Saturday, May 25, 2013

Counting Amphibians on the Move

We have tallied the numbers! 

For 175 nights of surveillance during the fall of 2011, and spring, late summer, and fall of 2012 the total count caught on camera was...
134 frogs and 95 salamanders! 

On average, one frog or one salamander moved through per night but there was a lot of variation. Some nights had none, others had over a dozen. The biggest count was in late April 2012 with a parade of 16 frogs and 3 salamanders! You can watch the action for that night in the video clip below.

Our mark-recapture results tell another story. A small proportion of the amphibians caught and marked on one side of the highway were recaptured on the opposite side: 5% of 631 Red-legged Frogs; 13% of 248 Northwestern Salamanders.

We know the exit traps did not capture every amphibian that traveled through the tunnel because we have pictures of some that were not trapped. But we also know many marked individuals stayed on the same side of the highway where they were first caught because we recaptured them there. We are investigating the exact location of recaptures to learn whether individual frogs and salamanders tended to head away from or toward the culvert after they were first trapped along the guiding fences.

At this stage, the tunnel has provided safe passage for over 200 amphibians that ventured through it. We will continue to look for interactions between amphibians and other wildlife using the tunnel, including a number of predators, such as mink, marten and ermine. 

Stay tuned!

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