Spiny Softshell {Trionyrx spiniferus) (=Apalone spinifera) 



Description: Spiny Soft-shells 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 (Ernst e/ 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 necessaiy, 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 painful bite. They can be safely handled by grasping the shell on 

 each side between the front and rear legs with the head pointing away from the captor. 



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

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

 helpful and surveys should be done on warm sumiy days; basking seldom takes place before 

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

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

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



Status and Distribution: Found mainly in the Yellowstone and Missouri Rivers and their major 

 tributaries. These populations may be separated from each other and are believed to be 

 disjunct form the population in South Dakota (Ernst et al. 1994); they have not been reported 

 from North Dakota (Wlieeler and Wheeler 1966). The Missouri River population is known 

 from the tail of Fort Peck Reservoir upstream to the first dam above, and from most of the 

 Mussellshell River; their presence on other tributaries is presently unknown. A specimen 

 was reported by Black (1970) from Canyon Ferry Resers'oir, however, no museum has 

 reported having one, nor have recent biologists in the area reported them here; it should be 

 treated as hypothetical given the long distance to the nearest record. Any located on the HNF 

 should be documented and reported. Considered a Species of Special Concern in Montana. 



Montana Natural Heritage Program Rank: G5 S3. Species of Special Concern. 



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