Demography and reproduction

The Wood Turtle's decline across a majority of its range in the United States and Canada has primarily been caused by human encroachment on its habitat, including the direct and indirect effects of habitat loss, fragmentation, and degradation. As noted in Chapter 8, threats include direct mortality from flooding, agricultural machinery, and motor vehicles, as well as illegal collection for pet markets and subsidized predation by mesocarnivores. Wood Turtles are unable to effectively respond—behaviorally or numerically—to these synergistic threats because they have evolved as extreme bet-hedgers: they are adapted to low (and variable) rates of juvenile survival and very high (and stable) adult survival. This is true of most of the turtles within the subfamily Emydinae, which generally exhibit late maturity and a long, iteroparous lifespan (7.1). Survival is low for eggs and hatchlings, but apparently increases throughout the juvenile life-stages until the turtle reaches adulthood. At this point, individuals generally experience high annual survival rates, and they often reproduce in most years for many sequential decades, replacing at least themselves and a mate in a stable population. In this chapter, we summarize key aspects of Wood Turtle biology, including lifespan, age of maturity, reproductive output, demography, and population dynamics.