Why won't the exterminator remove bats in June?

Because it's illegal and inhumane during maternity season. NH Fish & Game and UNH Extension are explicit: do not exclude bats from mid-May through mid-August, when flightless pups would be sealed inside and starve. A licensed Wildlife Control Operator will wait until mid-August, after young are flying, before installing exclusion devices, even if that means living with the colony a few more weeks.

Can I remove bats from my attic in winter?

Generally no. Little brown bats are typically off in hibernacula by then, but big brown bats may be hibernating directly in your walls or attic insulation. Sealing during winter — roughly November through late March or mid-April — can entomb hibernating bats inside the structure, where they die and create a serious odor problem. It's best to wait for the fall window or the period after mid-August, per NH Fish & Game guidance.

A bat is flying outside in winter — is that normal?

For big brown bats, yes. They sometimes hibernate in buildings and periodically rouse to fly on warm winter days in search of a quick snack, so bats seen in a neighborhood in winter are usually big browns. That said, a bat that's active and struggling by day in cold weather may be a victim of white-nose syndrome rather than a healthy bat out for a snack.

Are bats protected in New Hampshire?

Yes. All eight NH bat species are considered of conservation concern, with the little brown, tricolored, eastern small-footed, and northern long-eared bats listed as state endangered. The northern long-eared bat was also reclassified as federally endangered by the U.S. Fish and Wildlife Service, effective March 31, 2023. You cannot legally kill bats or exclude them outside the approved window, and any exclusion work must be handled by a licensed NH Wildlife Control Operator.

A bat got into my bedroom — what do I do?

Don't touch it with bare hands. If it was in a room with a sleeping person or child, or if anyone had direct contact with it, call the NH DHHS Bureau of Infectious Disease Control at 603-271-4496 and see a doctor — and don't release the bat, since it needs to be kept for rabies testing. This protocol applies any time bare-hand contact or sleeping-room exposure is possible.

When do bats come back in spring?

New Hampshire's bat hibernation runs roughly November through April. Some individuals emerge as early as late March, but most don't return to activity until mid-April. Females then form maternity colonies in May, which restarts the protected maternity season and the mid-May exclusion ban — so any exclusion project must be finished well before females settle in for the summer, or it will have to wait until the following fall.

What is white-nose syndrome?

It's a fungal disease, first documented in New Hampshire during the winter of 2008–09, that repeatedly rouses hibernating bats and burns through the fat reserves they need to survive winter, often leading to starvation. It has cut some NH cave-bat populations by nearly 99% — little brown bat hibernacula counts fell from 3,135 in 2008 to just one in 2018 — which is a major reason maternity colonies are so strictly protected today.

How do I find the bats' entry points?

In July, watch your house at dusk and note exactly where bats emerge — those gaps are your entry points. Then, after mid-August, a licensed Wildlife Control Operator can install one-way exclusion doors so bats can leave but not return, confirm the space is empty, and permanently seal the openings once the colony has fully cleared out. Common entry points include roofline gaps, soffit joints, and chimney flashing.

Five of New Hampshire's eight bat species hibernate — little brown, big brown, northern long-eared, eastern small-footed, and tricolored bats — mostly in caves and mines held at a stable 40–50°F, though big brown bats may also hibernate in buildings. The remaining three species migrate south for the winter instead. NH hibernation runs November through April, per NH Fish & Game surveys of the state's hibernacula.

Daniel Brady · NH-Licensed Pesticide Applicator · License #782664

|Reviewed by Daniel Brady

When Do Bats Leave the Attic? NH Legal Timing Guide

Overwintering Wildlife

Bats in New Hampshire generally leave the attic in mid-August, once young are flying and the colony begins to break up ahead of winter. That makes mid-August through October the only legal, humane window to exclude them — never during the mid-May-through-mid-August maternity season, when flightless pups would be sealed in and die, and never during winter hibernation (roughly November–April), when sealing can entomb hibernating bats. NH Wildlife Control Operators may install one-way exclusion doors but may not exterminate bats; all NH bat species are protected.

At a glance

Maternity season: Pups present mid-May to mid-AugustOne pup/year, born ~June; pups fly in July but roost weeks longer — NO exclusion allowed — NH Fish & Game / UNH Extension
Legal exclusion window: Mid-August through OctoberBats leave for winter quarters; use one-way doors after confirming all bats are out — NH Fish & Game
Winter strategy: Little brown bats → hibernacula; big brown bats → caves, mines, or buildingsHibernacula run 40–50°F, >80% humidity; NH hibernation is November–April — NH Fish & Game
White-nose syndrome: NH cave bats down nearly 99% for some speciesFirst documented in NH winter 2008–09; hibernacula mortality 79–100% — UNH Extension / NH Fish & Game

