Banana Slug!

Mike and I have discovered the Burnaby Central Park by our house. Yesterday as we walked through the park, I excitedly encountered this little fella:

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My first reaction was OH MY GOODNESS, BANANA SLUG! For the record, there aren’t any banana slugs in Ontario, so in general I find them very exciting. However, I wasn’t about to post about them until I knew for sure it WAS a banana slug. When you google banana slug you get images that look like this! Hardly seems like the same little guy; this one was only about 4cm, has black markings, and much darker pigmentation. Luckily I discovered that this is in fact the Pacific banana slug (Ariolimax columbianus), as opposed to the other two species (A. dolichophallus, and A. californicus) which seem to come in more yellow shades (based on google image searches…).

I also find them exciting because in first year biology they were one of the first examples of the interface between behaviour and evolution that I ever encountered. In brief, the basic story is that there are multiple populations of your regular old garter snake (Thamnophis elegans). They originated inland and slithered out to more costal habitats, where they discovered banana slugs. Some fraction of the colonizing snakes were able to smell the slugs (a physiological trait that is controlled by genes), so all of a sudden with this new prey source they were able to eat like snake kings (!!) while their scent-sensing-deficient siblings suffered (or did no better than in their old habitat). As a result of this difference in predation behaviour, some did relatively better, proliferated more, and the result is that today, only a few inland garter snakes are capable of recognizing banana slugs as food, while most coastal snakes can. BLAM behavioural ecology.

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