Spiny Softshell (Trionyx spiniferus) {=Apalone spinifera) 



Description: Spiny Softshells have flexible, leathery shells. The carapace is olive-gray, marked 

 with dark spots. The plastron is white or light cream-colored. Female carapace length is up 

 to 18 inches or more, whereas males are typically 6-8 inches. The nostrils are terminal, 

 allowing this turtle to remain entirely beneath the surface and take air through its "snorkel." 

 Eggs and Young. The nest is a flask-shaped excavation containing 4-39 (typically 12-18) hard- 

 shelled, spherical, white eggs. The individual eggs range in size from 24-32 mm in diameter 

 and average about 28 mm. Hatchlings resemble adults and are 30-40 mm in shell length 

 (Ernsts/ a/. 1994). 



Similar Species: None. 



Habits and Habitat: Spiny Softshells are active during the day. This highly aquatic turtle is found 

 in rivers or their connecting backwaters with muddy or sandy bottoms. Unlike other Montana 

 turtles, they do not move overland from one water body to another. Mud and sand banks and 

 bars are used for both basking and nesting. Hibernation takes place beneath the water, usually 

 beneath 5-10 cm of bottom substrate (Ernst et al. 1994). The retracted head and neck 

 combines with the profile of the shell to produce a wedge shape, which allows this turtle to 

 escape by literally diving into the bottom mud. If necessar\', additional strokes of the legs will 

 completely bury it in the substrate, hidden from view. Food items include fish, crayfish, frogs, 

 toads, aquatic insects, and carrion. Spiny Soft-shells have a surprisingly long, agile neck and 

 can inflict a painfiil bite. They can be safely handled by grasping the shell on each side 

 between the front and rear legs with the head pointing cmay from the captor. 



Surveying: various turtle traps can be used for surveys, although visual identification is suitable 

 since the three turtle species in Montana are easily distinguished. A pair of binoculars is 

 helpfiil and surveys should be done on warm sunny days; basking seldom takes place before 

 10:00 a.m. (Ernst et al. 1994). During cold or cloudy weather, turtles tend to remain 

 underwater for long periods and can be missed on a walk-through survey. Care should be 

 taken to watch for the snorkel-like nostrils projecting just above the surface of the water. 



Status and Distribution: Status of this species in eastern Montana is uncertain, as it is reported 

 infrequently. It was not encountered during the 1998 surveys. It may be more common and 

 widespread than current records indicate. For example, this species has been seen 3 

 consecutive years (1995-1997) on the Tongue River in Rosebud and Custer counties near 

 Brandenburg. It is found mainly in the Yellowstone and Missouri Rivers and their major 

 tributaries (such as the Tongue and Musselshell rivers). The Yellowstone and Missouri rivers 

 populations may be separated from each other, and are believed to be disjunct from the 

 population in South Dakota (Ernst et al. 1994); they have not been reported from North 

 Dakota (Wheeler and Wheeler 1966). The Missouri River population is known from the tail 

 of Fort Peck Reservoir upstream to the first dam, and from most of the Musselshell River. 

 They have not been reported from Fort Peck Reservoir or in the Missouri River downstream 

 from Fort Peck Dam. Any located on BLM lands should be documented and reported. 



Montana Natural Heritage Program rank: G5 S3. Species of Special Concern, BLM Special 

 Status Species. 



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