North American Recent Soft-shelled Turtles (Family Trionychidae) Part 18

?SOUTH DAKOTA: _County unknown_: Fort Mackenzie, Missouri River, 6-8 mi. below Cedar Island (Stejneger, 1944:15).

TENNESSEE: _Lake_: Mississippi River (Parker, 1948:29). _Pickett_: Obey River at Eagle Creek Ford (Shoup, Peyton and Gentry, 1941:75).

WISCONSIN: _Crawford_: _Pepin_: Mississippi River (Breckenridge, 1944:183; Pope and d.i.c.kinson, 1928:82).

=Trionyx muticus calvatus= Webb

Gulf Coast Smooth Softsh.e.l.l

Plate 47

_Trionyx muticus calvatus_ Webb, Univ. Kansas Publ. Mus. Nat.

Hist., 11:519, 1 fig., 2 pls., August 14, 1959.

_Type._--Holotype, UI 31071, hatchling, s.e.x undetermined, alcoholic; obtained from Pearl River, Roses Bluff, 14 miles northeast Jackson, Rankin County, Mississippi, by William F. Childers on August 25, 1952.

_Range._--Southeastern United States from the Florida Parishes of Louisiana eastward to the western end of the panhandle of Florida; rivers of the Gulf Coast drainage from the Escambia River drainage, Florida, westward to Louisiana and Mississippi including the Pearl River drainage. The eastern extent of geographic range is not known (see map, Fig. 22).

_Diagnosis._--Juvenal pattern of large circular spots, often ocellate; no stripes on dorsal surface of snout; pattern on dorsal surface of limbs of fine markings, not in contrast with ground color; pale postocular stripes having thick black borders approximately one half width of pale stripe on adult males.

_Description._--Plastral length of smallest hatchling, 3.0 centimeters (TU 17301); of largest male, 11.8 centimeters (KU 47118); of largest female, 18.0 centimeters (TU 13473).

Juvenal pattern of dusky, circular spots, some ocellate, lacking short lines and streaks; number of spots variable; some spots on carapace of hatchlings may have maximum diameter of three millimeters (TU 17301); pale rim of carapace having dusky, ragged, inner border; juvenal pattern on adult males absent or usually evident, at least posteriorly (TU 17306.1).

Dorsal surface of snout lacking pale stripes just in front of eyes; pale postocular stripe having thick, black borders on adult males, but narrower, dusky or blackish borders on juveniles and large females; lower border of postocular stripe usually in contact with dusky postl.a.b.i.al line; no other markings on side of head; pattern on dorsal surface of soft parts of body of closely approximated, fine markings that are not in contrast with ground color, over-all coloration grayish; occasionally few larger and more contrasting markings, especially on hind limbs and anteriolateral surface of forelimbs.

Underparts whitish, lacking markings, occasional black flecks or dusky marks posteriorly along ventral edge of carapace (TU 17306.3).

Surface of carapace smooth in adult males; large females lacking prominences posteriorly in center of carapace or in nuchal region; anterior edge of carapace smooth in both s.e.xes, but occasionally having regularly s.p.a.ced furrows or wrinkles on hatchlings.

_Comparisons._--_T. m. calvatus_ can be distinguished from _T. m.

muticus_ by the absence of pale stripes on the snout just in front of the eyes, in having pale postocular stripes that have thick, black borders on adult males, and in having a juvenal pattern of large, circular spots that are often ocellate and three millimeters in diameter (no short lines).

_Remarks._--I have not seen specimens of _calvatus_ from the Tombigbee-Alabama river drainage; presumably Cook's record (1946:185) from Lowndes County, Mississippi, represents this subspecies.

It is still not certain that _calvatus_ occurs in streams that drain into Lake Pontchartrain, Louisiana; TU 17236 from the Amite River that lacks a diagnostic character is questionably referred to _calvatus_ (Webb, 1959:524). As mentioned previously _T. s. asper_ shows little evidence of intergradation with _T. spinifer_ in the Mississippi River drainage; _asper_ is present in streams of the Lake Pontchartrain drainage. _T. m. calvatus_ presumably shows a corresponding relations.h.i.+p with _T. m. muticus_ in the Mississippi River drainage.

There are no specimens that indicate intergradation between _calvatus_ and _muticus_; _calvatus_ is expected in streams that drain into Lake Pontchartrain, Louisiana. Probably _calvatus_ occurs eastward in the Apalachicola drainage system.

_Specimens examined._--Total, 38 as follows: FLORIDA: _Escambia_: KU 47116, 50852, 50854-55, 50835-36, TU 13473, 16682, 17301, 17302 (2), Escambia River, 2 mi. E, 1 mi. N Century.

LOUISIANA: _East Baton Rouge_: TU 17236, Amite River, "near" Baton Rouge. _Was.h.i.+ngton_: TU 13795, Bogue Chitto River, Enon; TU 17303 (5), TU 17304 (4), Pearl River, "near" Varnado. _No data_: TU 17305.

MISSISSIPPI: _Lawrence_: KU 47117-19, TU 16956, USNM 7655, Pearl River within 4 mi. of Monticello; TU 17306 (4), Pearl River, 9 mi. S Monticello. _Marion_: USNM 95133-34, Pearl River, Columbia. _Perry_: MSC uncatalogued (3), 3 mi. SE New Augusta. _Rankin_: UI 31071, Pearl River, Roses Bluff, 14 mi. NE Jackson.

_Records in the literature._--MISSISSIPPI: _Forrest_: no data.

_Jones_: Crawford Bridge. _Lowndes_: Columbus, Lake Park (Cook, 1946:185).

