Nesting Habitat and Behavior of Spiny Softshell Turtles Apalone Spinifera Hartwegi in the Missouri River, MT

Scientific Disciplines
Biological Sciences - Terrestrial
Montana State University
missouri river
Montana cooperative fisheries research unit
spiny softshell turtle
apalone spinifera
western spiny softshell turtle
nestIng habItat
Volume 18, No. 1-4

Nesting habitat and behavior of spiny softshell 
Turtles apalone spinifera hartwegi in the missouri 
River, Mt
Brian J. Tornabene*, Ecology Department, Montana State University, Bozeman, Montana 59715
Robert G. Bramblett, Ecology Department, Montana State University, Bozeman, Montana 59715
Stephen A. Leathe, Pennsylvania Power and Light Montana, Great Falls, Montana 59404
Alexander V. Zale, U.S. Geological Survey, Montana Cooperative Fisheries Research Unit, Ecology 
Department, Montana State University, Bozeman, Montana, 59715 
Little is known about the nesting behavior and habitat of the western spiny softshell 
(Apalone spinifera hartwegi) in Montana where they are at the northern extent of their range 
and are a state Species of Concern.  Our objective was to document nesting behavior, habitat, 
and timing in a 97-kilometer reach of the Missouri River.  We radio-tagged 47 female turtles 
and attempted to locate nesting areas using telemetry, visual surveys from jet boat and on 
foot, and by observation from shore-based blinds.  We located 27 nests; 15 were on islands, 
12 were aggregated, and 2 were depredated.  Nesting occurred following the peak river stage 
from about July 7 to July 28.  Twenty-three nests were in mixed gravel and 4 nests were in 
sand substrates.  Distance from water’s edge to the nest ranged from 1.9 m to 27 m and height 
of nest above the water surface elevation ranged from 0.25 m to 1.9 m.  Vegetation at nest 
sites was sparse, ranging from 0 to 15 percent vegetative cover.  Emergence of hatchlings 
was documented for 17 nests and occurred from about September 1 to September 20.  All 17 
successful nests were in gravel substrate; we did not document any emergence from nests in 
sand.  Lack of emergence from sand nests may be related to the cumulative thermal regime in 
the nest chamber during the period from peak discharge until the onset of freezing in autumn.  
In 2012, we will investigate the thermal environment in gravel and sand nesting substrates.