Climate-Mediated Recruitment Failure in a Turtle Population and Its Bearing on Northern Limits of Distribution

Abstract. The eruption of Mount Pinatubo in the Philippines in June 1991 reduced global temperatures over the following 2 yrs. The greatest suppression (apart from Antarctica) was centered in the northern Great Plains of North America, directly over my long-term turtle study site. Temperatures at that site in 1992 and 1993 were the coldest in at least 50 yrs. Normal annual hatchling recruitment of yellow mud turtles (Kinosternon flavescens) in the spring following incubation at that site averaged 375; however, only 3 hatchlings emerged in 1993 (1992 incubation cohort), and none emerged in 1994 (1993 incubation cohort). The depressed temperatures apparently prolonged incubation times to such an extent in 1992 and 1993 that hatching was nearly impossible before winter mortality. The result was a gap in the age class structure that was still evident 26 yrs later. This site is at the northern range limit of this species, and this event suggests that incubation temperatures (i.e., summer season length) may be responsible for that limit.