Thursday, May 16, 2013

Conservation of the Western Pond Turtle

By Danielle Olivera, Pepperwood Volunteer

Western Pond Turtles enjoying their favorite log at Turtle Pond.
The white stick to the left is used to measure depth.
January: Note how close the water is to the two trees in the back left.
That little white line on the right is the top of the depth gauge.
When I was a little kid, I loved playing with tadpoles and turtles. Many years later, turtles are still high on my list of interesting animals, though now I know a lot more about them. Our research at Pepperwood Preserve has been focused on the Western Pond Turtle (Actinemys marmorata), the only native freshwater turtle in California. Unfortunately, this hard-shelled reptile has faced many challenges in the past few decades, including non-native species introductions, habitat fragmentation and human disturbance. Since then, their numbers have decreased dramatically, putting them on the International Union for Conservation of Nature (ICUN)’s List of Threatened Species in California.

Every other week, our team of three (Pepperwood Stewards Carrie Mammoser, Lloyd Cook, and myself) hikes out to Turtle Pond, where we work to monitor the health of the pond and surrounding habitat, which has a direct impact on the turtles themselves. Since this species of turtle is on a decline, we decided to figure out what features constitute their ideal habitat. One of the key factors we’d like to determine is if human and non-native animal disturbances were negatively affecting the population at the pond.

May: So much change in just four months! By the end of the
summer, almost all of the water will probably be gone.
Each visit involves counting the number of turtles present, the types and number of all other plant and animal species present, the temperature of the air and water, wind, water height from the bottom of the pond, pH, nitrite and nitrate levels of the pond. All of these factors can affect the survival and reproduction rates of the Western Pond Turtle.

Steward Lloyd Cook taking measurements in May 2012.
While we spend most of our time observing the turtles and recording water quality, we also keep track of the other types of animals present and how those numbers fluctuate over the year. The turtles are shy and tend to jump off of their log into the water when we begin taking measurements. We’ve found that Sierran Treefrogs, California Newts, garter snakes and various fungi species are also present when there is water in the pond.

Though we only have one year of data, it’s exciting to see the monitoring project come together. It’s too early to draw any conclusions, but we can provide a couple examples of our measurements. Nitrate levels, for example, have remained constant throughout the year. The pond’s pH has also held steady at 5.5 over the course of the year. Water levels vary seasonally and can change drastically depending on rainfall – see the graph to the lower right for an illustration.

We look forward to collecting a second year’s worth of data so we can begin to compare how Turtle Pond and its community of Western Pond Turtles is changing over time.

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