X Close The ventral colour, a useful tool to identify criptic mice species
A study recently published by researchers from the BiBio Research Group (Biodiversity and Bioindicators) in the journal Mammalian Biology has revealed a new variable that is very effective in distinguishing "cryptic species" of mice of the genus Apodemus: the wood mouse (A. sylvaticus) and the yellow-necked mouse (A. flavicollis), which are morphologically very similar and can coexist in the same habitats.
Although genetic analysis and identification through dentition in the case of the egagropiles allow the distinction between the two species, live identification of the specimens represents a major problem for monitoring their populations, since their external features are very similar and research teams have doubts about identification during their handling. Now, thanks to the analysis of the collection of skins at the Granollers Natural Sciences Museum, it has been demonstrated that the key to the correct identification of the wood mouse and the fawn mouse in the hand is not found in body dimensions, but rather that it is necessary to pay attention mainly to the color of their ventral fur.
Sample of four yellow-necked mouse (Apodemus flavicollis) skins from which colorimetric information has been obtained in order to carry out the study.
The study shows that the dorsal coloration of the two species tends to be quite similar, suggesting a convergent evolution driven by mimicry with the environment to avoid predators. This convergence means that the dorsal coloration is not useful for differentiating both species. On the other hand, the yellow-necked mouse has a much more accentuated dorsiventral contrast of the fur, with a lighter belly and greater color saturation. In conclusion, the variability of color between the two species is greater on the belly than on the back and, in fact, the characteristics of the ventral fur have a stronger discriminating power.
The two species of mice of the genus Apodemus represent the main bulk of the small mammal community in the most Pyrenean forest communities of Catalonia, since the yellow-necked mouse only appears in the most central European environments, with lower temperatures and greater precipitation. Of the Semice trapping stations located in the Pyrenean influence area, the wood mouse and the tawny mouse appear in 83% and 25% of the locations, respectively. In addition, the sum of the individuals of both species is equivalent to 51% of the small mammals captured at these same stations. Thanks to these results, the distinction between the wood mouse and the yellow-necked mouse can be clarified, and consequently the calculation of their population trend will be better adjusted.
Citation map of each species: wood mouse (in green) and yellow-necked mouse (in orange). The information comes from the results of live trapping and the analysis of owl pellets (SEMICE).
The work was based on the study of the collection of flat skins deposited at the Granollers Natural Sciences Museum (www.mcng.cat). To carry out the work, a desktop scanner was used under standardized lighting, which allowed more precise and comparable data to be obtained, which facilitates the detection of subtle chromatic variations that could go unnoticed with conventional techniques (e.g., digital photography). Works like this highlight the relevance of museum collections in research and in the conservation of current biodiversity.
Photographs: Ignasi Torre
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