 0 2 3
Kansas 2 0 2 0 0 0 0 0 2
Louisiana 2 0 2 0 1 0 0 1 1
Maine 9 2 11 4 1 2 0 5 6
Maryland 1 21 22 2 0 0 1 3 19
Massachusetts 0 5 5 1 2 1 0 4 1
Michigan 6 4 10 4 1 2 0 7 3
Minnesota 30 139 169 104 17 40 19 119 50
Mississippi 0 2 2 0 0 1 0 1 1
Missouri 14 0 14 4 0 0 0 4 10
Montana 0 1 1 1 0 0 0 1 0
Nebraska 3 0 3 0 0 0 0 0 3
Nevada 1 0 1 0 0 0 0 0 1
New Hampshire 2 6 8 6 0 2 0 6 2
New Jersey 8 9 17 11 1 1 2 11 6
New York 3 0 3 1 0 0 0 1 2
North Dakota 6 5 11 7 1 0 1 7 4
Ohio 2 4 6 4 2 1 1 5 1
Oklahoma 0 3 3 1 0 0 0 1 2
Ontario 0 1 1 1 0 0 1 1 0
Oregon 0 7 7 4 5 0 0 6 1
Quebec 0 19 19 9 0 0 0 9 10
South Carolina 1 0 1 1 0 1 0 1 0
South Dakota 10 4 14 6 0 2 1 8 6
Tennessee 0 1 1 1 1 0 0 1 0
Texas 0 1 1 0 0 0 0 0 1
Vermont 2 37 39 38 1 4 0 38 1
Virginia 3 0 3 1 0 1 0 2 1
Washington 0 6 6 3 4 3 1 5 1
West Virginia 0 1 1 0 1 0 0 1 0
Wisconsin 13 17 30 10 2 2 0 12 18
Total 136 316 452 236 48 69 27 276 176

The percentage of animals examined that had malformations varied widely among states and provinces (Table 2). Delaware, with 28.9% of 315 animals sampled showing malformations was highest by far. All malformed animals were bullfrog (see Table 3 for scientific names) tadpoles with missing appendages, from a single pond that also contained fish, so the possibility exists that they might have been injured, rather than malformed. In addition, regardless of the cause, the data reflect but a single site. Oregon had the next highest rate, 18.5%; most of the malformed animals were Pacific treefrogs with extra limbs. California, with a very large sample of more than 12,000 amphibians, had a high rate (17.2%), including large samples of long-toed salamanders, western toads, and Pacific treefrogs.

Table 2. Numbers of amphibians reported and percentage with malformations by state or province.
  Refuges Other Total
State/Province Number
malformed
Number
examined
Percent
malformed
Number
malformed
Number
examined
Percent
malformed
Number
malformed
Number
examined
Percent
malformed
British Columbia   0   0 1142 0.0 0 1142 0.0
California   0   2183 12,663 17.2 2183 12,663 17.2
Connecticut   0   5 43 11.6 5 43 11.6
Delaware 0 200 0 91 115 79.1 91 315 28.9
Florida   0   1 51 2.0 1 51 2.0
Illinois 3 793 0.4 6 703 0.8 9 1496 0.6
Indiana 2 66 3.0 0 3500 0 2 3566 0
Iowa 9 504 1.8   0   9 504 1.8
Kansas 0 125 0   0   0 125 0
Louisiana 6 92 6.5   0   6 92 6.5
Maine 10 383 2.6 3 106 2.8 13 489 2.6
Maryland 0 96 0 3 2037 0.1 3 2133 0.1
Massachusetts   0   14 374 3.7 14 374 3.7
Michigan 4 626 0.6 19 1005 1.9 23 1631 1.4
Minnesota 48 2980 1.6 909 12,022 7.6 957 15,002 6.4
Mississippi   0   1 8682 0 1 8682 0
Missouri 16 887 1.8   0   16 887 1.8
Montana   0   1 12 8.3 1 12 8.3
Nebraska 0 170 0   0   0 170 0
Nevada 0 123 0   0   0 123 0
New Hampshire 2 56 3.6 11 415 2.6 13 471 2.8
New Jersey 1 177 0.6   0   1 177 0.6
New York 17 272 6.2 32 697 4.6 49 969 5.0
North Dakota 6 493 1.2 34 568 6.0 40 1061 3.8
Ohio 4 209 1.9 8 284 2.8 12 493 2.4
Oklahoma   0   2 579 0.3 2 579 0.3
Ontario   0   2 364 0.5 2 364 0.5
Oregon   0   84 455 18.5 84 455 18.5
Quebec   0   108 1100 9.8 108 1100 9.8
South Carolina 2 178 1.1   0   2 178 1.1
South Dakota 27 556 4.9 5 121 4.1 32 677 4.7
Tennessee   0   5 55 9.1 5 55 9.1
Texas   0   0 2089 0 0 2089 0
Vermont 9 235 3.8 237 2815 8.4 246 3050 8.1
Virginia 4 180 2.2   0   4 180 2.2
Washington   0   51 471 10.8 51 471 10.8
West Virginia   0   1 51 2.0 1 51 2.0
Wisconsin 4 752 0.5 36 1352 2.7 40 2104 1.9

