This week the Marin Independant Journal reported the amazing find of Marin Municipal Water District aquatic ecologist Eric Ettlinger. This April, Ettlinger recovered a western pond turtle from a rotary screw trap in Lagunitas Creek. What makes this find remarkable is that Ettlinger had previously encountered this turtle in 2004, and again in 2009, in Phoenix Lake, a location approximately 18 miles to the southeast. Ettlinger marked the turtle in question – Turtle #9 – with a distinctive “notch” to one of its marginal scutes, a standard marking procedure to differentiate individual turtles, when he first found it in 2004 in Phoenix Lake. For those of you without a map at your fingertips, this amounts to the turtle having traveled westward across Marin County from the town of Ross, circumnavigating the not-insignificant waterbodies of Lake Lagunitas, Bon Tempe Lake, Alpine Lake, and Kent Lake, until reaching the town of Point Reyes Station in just two years.
That’s a long walk indeed. Right?
Assuming the turtle trekked the entire 18 miles unassisted, that breaks down to an average crawl of 130 feet per day, which isn’t all that far. Even if you take into account the western pond turtle’s typical period of inactivity in the fall and winter – when they overwinter in a muddy stream bottom, or bury themselves in the leaf litter within a stand of poison oak – a trek timed in the spring and summer months (March – September) would still break down to an average rate of 223 feet per day. That’s 41 feet shy of a small city block.
Speaking from experience, this rate of travel is by no means far fetched; I will be the first to tell you that western pond turtles fail to live up to the archetypical turtle’s pace made famous by Aesop’s fable “tortoise and the hare.” During last year’s field season, I had the distinct pleasure of nearly being outrun by a radio-tagged female western pond turtle retreating after a nesting foray. In under an hour, the female in question – first seen well upland in the initial stages of nesting – had fully excavated a nest chamber, deposited her eggs, back-filled the cavity, tamped down the nest plug, and high-tailed it back to within 5 feet of the water’s edge. Her path of flight comprised 500 feet, as-the-crow-flies, across a woodland strewn with downed trees and a minefield of knee-high boulders.
If we assume that this rate of travel isn’t impossible (and clearly it isn’t), maybe the real questions we should be asking are where it was headed, and why? I suspect those will remain a mystery…
(bio)accumulation 