The seasonal diet of British pine marten determined from genetically identified scats

Abstract

Knowledge of a carnivore's foraging behaviour is central to understanding its ecology. Scat-content analysis provides a non-invasive way to collect such information but its validity depends on attributing scats to the correct species, which can prove problematic where similarly sized species occur sympatrically. Here we provide the first description of the diet of European pine marten Martes martes in Scotland based on genetically identified scats (n = 2449). Concurrent small mammal live trapping also allowed us to determine preferential selection of small mammal species. We found the marten diet was almost entirely formed by three principal foods: Microtus agrestis (39%), berries (Sorbus aucuparia and Vaccinium myrtillus: 30%) and small birds (24%). The seasonal dominance of these foods in the diet suggested a facultative foraging strategy, with a short period in which the diet was more generalized. A discrepancy in the occurrence of Microtus in the diet (77% of small mammals consumed) and marten home ranges (12% of small mammals trapped) indicated a frequency-independent preference for this prey, one which differentiated British marten from marten in continental Europe. Microtus were the marten's staple prey and taken with relative consistency throughout the year, even at times when rodent populations were at their least abundant. Martens supplemented their diet with small birds and fruits as these foods became abundant in summer. The diet became generalized at this time, reflected by a threefold increase in diet niche breadth. Microtus consumption was significantly reduced in autumn, however, when their populations peak in abundance. The autumn diet was instead dominated by fruit; an abrupt dietary switch suggesting a frequency-dependent preference for fruit irrespective of the abundance of alternative prey.