Weight operated see-saw feeding hoppers are not selective for red squirrels when greys are present

The competition for food resources between the native red squirrel and the introduced American Eastern grey squirrel is well known, and can lead to the extinction of the native species. Providing supplementary food resources for the red squirrel, by adopting selective feeding hoppers, has been proposed as a possible support for the short term conservation of native populations, but studies that investigate its effectiveness havenotyetbeenperformed.Inthisstudyweevaluatetheeffectivenessofthefeedinghoppers,intermsof selectivity towards the smaller native species, quantifying their utilization by the two species in sympatry and allopatry. Feeding hoppers were not selective toward the native species. The success in the attempts to enter the hopperswas95%forredand86%forgreysquirrels.The50hazelnutsprovidedduringeachfeedingsession, covering the energetic requirements of an individual for 6 (reds) or 3.5 (greys) days, were consumed in 45:43 ± 38:26 hh:mm by red and 31:07 ± 37:18 hh:mm by grey squirrels. The average weight of grey squirrels that entered the feeding hopper (490 ± 47 g) was higher than the calibration weight of the seesaw floor (400 g). This highlights that weight operated see-saw feeding hoppers are poorly selective. Structural modification of the feeding hoppers should be considered to obtain a real selectivity according to species before their implementation in the conservation of red squirrel populations. However, feeding hoppers were selective in feeding squirrels when using hazelnuts, excluding the access to food supplies by other species. Therefore they can be used with success in supplementary feeding studies or behavioural and ecological studies, especially if combined with camera traps and individually marked animals.