If you live in a more natural area like I do, consider adding several feet of hardware cloth or fine screen to an existing fence. (drnelsonsveterinaryblog.com)
You'll need to modify the lids for proper ventilation by cutting a large hole in the center of the lid and replacing it with hardware cloth. (smallanimalchanel.com)
Coyotes dig extraordinarily well, so hardware cloth sunk 2 feet at the base of the fence is recommended. (morenapethospital.com)