Nutritional ecology of martens (Martes foina and Martes martes) in the western Italian Alps

The macronutrient requirements of the strictly related pine marten (Martes martes) and stone marten (Martes foina) are almost identical, but, at range scale, in areas of putative sympatry (overlapping European ranges) the stone marten tends to be more frugivorous, which makes the contribution of carbo- hydrate energy to be higher than the target. In contrast, the macronutrient intake of the pine marten would be unaffected by the occurrence of the stone marten, supporting the putative dominance of the first in interspecific interac- tions. Most available studies examined marten diets separately, highlighting the need for further studies in areas of actual co-occurrence. With this aim, we compared the two martens' diets in the Italian Alps both in sympatric and allo- patric conditions, as assessed by the genetic identification of scats. Although fruit and rodents formed the bulk of both species' diets, as predicted the stone marten consumed twice as many fruit species as the pine marten and ate fruit more often in areas of sympatry, thus consuming less protein and more carbo- hydrates respect to its intake target. This competition-driven, nutritionally imbalanced diet may affect the fitness of stone marten populations and play an important and still underreported role in regulating the relative abundance of marten communities.