In Southern Illinois, Cagle (1942:160) recorded spinifer in drainage ditches (normally having several feet of water and a lush growth of aquatic vegetation) that connect inland swamps to the Mississippi flood-plain but dry up periodically, and in Elkville Lake, an artificial lake having much aquatic vegetation in shallow areas (op. cit.:157). Myers (1927:339) recorded a spinifer from Indiana from a "tiny brook." In east-central Illinois P. W. Smith (1947:39) recorded spinifer in mud-bottomed dredge ditches, lakes, ponds, small streams and rivers, whereas muticus was found to prefer rivers having clean, sandy bottoms and was not taken from lakes or small streams. This restriction in habitat preference of muticus is again emphasized by Smith and Minton (1957:346) who wrote that in Illinois and Indiana, muticus "generally avoids lakes and minor streams." Weed (1923:48), however, recorded muticus (and spinifer) from Meredosia Bay, Illinois, presumably a broad, shallow, muddy ox-bow lake of the Illinois River.
In Minnesota, spinifer has been taken from the Mississippi River, which is described as fairly swift having a fluctuating water level, sandy islands, mud banks, a bed of pebbles and large boulders, and abundant crawfish (Breckenridge, 1955:5). In Michigan, Edgren (1942:180) recorded spinifer from a "very small muck-bottomed lake." Evans and Roecker (1951:69) recorded spinifer from Long Point, Lake Ontario, which is a "broad sand spit, straight on the lakeward side but irregular with wet flats and lagoons on the bayside."
In Kansas, Brumwell (1951:207-08) found "mostly young [muticus] … in the old ponds left during flood stages of the Missouri River" … and spinifer occasionally … "in the backwaters where stagnant ponds had been formed." In southcentral Kansas, Burt (1935:321) reported muticus from "a sandbar at junction of a small creek and Medicine River" … and … a "shallow sand-bottomed, algae-filled pasture streamlet." The same author reported spinifer from a "sand-bottomed prairie streamlet" … and … "an alga-filled pool near a stream." Burt (loc. cit.) remarked that "No ecological differences in general habitat and field behavior of mutica and spinifer are evident in Kansas." Clarke (1958:21) observed spinifer in Long Creek (Osage County, Kansas), which is a winding stream, characterized by numerous deep holes alternating with rocky riffles, and having high and wooded banks, and mostly mud bottom but occasional rock bottom.
Marr (1944:490) mentioned a spinifer that was obtained on the bank of a small, mud-bottomed stream in the Texas panhandle, and Linsdale and Gressitt (1937:222) recorded spinifer from irrigation canals in Baja California.
In southern Florida, ferox occurs in all fresh-water habitats (Duellman and Schwartz, 1958:272). Carr (1940:107) reported ferox as widely distributed in streams, lakes, big springs and canals. Judging from the numbers of turtles, "the larger canals in the Everglades must represent something like an optimum habitat" (Carr, 1952:417). Wright and Funkhouser (1915:119) wrote that in the Okefinokee Swamp, ferox was especially abundant where the water is deep and the bottom soft, and the species was found wherever there were alligators. Deckert (1918:31) wrote that young ferox were taken in springs and brooks near Jacksonville, Florida. Marchand (in Carr, 1952:417-19) observed ferox while water-goggling in Florida and noted that individuals buried themselves in deep water in white sand, mud or bubbling mud-sand springs, sometimes where there was vegetation overhead. [543] Neill (1951:16) collected ferox in marshes, "prairies," flood-plain lakes, lagoons, ox-bow lakes, mangrove swamps, rivers, creeks, calcareous spring runs, man-made lakes and lime sinks. The same author (loc. cit.) reported taking agassizi (= asper) in large muddy rivers, clear "blackwater" streams, calcareous spring runs, creeks, marshes, lagoons, ox-bow lakes, flood-plain lakes, lime sinks, man-made lakes, and smaller ponds. Crenshaw and Hopkins (1955:16), however, stated that in the area where T. ferox and T. spinifer asper overlap, "asper is nearly always an inhabitant of fluviatile situations whereas ferox is equally closely confined to non-fluviatile lakes and ponds"; in the region of sympatry, Schwartz (1956:8) reported ferox from "a moderately fast, blackwater stream [Combahee River, South Carolina]."
