Close Encounters: A Really Rare Ranid
ALBINO NORTHERN LEOPARD FROGS, Rana pipiens, are so uncommon that I was excited indeed to learn from DNR zoologist and research coordinator Rich Baker that one had just been captured in Minnesota. Baker received a phone call from Brad Johnston, who had caught the albino near his home in Mound Aug. 10, 2004. Baker knew that I have studied northern leopard frogs for almost a half century and that is why he called me. Although I am a retired University of Minnesota professor, I have never "retired" my research interest in frogs. I jumped at the chance to see the rare frog even though it was 70 miles round trip from my home.
I have captured, examined, and released many thousands of frogs in Minnesota, but I had never collected an albino leopard frog. Nor had any of my friends or colleagues who know frogs.
Albino northern leopard frogs in Minnesota are so scarce that it is essentially impossible to estimate their prevalence in a natural population. In short, the prospect of seeing such a rare creature generated in me about as much excitement as any Scot would display upon seeing the Loch Ness Monster.
I was skeptical when I called Johnston because I am always dubious of frog reports that come from nonexperts. But a few minutes on the phone with Johnston made it manifestly clear that he knew what he was talking about. Johnston grew up in Excelsior, and as a boy worked in Roy's Live Bait shop collecting leeches, minnows, and frogs. While that was a couple of decades ago, Johnston still knows his natural history in general and frogs in particular. When I got to Johnston's place, I found the frog comfortably ensconced in a terrarium. One look confirmed this frog was indeed an albino.
Albinism, a genetic condition due to the absence of the black pigment melanin, occurs in most, if not all, animals; and frogs are no exception. This albino frog had "spots" as leopard frogs should; however, its spots were entirely lacking in melanin. Thus the frog's skin was a cream color. The eyes, also devoid of melanin, looked pink because the blood vessels were visible.
The frog was a juvenile, about 2 inches long. I judged the albino had little chance of making it to maturity in the wild. An ordinary frog's coloration serves as camouflage, which helps survival. A pale frog is a pretty good target for a raccoon, mink, or great blue heron-or for Johnston's fast hands, for that matter.
For now, the frog is safe in Johnston's terrarium.
In times of so much disturbing news in the frog world-such as grossly malformed frogs and disappearing frog populations-it is especially refreshing to witness a rare natural variant that does not portend bad news for either frog or human populations.
Marveling at the rare color variation of this frog, I realized that my inquisitiveness as a researcher is sparked by simple wonder and pleasure at the diversity of life.
Robert G. McKinnell, professor
emeritus of genetics and cell biology
For more information on northern leopard frogs, see MN DNR Nature Snapshots.