Tag Archives: Ferries

Bumblebees, ferries, and mass migrations: an update

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The post earlier this week on the question of “Why do bumblebees follow ferries?” generated quite a few comments, both on the blog and on Facebook.  As I’d hoped a number of people have chimed in to say that they have observed the same thing, or commented that they often see bumblebees when sailing or kayaking out at sea.

Here are the additional observations in increasing distance order to nearest larger area of land.  Distances are approximate and in some cases it’s unclear where exactly the observations were made:

Isle of Mull to the Isle of Staffa: 6.5km

Skye and the Outer Hebrides going in both directions: 24km

Ferry to Jersey: 28.4km

Estonia to Helsinki: 80km – described in a short paper by Mikkola (1984).

However this is nothing compared to evidence that queen bumblebees may engage in mass migrations (involving thousands of bees) across the North Sea from England to Holland, a distance of 165km!  See Will Hawkes’s short article “Flight of the Bumblebee“.

This idea of mass migration is new to me, though the Mikkola (1984) paper cites some earlier literature on the topic.  And this morning I had a quick phone chat with Dave Goulson who tells me that he occasionally gets people contacting him to tell him about such events.  But it’s unclear why these bees should be flying such large distances, how they coordinate their migrations, or indeed how much energy they need to store to travel that far. In addition there are implications for gene flow between British and Continental subspecies of bees such as the Buff-tailed Bumblebee (Bombus terrestris). Even a relatively well studied group of insects such as the bumblebees can continue to surprise us with new questions!

Thanks to everyone who contributed observations and ideas, it’s much appreciated.

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Why do bumblebees follow ferries?

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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):

  1.  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).
  2. These bumblebees are taking advantage of the slipstream created by the ferry to reduce the energy required to fly these long distances.
  3. The bees are hitching a lift on the ferry and I only observe them as they arrive or depart.
  4. 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….

 

 

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