frogs

This morning five of us went to survey a restoration site for northern red-legged frog (Rana aurora) egg masses. There were two of us from the office, myself and the design engineer for the project; a department of Fish and Game biologist; and two young temporary DFG folks.

It was an interesting day, weatherwise. It was mild, in the upper 50s, with occasional rain, mostly light, a few short intervals of heavier stuff. The site, covering several hundred acres, is on relatively level riparian lands close to the coast, but we could see the clouds lifting over the nearby coast ranges, hanging in some of the ravines.

The site is at the edge of tidelands, and some of the wetlands are brackish. There is an an ambiguous line, where Spartina has dropped out of the plant assemblage and saltgrass is becoming sparse, and is being replaced by sedges and rushes. Here, in the upper ends of shallow meandering sloughs and in knee-deep rain pools in pasturelands, we found what we were looking for.

Most of the eggs were in the deeper parts of these relatively shallow pools, where emergent vegetation becomes a little more sparse but before the open waters of the very centers of the pools. Outside of this transition zone, in shallower and more densely vegetated water, Pacific chorus frogs (Pseudacris regilla) called all around us.

Most of this parcel was once salt marsh, before the construction of levees, in some cases over 100 years ago. Soon, we hope, those levees will be breached, and the tide will return. This means the frogs will need to find new refugia, on the other side of new low berms which will be built to protect adjacent landowners, or a little upstream above tidal influence. We will most likely help things along a little, by incorporating fresh water pools into the design, and by relocating egg masses or tadpoles from some of the areas which will be directly impacted by project construction.

But first, we need to understand where the frogs are today, and how common they are. That work will continue for a little while, since the northern red-legged frog has an extended breeding season which is thought to extend from December into March (today in one case I found two egg masses six inches apart, one in the process of hatching, the other very freshly deposited). Unfortunately I can't be out there every day, today was intended to orient those who will actually be doing the field work.

I thought it was important that the design engineer accompanied us. I can describe things to him easily enough, pointing at drawings on a desktop. That's not the same as seeing it with one's own eyes. He even found one egg mass himself. He's going to remember that, and it will perhaps make the design just a little more personal.