Winter (Dec–Feb)
Mice and pack rats move into attics, crawlspaces, garages and vehicles. Skunks begin breeding in late winter. This is a good time for interior inspections and cleanup.
Spring (Mar–May)
Raccoon, skunk and squirrel young are born. Snakes become active as it warms up. Plague activity in wild rodents tends to rise from spring into fall, according to NMDOH. Exclusion has to be timed to protect young animals.
Summer (Jun–Aug)
Bat maternity season: no bat exclusions until the pups can fly. Snakes are active. Rodent activity continues, and it's a good time for roofline and foundation sealing on homes without bats.
Fall (Sep–Nov)
The biggest season for rodent entry as nights get cold, especially at higher elevations like Los Alamos and Pecos. Late summer and early fall, after the young bats can fly, is a common time for bat exclusion. It's also the best time for whole-home sealing before winter.
Frequently asked questions
When is the best time to seal my home?
Late summer through fall, before rodents move indoors for the winter. If bats are present, timing depends on maternity season.
When are baby animals most likely in my attic or under my deck?
Spring and early summer for most species. Squirrels may have a second litter in late summer.
Why can't bats be excluded in summer?
Pups can't fly yet, so exclusion would seal them inside.
Sources
- NM Dept. of Health: Plague
- CDC: Preventing Rabies from Bats
- NM Dept. of Game & Fish (NMDOW): Living With Wildlife
- CDC: Hantavirus Prevention
This page is general information, not medical, legal or regulatory advice. For health concerns, contact a healthcare provider or the NM Department of Health. For wildlife regulations, contact NM Game & Fish (NMDOW). Last reviewed Oct 2026.
