Trailing/queueing or tail-gating

February 27, 2006
From: Dave Behrens

Hi Bill:
I was speaking to a rather large assemblange of Branch lovers at the Monterey Bay Aquarium this week when confronted with a question - new to me.

I had just shown examples of trailing when a guest asked if the real purpose of trailing was to save crawling energy for the tail-gaters by taking advantage of the slime trail laid down by the leader. Her analogy was drafting or slip-streaming in race cars and speed skaters. Certain pelicans and geese use this behavior to save energy inflight.

Terry Gosliner and I have always felt that this practise was simply to stay close to a potential mate. Even when the two or more individuals might represent different species (an example of the followers confusion).

Have you any thoughts on this, or know of any experimentation or research?

Thanks in advance.
Dave Behrens

Behrens, D.W., 2006 (Feb 27) Trailing/queueing or tail-gating. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Dave,
I must say I hadn't thought of saving energy - at the speed they go I don't think windresistance would enter the equation but I guess if you didn't have to produce your mucus trail as you crawled along, the would surely be an energy benefit. I guess you would have to first see if they can regulate the flow of mucus as they crawl along. Can they produce more when the going gets tough, and less when they can slide on someone else's trail.

I agree that I had always thought that following trails was a response the chemicals in the mucus - either a predator chasing down its prey or a 'suitor' chasing down a mate. There are quite a few references to trail following on the Navanax inermis Fact Sheet, but I don't know of any work in other opisthobranchs. It would be an interesting topic for a student to take up.
Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Feb 27). Comment on Trailing/queueing or tail-gating by Dave Behrens. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Trailing behaviour