Let's Talk About Turtles! Western Pond Turtles and More

Because who doesn't love turtles?!  Turtles and tortoises, members of the order Testudines, are by far my favorite group of reptiles (though I am a fan of lizards as well!) and it is always a treat to come across one of our native turtles in the wild. 

California's native Northwestern Pond Turtle

But first, what is the difference between a turtle and a tortoise?

Worldwide, there are fourteen turtle families (taxonomic groupings below order) and one tortoise family.  The turtles, which include such disparate families as the pond turtles, the sea turtles and  the snapping turtles, are generally at least partially aquatic, while tortoises are differentiated by their entirely terrestrial lifestyle.

All turtles and tortoises are protected by architecturally advanced shells, rivaled by no other animals in their structural complexity and durability.  Hard shells provide a measure of protection for adult turtles, compensating somewhat for their slow speed which would otherwise make them easy prey.  Turtles and tortoises lay eggs on land, often in large numbers, the nests of which are frequently targeted by predators as well as humans.  Around the world, many species of turtles are in great danger from overhunting and exploitation.

California's endangered Desert Tortoise

California is home to just two native species of turtles, the Northwestern and Southwestern pond turtles (Actinemys marmorata and A. pallida, respectively), which were formerly considered to be a single species, the Western pond turtle.  A few years ago, the two subspecies were elevated to the status of distinct species, separated by geographic range.  

Habitat of the aquatic Western pond turtle includes relatively still, quiet bodies of water, such as ponds, marshes, and calm river edges.  Of course, California's Central Valley once abounded in this kind of habitat; today, suitable quiet water areas have been reduced considerably, but pond turtles can still be found around man-made irrigation ditches, provided they aren't lined with concrete!  During the winter, pond turtles hibernate in the soft mud of their aquatic home, though in the absence of a suitable substrate, they have been known to hibernate underground in nearby abandoned ground squirrel burrows.  

Basking sites, like this partially submerged log, are critical components of Western pond turtle habitat. 

One species of tortoise, the Mohave desert tortoise (Gopherus agassizii), also calls California home and is endangered.  A fourth native species, the desert mud turtle (Kinosternon sonoriense sonoriense), was once found along the Colorado River and is now presumed extinct in the state due to habitat loss.  

At least four species of non-native turtles are found with varying degrees of regularity in California, most of which are descended from released pets.  These are, in order from most common to least common, the red-eared slider, western painted turtle, Texas spiny softshell turtle, and common snapping turtle (all of which are native to the mid-west and eastern U.S.).  Red-eared sliders are common pond residents in just about every city park in the Valley, but I was surprised to spot a spiny softshell turtle along the San Joaquin River in Stanislaus county a few years ago!  Really, there's no telling what exotic escaped/released species might show up in California's waterways, especially near population centers like the greater Los Angeles and San Francisco Bay Areas.  

Red-eared sliders and painted turtles are both well-adapted to compete with other species of turtles, with which they share their native range.  Here in California, however, in the absence of their natural predators and competitors, these introduced species of turtles often experience higher reproductive success and out-compete native pond turtles, edging them out of remaining habitat and further jeopardizing California's native turtles' already precarious position in a severely reduced and  highly fragmented ecosystem.

Non-native, introduced Red-eared Sliders are common turtles in city park ponds across California.  In many places, they displace native Western pond turtles.

Additionally, five species of sea turtles can be found in Californian coastal waters.  These are the green sea turtle (which are occasionally seen off the coast of Southern California), the leatherback sea turtle (which visit Monterey Bay during summer on their annual migration from nesting beaches in Indonesia), the loggerhead sea turtle (rare), the olive ridley sea turtle (rare), and the Pacific hawksbill sea turtle (which is possible but very rare).  Click each link to learn more about sea turtles!

Endangered Leatherback Sea Turtle in Monterey Bay
Photo credit: Kate Spencer, Fast Raft Ocean Safaris
Accessed from biologicaldiversity.org