Ask the Steward
Question 1: I have not seen many squirrels this past winter. Do they migrate?
Answer: Squirrel are not migratory, but populations do go up and down over time based on food availability, predator populations and other stressors. This could be a factor in your area as squirrels possibly relocate or roam a few miles in search of food. Populations will generally rebound within a couple years as food sources recover and squirrel reproduction returns to the normal cycle of two litters/year with 2-3 pups each litter for both Gray and Fox squirrels.
However, there is a very interesting phenomenon noted in historical writings and journals of mass one-way migrations, or more accurately stated, ‘movements’ of primarily Gray squirrels (the most abundant squirrel species in North America) in the 1800’s. Reports describe what would look like an invasion of squirrels marching across the landscape laying waste to crop fields and gardens along the route to who knows where- like lemmings marching to the sea. According to some writings the wave of squirrels could last for days, or weeks as tens of thousands or even millions of squirrels passed through. These extreme mass movements seem to be correlated with major squirrel population booms followed by a year of food scarcity. As September loomed and no food (acorns, hickory nuts…) was to be found squirrels groups began to form and move in search of food, gathering more squirrels as they went. It must have been an impressive site- but to early farmers with ripening crops a potential disaster.
The days of such mass movements have long been gone from Indiana, but similar movements on a much smaller scale may still occur in areas of the eastern United States with vast areas of suitable woodlands. Want to learn more, check out the ‘great squirrel stampede’ which occurred in central Indiana in 1882.
Question 2: Something has made a row of small ¼ inch, oblong holes in a straight horizontal line on some sugar maples in my woods. Any thoughts of what it might be?
Answer: Your description is a perfect description of damage that can be found broadly across Southern Indiana and much of the Eastern US. Fortunately, it is not caused by some exotic invasive species like the Asian Longhorned Beetle, which can be quite damaging, or any other wood boring insect. The culprit is the Yellow-bellied Sapsucker, a small to medium sized (red capped-yellow breasted) woodpecker, relatively common throughout the southern half of Indiana. As a youth when I heard someone talk of the Yellow-bellied Sapsucker, I thought it was some made up bird with a wild and crazy name- but a name I never forgot. It was not until forestry school that I learned this strange sounding bird was actually real! The sapsucker, much like you say, creates a series of round to oblong holes in straight lines across the tree trunk just beyond the bark and into the cambium (sap) layer of the tree to induce sap flow. The ‘sap sucker’ then feeds upon the rich, nutritious sap and insects that may be attracted to the sweet treat. They will periodically refresh the wound to keep the sap flowing and even return to the same tree year after year creating new sapwells. Damage is normally non-threatening to the tree, but heavy damage (many rows of sapwells) may open the tree to secondary pests and tree decline. Favored tree species of the sapsucker are those with higher sugar content, including sugar maple, apple, pear and some pine species. Interesting sidenotes: Hummingbirds will also seek out the sapsucker sapwells for nutrition in early spring before other flower sources are available. And, unlike Indiana’s other woodpeckers the Yellow-bellied Sapsucker is a migratory species with Southern Indiana being within its’ winter range and Canada its’ summer range.
Dan Ernst is a professional forester and past Assistant State Forester with the Indiana Division of Forestry. He has authored ‘Ask the Steward’ since 1992 and can be reached at foresterdan@yahoo.com.