SITE PREFERENCE OF SOFTSHELL TURTLE NESTING ACTIVITY, LOCK AND DAM 19
TAILWATERS, MISSISSIPPI RIVER.

Colleen M. Riley and Richard V. Anderson.  
Dept. of Biological Sciences, Western Illinois University, Macomb, IL 61455.

Softshell turtles have been found to be the dominant turtles species in the open water habitat
below Lock and Dam 19, Mississippi River.  The sandy shoreline on the Illinois side of the river
was used as nesting sites by this turtle species.  This area is part of Kibbe Life Sciences Field
Station and thus access to the shoreline area is limited, reducing human disturbance of the site. 
The study occurred between mid-June and mid-July, 1999, when turtles were actively nesting in
the area.  To characterize the type of nesting habitat preferred by the smooth softshell turtle, the
shoreline was examined in terms of substrate type, amount of covering vegetation and amount of
sunlight.  The shoreline was divided into 15 equal areas and after characterizing habitat
conditions, was examined for the presence of turtle nests.  One hundred and forty-eight nest sites
were discovered.  Of these nest sites approximately 40% were false sites, no eggs having been
laid at the site.  Of the remaining sites over 65% successfully hatched turtles.  The majority of
hatched nests were in areas of complete sunlight, little to no vegetation and a sandy substrate. 
The greatest number of nests were located in areas where the substrate temperature during the
day was above 30C yet did not exceed 45C.  Most of the unsuccessful nests were in areas where
habitat conditions differed in terms of substrate, vegetative cover or sunlight intensity.  The study
suggests that optimum nesting habitat can be identified for this turtle species and if necessary
human activity can be limited during nesting periods.

Keywords:  smooth softshell turtles, nesting sites, habitat characteristics, Mississippi River, Pool
19 tailwaters