The mission of Turtles for Tomorrow is to implement conservation, habitat management and landowner education to benefit Wisconsin’s rare reptiles and amphibians, with an emphasis on endangered and threatened turtles. Our goal is to help stabilize and rebuild populations of these animals and work toward their ultimate recovery.
INTRODUCTION TO TURTLES FOR TOMORROW
Wisconsin is home to 55 species of amphibians and reptiles, known collectively as herptiles. Amphibians number 19 species, including 12 frog and 7 salamanders. The reptiles, numbering 36, include 21 species of snakes, 4 lizards and 11 turtles. Reptiles are often more vulnerable than amphibians to landscape scale human impacts on natural habitats for several reasons.
- Reptiles require much larger home ranges than amphibians. For example, many amphibians can accomplish their full life cycle within 300 feet of their natal breeding pond, whereas a Gophersnake may often range in excess of ½ mi. and sometimes much further from its overwintering site in order to accomplish its life cycle.
- Reptiles are slow to mature (requiring 3 to 20 or more years), increasing the time it takes to replace lost adults in the population, whereas amphibians generally mature quickly (1- 3 years). This difference is somewhat balanced by the fact that reptiles generally live much longer than amphibians.
- Amphibians have much higher reproductive capabilities than reptiles. A female Northern Green Frog can lay 1,000 to 4,000 eggs annually, whereas an Ornate Box Turtle averages laying 4 eggs per year.
As a result, reptiles are doing much more poorly than amphibians in today’s world, including here in Wisconsin. The figure included below shows the status of the various herptile species by groups. You will quickly notice that reptiles face a far less certain future than amphibians. In fact, of the herptile species currently listed as endangered or threatened, ~ 90% are reptiles!
Of the rare reptiles, turtles perhaps face the most uncertain future. A number of U.S. and international conservation organizations consider turtles to be the most endangered species group in the world. Of the greater than 300 species that occur worldwide, more than 40 percent face potential extinction (Conservation International 2010; Rhodin et al. 2018).
Threats to Wisconsin’s Rare Turtles
Several factors contribute to the decline of both common and rare turtles in Wisconsin. Of the two listed species, the endangered Ornate Box Turtle and the threatened Wood Turtle are both very slow to mature as is the formerly listed Blanding’s Turtle. Ornate Box Turtles and Wood Turtles typically take 12 – 15 years to mature, while Blanding’s mature in 17 – 20 or more years. Compare this to Wisconsin’s threatened or endangered snakes, where the slowest matures in 3 – 4 years. Blanding’s Turtles and Wood Turtles face some additional challenges since they are semi-terrestrial, requiring both aquatic and upland habitats to complete their annual life history. These species spend considerable time on land, with the Blanding’s Turtle often making long overland forays to various wetlands throughout the active season to find suitable foraging sites and favorable habitat conditions. Habitat fragmentation often forces turtles to cross roads to reach other suitable habitats or to nest, often resulting in unsustainable adult road mortality, particularly with females. Turtles often nest in agricultural fields that have excellent sun exposure during the June nesting season only to face excessive shading (cooling) of their incubating eggs as crops mature. These cooler temperatures can result in embryo mortality if they are too cool and/or can produce mostly male hatchlings, since the sex of most Wisconsin turtles is determined by incubation temperatures (Warmer than an average incubation temperature of 80° F produces more females and cooler temperatures produce more males). Turtle nests are also threatened by agricultural equipment used to cultivate soils.
Turtle Nest Predation and Other Threats
Turtle nest predation rates have also skyrocketed in recent decades. A long-term nesting study involving Blanding’s Turtles and Painted Turtles in Michigan showed that nesting success rates decreased from 8 – 44% in the 1970s to 0 – 5% in the late 1980s and early 1990s (Congdon et al 1993). There is no evidence to show that this trend has changed since the early 1990s. A lack of sufficient recruitment will eventually lead to further population declines and eventual extirpation (loss of population). Over-collecting of turtles for the pet trade is a factor affecting populations. Other impacts include the introduction of diseases and exotic species, with some invasive plants significantly simplifying wetland habitats (e.g. Phragmites, also called Common Reed, Phragmites australis and Purple Loosestrife Lythrum salicaria). This may help explain why Turtles For Tomorrow places an emphasis on turtle conservation above the other species groups.