Wednesday, April 15, 2015

Tree trimming squirrels

Two falls ago I noticed squirrels chewing off the ends of the box elder trees (Acer negundo) that grew along the railroad tracks by the house. Only a few branches were long enough to reach over the street so it was hard to judge how extensive their activities were. 

A few days ago, leaving the Y and half delirious (as I always leave that place), I noticed a few twigs. The next day the sidewalk was covered and this time the tree was an old maple - I think red (Acer rubra). 

I talked to our resident squirrel expert, Dr. Mike Steele, and it ends up this is a well known but not well documented behavior. According to Mike, squirrels bit the ends of the twigs off to get the sap that drips from the end but this also serves to increase the size of the samaras (winged seeds) that come from that tree. He did an experiment years go to test this and the results supported that hypothesis. That study remains unpublished but should be repeated with a few more trees. 

It can't just be the sap, for that they could just chew the end. But they chew both ends and drop the twig. Intriguing. 


  1. Are they eating the bud and sucking the sap from both ends?


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  3. Yea, that's a good question. I thought so myself but they snip one end, snip the other and drop - thousands of times. If they were like the red squirrels then it would be just the end. They might though, snip, get the sugar then snip again and they figured out that there isn't sugar again for another 20-30 cm. Mike wants to explore this again so we'll see. I bet this is sugar related either way.