Ecology and Vulnerability

Blanding's Turtle

Background
The Blanding’s turtle's range is centered in the Great Lakes region and west to Nebraska, but there are also three disjunct populations in New York, eastern Massachusetts into southern Maine, and southern Nova Scotia^1,2.  Habitat fragmentation and road kill mortality^2,3 appear to be causing a decline in populations.  Such mortality can significantly impact populations because the species is very long-lived (70+ years), has delayed sexual maturity, and low fecundity or fertility^1,4.  As a result, the species is listed as "at risk" in 17 of 18 states or provinces across its range³.  In Massachusetts, it is currently listed as "threatened"².

The Blanding’s turtle is generally considered a northern species that inhabits productive wetlands including ponds, creeks, and marshes^5,6.  Compared to more southern turtle species, it tolerates lower maximum temperatures and seeks out microhabitats that result in lower body temperatures⁵.  Though largely aquatic, it can make long overland movements for nesting⁷.  The species has a relatively large home size and will travel extensively between wetlands^2,6.  Females nest in upland locations with nesting peaking in June^4,8.  Turtles move to overwinter locations in September and October and remain moderately active until ice formation⁶.  They emerge from hibernation under the ice between March and April⁹.

Climate Impacts
Blanding’s turtles inhabit a fairly narrow latitudinal range¹⁰.  They are restricted by temperatures at the northern and southern boundaries^1,3, and have a relatively low tolerance for high temperatures^5,7.  This suggests that their optimal climatic range will likely shift north as climate changes.  However, the ability of Blanding’s turtles to move north with such changes may be hampered by habitat fragmentation, as road crossings are hazardous and vehicles cause significant mortality^3,4.  Habitat suitability for Blanding’s turtles decreases rapidly as road density increases³.

Temperature can also impact male to female ratios, as some turtles, including Blanding’s turtle, exhibit temperature-dependent sex determination¹⁰.  In such turtles, temperature changes during incubation of eggs can alter sex ratios.  However, to date, studies have failed to find any connection between changing climate and sex ratios in populations that are known to have experienced warming temperatures¹⁰.

Additionally, climate change is projected to increase the frequency of short-term summer drought conditions in the Northeast¹¹.  This has the potential to impact turtles through reduction of suitable habitat.  In some populations, Blanding’s turtles have been observed to reduce activity during drought conditions, and to prepare for hibernation earlier in the season⁷.