p.a. University of Amsterdam,
Institute of Systematics and Population Biology
Department of Herpetology
P.O. Box 94766 1090 GT
Amsterdam, The Netherlands
Very occasionally, Dutch naturalists have found unusually-coloured frogs in the field: white- and pink-coloured grass and green frogs (Rana temporaria and species complex: Rana klepton esculenta) and blue-coloured green frogs.
In the Netherlands, about ten documented observations of albinism or partial albinism are known among grass frogs, green frogs and common toads from the period 1950 to 1995 and three such observations of blue-coloured green frogs.
However, dating from the summer of 1995, 'an explosion' of pink -, yellow -, orange -, and blue-coloured frogs of the species Rana temporaria and Rana klepton esculenta (normally brown and greenish-brown) has occurred in the Netherlands.
The white-pink coloured frogs were albino or partial albino. They were found in three places: two garden ponds -- each of them with grass frog breeding populations of which a small percentage was albino -- and a natural fen in which an albino green frog metamorphosed.
Yellow- and orange-coloured frogs were observed in many places in several regions of the country in 1995 and again in 1996 in even more places. Most, especially the orange ones, belonged to R. temporaria. The blue-coloured frogs were seen in 1996 at six different localities. All of them belonged to Rana ridibunda (species-group Rana klepton esculenta).
In all cases the unusually-coloured frogs seem to function as part of a group of normally-coloured frogs of the same species. All observations to date mark their behaviour as similar to normally-coloured frogs: for example, they were seen in amplexus with normally-coloured specimens.
The appearance of orange-, yellow-, cream- and pink-coloured frogs was noticed in spring 1995 in several parts of England (the Independent (journal), February 21, 1995). The article pointed to global warming as a possible reason: Young albino frogs in their early life-stages might be more likely to survive in increasingly warmer climates.
It would be interesting to continue the discussion on unusually-coloured frogs and possible climate factors. Moreover, the global and temporal distribution of this phenomenon is unknown. Is it restricted to part of the European area? or are there further records of these findings?
Common (grass) frogs