NATURAL HISTORY

Habitat

Most writers who describe the general habitat of soft-sh.e.l.led turtles mention large rivers and streams having some current, and large permanent, quiet bodies of water having soft mud or sand bottoms, but note the general avoidance of temporary water. The impermanence of water in the ponds and "charcos" of headwaters of streams may preclude the presence of softsh.e.l.ls from these otherwise suitable habitats.

Seemingly, soft-sh.e.l.led turtles are not restricted to particular local situations or microhabitats in a continuous aquatic environment as are some kinds of fish, which seem to be more or less confined to riffle areas or deep holes. Certain activities of softsh.e.l.ls such as burying themselves in soft sand in shallow water or seeking crawfish and other food over a gravel-rock substrate or one that is debris-laden, are best carried on in different habitats. Repeated observations of turtles that are probably engaged in a specific activity in a restricted area may lead to erroneous general conclusions regarding the over-all preference for a specific habitat. Perhaps this accounts for Conant's statement (1951:156) that "In the lower portion of the Scioto River [Ohio] it appears that the present species [_muticus_] is abundant while _spinifer_ is almost entirely absent."

Cagle (1954:181) wrote that softsh.e.l.ls "inhabit the extreme headwaters and smaller tributaries." Other statements in the literature indicate the variety in kinds of habitat. In Louisiana, Beyer (1900:44) mentioned _spinifer_ as abundant "in all inland waters, preferring, however, such bayous which have sloping and sandy banks upon which they are fond of sunning themselves." Viosca (1923:41) reported soft-sh.e.l.led turtles as characteristic "of the large silt-bearing rivers ... such as the Pearl, Amite, Mississippi and Atchafalaya."

Cagle and Chaney (1950:386) wrote that _spinifer_ in Louisiana was found in greatest abundance in streams having some current, but that individuals were also common in quiet areas; the habitats recorded were: False River--a lake of clear water supporting an abundance of submerged vegetation, the shallow ends having mats of water hyacinth; Lakes Iatt and Bistineau--cypress swamps having clear or muddy water; Caddo Lake--a large lake having a light oil film on the surface of the water, and vegetation toward the sh.o.r.e consisting of cattails, water lilies and water hyacinths, and along the bank of cypress and willow trees; Caddo Lake Spillway--muddy with swift current; Sabine River--swift current, traps set in quieter backwater areas or near cypress logs in river; Laca.s.sine Refuge--traps set in inlets and coves of s.h.i.+p channel having vegetation of water hyacinth, alligator gra.s.s, and along bank, saw gra.s.s, cypress knees and snags. Stejneger (1944:59) reported _spinifer_ taken in barrow pits in Mississippi.

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 ca.n.a.ls 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 ca.n.a.ls. Judging from the numbers of turtles, "the larger ca.n.a.ls 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.

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 _aga.s.sizi_ (= _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 salt.w.a.ter herpetofauna, off the coast of Brevard County, Florida. Loding (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-sh.e.l.led 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 debris intermittent along the sh.o.r.eline; the banks may be steep and of mud having a spa.r.s.e 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 sh.o.r.e and many oolitic, 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, 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, debris along the sh.o.r.eline, and mud-gravel banks (Pet.i.t 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 3-1/2 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 debris, 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).

Three _spinifer_ were taken from the Llano River (near Llano, Texas) in a period of low water level in hoop-nets set in a large quiet-water pond about four feet deep and having patches of rushes encroaching into the water from the sh.o.r.e. The river bed of sand, gravel and large boulders consisted of narrower, swift-water channels, small pools and riffles, and large ponds.

Individuals of _T. s. emoryi_ have been taken in large ponds having little or no current, turbid, deep water, and clay or sand-gravel banks (Rio Purificacion, Padilla, Tamaulipas). Two _emoryi_ were collected from a large pond (Rio Sabinas, near Sabinas, Coahuila), which was connected to an adjoining one by riffle areas and had little or no current, relatively clear, greenish water, clay or mud banks, a sand-gravel bottom, and was flanked by brush and large cypress trees.

A few _emoryi_ were trapped in hoop-nets that were set in the Rio Mesquites, a stream in central Coahuila approximately 20 feet wide and six feet deep, flanked by dense stands of _Phragmites_, and having a moderate current, relatively clear, pea-green water and a mud-sand substrate with some gravel; the stream enlarged in some places to form quiet-water coves (Pl. 48, Fig. 2). One adult male _emoryi_ was taken from a crystal-clear, dendritic, pond (El Mojarral, near Cuatro Cienegas, Coahuila), having shallow areas averaging about two feet but several deep holes--in one of these at the west end of the pond the water was being emitted under pressure from an underwater cavern and "bubbling" at the surface; the vegetation consisted of scattered patches of water-lilies and stonewort; the bottom was a soft mud-marl, and in some places was carpeted with sh.e.l.ls of small gastropods. This habitat corresponds to that of the type locality of _T. ater_ (Pl. 49, Fig. 2); see description in Webb and Legler (1960:26). The water of the ponds is warm; at 8 p. m. on July 31, 1959, the temperature of the water at the type locality of _ater_ was 29 C., and the air was 27 C.

An immature female _spinifer_ was taken on a trotline in a swift, clear, cold-water habitat having mud banks and an abundance of brush piles (Little Tennessee River, Monroe County, Tennessee). _T.

spinifer_ occurs also in large ox-bow lakes having relatively clear water, extensive mats of submerged vegetation, a soft mud bottom, and several emergent stumps and fallen logs (Lake Concordia, Concordia Parish, Louisiana); alligator gra.s.s and cypress trees encroached to the sh.o.r.eline.

Locality data of some individuals of _spinifer_, _hartwegi_, _asper_, _pallidus_ and _emoryi_ that were examined indicated that turtles were captured in ponds, bayous, sloughs, lakes, impoundments, rivers and creeks, indicating habitation of essentially all permanent waters.