Humans versus dogs; a comparison of methods for the detection of bumble bee nests

This study investigates alternative approaches to locating bumble bee nests for scientific research. We present results from three trials designed to assess: 1. The comparative efficiency of two detection dogs; 2. The ability of a dog to locate nests when carrying out repeat searches of agricultural habitats through the season; 3. The efficiency of a dog compared with human volunteers at finding nests in woodland, with the human volunteers using two methods: ‘fixed searches’ and ‘free searches’. The two dogs varied in their efficiency in finding buried portions of bumble bee nest material (62.5% and 100% correct indications). Searching for real nests in rural habitats, a detection dog located nine nests of four bumble bee species, in a range of habitats, at a rate of one nest for 19 h 24 min of searching time. A comparison of ‘free searches’ using human volunteers and the dog in woodland found that they located nests at similar rates, one nest for 1 h 20 min of searching time. Fixed searches located nests more slowly (one nest for 3 h 18 min of searching time), but probably provide a reliable estimate of nest density. Experienced volunteers performed no better than novices. Given the investment required to train and maintain a detection dog, we conclude that this is not a cost effective method for locating bumble bee nests. If the aim is to estimate density, then fixed searches are appropriate, whereas if the aim is to find many nests, free searches using volunteers provide the most cost effective method.