Bumblebee Nest Predation

In last August’s edition of the newsletter some of you may remember the discovery by Alison Mosson who found an exposed red- tailed bumblebee nest that had fallen victim to predation (possibly by a badger)! One year on and we thought it would be interesting to follow up on this kind of event by investigating a project being undertaken by Steph O’Connor at the university of Stirling looking at bumblebee nest predation.
In this study, Steph trained sniffer dog Toby (pictured right) to search for the nests of common bumblebee species. A total of 19 bumblebee nests were found and their entrances filmed until the nest died out at the end of the season. During this time a number of interesting observations were noted; animals found to be preying on bumblebees coming in and out of the nests included great tits, robins and crows, while shrews and voles were also spotted visiting the nests (although what they did inside the nest remains a mystery). Hedgehogs and squirrels were also found to show some interest in the nests. There were kills or attempted kills observed at 5 of the 19 nests with great tits the most prevalent predators in this study; they were found mainly to prey on large nests with lots of bee traffic. However Steph emphasizes that these nests were large enough to recover from the predation and all of the nests preyed upon produced new queens before the season was over. She also notes that the study focussed on the most common species of bumblebee, while the question remains as to how nest predation affects our less common species?

These amazing photographs taken by Linda Turner on her BeeWalk show a blue-tit preying on a buff-tail bumblebee and providing a meal for its offspring.

There was an interesting discussion earlier this month within the BeeWalk Google group, in which one volunteer told how they accidently discovered a common carder bee nest under some grass cuttings in his garden. Upon further inspection, they noticed fast-moving white grubs within the nest that were roughly half an inch long. Another volunteer writing in the forum guessed that they could be the larvae of a Wax moth and provided some interesting information on these nest parasites (sourced from www.thegardenprince.co.uk) “the female wax moth stakes out the bumblebee nest and hangs around outside for a few days to pick up its scent. Once she has done this, she enters the nest undetected to lay her eggs. These hatch into caterpillars, which start off by eating the nest debris before moving to the wax pots containing honey, pollen, and grubs. They create tough, silk tunnels, presumably to protect themselves from the adult bees. Before long the entire nest is gone, prompting the caterpillars to leave to pupate into next year’s wax moths.” A third volunteer mentioned that their daughter had been through exactly the same scenario, and also told of their experiences of the damage a wax moth can do to a hive of honeybees. It really is inspiring to see a BeeWalk community developing on this forum; asking questions, sharing information and helping each other out!

Bumblebee Mating Strategies explained
These curious pictures taken by Elizabeth Winder (left) and John Taylor (both below); show a male and queen red tailed bumblebee mating. Possibly just as astonishing as these pictures is the story John told in his email as to how he managed to take this photograph. Despite being a mile and a half from home with no camera when he first saw the male red-tail jump the queen mid flight, at 64 years old he managed to run all the way home, grab his camera and drive back up to the spot where the two bees were amazingly still present!

After hearing John’s story and seeing these photographs we decided to consider the topic of bumblebee mating strategies for this edition of the newsletter. Male bumblebees are born late in the season and are the direct offspring of female bees laying eggs without mating (males therefore only have half the genes that females have). After spending a few days in the nest drinking nectar and building up strength, male bumblebees leave the nest and from then on fend for themselves, foraging for nectar and taking refuge in flowers and vegetation over night or when it rains. Male bumblebees are born with one goal in life – to mate. They achieve this by patrolling an area and depositing a scent on prominent objects such as tree trunks, rocks and flowers. Newly emerging queens who are ready to mate are attracted to the pheromones in the scent and subsequently enter the male bumblebee’s patrol area. The male will try to intercept a queen flying within his area in order to mate with her (apparently he will try and intercept anything queen shaped flying at the right height – even a rock thrown through the air). Once he has latched on to a queen, the pair usually settle down on the ground or in the undergrowth to mate, this can take anywhere between 10 and 80 minutes. After the mating has taken place the new queen will spend time provisioning the fuel she needs for the winter and find a place in which to hibernate. For a more detailed outlook on bumblebee mating seehttp://www.bumblebee.org/lifeMate.htm .