Rumor has it that Squirrels don't like strobe lights. See for example: ​https://www.evictor.com/products/10k

This thing is fine but requires AC power and costs $150. I'm thinking much cheaper flashers made of high-power LEDs. Digikey has a bunch from Bridgelux which seem possible, e.g.:

BXRE-40E6500-C-73  @ $14.64 ea

  nom 1440mA 52V  75W  12,400lm
  max 2800mA 56V  161W 22,000lm

See ​datasheet

Maybe a 1000uF capacitor charged to a programmable voltage in the 52-56V range discharged through the LED through a MOSFET?