Inventory and nesting characteristics of northwestern pond turtles (Actinemys marmorata) in Point Reyes National Seashore and North District Golden Gate National Recreation Area
Gallanty E, Fong D, Kentner V, Bernot T, Halstead BJ. 2025. Inventory and nesting characteristics of northwestern pond turtles (Actinemys marmorata) in Point Reyes National Seashore and North District Golden Gate National Recreation Area. Science Report. NPS/SR—2025/233. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/2307219
Northwestern pond turtles have gained much attention in the past few decades due to dramatic population declines. We compiled data on the pond turtle’s historic occurrence within northern Golden Gate National Recreation Area (GOGA) and Point Reyes National Seashore (PORE), including recent incidental observations by U.S. Geological Survey (USGS) staff. To build on that past data and better understand current pond turtle distribution, abundance, non-native co-inhabitants, demographics, nesting behavior, and nest site characteristics, we conducted distribution surveys here from 2015–2019. We found northwestern pond turtles using visual encounter and trapping surveys at 11 sites, mostly confirming past USGS observations at those sites. However, we detected pond turtles in only 38% of sites previously identified by USGS as having pond turtles. In our surveys, pond turtles were most abundant at two Martinelli ponds along the southeastern slopes of Tomales Bay. At this location, we have an estimated population size of 94 adults (carapace length range from 68 to 300) from mark-recapture trapping surveys. This site is also the largest nesting population in the park, with annual nest abundance of 13.75 nests per year and a mean clutch size of 4.9 eggs per nest. The demographic data from the Martinelli Ponds indicates a population skewed towards larger individuals, which is consistent with other locations elsewhere in California. This population data served to identify the Martinelli Ponds population as the donor site for a GOGA pond turtle headstart project. Nesting activity in 2017–2019 occurred from late May with activity peaking in mid-June and tapering off in mid-July. Visual surveys proved to be the most effective means of finding nesting females and nests; camera traps, VHF telemetry, and PIT antenna array costed time and money while not providing the desired information. Future inventory efforts should focus on resurveying lightly surveyed sites where we were not able to find northwestern pond turtles, periodic monitoring of abundance and demographic structure of main PORE population (Martinelli Ponds), and surveillance monitoring for invasive bullfrogs and turtles. Increasing public awareness of the status of northwestern pond turtles is another key action that will play a major role in their conservation.
- Type
- Published Report
- Authors
- Gallanty, Ellen; Fong, Darren; Kentner, Victoria; Bernot, Tim; Halstead, Brian
- Date of Issue
- 2025-01
- Publisher
- National Park Service
- DOI
- 10.36967/2307219
- Units
- GOGA , NRSS , PORE
- Keywords
- abundance, at-risk biota, demographics, distribution, northwestern pond turtles, reproduction, reptiles, special status species, turtles
- Subjects
- Ecological Framework: Biological Integrity | Focal Species or Communities | Wetland Communities , Ecological Framework: Biological Integrity | Focal Species or Communities | Freshwater Communities , Ecological Framework: Biological Integrity | Focal Species or Communities | Amphibians and Reptiles