Foraging behavior of bees in Wisconsin Cranberry Marshes

Hello - Laura and Jensen here! 

We are a part of the Biology Research Scholars Program at UW-Eau Claire where we get to understand the processes of research with a faculty mentor [Dr. Bernauer-the best!]. This past summer we looked into the difference between Honeybee and Bumblebee foraging behaviors including buzz pollination, flowers visited per minute, stigmal contact, and temperature effects at the Wisconsin Cranberry research station near Black River Falls. 

We were able to travel to the cranberry marshes at the research station many times during peak bloom of the cranberry flowers [June/July]. The flowers are stunning, pretty monochromatic pink structures, not like anything we had seen before!

Laura observing bees visiting cranberry.

Cranberry flowers in bloom!

During our time in the field, we collected a lot of data from timing bees with a stop watch for a minute to see how many flowers they visited, to following bees around the marsh with a video camera to capture their individual foraging behaviors like buzz pollination and stigmal contact rates. We had some long days under the sun in the hot marsh, battling sunburn [our own doing] and angry bumblebees, but it was all worth it, and we look forward to further field work experiences!

After our field season came to a close, we were stuck inside watching the hundreds of videos we had taken and analyzing them using a behavioral observation software called BORIS. After completing that seemingly endless task, we were able to compile all of our results and come to conclusions. We overall concluded that Bumblebees are the ideal Cranberry pollinator due to their ability to buzz pollinate, their efficiency per minute visiting flowers throughout the marsh, and their increased stigmal contact rates - leading to better pollination for the flowers.

Stigmal contact rates by bee species in cranberry.

Laura, in her analyses, found that bumblebees made contact with the stigma of the cranberry over 30% more often than honeybees. Honeybees are the most common providers of pollination services in cranberry marshes, even though we found that bumblebees are the more efficient pollinators. This data could be used to inform growers on more efficient, ecologically friendly pollinating practices!

Buzz pollination frequency by bumble bee species and on flowers with the stigma in or out.

Jensen looked into specifically buzz pollination by bumblebees, a behavior that bumblebees perform by holding onto the anther cone of the cranberry flower and vibrating its flight muscles, releasing pollen from the flower onto the bees’ bodies. After timing the duration of buzz pollination of hundreds of bumblebee visits, she found that bumblebees buzz pollinated over a third of a second longer when the stigma of the flower was still inside of the anther cone, indicating that the flower had bloomed more recently and had more pollen available. These findings give us more insight into the complex mechanisms involved in plant-pollinator interactions!

We then presented our findings individually at the Entomology Society of America Conference in Portland, Oregon in November. Jensen did a talk on Bumblebee buzz pollination, and Laura did a talk comparing the foraging behaviors of Bumblebees and Honeybees. To read more about our time there with Kinsley and Orlean, and our little day trip adventure, check out this post!

Currently we are working on writing up everything we did and found into a research paper that we can publish in a scientific journal. We are excited to see what comes next, thanks for reading!

• Laura & Jensen