by Michael Paccassi
As California’s only native freshwater turtle, the western pond turtle (Actinemys marmorata) isn’t really getting all the attention it deserves. This unique and charismatic creature is listed as a vulnerable species in California, making it only one step away from joining the far-too-massive list of endangered species. Although the western pond turtle’s native habitat extends from northwestern Washington down to northern Baja California, habitat fragmentation, human catch, pollution and non-native turtle introduction are increasingly causing them to disappear.
In case you were unaware, many western pond turtles also call MMWD’s Mt. Tamalpais Watershed their home. In fact, each spring you can go out to one of a few specific locations on the reservoirs and witness dozens of turtles basking in the sun. Aided with a pair of trusty binoculars, one might notice a plethora of exotic turtles as well, including sliders, cooters and others. These non-native species are not merely living harmoniously with the western pond turtles, but rather outcompeting and, according to data, now greatly outnumbering them on our watershed. How did the non-native turtles get here in the first place you ask? Pet release, of course! Free Speedy and never look back.
For years MMWD has been training volunteer turtle observers to help educate the public and monitor the status of the western pond turtle on the watershed. The goal is to utilize volunteers as citizen-scientists in helping us keep an inventory of the turtle populations on the watershed, and to educate the public on the dangers of exotic species release. This year I trained 60 new turtle observers in turtle biology, species identification and observation skills. Forty-five of these volunteers actively participated throughout the duration of the program along with three returnees. Needless to say, the turtles were shown a lot of love from volunteers this year.
Unfortunately, the results of this year’s program paint a concerning picture about the status of non-native turtles on the watershed (see graph below). While it seems that western pond turtle (AM) populations are relatively stable (excluding 2012, which had low volunteer participation and high “unknown” turtle observations), non-native (NN) turtle populations seem to have sky-rocketed. The 2013 data also show that non-native turtle populations are nearly twice the size of western pond turtle populations on the watershed. A consistently growing non-native turtle population can only mean less food, shelter and habitat for the native western pond turtle.
It seems obvious that we have a problem on our hands, but what can we do about it? First of all, we need volunteers like you to help us continue monitoring and educating the public for years to come. Were it not for the benevolence of hard-working volunteers wanting to make a difference, we might not even know just how urgent the need for action is. Furthermore, turtle trapping (which was not done in 2013 and only cursorily done in 2012) should be, and hopefully will be, continued if we wish to keep non-native populations in check.
Stay tuned for the full 2013 Turtle Observer Report which will be available to read online. Also, be on the lookout for information about the next turtle observer training happening sometime next spring! TURTLE POWER!