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I was over at Sweetwater Wetlands the other day. Not much was going on and I was almost finished with my walk when I noticed a Red-eared Slider, an aquatic turtle, sitting at the edge of a reed-choked pond. Sliders are native to the southern United States and are an invasive species in Arizona. Indeed, they are an invasive species with virtually a world-wide distribution. Back in the 1950s very young sliders were enormously popular pets. You (or, more likely, your parents) would buy the turtle, perhaps two or three inches in diameter, and a little plastic tank (usually equipped with a tiny plastic island and plastic “palm tree”) and put the turtle in it along with an inch or two of water. The stores sold dried turtle food that appeared to be dehydrated flies or some other insect. Millions of these little turtles were sold and they were quite popular until someone discovered that sliders were a natural reservoir for salmonella bacteria. That ended the slider fad (I was surprised to discover that these turtles are still sold as pets albeit in fewer numbers than during the heyday of the turtle trade).
My guess is that many of these turtles were flushed down toilets or disposed of in local waterways. Some of them survived the trauma of abandonment and grew. And grew, and grew. The tiny sliders matured into big turtles, some of them more than a foot in diameter and weighing several pounds, with a lifespan of up to 30-40 years. And, they took over the ponds and lakes into which they’d been dumped.
There are many of these Red-eared Sliders presently living at Sweetwater Wetlands and they seem to be present in every pond and lake in the Tucson area. Not only have they grown and matured, but they are reproducing. Which is exactly what the slider that I encountered was in the process of doing. She had found an area of soft dirt at the pond’s margin. With her back legs she’d dug out a basin, approximately a foot in diameter or a bit larger, and seven or eight inches deep. Now, she was depositing eggs into the basin.
When she finishes laying her eggs, she’ll cover them with dirt and vegetation and abandon them, her maternity completed. With luck, her eggs will remain buried and undisturbed. The sun will warm the surrounding earth, the eggs will incubate, and they will hatch in about seven weeks, producing a clutch of tiny turtles that will instinctively head for water. A fun fact: the sex of the babies will be determined by the warmth of the earth surrounding the eggs. The warmer the earth, the more likely that the hatchlings will be females.
The process of egg-laying and development is fraught with peril. While she is laying the mother is helpless and could easily be the prey of a passing Bobcat or Coyote. The eggs are vulnerable to being unearthed by predators. The wetlands are populated by a number of Raccoons that would love a turtle egg meal. Baby turtles are potentially snacks for a host of predators. What offsets that is that female sliders are prolific egg layers. They can lay up to five clutches of a dozen or more eggs a year. Obviously, the reproduction is sufficiently successful so that the slider population seems to be doing extremely well. There are a lot of Red-eared Sliders at Sweetwater Wetlands.
Image made with a Canon 5Diii, 400 DO, aperture priority setting, ISO 500, f13 @ 1/640.