Front (left to right): Annika Greenleaf (junior), Ana-Maria Murphy-Teixidor (senior), Gabriela Garcia (1st year grad student), Elizabeth Crone (Professor), me, Genevieve Pugesek (2nd year grad student) Back: Colin Orians (Professor)
This year, I had the pleasure of spending spring break in Costa Rica, on a coffee farm in the Central Valley! Our team was funded by the Sandler International Research Program to study stingless bee foraging behavior. Although coffee is capable of self-pollination, bee visitation can increase crop yields and quality (Ricketts et al. 2004). Regarding quality, bee visitation has been associated with increased berry size. Berry size? I thought we were talking about coffee…
On my first visit to Costa Rica last January, I was surprised to find that aromatic roasted coffee beans actually come from mildly sweet, red berries. Coffee berries! Once the berry turns red, it is ripe! Then, the berry is harvested and the bean is squeezed out of the berry for roasting and processing.
Since the quality of coffee berries (and thus, coffee beans) is partially dependent on stingless bees, we were interested in studying how stingless bees move around the coffee farm and what kind of nutrients the bees are are looking for while foraging. We spent the weeks leading up to spring break refining our plan and fitting field gear into suitcases. We were ready!
But, when we arrived in Costa Rica, we discovered that the coffee plants were not flowering. This put a serious kink in our foraging study—there weren’t any flowers for the bees to forage from! Generally, this time of year, the coffee plants are flowering but, with the changing climate, the rains seem to be coming later and later. It was too dry for the plants to bloom. Naturally, we tried watering the plants. After a few bucket-fulls, we decided to cut our losses. The trees simply weren’t blooming. Back to the drawing board.
We put our heads together and thought about what we knew and what we wanted to know. We had spent our first days on the coffee farm locating stingless bee nests so we knew where to find stingless bee homes. We also knew that based on a paper by Greenleaf et al., “our” stingless bees should be able to find their way back home from up to about 100 meters (about 300 feet) away from their nest. This prediction had yet to be tested in the field. Thus, our new experiment began! We collected stingless bees from one of our nests, carefully paint-marked them, and watched (with a GoPro and some insect binoculars) as the bees returned home.
In the end, we collected some good pilot data but not enough to draw any conclusions about homing distances in our stingless bees. We hope to return to the same coffee farm later in the year to collect some more data. Determining homing distance in stingless bees can serve as a proxy for foraging distance. If the bees can only go a certain distance away from home before they lose their way, they may only forage up to a certain distance too. Understanding homing distances can also give us an idea about how habitat fragmentation—which can be caused by establishing coffee farms in the midst of forest—might affect stingless bee behavior and thus, pollination services.
Stingless bee on a banana plant. Cute, right?