04 January 2009

A slug tree fell in the woods. Did it make a sound?

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This American beech (Fagus grandifolia) broke at its base and fell between 28 December and 2 January in the park near my house. When I discovered it yesterday I got quite excited for 2 reasons. First, if the park maintenance people do not chop it up, and they shouldn't, because it's not blocking any paths, it will be interesting to monitor its slow decomposition over the years starting practically from day one. The tree was alive when it fell and there is at the moment only a few small sections that are already rotten.

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Second, the bark is covered with the feeding tracks of the local philomycid slug, Megapallifera mutabilis. Some of the tracks were very clear: one could see the marks the teeth on the radula left as the slug was scraping off its food, cyanobacteria growing on the bark.

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Here is another cluster of tracks.

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Using a 10-m tape, I estimated the total length ("height") of the tree as 30 m; I couldn't get an accurate number, because the topmost branches had broken off when the tree hit the ground. According to Frank Brockman's Trees of North America (1968), the American beech grows "60 to 100 feet tall" or up to about 30 m. So this tree was about as tall as it was going to get.

Yesterday and today I spent quite some time among the branches and climbing up and down the huge trunk, which has now turned into a natural bridge across the small creek under it, all the while looking for slug tracks and photographing them. I slipped and fell a few times, but amazingly got only a minor cut on my hand. When it comes to playing with trees, I will always be a kid, especially if there are also slugs on them. What was really neat was that by following their feeding tracks I was able to get a pretty good idea of how high the slugs went up the tree.


Updates on the status of this tree are in this and this post.

4 comments:

m.e. said...

slugs have TEETH??? omg

Megan said...

Aydin, are you going to map out the positions of feeding trails along the trunk? I would be intriguing to see where they concentrate on feeding, if they have any hidey-holes higher in the tree, if there is a difference in slug body size (as related to radula scrape size) in height along the tree, etc.

Michael said...

So how high up the tree did they go? If I didn't read your blog I would still be under the impression that slugs only live on the ground just because that's the only place I've seen them.

AYDIN ÖRSTAN said...

Let's say they didn't reach the top. I don't intent to reveal the exact figure at the moment.