A few years ago I mentioned in my post “Garlicky archipelago” that I had seen bumblebees (Bombus spp.) following the ferry from Southampton to the Isle of Wight, a distance of about 1.5km across water. If I remember correctly it was my colleague Scott Armbruster who first mentioned this to me: he lives on the Isle of Wight and commutes regularly to the mainland.
I’ve not thought much about this since then as 1.5km is a fairly modest distance for a bumblebee to fly. But then a few weeks ago I saw the same thing in Denmark, but this time over a much longer distance.
Karin and I were visiting friends on the small island of Sejerø, which (at its closest point) is about 8km from the mainland of Zealand. To get there you have to catch a ferry which takes about an hour to cross this stretch of water. About half-way across, whilst looking over the stern of the ship, I spotted a bumblebee following the ferry.
So that’s twice, on two different ferries and under very different contexts, that I’ve seen this phenomenon. A pattern is starting to form…. Has anyone else observed this? Please do comment.
I can think of a few explanations/hypotheses for what’s going on here (some of which are not mutually exclusive):
- Clearly bumblebees do fly across significant stretches of open seawater. Perhaps all I’m seeing is bees that do this, but spotted from the only vantage point where it’s viewable (i.e. the ferry).
- These bumblebees are taking advantage of the slipstream created by the ferry to reduce the energy required to fly these long distances.
- The bees are hitching a lift on the ferry and I only observe them as they arrive or depart.
- The bees are following the wake of the ship to navigate between the island and the mainland, in order to exploit significant flower patches. Work by one of my PhD students, Louise Cranmer, a few years ago showed that bumblebees follow linear features such as non-flowering hedgerows to navigate – see Cranmer et al. (2012) Oikos. Perhaps something similar is happening here?
There’s probably other possibilities I’ve not thought of. But whatever the explanation, it looks to me as if there’s some potential for interesting experiments marking and recapturing bees on islands/mainland, releasing bees on ferries to see if they follow the wake, etc. If only Northampton wasn’t so far from the coast….