Demographic studies of wildlife populations are needed to guide management decisions for threatened species. Without data on population vital rates, decisions are often speculative and based on general information about a species rather than at the population level. The Ornate Box Turtle (Terrapene ornata) is a threatened species in Illinois and lacks essential demographic data. Over the last two centuries, nearly all Illinois prairie has been converted to agriculture, and consequently, Ornate Box Turtles are now confined to small isolated habitat fragments. Despite their threatened status and patchy Illinois distribution, we understand little about the demography of remaining populations. I collected population vital rates and projected persistence for two Ornate Box Turtle populations in northern Illinois. I estimated reproductive output by radiographing female turtles, and of the 70 females radiographed, 28 had visible eggs. Clutch size ranged from 1 to 6 eggs, with a mean of 2.53 at Ayers Sand Prairie and 4.20 at Nachusa Grasslands. To estimate annual survival, I conducted capture-mark-recapture surveys. Annual apparent survival was 0.970 at Ayers Sand Prairie and 0.860 at Nachusa Grasslands. Matrix population models showed the Ayers Sand Prairie population as stable, whereas the Nachusa Grasslands population was in decline. Population growth was most sensitive to adult survival. My results highlight the importance of long-term demographic studies for threatened species and show protecting adult female Ornate Box Turtles is critical for ensuring populations continue to persist in Illinois.
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Ornate box turtle (Terrapene ornata) demography in northern Illinois
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