Lake Judy is what I would call a residential pond. It has a park and playground on one side and is surrounded by nicely landscaped backyards. It is rather shallow, not even 2 meters deep at its greatest depth, and at 15 acres, it is one of the smallest of the 111 lakes in Ramsey County, Minnesota.
But Lake Judy has a teeming population of painted turtles, perhaps as many as 2000 of them. About 350 of the turtles have been marked with implanted chips over the past few years to help biologists like my buddy Tim identify them upon recapture in his turtle traps.
Today, Tim was helping young scientists from Warner Nature Center camp learn more about his turtles.
Kids got to hold the turtles while they were processed. Grandson Matthew volunteered.
Then the turtles got weighed, measured, sexed, and IDed, or implanted with an ID chip if they had never been caught before. The process looked something like this.
Greater distance of the cloaca (i.e., anus) from the edge of the plastron (lower shell) indicates maleness.
Weighing turtles in a cloth bag big enough for the largest snapper.
You can count rings of scutes (scaly squares on the carapace) until Painted Turtles are about 12 years, when they start to slough some of their scutes making accurate aging impossible.
Measuring every dimension of the carapace and plastron can be used to monitor growth in turtles instead of counting rings of scales in their carapace.
A microchip reader is used to detect and read the number ID of previously tagged turtles. Simply holding the detector up to the turtle enables the number to be displayed on a screen.
A microchip the size of a one-half inch length of fat pencil lead can quickly be inserted under the skin of the shoulder area in untagged turtles. This little guy doesn’t look like he enjoyed the process.
Why should we care about the turtles of Lake Judy? What does Tim want to know from this study? It turns out that Painted Turtles are surprisingly mobile, even in the middle of winter when they cruise around the length of a football field on the bottom of the frozen lakes. Where do they go? What are they doing in the lake at different times of year? Who leaves and who stays in the lake? Are they territorial within the lake, even a lake as small as this one? Do they move from one lake to others in the nearby vicinity? How do turtle movements change over time, year to year? The more data Tim collects from this turtle population, the more questions he hopes to be able to answer.