Elusive pond turtles

Walking along Craggs trail by the creek in Malibu Creek State Park, I heard a distinctive "plunk" and saw large concentric waves radiating from the point where an animal had entered the still water. I went through a mental checklist of all the possibilities: frog, water bird, snake, turtle?

Waiting and watching, I was able to eliminate all options but one. The waves were much too large and the sound much too loud to be made by a small frog or an elegant snake entering the water.

A submerged water bird would have had to breathe in the time I was watching, and the area was so small I would have seen it surface. So that left only the turtle, the western pond turtle. Although it would eventually have to emerge for air, turtles are expert at exposing only the smallest portion of their snout above water.

Although I had no confirmation that a turtle had made the "plunk," it started me thinking about the life of our western pond turtle, Clemmys marmorata pallida, and its defense mechanisms.

Western pond turtle

Most often we are aware of defense mechanisms because they are obtrusive or painful, or otherwise catch our attention: a skunk's smell, a cat's claws, even one person verbally attacking another. But what about defense mechanisms that occur under our radar- the camouflage of a stick insect, the child who "crawls inside herself" to avoid being noticed, or the vanishing tactics of the pond turtle.

Dunk and cover

This 6- to 7-inch reptile has no loud cry or call or sharp teeth to protect itself so it depends solely on the arts of hiding and escape.

Over 200 million years of evolution, when their first ancestors appeared, the western pond turtle developed senses so acute that it can detect my quiet presence from 250 feet away, sending it cascading into the water for escape. If feeling especially vulnerable, pond turtles can hide underwater for 60 minutes.

If no water is available, this creature depends on the strength of its carapace (top shell) and plastron (bottom shell) to protect it from predators.

Western "pond" turtle is a bit of a misnomer as historically true ponds did not exist in Southern California before the arrival of agriculture. Rather the pond turtles were and are found in streams, large rivers, and slow moving water, especially those with bank undercuts and large rocks and boulders.

Their range stretches from western Washington, where they actually may now be extinct, to northwest Baja California. Primarily they are found west of the Sierra Nevada.

Pattern and coloration

The western pond turtle is identified by its dark brown to olive carapace with a radiating pattern from each shield. The plastron is cream to pale yellow to light brown with black mottling. "Marmorata" from the scientific name refers to the marbled pattern on the carapace and skin.

The head and neck are spotted or have a network of black lines. With maturity the carapace darkens and the patterning on skin and shell becomes less distinguished. The species Clemmys marmorata has been split into two subspecies, northwestern and southwestern pond turtle.

In the Santa Monica Mountains we find the southwestern pond turtle, C. m. pallida, generally differentiated by a lighter color then its northern counterpart. Males tend to be smaller, with a paler throat and flatter carapace than females.

In Southern California pond turtles are active all year, laying a clutch of three to 14 eggs from April to August. While proximity to water is essential, soft soil or sand is equally important so that they may deposit their eggs. Mature adults lay eggs when they reach 10 to 12 years of age or 6 to 7 inches in length.

On their menu

Pond turtles are omnivorous, finding their food primarily through sight and smell. Their diet consists mainly of insects and their larva, small fish, amphibian eggs, and occasionally plants.

They have been observed to eat small bird and mammal carcasses, but this is thought to be scavenging behavior rather than predatory as they have no teeth. Their upper and lower jaws have adapted into a horny billlike structure for crushing and tearing food.

And on others'

Just as they have a diverse diet, they also serve as a food for a variety of predators. When young they fall prey to raptors, weasels, large fish, bullfrogs, and human poachers. Coyotes and raccoons, detecting turtles from their urine's scent, become the greatest risk to adult turtles.

While concealment is monumentally important for avoidance of aggressors, it is also essential for surviving environmental dangers. Through summer droughts, pond turtles' best defense is hiding in wet mud that remains from seasonal creeks.

As turtles have lived effectively on the planet for 150 million years, I wonder if sometimes the tactic of retreat is better than attack. Possibly the Earth would be more peaceful if we learned from the turtles.