What happens to conservation when the water runs dry???
Thoughts by Ashley Terry
Western Pound Turtle
The Western Pond turtle (or WPT as we refer to them around the zoo) is the only freshwater aquatic turtle native to California. Traditional habitats range from Baja California to British Columbia, but in recent years that habitat has begun to shrink due to habitat destruction and the introduction of non-native species into their environment. They are now extinct in British Columbia, critically endangered in Washington and endangered in Oregon. Here in California, they are considered a species of special concern.
Each nesting season, Oakland Zoo and Sonoma State students and biologist spend a month tracking, marking and monitoring gravid female WPT’s and viable nests at our field site in Lake County. This is the sixth consecutive year that zookeepers have spent in Lake County, and to date, we have successfully Each nesting season, Oakland Zoo and Sonoma State students and biologist spend a month tracking, marking and monitoring gravid female WPT’s and viable nests at our field site in Lake County. This is the sixth consecutive year that zookeepers have spent in Lake County, and to date, we have successfullyraised and released close to 450 turtles- each season yielding around 45 hatchlings or more – through our head start program. Check out this cool video of the WPT at the Zoo. The goal of the Head Start program is to raise the hatchlings for the first year under optimal conditions. By creating the best possible environment for the turtles, they grow 3-4 times faster than they would in the wild. At the end of the first year, the juvenile turtles are then released back into Lake County, having grown too large to be eaten by common predators like big mouth bass and eastern bull frogs.
WPT’s live in typically riparian habitats where they can most often be found in sloughs, streams, and large rivers, although some may inhabit bodies of water such as irrigation ditches and other artificial lakes and ponds, too. Turtles are generally active from late May to October. WPT’s overwinter, or hibernate, in both aquatic and terrestrial habitats. Terrestrial overwintering habitats consist of burrows in leaf litter or soil. In more wooded habitats along coastal streams in central California, most pond turtles leave the drying creeks in late summer and return after winter floods.
California has experienced continuous dry conditions since 2012; alternatively known asdrought. According to the National Drought Mitigation Center at the University of Nebraska, Lincoln, 99% of California is currently abnormally dry; 67% of California is in extreme drought, and almost 10% is experiencing exceptional drought. The repercussions of our drought emergency are relatively simple: there is an extreme lack of water. The absence of water impacts Californians in several different ways, whether it is economically or socially. But how does it affect the state’s wildlife or our conservation projects here at the zoo?
Those involved with our Head Start program have noticed that the last few drought years in the field have been incredibly stressful on the Lake County turtles in several distinctive ways. In some less permanent waters, such as our field site, the fact that the ponds have dried up completely for the first time in many years has certainly affected the behavioral patterns of WPT in some key ways, thus affecting the numbers of gravid turtles and viable nests sights during our field seasons. Since the ponds dried up by July and August of the last 2 years, the turtles were forced to estivate – spending a hot and dry season in an inactive or dormant state – when they would normally have been feeding and stocking up their internal reserves of protein and fat. The extended time they spent in this state of “suspended animation” also leaves them much more vulnerable to any manner of disturbance – especially in the case of predators, temperature extremes, etc. Lastly, and maybe most important for our head start program, the non-permanent lakes & ponds were dry when the turtles should have been feeding and mating. This was reflected in the very low numbers of nesting females last summer, giving us only 4 hatchlings this season.
Although these impacts of drought do indeed bring about urgent circumstances for wildlife, it is important to remember that droughts are, unfortunately, natural phenomena. Climate scientists predict that California will get even hotter and drier. As more of the state’s precipitation falls as rain instead of snow in the mountains, it will run off the land more quickly, ending up in the ocean. Scientists say that with global warming, we’ll see more instability in California’s climate, with more intense storms, longer dry periods, and less snowpack. It will be interesting in the upcoming future to see how long it takes to get back to the normal population numbers at our site, and to track the behavioral changes due to impact of habitat change. In the meantime, we are also looking at other possible locations where population numbers can be monitored. Wildlife and drought have coexisted for generations upon generations. For the most part, wildlife populations are able to bounce back from drought events once typical weather patterns return. For the time being, we’ll keep our fingers crossed for a very wet and rainy winter, resulting in turtles returning to our pond.