Wednesday, September 14, 2005

Re: Found a Black Frog

As a follow up on the curious black frog I sought out the opinion of some more informed persons. In my past wanderings, I had come across the Bishops Mills Natural History Centre. So I fielded the question to Frederick W. Schueler of the Centre.

The co-ordinates for the centre are:

Bishops Mills Natural History Centre
Frederick W. Schueler, Aleta Karstad, Jennifer Helene Schueler
RR#2 Bishops Mills, Ontario, Canada K0G 1T0
on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W

Following is the discourse:

Pieter wrote:

> From your website, I gather that you specialise in reptiles and amphibians. Can I ask you a question about an unusual find?
> I found a pitch-black frog in our woodlot. It definitely had the shape and behaviour of a frog and not a toad. Its skin was pitch black and glossy. It is a bit smaller than a full sized leopard frog. Following up in the Peterson Field Guide on Reptiles and Amphibians, I was expecting to find an explanation, but much to my surprise no frog nor toad exists in the guide that meets this description. An Internet search only identified black frogs in other and usually tropical continents.

Response from Fred:

there are two possibilities - it's either a very cold Frog (Rana sp.) reacting to cool moist temperatures in an unseasonable way, or it's a melanistic variant of one of these species. The melanic pigmentation of
any animal can be overproduced and result in a black individual. On the other hand, the melanaophore pigment cells of many frogs can expand in certain circumstances - characteristically on dark background or when
it's cool and wet - and produce a black colouration, This is most frequent in Wood Frog males in the spring, and in small toads taken from under cover in black soils in the summer.

Did you retain the frog? And if so is it still black?


To that I replied and the following discourse ensued:

Pieter wrote:

> Your explanation sounds plausible. The frog was found when I stirred up a rotting woodpile. It emerged from under plastic that was covering the pile.


I would think a Wood Frog or Green Frog is most likely. I didn't mention that young Green Frogs have a variant called "melanoid" in which their skin is dark and fairly transparent - this is a graduated thing so an individual can have more or less of it - so if it was a Green Frog it might have been predisposed to blackness by having a bit of melanoid in its makeup.


Fred also directed me to an interesting bulletin board which is the NatureList or Eastern Ontario Natural History list-serve at:

I have subscribed to the site and it is quite intriguing. It does a good job at connecting those who are inquisitive with questions about nature related topics with those who are informed and have the answers.

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