Tuesday, October 6, 2009

Field Photos: Caster canadensis does some landscaping

While doing some fieldwork in north Florida last week, I stumbled across a small duckweed covered pond. This discovery was unexpected…

It was unexpected because, prior to going to field, I had reviewed aerial photos of the area in hopes of identifying any potential wetlands on site – this pond wasn’t on the aerials.

On closer examination of the pond, I noted that several upland species of trees had recently been inundated by the pond and appeared to be in poor condition; it was a new pond and the trees were being overtaken by the water and slowly drowned…

Then I happened onto direct evidence of the crime and suddenly realized the identity of the culprit!

Looking at the scene, I was reminded of Richard Dawkins’s description of beaver-effects in his book The Extended Phenotype.

I guess that the new pond can be viewed as being the result of rodent genes…

At any rate - and despite the ecological renovations shown above - beavers (Caster canadenis) don’t have quite the impact on the landscape down here in the southeastern United States as they do in more northern regions of the Americas. A recent study published to The American Midland Naturalist examined the affects that beavers have on the landscape in southern Georgia – which is less than 90 miles from where the above images were taken in Florida.

What the scientists found was that lower population densities of beaver in the southeast, in conjunction with the year around availability of food, lessened the intensity of beaver induced impacts.

Brzyski, J., & Schulte, B. (2009). Beaver (Castor canadensis) Impacts on Herbaceous and Woody Vegetation in Southeastern Georgia The American Midland Naturalist, 162 (1), 74-86 DOI: 10.1674/0003-0031-162.1.74