The use of species-specific cone remains of sympatric arboreal rodents to monitor their distribution

Abstract

The red squirrel (Sciurus vulgaris) is threatened with local extinction in those parts of its distribution range colonised by introduced alien squirrel species. Therefore, developing fast and economic monitoring techniques is becoming of increasing importance in relation to conservation and/or management of this species as well as for developing early-warning systems for undesired species (e.g. non-native, invasive species). We present a detailed description of cone-feeding techniques by edible dormouse (Glis glis), black rat (Rattus rattus) and Finlayson's squirrel (Callosciurus finlaysonii), that recently colonised a small area in the south of Italy, and compare these with signs left by red squirrels in conifer forests dominated by different tree species (Pinus halepensis, P. nigra, P. laricio, P. pinaster and P. leucodermis) in southern Italy. A total of 15,777 consumed cones were collected in 1997-2005 from 33 localities in Calabria and Lucania. Exact determination of consumer species of 100 cone remains by five trained observers was high (98.8%). We conclude that determination of consumed cones on cone feeding transects is an accurate and economic method for monitoring presence/absence of red squirrels in those parts of their range where they are sympatric with either edible dormice and/or black rats.