Posts Tagged ‘Chytrid Fungus’

Western Pond Turtle

by | December 2nd, 2014

 

What happens to conservation when the water runs dry???

Thoughts by Ashley Terry

western pound turtle

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.

 

turtles

The larger of the two turtles was head started, the smaller not. Both are the same age.

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.

 

Lake County Field Site

Lake County field site

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.

 

Drought ridden lake

Drought ridden lake

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?

western pond turtle hatching

Western Pond Turtle hatching

hatching size comparison

Hatchling size comparison

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.

western pond turtle basking

Western Pond Turtles basking

 

 

 

Visit http://www.saveourh2o.org/tips to find out how you can help save water at home, and http://www.oaklandzoo.org/Conservation.php to find out more about Oakland Zoos conservation programs.

 

Conservation On-Site: The Mountain Yellow-Legged Frog

by | January 29th, 2014

As you visit Oakland Zoo this winter and spring you may notice that the animals and projects we are supporting at our Quarters for Conservation booth in Flamingo Plaza have changed.   I would like you to pay special attention to the developing partnership with the San Francisco State University Mountain Yellow-Legged Frog project.   This project teams up Oakland Zoo with San Francisco State University in bringing awareness to and supporting the recovery of this critically endangered species that is found right here in the mountains of California.

Yellow-legged_frog_Point_Reyes

Once one of the most numerous species found in their alpine habitat in the Sierra Nevada, Transverse, and Peninsular ranges they are now one of the rarest despite this habitat being found in some of the most well-managed and inaccessible areas of the state.    During some of the initial research looking into this decline the focus was on the impact and removal of game fish that were introduced to their alpine habitats, such as trout.   The Mountain Yellow-Legged Frog evolved in a habitat where such efficient predators were not common and the eggs, tadpoles, and frogs themselves became easy prey.  With the management and removal of these introduced fish species some areas showed rapid recovery of frogs.    However, some did not, and in fact the overall population continued to decline.    The emerging disease known as the chytrid fungus (Batrachochytrium dendrobatidis) was found to be the cause of this continued decline and was attacking the frogs during one of their most sensitive transitions in life, the one between tadpole and juvenile life stages.    The chytrid fungus works by attacking the keratin in the skin of juvenile and adult frogs preventing them from being able to use their skin to respirate and exchange water leading to their deaths, wiping out whole populations.   For some reason the disease does not affect the tadpoles of the Mountain Yellow-Legged Frog, but it will remain with them through the several years they spend as a tadpole.    This makes the tadpoles, along with several other frog species that are not affected, a means to not only infect their own kind with this deadly fungus, but to make it almost impossible to eliminate from the environment.

With this revelation the focus to save the Mountain Yellow-Legged Frog changed to not only manage and remove non-native fish, but to support the frogs in gaining resistance to the chytrid fungus during this transition in their life.   The support comes in the form of a bacterium called Janthinobacterium lividum.    The bacteria was discovered on the skin of a fellow amphibian, the red-backed salamander, and later discovered to also be present on the skins of Mountain Yellow-Legged Frog in varying levels.   This bacterium has the unique feature of having anti-fungal properties and when found in greater numbers on amphibian skin can help to increase resistance to the chytrid fungus.    Now, in steps Dr. Vance Vredenburg and the San Francisco State University Mountain Yellow-Legged Frog Project.   Dr. Vredenburg has been pioneering skin bio augmentation treatments using Janthinobacterium lividum to support juvenile frogs that are being rereleased or will be re-released into their habitats in both Northern and Southern California.     Through a partnership with San Diego Zoo, San Francisco Zoo, and soon Oakland Zoo, San Francisco State University is hoping to tip the balance for these frogs by collecting them as eggs from their habitat, hatching them in captivity, raise them to juvenile frogs, treating them with this anti-chytrid bacterium, and release them back into their natal ponds and streams.   It is hoped that not only will this prove to provide long term resistance to chytrid, but will be naturally passed between frogs as they naturally congregate together in the shallows off the banks of the rivers and lakes they live.

If you are interested in learning more about the plight of the Mountain Yellow-Legged Frog and supporting them as well during their most vulnerable transitions you can join us on Wednesday February 5th at 6:30 p.m. in the Marian Zimmer Auditorium at our Conservation Speaker Series event when Dr. Vance Vredenburg joins us to discuss his work with the Mountain Yellow-Legged Frog and the implications his research has to save this and potentially numerous other amphibian species worldwide.

 by Victor Alm, Zoological Manager