SREL Reprint #2193

Life history and ecology of the Sonoran mud turtle (Kinosternon sonoriense) in Southeastern Arizona: a preliminary report

Richard C. van Loben Sels1, Justin D. Congdon2, and Josiah T. Austin3

1Red Mountain High School, 7301 East Brown Road, Mesa, Arizona 85207 USA
2Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802 USA
3El Coronado Ranch, Star Route, Box 395, Pearce, Arizona 85625 USA

Abstract: From 1990 through 1994 we conducted a mark-recapture study of Kinosternon sonoriense in the West Turkey Creek area of the Chiricahua Mountains in southeastern Arizona. A total of 580 individuals was marked, and 913 recaptures were made. Approximately 90% of the individuals were initially captured in stock tanks, 5% in stream pools, and 5% on land. Sex ratio of adults was 1 male to 1.29 females. Of the 573 individuals captured alive, 18.5% were classified as juveniles, 35.8% as adult males, and 45.7% as adult females. Four hatchlings captured in early August averaged 3.0 g body mass and 22.2 mm carapace length (CL). Growth rates of juveniles from hatching to age 6 averaged 17.5 mm CL/yr. The youngest gravid female was 5 years old and the smallest had a CL of 106 mm. Maximum CL of adult males and females was 168 and 160 mm, respectively. There was no sexual size dimorphism between age classes 5 and 10 yr. Based on 39 females captured twice during the reproductive season, a minimum of 23% of the females in the population produced at least 2 clutches of eggs in a single year. Over all years clutch size averaged 6.7 eggs (range 2-11) and the sizes of first and second clutches were similar. Clutch means of actual egg widths from six females averaged 16.85 mm and were similar to mean egg widths taken from radiographs (XREW) of the same females (16.95 mm). Both clutch size and egg widths taken from radiographs were significantly and positively related to body size. No pelvic constraint on egg width was apparent since the slope of the relationship of CL to the pelvic aperture width determined with radiography (0.144) was significantly steeper than that of egg widths (0.041). The relationship between the residuals of clutch size with CL to XREW was negative. The average dry mass of egg yolks averaged 0.96 g (range 0.73-1.25 g), and comprised 28.75% non-polar lipids (range 26.47-29.87%). Egg shells averaged 32.75% of the total dry mass of the egg and were similar in proportion to eggs of other Kinosternon.

Keywords: Reptilia; Testudines; Kinosternidae; Kinosternon sonoriense; turtle; ecology; life-history; reproduction; morphometrics; eggs; Arizona; USA

SREL Reprint #2194

van Loben Sels, R.C., J.D. Congdon, and J.T. Austin. 1997. Life history and ecology of the Sonoran mud turtle (Kinosternon sonoriense) in Southeastern Arizona: a preliminary report. Chelonian Conservation and Biology 2:338-344.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).