Hotels are usually built for travelers, but some are designed for creatures no bigger than your thumb. Scientists and conservationists have spent years creating these miniature refuges for wild bees in the form of small nesting structures equipped with narrow tunnels that mimic the hollow stems and cavities that many solitary bee species naturally use to lay their eggs.
In the hope that they could provide additional nesting spaces in growing urban areas, Canadian researcher J. Scott McIvor installed 200 bee hotels across the city and monitored them for three years. What started as a simple conservation experiment soon revealed an entire hidden community of insects, prompting researchers to rethink how artificial nesting sites affect pollinators and urban biodiversity.
Why do scientists build bee hotels?
When most people think of bees, they imagine honeybees living in crowded beehives. In fact, honeybees make up only a small portion of the world’s bee diversity. About 90% of the approximately 20,000 known bee species are solitary bees, with each female building and securing her own nest without the assistance of a queen or worker bees.Many of these solitary species nest inside hollow plant stems, beetle burrows in dead wood and other natural cavities.
However, urban development, intense landscaping, and removal of dead wood have reduced nesting opportunities in many places. Bee hotels have been developed to replace some of this lost habitat by providing finely sized tunnels in which cavity-nesting species, including mason bees and leaf-cutter bees, can lay their eggs.
Unlike honey bee hives, these structures are not colonies but groups of individual nesting chambers, each occupied by a single female and her developing offspring.Most bee hotels are made from untreated blocks of hardwood drilled with narrow holes of various diameters, bundles of disposable paper, or cardboard tubes placed inside a protective frame. Each tunnel is closed at one end and left open at the other, allowing the solitary female bee to lay an egg, leave behind a ball of pollen and nectar for the developing larvae, seal the chamber with mud or leaves, and repeat the process until the tunnel is filled.
In the wild, these bees typically use hollow stems, beetle burrows, or natural crevices in dead wood to do the same thing.At the time McIvor began his research, bee hotels were already being widely promoted as a simple way to help pollinator populations decline, but there was surprisingly little scientific evidence to show how well they actually worked for native bees. This gap in knowledge became the focus of his study.
Three-year experience with 200 bee hotels
To find out if bee hotels truly support native pollinators, we’ll see if bee hotels really support local pollinators.
Scott McIvor and co-author Lawrence Packer installed about 200 bee hotels each year throughout Toronto and the surrounding area, and monitored them for three consecutive years.Published in PLOS ONE, the study examined nearly 600 bee hotels and recorded more than 27,000 emerging bees and wasps. Instead of simply counting the number of bees that arrived, the researchers identified each inhabitant, compared native and introduced species, documented parasites and assessed which species inhabited the hotels and how these artificial nesting sites affected local bee communities.Bee hotels quickly proved to be more than just homes for solitary bees. Native bees used nesting tunnels, but they shared them with an amazing variety of other insects. Native wasps occupied nearly three-quarters of hotels each year, while introduced bee species were also common. Ants, spiders and parasitic insects frequently appeared, transforming the structures into thriving miniature ecosystems rather than habitats for a single species.The results suggest that bee hotels can affect entire insect communities, providing researchers with a rare glimpse into the complex relationships that unfold within these artificial nesting sites.
What the study revealed about biodiversity
The research did not conclude that bee hotels are inherently harmful. Instead, it showed that their environmental impacts are much more complex than many people had assumed.The researchers wrote, “Overall, the results of our study show that bee hotels appear to differentially increase wasp populations rather than native bee populations.”
They also noted that the results “Highlight the need for increased study of bee hotels and their associated impact on bee biodiversity and pollination in urban areas.”Rather than providing a simple conservation solution, bee hotels can influence which species occupy an area, how insects compete for nesting space, and how urban ecosystems function over time.
“If you build it, they may come”
McIvor has consistently argued that the findings should not discourage people from supporting native bees, but instead encourage better designed conservation efforts.While contemplating the study, he said: “If you build a nest box, they may come. Maybe not. Or they may come next year.” His point was that bee hotels should be treated as carefully managed conservation tools, not as foolproof solutions to pollinator declines.Subsequent studies have refined best practices for bee hotels, recommending untreated hardwood, appropriately sized nesting tunnels, regular cleaning and thoughtful placement to maximize benefits to native cavity-nesting bees while minimizing the chances of parasites and disease.
Bee hotels are only part of the solution
The study also highlights an important limitation. Most native bee species nest in the ground rather than in wood or hollow stems, which means bee hotels can only benefit a minority of bee species. Ground-nesting bees rely instead on healthy soil, flowering plants, and quiet habitats.For this reason, conservationists view bee hotels as just one part of a much larger strategy. Protecting native wildflowers, reducing pesticide use, preserving deadwood, and preserving natural habitats remain equally important to support healthy pollinator populations.Bee hotels may never support every species of bee, but they have given scientists an unusual window into the hidden lives of pollinators. In doing so, they showed that even the smallest conservation projects can reveal new insights into biodiversity and the complex web of life that supports our ecosystems.