A number of species were involved in the reports examined (Table 3), although not all were included in the analysis, due to the criterion of having at least ten animals at a site. Most frequent were the northern leopard frog (352 reports) and green frog (142 reports).

Table 3. Species included in North American Reporting Center for Amphibian Malformations files, and number of sites with reports for each.
Species Number of sites
Northern leopard frog (Rana pipiens) 352
Green frog (Rana clamitans melanota) 142
Bullfrog (Rana catesbeiana) 72
Wood frog (Rana sylvatica) 65
American toad (Bufo americanus) 61
Southern leopard frog (Rana utricularia) 53
Mink frog (Rana septentrionalis) 40
Gray treefrog (Hyla versicolor/chrysoscelis) 28
Fowler's toad (Bufo woodhousii fowleri) 24
Pacific treefrog (Hyla regilla) 22
Spring peeper (Pseudacris crucifer) 20
Pickerel frog (Rana palustris) 15
Tiger salamander (Ambystoma tigrinum) 12
Western toad (Bufo boreas) 10
Chorus frog (Pseudacris triseriata) 9
Northern cricket frog (Acris crepitans crepitans) 9
Spotted salamander (Ambystoma maculatum) 7
Rough-skinned newt (Taricha granulosa) 7
Cascades frog (Rana cascadae) 6
Blue-spotted salamander (Ambystoma laterale) 6
Cricket frog (Acris crepitans) 6
Green treefrog (Hyla cinerea) 4
Canadian toad (Bufo hemiophrys) 5
Northwestern salamander (Ambystoma gracile) 5
Red-legged frog (Rana aurora) 5
Long-toed salamander (Ambystoma macrodactylum) 4
Eastern narrowmouth toad (Gastrophryne carolinensis) 3
Eastern spadefoot toad (Scaphiopus holbrookii) 3
Southern cricket frog (Acris gryllus) 3
Woodhouse's toad (Bufo woodhousii) 3
Barking treefrog (Hyla gratiosa) 2
Blanchard's cricket frog (Acris crepitans blanchardi) 2
Dusky gopher frog (Rana capito) 2
Mississippi slimy salamander (Plethodon mississippi) 2
Mole salamander (Ambystoma talpoideum) 2
Ornate chorus frog (Pseudacris ornata) 2
Pine woods treefrog (Hyla femoralis) 2
Plains leopard frog (Rana blairi) 2
Smallmouth salamander (Ambystoma texanum) 2
Southern chorus frog (Pseudacris nigrita nigrita) 2
Southern toad (Bufo terrestris) 2
Upland chorus frog (Pseudacris triseriata feriarum) 2
Red-spotted newt (Notophthalmus viridescens viridescens) 2
Western redback salamander (Plethodon vehiculum) 2
Great Plains narrowmouth toad (Gastrophryne olivacea) 1
Jefferson salamander (Ambystoma jeffersonianum) 1
Boreal toad (Bufo boreas boreas) 1
Bronze frog (Rana clamitans clamitans) 1
Clouded salamander (Aneides ferreus) 1
Cope's gray tree frog (Hyla chrysoscelis) 1
Couch's spadefoot (Scaphiopus couchii) 1
Carpenter frog (Rana virgatipes) 1
Eastern American toad (Bufo americanus americanus) 1
Eastern green toad (Bufo debilis debilis) 1
Eastern newt (Notophthalmus viridescens) 1
Gulf Coast toad (Bufo valliceps) 1
Marbled salamander (Ambystoma opacum) 1
Northern redback salamander (Plethodon cinereus) 1
Pig frog (Rana grylio) 1
Rich Mountain salamander (Plethodon ouachitae) 1
Rio Grande leopard frog (Rana berlandieri) 1
Redback salamander (Plethodon cinereus) 1
Silvery salamander (Ambystoma platineum) 1
Southern redback salamander (Plethodon serratus) 1
Spotted frog (Rana pretiosa) 1
Squirrel treefrog (Hyla squirella) 1
Texas toad (Bufo speciosus) 1
Western (California) toad (Bufo boreas halophilus) 1
Western chorus frog (Pseudacris triseriata triseriata) 1

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