We are interested in Blanding’s turtles because it is a Threatened species in Wisconsin and has experienced large population declines (Kofron and Shreiber 1985, Congdon et al. 2000, Evrard and Canfield 2000, Bury and Germano 2002). Blanding’s turtles have been spotted in the Arboretum, thus fueling our interest in locating and conserving this rare species. Historically, they have been found inhabiting permanent pools and forested swamps, using uplands for nesting (Joyal et al. 2001). Losses to these types of habitats may affect the status of Blanding’s turtles. We feel our research will help further conservation efforts for this species.
Blanding’s turtles are one of the longest-lived freshwater turtle species (Brecke and Moriarty 1989). It is important to find the demographics of Blanding’s turtles because they do not reach sexual maturity until age 14 to 20 (Congdon and van Loben Sels 1993). If we determine the ages of the population, then we will find out if they are possibly able to breed.
Many researchers that studied Blanding’s turtles have emphasized their low recruitment into the breeding population and a scarcity of sexually immature turtles. Both are critical characteristics for quick population growth and recovery from habitat degradation, such as the loss of water quality (Wilson 2002). So, we would like to see if there are any sexually immature Blanding’s turtles in the Arboretum.
Extensive research is being done on Blanding’s turtles in Nova Scotia, which has a similar environment to Wisconsin and is nearly on the same latitude (Wisconsin latitude – 43˚ 08′ N, Nova Scotia latitude – 44˚ 37′ N), so we may be able to compare our data to studies already conducted (Dobson 1971, Herman 1995, Power 1995, Herman 1999). Researchers have aged turtles in this Canadian environment by looking at scute rings (Litzgus 1998). Several literature reviews have evaluated the efficiency of aging turtles from counts of growth rings on scutes. One examined 150 case studies that used counts of growth rings to estimate the age of turtles, and 101 of these cases presented no data to support their aging techniques. This suggests that growth ring counts are not always reliable in determining turtle age (Wilson, 2002). We plan to take into consideration the shell condition, knowledge of adult size, growth ring counts and shell size to be as accurate as possible in aging turtles. This may allow us to determine the validity of the Canadian aging techniques.
Painted turtles (Chrysemys picta) are known to exist in the Arboretum. In contrast to the Blanding’s turtle, the painted turtle is a widely distributed species throughout North America, and is often the most abundant turtle within its range (Ernst 1971, Ernst et al. 1994, Bury and Germano 2002). We expect to find many painted turtles in the Arboretum, and would like to see how they respond to water quality changes over the time of the study.
Other turtle species that may be present in the Arboretum are the common snapping turtle (Chelydra serpentina), common musk turtle (Sternotherus odoratus), and Eastern spiny softshell turtle (Apalone spinifera). The snapping and musk turtles are common, while the softshell turtle’s population has been shown to be declining (Christoffel et al. 2002). The softshell turtle is a species, like the Blanding’s turtle, that may need conservation efforts to ensure its survival. If this study indicates that these turtles are sensitive to changes in water quality, then this data could assist in designing future conservation efforts.
Literature Cited
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