Solve this mystery! What left a spiral pattern on this pear?

My folks have a pear tree at the end of the garden. It never really produces much in the way of fruit - I think it's too close to the much bigger apple tree. I found this pear lying on the ground in some long grass. It has a weird pattern of holes made in a perfect spiral along the fruit. What happened?

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I must admit my first reaction is 'bored human' - could anyone have reached a pear, damaged it and thrown it back? There are various creatures that make holes in pears (wasps, squirrels), but I can't think of anything that would make such a regular pattern.

Unlikely anyone tampered with it, but not impossible. I wondered if maybe it was damaged by a rake, rolling at an angle under the tines, but the holes don't look right for that, and there's no dirt or bruises on it.

Did it happen while on the tree or on the ground d'you think? It might be something with quite a small mouth trying the grab it repeatedly, while turning it in its mouth trying to get a purchase on it?


Looks like something ate all it could reach in one spot without moving its body, advanced till its head had a similar sized area of unbrowsed fruit underneath it and repeated working from one end to another. Dunno anything that size that could handily process that amount of fruit, unless it was squeezing extra water out as it ate. Hmm, maybe it wasn't eating the flesh, just spiral juicing its way along. Ripe pears are pretty sweet, the juice itself would make for good bug fuel.

By Stacy Mason (not verified) on 31 Aug 2011 #permalink

A large slug?

By Nonesense on Stilts (not verified) on 31 Aug 2011 #permalink

Acorn woodpeckers make spiral patterns of holes on tree trunks that look pretty similar. Of course, the holes are deeper, and they usually proceed to fill them with acorns. But that's what your pear reminds me of, FWIW.

Pure speculation, but what if the pitch, combined angle of the spiral and slope of the pear were related to the latitude of the location. Also assume the presence of large fruit, juice, loving wasps.

Sun comes up and a wasp finds the pear and consumes a bit of it. It flies home and returns for more using the sun as a guide. The spacing of the holes represents the time laps between feedings and the travel time to the hive. The patterns repeat the second day but the wasp uses the altitude of the last feed the previous day. This repeats for roughly three days and then the ripe pear falls to the ground where it becomes an interesting artifact of how domestic pears, fruit eating wasps, and the movement of the sun combine.

Lightly clipped by a fast-moving garden tool (strimmer if on the ground, hedge trimmer in the tree) etc? I accidentally made similar marks on a small log with a chainsaw when it spun in the saw-horse yesterday, so was wondering...

@ 11 My mum is claiming mechanical damage too, but the holes are almost perfect, no bruising or tearing at all. Looks like it's been eaten from the inside, by a grub.

@10 Art
I love your theory! Karl von Frisch's work on bees showed that bees are able to compensate for changes in the sun's position over time (clever things), and I seem to recall an experiment that involved moving local landmarks (pine cones, etc) that showed solitary bees use eyesight to find things once they get quite close, but nevertheless, yours is my favourite so far.

It's a miracle! You may claim $1 million from Randi!

The very hungry caterpillar?