Tag: Denver wildlife calendar

Denver’s Wildlife Calendar — A Month-by-Month Guide

Denver’s wildlife doesn’t operate on a human schedule, but it does follow remarkably predictable seasonal patterns. Understanding when different species are most active — and when they’re most likely to cause conflicts with homeowners — allows Denver residents to take preventive action before problems develop. This month-by-month guide covers the species most commonly involved in residential wildlife conflicts across the Denver metro area.

Winter: January Through March

January – February: The quietest months for most wildlife conflicts in Denver, but not entirely dormant. Great horned owls begin nesting in January — the earliest nesting raptor in Denver. Coyotes enter their mating season, and vocalizations (howling and yip-howling) increase dramatically during evening hours. Mule deer are at their lowest elevation, concentrated in Denver’s western suburbs where they browse on ornamental plantings.

March: The first true transition month. Raccoon mating season begins in late February and continues through March, with males ranging widely and sometimes entering structures they wouldn’t normally investigate. Skunks emerge from winter dormancy and begin searching for mates — skunk odor complaints spike across Denver as males spray during territorial disputes. Squirrels begin their first of two annual breeding cycles.

Spring: April Through June

April: Wildlife activity accelerates rapidly. Raccoon females begin selecting denning sites for their spring litters — attics, chimneys, and crawl spaces become targets. Fox vixens give birth in their dens, and fox families become conspicuous in Denver neighborhoods as adults increase foraging activity to feed nursing kits. Migratory songbirds return and begin nest-building on residential structures.

May: Peak conflict month for many species. Raccoon kits are born and mothers become highly defensive of attic den sites. Squirrel spring litters are active in attics. The bat maternity exclusion blackout begins on May 1st, prohibiting bat removal from Denver structures until August 16th. Bird nesting activity is at its highest on residential structures.

June: Baby wildlife is everywhere. Young raccoons begin exploring outside den sites. Fox kits emerge and play visibly near den entrances. Fledgling birds leave nests and appear “abandoned” on the ground — in most cases, parents are nearby and the young should be left alone. Skunk kits begin accompanying their mothers on foraging trips at dusk.

Summer: July Through September

July – August: Wildlife families begin dispersing. Juvenile raccoons start ranging independently from their mothers. Young coyotes explore beyond their natal territories. The bat exclusion window reopens on August 16th — Denver homeowners who discovered bat colonies in spring can now schedule professional exclusion work. Beaver activity on Denver waterways is visible as families maintain and expand their dams and lodges.

September: Fall preparation begins. Squirrels enter their second breeding cycle and become aggressive about claiming attic spaces. Raccoons increase foraging to build winter fat reserves. Mice and rats begin seeking indoor shelter as nighttime temperatures drop — the beginning of rodent infestation season in Denver homes.

Fall: October Through December

October – November: Mule deer rut (breeding season) begins, and deer-vehicle collisions surge across the Denver metro area. Coyotes form winter hunting partnerships and expand their ranging territories. Mice and rat intrusions into Denver homes accelerate as cold weather arrives. This is the ideal time to schedule preventive exclusion work on your home before spring wildlife conflicts begin.

December: Most nuisance wildlife activity decreases. Skunks enter semi-dormancy, emerging only during warm spells. Raccoons reduce activity but do not truly hibernate. Squirrels remain active year-round but are less likely to seek new den sites in mid-winter. December through February is the optimal window for sealing potential wildlife entry points on Denver homes, as most species are less likely to be actively using structures during this period.