Every safari truck that departs from our boarding area takes a different route as they go searching for our many flocks and herds. Some head up the road into wildebeest country while others strike out into the 12-acre in search of giraffes. No matter which road they take, however, every safari eventually winds up at Watusi Lake. The lake is essentially the hub of Safari West, marking the center of the property. Day in and day out, our fleet of Power Wagons trundles along its shorelines en route to one wild animal or another and our guests enjoy the view of its placid waters and reed lined shores. It’s a tranquil scene. What we don’t often see is that this mellow pond is also a battleground. There is a fight going on here; a fight between turtles.
The western pond turtle is Northern California’s only native freshwater turtle species. They are an unremarkable looking species, dull greenish brown in color with no obvious markings or features. Some turtles have bright stripes or serrated shells, long snake-like necks or snapping jaws. Not the western pond turtle. They are the basic turtle model as far as appearances go. All the same, they are an effective species once found throughout most of the Pacific states, inhabiting virtually all fresh-water and marshy habitats (so long as the current doesn’t run too fast). They are omnivorous and not overwhelmingly picky, making meals of small fish, frogs, and insects, as well as numerous types of plant life, some carrion, and essentially anything small enough to get into their mouths. This makes them an important contributor to their ecosystems as they help to recycle nutrients and control populations of other species.
Western pond turtles once numbered in the millions and according to records from the pioneer days, could be found in huge numbers that, when startled, fled into the water with a sound like the rumble of surf on a beach. In those days, the turtle was a bit of a delicacy and a market for the readily available species flourished. Around the 1930’s or 40’s turtle began to disappear from restaurant menus in large part because they were also disappearing from the wilds. Now that their numbers have been knocked down, they are having a hard time getting them back up. Western pond turtles are slow-moving and slow-living animals. They don’t reach sexual maturity until after 8 to 14 years and even then only produce small clutches of eggs. The infant turtles hatching from those eggs have only an 8-12% chance of surviving long enough to reproduce themselves.
Western pond turtles aren’t being served up for dinner anymore (at least not commonly), but they face another threat, one which is readily apparent here at Safari West. Watusi Lake, the Lower Lake pond where our red river hogs swim, and Catfish pond in the tent camp are all home to western pond turtles. They are also home to an alien menace; the red-eared slider.
The red-eared slider is a much more charismatically colored species of pond turtle. Their belly armor (called a plastron) is striped with yellow, as are their necks and heads. Their name stems from a brilliant red stripe that originates just behind their eyes and runs down their necks. These turtles are native to the United States, though it should be noted, not the Pacific coast. Their native range extends throughout the lower right quarter of the continental US as seen on a map; roughly from the South-East corner of Colorado to Florida. Their habitat and dietary preferences are more or less identical to that of the western pond turtle. These turtles are very popular as household pets and are by far the most commonly kept freshwater turtle species. It is estimated by the California Department of Fish and Wildlife that 52 million of these unassuming turtles were exported from this country between 1989 and 1997. Those numbers don’t include the millions sold domestically. With a lifespan of 20 to 40 years, many turtle owners tire of their pets and make the fateful decision to “free” them.
Red-eared sliders released into neighborhood ponds and streams often find themselves in a habitat, not all that dissimilar from what they would have lived in back in Louisiana, Georgia, or Florida. In California as in so many other places, released sliders thrive. As they breed and their wild population’s increase, they inevitably move into ponds and streams occupied by western pond turtles. Neither species specifically preys on the other, but both species need the same things from their habitat; food, nesting sites, and a place to bask. Basking is of vital importance to a cold-blooded reptile like a turtle. They depend on sitting in the sun to maintain a functional body temperature. This is the first area in which the red-eared sliders have a fighting edge. They grow significantly larger than their native cousins; maxing out at a foot or more in length compared to the 8 inches of the western pond turtles. Their larger size coupled with a more aggressive demeanor means that the red-eared sliders quickly claim the most choice basking spots, leaving the western pond turtles basking less regularly and in places where they are far more vulnerable.
The next point of conflict comes from their breeding habits. Whereas the western pond turtles lay only 5 to 13 eggs at a time, often only every other year and at most, only once or twice within a given year, the sliders lay clutches of up to 30 eggs as many as 6 times in a year. In these hotly contested waterways, there are often 6 or 7 baby sliders for every 1 western pond turtle hatched.
These factors have led the western pond turtle to a tenuous existence. They are now classified as “vulnerable” by the International Union for the Conservation of Nature (IUCN), a classification just above endangered. The situation at play here is exactly what we expect to see in ecosystems dealing with invasive species. As explored in depth in this month’s Conservation Corner, these invasions of alien species can have absolutely devastating impacts on native species ill-equipped to compete with the invader.
The population of western pond turtles thriving here at Safari West has been the center of a great deal of attention. Several researchers from Sonoma State University have set up camp on the shores of Lake Watusi to observe these shy reptiles and to try and document their long, slow battle against invasive red-eared sliders. The information they’ve collected on diet and habitat use have been put to use by Sonoma State in a head start project they are working on in conjunction with the San Francisco Zoo, the Oakland Zoo, and the Department of Fish and Wildlife. In this project, eggs are collected and incubated. The hatchlings are raised in captivity for a year or until they reach a size that makes them relatively safe from predation. The goal of this program is to help the local western pond turtle population rebound to a size that can more effectively combat the expansion of their south-western cousins.
The Safari West turtle situation makes for an interesting exploration into the guiding principles and ideas behind conservation science. We choose to defend the western pond turtle because it currently faces a threat that wouldn’t exist had it not been for human intervention. That said, the competition between species and the dominance of one over another is an unavoidable and important characteristic of life on earth. Had we not introduced the red-eared sliders, the western pond turtles would still have faced the struggles of life in an increasingly dry region; where the confluence of climate change and human-caused diversion of water and conversion of wetlands will make their lives increasingly difficult. As the situation on the ground continues to change, the turtles will be forced to adapt or die. If during this process, another turtle species (or even another amphibian, reptile, mammal, or bird) is able to out-compete the turtles and fulfill their role in the ecosystem more effectively than they can, would our defense of them still be justified? Or would we then be propping up an evolutionary dead-end in the face of natural ecological evolution? These are the gray areas of conservation; the areas in which we must carefully consider what we’ve done, what we’re doing, and what we will do as the situation continues to evolve. For now at least, to work toward mitigating a problem that we’ve clearly had the lion’s share in causing is the right thing to do, both ecologically and ethically.
The next time you come to Safari West, enjoy the rumbling ride, your talkative guide, and of course all the stamping, snorting creatures who live here. When you circle the shores of Lake Watusi, enjoy the panoramic views and the calm waters but while doing so, take a moment to reflect on the ongoing struggles beneath the surface. Not every endangered animal is exotic. Some of the species battling most valiantly for survival are living quietly, almost invisibly, right here in our very backyards.