‘Bee hotels’ have unwanted guests

It sounds like an adorable conservation idea: Create “bee hotels” where threatened native pollinators can nest and boost their numbers. These man-made abodes, which typically contain tubes or hole-riddled wood or plastic for the bees, have become popular projects among environmentally-minded folks.

But these well-meaning hoteliers may not be helping native bees as much as they think, researchers argue in PLOS ONE. Instead, a new study suggests that bee hotels can favor other insects such as wasps and non-native bees. People who sell and encourage the use of these artificial nests should “avoid ‘bee-washing’: that is, green-washing… as applied to potentially misleading claims for augmentation of native and wild bee populations,” the team writes.

Examples of bee hotels

Examples of bee hotels. In image D, an abandoned hotel has been swarmed by ants; in image E, a wasp is parasitizing a bee; and in image F, a bird has damaged the hotel.

The researchers installed 200 bee hotels per year in the Toronto area from 2011 to 2013. Each hotel contained 30 cardboard tubes of various sizes for nesting, and the sites ranged from gardens to rooftops. Each year, the team removed brood cells from the tubes, reared the insects in the lab, and identified their species. Over the course of the study, the authors recorded more than 27,000 bugs from 574 bee hotels.

Native and non-native bees occupied a similar number of hotel sites, the team reports. But overall, native bees represented a relatively small fraction of the insects. Among all the bees and wasps reared, 38 percent were native wasps, while only 28 percent were native bees. And parasites were more likely to infect native than non-native bees.

Figure 2

The percentage of bee hotel sites occupied and the number of brood cells produced by bees and wasps from 2011-13.

“At their worst, bee hotels may act as population sinks for bees through facilitating the increase of parasites, predators… and diseases” because the nests are so tightly packed, the team writes. Just as roaches can crawl from room to room in a dingy motel, parasites may be able to sneak through thin nest tube walls.

The researchers did find that some hotel sites were friendlier to native bees than others. Hotels in residential gardens tended to house more native bees than those at community gardens, parks, and building rooftops. And owners could tweak the materials and design — for instance, the size of tubes — to make the nests more welcoming for native bees. Roberta Kwok | 26 March 2015

Source: MacIvor, J.S. and L. Packer. 2015. ‘Bee hotels’ as tools for native pollinator conservation: A premature verdict? PLOS ONE doi: 10.1371/journal.pone.0122126.

First image © thomas eder | Shutterstock

Second and third images: MacIvor JS, Packer L (2015) ‘Bee Hotels’ as Tools for Native Pollinator Conservation: A Premature Verdict? PLoS ONE 10(3): e0122126. doi:10.1371/journal.pone.0122126