Variation in North American bumble bee nest success and colony sizes under captive rearing conditions

Of the 265 known bumble bee (<em>Bombus</em>) species, knowledge of colony lifecycle is derived from relatively few species. As interest in <em>Bombus</em> commercialization and conservation grows, it is becoming increasingly important to understand colony growth dynamics across a variety of species since variation exists in nest success, colony growth, and reproductive output. In this study, we documented successful nest initiation and establishment rates of colonies produced from wild-caught gynes, and created a timeline of colony development for fifteen western North American <em>Bombus </em>species captively reared from 2009 to 2019. Additionally, we assessed variation in colony size among five western North American <em>Bombus </em>species from 2015 to 2018. Nest initiation and establishment rates varied greatly among species, ranging from 5–76.1% and 0–71.8%, respectively. <em>Bombus griseocollis </em>had the highest rates of nest success across the eleven-year period, followed by <em>B. occidentalis, B. vosnesenskii, </em>and <em>B. huntii. </em>Further, we identified that colonies reared from two gynes had significantly higher nest initiation and establishment rates per nest box compared to those reared from a single gyne. Colony size also differed significantly among species with <em>B. huntii </em>and <em>B. vosnesenskii </em>producing more worker/drone cells than <em>B. griseocollis, B. occidentalis, </em>and <em>B. vancouverensis. </em>Additionally, gyne production differed significantly among species with <em>B. huntii </em>colonies producing more gynes than <em>B. vosnesenskii. </em>Results from this study increase knowledge of systematic nesting biology for numerous western North American <em>Bombus </em>species under captive rearing conditions, which can further improve rearing techniques available to conservationists and researchers.