Anyway, several weeks ago, Rachael Bonoan, a PhD candidate at Tufts and president of the Boston Area Beekeepers Association, spoke at our bee club meeting. She was positively delightful -- sweet, humorous, and insightful -- it was a joy to hear her talk.
She gave two talks -- one on why honey bees drink dirty water and another related to the effect of diet on honey bee immune systems. Sadly, I've misplace my detailed notes, but I'll share the highlights. Also, you can read the full paper on the "dirty water" study here.
Talk 1: Seasonality of salt foraging in honey bees
- Beekeepers have long observed that honey bees seem to prefer dirty puddles of water to fresh clean ones. One study has even shown bees to drink human tears! [Banzinger H, et al. Bees (Hymenoptera: Apidae) That Drink Human Tears. J of the Kansas Entomological Society. 2009; 82(2): 135-150.)]
- Bonoan hypothesized that honey bees are selectively foraging in soil and water for minerals that nectar may lack.
- She sampled and tested water from around the university where honey bees were known to collect water (barrels, cinder blocks, puddles, truck cabs, puddle behind gym) and found that the water in these places were rich in calcium, magnesium, potassium, and sodium. She focused on these minerals because of they are known to be necessary for certain biological functions.For the study, she set up watering stations (basically watering tubes on a table). Each station contained water mixed with a different salt (NaCl, KCl, CaCI2, MGCL2, NH4CL, KH2PO4). The control tubes contained sucrose and deionized water. She also had another screened in table with tubes full of the same solutions so that she could account for evaporation.
- One of the things I found fascinating was seeing bees come to the tables, tasting a solution and then moving on to one they liked better. So they definitely showed preferences.
- Additionally, the results showed that overall, the bees had preferences for certain minerals during different seasons. Preferences also varied depending on which floral sources were available.
- As part of the study, she also measured the effect of salt foraging on hive health. Colonies that gathered a wider variety of salts were healthier overall than ones that didn't.
- She recommended providing bees with a supplemental mineral source. It could be as simple as giving them a dirty puddle or a mineral salt lick. Also, bees should have diverse floral resources throughout the year.
If you are interested, you can view a copy of the slides for this presentation.
Talk 2: Physiological and behavioral immunity in the honey bee
- Honeybees have 3 types of disease resistance: Genetic, Physiological (Individual Behavior), and Group Behavior
- Honey bees have far fewer immune genes than other insects (about 50). Fruit flies and mosquitoes have closer to 200 immune genes. This is why genetic diversity is so critical for honey bees. The more baby-daddies a colony has, the more likely that the population will have a greater mix of immune genes. This provides population-level resistance. In other words, while certain bees with one immune gene might be susceptible to a disease, other bees in the population with different genes may not be.
- Bees also exhibit various behaviors that increase their disease resistance. Some of these are individual behaviors like grooming, biting, etc. Others are group behaviors like collecting propolis, balling invaders, and thermoregulation.
- She called thermoregulation a "honey bee fever" because it acts just like a fever in humans. Bees raise the temperature of the hive in order to kill an infection like chalkbrood.
- She discussed her research infecting colonies with chalkbrood and measuring their ability to raise hive temperatures. Here my memory is spotty, but I believe that her group also fed various pollen mixes (monofloral vs. polyfloral) to the bees to see if that affected their ability to thermoregulate. They chose to provide monofloral and polyfloral pollent because pollen is what the young bees eat. Pollen contains protein, 10 essential amino acids (EAAs), and trace minerals that are essential for honey bee health. However, not all pollens contain the same EAAs in the same amounts. Bees cannot get all 10 EAAs from monofloral crops like almonds, sunflowers, etc.
- What she found is that colonies fed pollen mixes from diverse sources had better overall health. Also, the amount of protein that bees receive from pollen is not as important as the diversity of EAAs that they get. In other words, pollens with higher protein content did not necessarily translate into better colony health. However, pollen diversity did.