Big bumble breeding breakthroughs
Posted onJune 29, 2023by|,
Conservation breeding and release programs are an established way to restore populations of at-risk species, but such programs for invertebrates are very rare compared to those for vertebrates. One common challenge for conservation programs for insects is the development of reliable breeding and rearing techniques. Since WPC’s Native Pollinator Initiative’s inception, we have developed and tested different husbandry techniques for increasing the success of bumble bee conservation breeding colonies, focusing on the Special Concern yellow-banded bumble bee, Bombus terricola. The ultimate goal of the Bumble Bee Recovery Program is to establish a self-sustaining pool of captive colonies to supplement wild populations of this species.
Although the yellow-banded bumble bee has been our main focus in the breeding program, we had a two-year break from breeding in 2020 and 2021, in part because of the pandemic, but also so we could set up a new lab space at African Lion Safari, in Southern Ontario. After this hiatus, we were very excited to resume breeding this species last year.
Along with the yellow-banded, we also reared brown-belted bumble bees, Bombus griseocollis, which is a common species that we use to increase sample sizes and compare needs of common versus declining species. We had been breeding brown-belted bumble bees for two years prior (2019 and 2021) and had a high success rate in 2021.
The 2022 yellow-banded breeding season saw multiple exciting accomplishments, including the lowest number of early-season queen losses. Some level of mortality is to be expected with any conservation breeding program, so we were happy to see our methods minimizing that as much as possible this year.
The largest yellow-banded colony to date (photo taken before the peak of 78 workers) Photo: P. Smale
Most of the queens produced eggs (75%), which is the second-highest proportion compared to all previous years breeding this species. However, only a few colonies (17%) produced workers and one colony produced males and new queens (gynes). Although these proportions may not seem high in terms of colonies producing offspring, it was a big win for our team as it marked the first time since 2018 that workers were produced and the first time males and gynes were produced since 2017. Last season we also had our biggest colony to date, with 78 workers.
We also had a record-breaking year breeding brown-belted bumble bees, with about four times the number of new queens (gynes) and two times the number of males produced compared to 2021. From this many males and gynes we were able to run extensive mating trials and finally observed our first successful mating of this species, which gives us a lot of hope that our current set-up will work for mating other bumble bee species!
First observed successful mating of brown-belted bumble bees. Photo: S. MacKell
We think that temperature and colony disturbance might have been the main issues with breeding yellow-banded bumble bees previously, and in 2023 we plan on keeping the colonies at a higher temperature (approximately 28-30C) and decreasing colony disturbance, especially during early establishment. Small changes like this each year will help us perfect the ideal breeding conditions for bumbles.
We have made great improvements for breeding both species in 2022, and have come a long way from where we started in 2017. The whole bumble bee recovery team is looking forward to a successful and record-breaking 2023 season!
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