What the heck is making these holes?

[Chaos USMC]

Did we ever figure this out?

Great followup, interested to hear what the update might be....

 

[DMW]

Ha! Got the culprit, maybe? Don't even know what this is, but could it chew such nice even holes?

View attachment 610748

Chipmunks. They seem to have spread out their habitat in Ontario the last few years. They are quite destructive for their size.

 

[CoyPatton]

Chipmunks. They seem to have spread out their habitat in Ontario the last few years. They are quite destructive for their size.

Yes chipmunks! Also sometimes called ground squirrels by old timers. I am getting to be one of those I guess. Your holes look like carpenter bees to me. Usually the will chew into boards from the bottom then possibly turn in there bore to run the length of a board. They build nest and then you get a whole new batch.
They can affect the structural integrity of wood. You should be able to spray for them, but it is a continual process.

 

[Loaderman22]

Yes chipmunks! Also sometimes called ground squirrels by old timers. I am getting to be one of those I guess. Your holes look like carpenter bees to me. Usually the will chew into boards from the bottom then possibly turn in there bore to run the length of a board. They build nest and then you get a whole new batch.
They can affect the structural integrity of wood. You should be able to spray for them, but it is a continual process.

I've never seen a rodent ( mouse, rat, squirrel, chipmunk, etc.) chew a hole with smooth sides, there will always be teeth marks. Carpenter bees cut holes that are 3/8" diameter, the OP said these were about 1". Not convinced that these are the answers.

 

[Diggin It]

How they doin' Check?

More?

Less?

 

[jyoutz]

Wood borers

 

[Threepoint]

Wood borers

Yup, definitely!

My lingering question is, what kind? Given the 1" size and apparent pattern, here's my latest
guess.

 

[jyoutz]

Yup, definitely!

My lingering question is, what kind? Given the 1" size and apparent pattern, here's my latest
guess.

View attachment 728242

Wood boring grubs can make large holes.

 

[Loaderman22]

But these holes are 1" diameter with smooth sides, any bug will make the sides a bit rough. And since these holes are evenly spaced and all in a row, I'm sticking to this was an old beam that had a pin in it, boards were sawn from this beam, and after all this time, they finally shrunk and fell out or rotted away.

 

[jyoutz]

But these holes are 1" diameter with smooth sides, any bug will make the sides a bit rough. And since these holes are evenly spaced and all in a row, I'm sticking to this was an old beam that had a pin in it, boards were sawn from this beam, and after all this time, they finally shrunk and fell out or rotted away.

Very well could be. If not, they are probably powder post beetle larvae.