Population distribution and range limits in Blanding’s Turtle (Emydoidea blandingii) using Presence Program

Background/Question/Methods:

Blanding’s turtles (Emydoidea blandingii) are in the northern US and in southeastern Canada.  This species became a threatened species in New York State and has been surveyed for numerous studies during the past 12 years. This project is about the analysis of the data that are reported during the surveys to evaluate whether a site at which no turtles are detected really absent of turtles. Typically, there is no guarantee that the species will be detected, even when present at a site. To perform this investigation, we are using the program Presence. This software was developed to enable estimation of the proportion of area of occupied (PAO), or similarly the probability a site is occupied, by a species of interest according to the model presented by MacKenzie et al. (2002). In this investigation, the software will help to estimate patch occupancy rates and give us the probability of the presence or absence of Blanding’s turtles in the wetlands. To realize this project we have data from 12 years (1999-2011) from the trapping turtles in northeastern New York.

Results/Conclusions

As the results we have 100 sites where the turtle was not detected. Eighty-four sites of those 100 where we do not know if the turtle is present or absent because the probability of detection is less than 0.95. Another 16 sites where we know the turtle is present but it was not detected because the probability of detection is more than 0.95. The importance of this project is that it can help to do direct surveys to areas that we will be sure that Blanding’s turtles will be present. Also important because is necessary to know which wetlands are truly unoccupied to compare ecological characteristics of occupied vs. unoccupied sites.