Thursday, February 5, 2009

The Rough skinned Newt and the Mallard

Mike from Maple Valley wrote in about Rough skinned Newts. He had heard that they could be toxic, and was wondering about this. It reminded me of a nature experience I had had.

It was in May several years ago that I was out at McClane Creek. For you out-of-towners, this is a DNR park with a freshwater stream and series of beaver ponds, enclosed by second-growth forest and surrounded by the Black Hills which rise west of Olympia. Local nature watchers love this place, Glen and I included.

In May there's a lot to see. On sunny days, the beaver ponds warm up and you can watch the Rough skinned Newts in great numbers.

So one sunny day, I'm sitting there, watching the birds, the newts, the blue sky overhead, enjoying the season. My attention is caught by some vigorous splashing by an adult male mallard duck, who has just come up with a Rough skinned Newt, and is happily chowing down on it. I watch in horrified fascination as this mallard gums and gags it down, softening it up enough to get it down his throat.

I had heard that these newts are extremely poisonous. I continued to watch the duck for some time, but it showed no ill effects. I later contacted Kelly McAllister, one of our local herpetologists who lives in Olympia. I told him this story; as I recall he said to me: "Well, that's one dead duck".

Apparently there is enough toxin in one rough skinned newt to kill 25 people (or ducks). That's how toxic they are. The toxin is extruded through the skin of the newt, and then has to get into the victim's stomach and be at least partially digested: it's when it hits the liver that it does its damage. That's why the mallard showed no ill effects right away. It also may be true that if you handle a newt, and you have a cut on your hand, it is possible enough toxin could get in to cause some trouble. So the rule of thumb is: either wear gloves when handling these guys, and/or wash your hands well afterwards.

Now I wouldn't necessarily give male mallards a membership to Mensa, but I still don't get it: how does this duck who spends his whole life in wetlands not know these newts are a problem?
Did he not taste the toxin on the newt's skin? Was he blind to the warning coloration?

You got me.


Photo by Miguel Vieira from flickr creativecommons

1 comment:

  1. The newts actually only contain poisons in relation to the resistance to toxin that their main predators, the garter snake have evolve. So in some regions they may be extremely toxic but in nearby ponds they could be hardly poisonous at all. Its in a book by Carl Zimmer on evolution, called(oddly enough) Evolution.