Carr (1952:417) wrote that ferox is not uncommon near the mouths of streams in brackish waters, where the tide must occasionally take it to sea, and cited Conant, who told of an individual found at sea in Bahaman waters; Carr (1940:25) listed ferox as occasional in the marine-littoral, mangrove swamps, as did Neill (1951:16). Neill (1958:26-27) mentioned his observance of ferox at the mouth of the Pithlachascotee River, Pasco County, Florida, where the water is sufficiently saline to favor the growth of oysters, and added that commercial fishermen had told him that these turtles are sometimes netted with loggerhead sea turtles (Caretta) in the Indian River. Neill (op. cit.:5-6) also noted the presence of ferox on Meritt Island, which supports an extensive saltwater herpetofauna, off the coast of Brevard County, Florida. Löding (1922:47) recorded spinifer from Fig Island, Mobile County, Alabama, which is probably a marine or brackish water habitat. Cagle and Chaney (1950:386) obtained one spinifer in a brackish marsh of the Sabine Wildlife Refuge, Louisiana; the poor trapping returns here (one Trionyx and one Pseudemys in 408 trap-hours) suggest that fresh-water species are not abundant in brackish habitats. Neill (1958:26-27) has summarized the occurrence of soft-shelled turtles in marine and brackish habitats.
My own observations indicate a variety of habitat preferences; the term "relatively clear" refers to waters in which visibility extends four to six inches below the surface at night using a head-light.
Individuals of spinifer have been taken in large, deep rivers having a moderate to swift current, relatively clear water, mostly sand and clay bottoms, and emergent débris intermittent along the shoreline; the banks may be steep and of mud having a sparse growth of herbs (Black Warrior River, south of Tuscaloosa, Alabama), or of low extensive, sandy bars and beaches (Escambia River, near Century, Florida, [Pl. 50, Fig. 1]). A juvenile spinifer was taken by hand among rocks in quiet water behind a rocky shoal in the large, deep-channeled Ocmulgee River (near Hawkinsville, Georgia). Several individuals of spinifer were seen in the Flint River (near Bainbridge, Georgia), which had a swift current in a wide, deep channel, sandy or sand-silt banks, few brush piles along shore and many oölitic, submergent snags on an otherwise sandy bottom; the water was exceedingly clear and permitted water-goggling (this habitat has been obliterated by a dam on the Apalachicola River). A large female spinifer was taken on a set line from the bottom of one of several deep holes (approximately seven feet) that were connected by shallow areas or riffles (near headwaters of Escambia River—Escambia Creek, Escambia County, Alabama). Two large females of spinifer (one escaped) were taken on a trotline set in a large, [544] deep, isolated barrow pit near the Escambia River (near Century, Florida); there was no aquatic vegetation, the water was slightly turbid, and the substrate was of a sand-silt or mud.
In Arkansas, spinifer has been taken in large deep rivers having relatively clear water, a moderate current, steep banks four to 15 feet high, and a substrate of mud with few rocks (one taken on trotline, escaped; Black River, near Black Rock, Lawrence County). Two spinifer were taken (trotline and hoop-net) from a smaller (approximately 50 feet wide) turbid river having a swift current, débris along the shoreline, and mud-gravel banks (Petit Jean Creek, Yell County). Several spinifer and muticus were taken from the White River (Marion County) having a sand-gravel or bed rock bottom and clear water; individuals were collected by hand in shallow water (approximately 31/2 feet deep) as they lay on the bottom in the main channel where the current was moderate to swift or in a quiet-water side channel having submergent vegetation.
Lake Texoma, an impoundment on the Red River, having a fluctuating water level with no permanent stand of aquatic vegetation, a mud-rock or sand-silt bottom, and turbid water ([Pl. 49, Fig. 1]) is a suitable habitat for spinifer and muticus. T. spinifer is found in large rivers having relatively clear water, moderate currents, emergent logs and débris, and mud or sand banks (Little River, McCurtain County, Oklahoma, [Pl. 48, Fig. 1]), or small, shallow, turbid creeks having sand-gravel channels of pools connected by riffle areas (Mayhew Creek, Choctaw County, Oklahoma).