Bait palatability influences the caching behaviour of the red fox (Vulpes vulpes)

Abstract

In a free-choice experiment conducted in a series of pen trials, the influence of food preference on caching behaviour by the red fox (Vulpes vulpes) was investigated for three unpoisoned bait types: deep-fried beef liver (DFL), dried deep-fried beef liver (DDFL) and a commercial bait (Foxoff®). Although some variation in individual preferences for the DDFL and Foxoff was observed, all of the foxes in the pen trials preferred the DFL (P < 0.01) and all cached it least often (P < 0.01). Field trials then compared the uptake, consumption and incidence of caching for the most preferred (DFL) and least preferred (Foxoff) bait types. Radio-transmitters were inserted into unpoisoned Foxoff and DFL baits and a free choice of either was provided at bait stations at three independent sites. A clock module recorded the precise time that each bait was taken from the bait station. The fate of each bait (it could either be eaten, cached or remain in situ) was recorded daily and baits were replaced for five consecutive nights. There was no difference in the rate of uptake for the two baits (P > 0.05) and, despite some variation between the sites, DFL was the most often eaten (P < 0.001) and Foxoff the most often cached (P < 0.001). These data strongly suggest that a highly palatable bait will increase the likelihood of rapid consumption of baits and reduce the incidence of caching. This is likely to increase the cost-effectiveness of baiting and limit the potential for nontarget impacts due to the movement of baits. The high degree of concordance between the results of the pen and field trials suggests that pen trials can assist in the development of more effective bait types. However, conclusions about the relative efficacy of bait types drawn from the results of baiting programs that measure only bait uptake are unlikely to be reliable.