If you are a beekeeper, you have probably asked this question...
Why do honey bees like dirty water? It is a common question—in fact, this is not the first blog post concerning honey bees and dirty water (see Mud Songs and Honey Bee Suite)—and yet, there is not a definitive answer.
I first started keeping bees when I joined the Starks Lab in the summer of 2013. Toward the end of the summer, I was on the library roof (there is a beautiful view of Boston from the Tisch Library roof!) doing some reading when I got a concerned call from one of the lab's undergraduate interns. "The bees are acting weird and I think they are going to be sick," Georgie Burruss (now a Research Technician for the Flats Ecology and Conservation Program in the Bahamas) blurted out as I answered my phone. I promptly shut my book, grabbed my backpack and told her I was on my way.
When I arrived at the bee hut (we have a shed that houses 8 observation hives, affectionately referred to as ‘the bee hut’ or simply, ‘the hut’), I saw that the bees were drinking from a dirty-looking puddle rather than the much clearer puddle nearby. The bees looked fine but it did seem weird that they would choose the dirty puddle when there was clearly a better one (by our standards) close by.
The new beekeeper in me wanted to shoo the bees away from this puddle that seemed like it was going to make them sick, but the scientist in me told me to collect data. So, I snapped this picture with my iPhone, and Georgie and I took samples of the dirty water the bees seemed to like so much.
Back in the lab, I froze our water samples, took out my laptop, and began my web search. Why do honey bees like dirty water? It was certainly a question asked by many beekeepers but it had not been asked by a scientist since 1940. Conducted by C.G. Butler, the 1940 study measured honey bee preferences for very dirty water sources (i.e. cow dung distillate) over clean water sources by training honey bees to feed from artificial feeders at a table. At the table, Butler put out different types of water, each in their own feeder, and counted the number of visits bees made to each feeder. The bees loved the cow dung distillate. But, this preference disappeared when Butler added activated carbon to the water sources, effectively making all the sources scent-free.
So, honey bees likely find dirty water via scent. But why might they be looking for dirty water in the first place? Honey bees are highly efficient, so there must be a reason, right?
Well, that's the question I have been investigating for the past year and a half. Since minerals are physiologically important to all living organisms, and are typically found in only trace amounts in the honey bee's floral diet, it is logical to hypothesize that dirty water may be a supplemental source of minerals for honey bees. My initial thought process:
What’s in cow dung? A whole lot of nitrogen (among other things).
What’s in the plant tissue eaten by insect herbivores? Generally, not a whole lot of nitrogen (insect herbivores tend to be nitrogen-limited).
How did my initial ideas pan out? Stay tuned!
UPDATE (April 2017): Honey bees likely drink dirty water as a way to supplement the minerals in their floral diet! You can read about my findings in American Bee Journal or Ecological Entomology (check out my Publications & Press page).
Photo: My Secret Boston