Some look different – atypical colouration in garden dormice in Germany

Abstract Aberrant colours are commonly observed in many mammalian species, including dormice. The only way to accurately estimate the frequency of an unusual colouration is to use large datasets. In Germany, a citizen science project asked volunteers to report observations of garden dormice ( Eliomys quercinus ) using an online tool. The project received a total of 5,448 photographs and videos of living and 1,281 of dead garden dormice, which were verified by experts. Only one aberrantly coloured garden dormouse was documented in this dataset. This young individual was a true albino, it was killed by a domestic cat. No leucistic or melanistic individuals were observed among the 6,729 garden dormice. Colour anomalies in European dormouse species are a rare phenomenon and melanistic individuals have been most commonly documented. In edible dormice ( Glis glis ), only 0.5% of specimens are affected. With only 0.01%, aberrantly coloured garden dormice appear to be extremely rare in Germany. This could be related to higher predation rates of the more conspicuous light-coloured animals. During additional long-term observations at two sites, ten juvenile garden dormice were observed with pale fur, lacking the typical black face mask when first seen. Five of them were seen frequently over a period of 3 to 4 weeks. During this time, the normal colouration gradually appeared, indicating that the aberrant coat colour may only be temporary.