What did this...?

[The Big Lebowski]

My guess, a woodpecker... Never seen so many uniform holes though.

 

[Mesquite]

A woodpecker with OCD?

 

[Ivan...]

My guess, a squirrel with an uzi 9mm ( 600 rounds per minute ! )

 

[Hugo]

Well Leb, I and Kepis found the same thing on a group of trees whilst out for a bimble awhile back.
On the inner bark there were some sighs of grub larvae.
Be interesting to know what others think it is.

 

[geordienemisis]

I have read that a woodpecker called the Sapsucker has made similar holes in other trees (Bur Oak). From what I have found out they are prevalent in the UK, there is quite a bit of info. Just Google Sapsucker. I think that has nailed it (Pardon the pun)

 

[The Big Lebowski]

Hmmmm, good call geordie.... Just looked up sapsucker, and although is says habitat south America or the Caribbean. This is its call sign.

Some cracking alternative theory's though