Mice can enter your home through very small holes. You don't want your dryer vent to become a thoroughfare for these pesky rodents. This is a guide about keeping mice out of a dryer vent.
I'm having trouble keeping mice out of my dryer vent. They sneak right in through the louvers.
Granny from El Paso, IL
I bought a plastic cover that just screws into the wall. It covers it but has small slits for the air to vent so nothing can get through it. Very cheap fix.
Attach a piece of metal window screening to the pipe. Just make sure to clean the lint so the vent does not get clogged, or it can pose a fire hazard.
a metal grate or strong mesh with games no bigger than 1/5 of an inch will go a long way to keeping them out.
Also, you can get rat bait stations and bait from a do it yourself pest control store fairly cheap now a days and put it a few feet away from the vent (look for grease stains around the vent to see where they traffic) and wipe them out for good.
Hardware cloth is great for keeping mice out. You can find large rolls of 1/2 inch, chrome or nickle plated 23 gauge hardware cloth that will keep them out. Steel wool is good, too, but be sure to secure it or the mice will just push/pull it out.