Preadaptation to the vertical: an extra dimension to the natural history and nesting habits of the Tree Bumble Bee, Bombus (Pyrobombus) hypnorum

Abstract

The Tree Bumble Bee, Bombus hypnorum, is a native of forest environments but has now successfully colonised urban areas. To better understand its success in an anthropogenic context, this review considers aspects of its natural history and nesting habits using a combination of published literature, anecdotal field observations by entomologists from a number of countries, and information from the BWARS database. Where man’s influence is minimal, B. hypnorum appears to nest almost exclusively in tree cavities. Modern woodlands tend to be managed and nest-cavity poor. Urban areas with gardens provide foraging opportunities together with a large supply of well-insulated and well-protected aboveground nest sites. B. hypnorum currently appears to do better in urban areas than managed woodlands, and quite possibly better than it ever did in primeval forest. In Britain, where it was first found in 2001, its notable success appears to reflect the absolute quantity of suitable anthropogenic, and specifically urban, nesting habitat. Conspicuous nest placement has resulted in more nest records for this recent arrival than exist for any native British bumble bee species. In “helping itself” to an anthropogenic nesting niche, B. hypnorum highlights how important appropriate nesting sites are in determining which bumble bee species can live in any given area. Detailed information on nest site preferences and availability needs to inform conservation measures for threatened native species.

Keywords:

• Tree Bumble Bee
• nesting requirements
• nest sites
• distribution
• colonisation
• anthropogenic effects
• urban ecology
• community ecology

Acknowledgements

For unpublished information and observations, and permission to use them, I am most grateful to: Karin Ahrné, Alexandr Byvaltsev, Bjorn Cederberg, Dorota Czeszczewik, Bogdan Jaroszewicz, Rimvydas Juškaitis, Tadeusz Pawlikowski, Grigory Potapov, Stuart Roberts (for access to the BWARS database), Maj Rundlöf, Mark and Christine Turner and the “Worcestershire Record”, Tomasz Wesołowski and Paul Westrich. I hope I have accurately conveyed their observations. For discussion I would like to thank the above, and also Yiannis Anagnostopoulos, Paul Bahn, Andreas Bertsch, Silas Bossert, Rob Fuller, Andy Musgrove, John Birks, Nicky Milner, Johann Neumayer, Robert Prŷs-Jones, Franz Schmidlechner, Vladimir Smetana, Herwig Teppner and Paul Williams. For help with translation I am grateful to: Anna Persson (Swedish); Andreas Bertsch, Pia English Darmstadt and Claus Darmstadt (German); and Ewa Turczanska (Polish). I am very grateful to Sally Corbet, Robert Prŷs-Jones and three reviewers for constructive comments on the text.

Disclosure statement

No potential conflict of interest was reported by the author.

Supplementary material

Supplemental data for this article is available online at https://doi.org/10.1080/00218839.2019.1634462.

Notes

1 “Natural” and “uninfluenced by man” are relative and subjective terms. Here they are used in relation to nest sites that are not directly anthropogenic. For example, a nest in a tree hole is considered “natural”, even if the tree itself was planted.