Maternity season
Pups present mid-May to mid-August
One pup/year, born ~June; pups fly in July but roost weeks longer — NO exclusion allowed — NH Fish & Game / UNH Extension
Legal exclusion window
Mid-August through October
Bats leave for winter quarters; use one-way doors after confirming all bats are out — NH Fish & Game
Winter strategy
Little brown bats → hibernacula; big brown bats → caves, mines, or buildings
Hibernacula run 40–50°F, >80% humidity; NH hibernation is November–April — NH Fish & Game
White-nose syndrome
NH cave bats down nearly 99% for some species
First documented in NH winter 2008–09; hibernacula mortality 79–100% — UNH Extension / NH Fish & Game

The timing answer

The short of it

The verdict · overwintering wildlife

Legal exclusion only mid-Aug–Oct (never mid-May–mid-Aug)

In New Hampshire, bats generally leave the attic in mid-August to seek winter quarters — and mid-August through October is the ONLY legal, humane exclusion window; removal is banned during the mid-May–mid-August maternity season.

NH activity calendar

When are they active — the whole year at a glance

This calendar tracks legal status alongside presence, not just 'pest risk' — the mid-May–mid-August maternity ban and the mid-August–October legal exclusion window are the two dates that matter most for homeowners.

12-month activity · New Hampshire

Peak · Jun, JulYou are here · Aug

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

PeakActiveBuildingDecliningDormantCurrent season · Summer

Best window to act · Late August through October — after young are flying and before hibernation begins. In July, scout dusk exit points to identify entry holes ahead of time. NEVER exclude bats mid-May through mid-August or during winter hibernation.

What else peaks thenJun Jul

Levels here track presence and legal status, not pest pressure. NH hibernation runs November–April, per NH Fish & Game; the legal exclusion window is mid-August through October, anchored ahead of Manchester's ~Oct 19 first frost (NOAA 1991–2020).

Where they go in winter

Winter behavior

Bats in New Hampshire split into two very different winter strategies, and knowing which one applies to the bats in your attic matters for both biology and the law.

Overwintering strategy

Hibernates

Little brown bats migrate to caves and mines — hibernacula that stay a stable 40–50°F with over 80% humidity. Big brown bats hibernate in caves, mines, OR buildings, including attics, wall voids, and under insulation. Three of New Hampshire's eight species migrate south instead of hibernating.

Move in
Bats settle into winter roosts in November; hibernation runs November through April.
Hibernates
Little brown bats migrate to caves and mines — hibernacula that stay a stable 40–50°F with over 80% humidity. Big brown bats hibernate in caves, mines, OR buildings, including attics, wall voids, and under insulation. Three of New Hampshire's eight species migrate south instead of hibernating.
Spring exit
Most bats emerge by mid-April, with some individuals appearing as early as late March. Females then form maternity colonies in May, which restarts the protected maternity season and the exclusion ban.

Season by season

A year in the life

A New Hampshire bat's year is governed as much by law as by biology — the two line up, but the legal window is narrower than the biological one.

01
Spring
Bats emerge from hibernation in March and April, with most out by mid-April. Females then form maternity colonies in May, which triggers the start of the mid-May exclusion moratorium — no removal work should begin from this point forward.
02
Summer
Pups are born around June and begin flying in late July, but they still roost in the attic for several more weeks after that. Exclusion remains illegal for the entire maternity season, through mid-August, because flightless or newly flying pups could be trapped and die.
03
Fall
Bats swarm, mate, and fatten up through September and October — the single best exclusion window of the year, opening in mid-August once the colony has broken up and before hibernation begins.
04
Winter
Hibernation runs roughly November through April. Little brown bats retreat to hibernacula, but big brown bats may be hibernating directly in your walls or attic insulation, which is why winter exclusion is discouraged — sealing then can entomb hibernating bats. A big brown bat flying on a warm winter day is normal, not cause for alarm.

New Hampshire context

Bats in southern New Hampshire

All eight New Hampshire bat species are of conservation concern, and white-nose syndrome has devastated cave-hibernating populations across the state since it was first documented in the winter of 2008–09. Because of that collapse, and because several species are state or federally endangered, NH Fish & Game treats bat exclusion as a narrow, legally defined window rather than a homeowner's choice of convenience — Wildlife Control Operators may exclude bats with one-way doors but are not permitted to exterminate them.

Key local data

NH hibernacula counts illustrate the scale of the decline: little brown bat counts fell from 3,135 bats in 2008 to just one in 2018 — a nearly 99% drop for some species — per NH Fish & Game winter hibernacula surveys.

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Southern New Hampshire

When to act

Timing your treatment

Bat exclusion in New Hampshire is one of the most legally constrained pest-timing decisions a homeowner will make — get the window wrong and you risk both animal welfare and legal violations.

The right window

Late August through October — after young are flying and before hibernation begins. In July, scout dusk exit points to identify entry holes ahead of time. NEVER exclude bats mid-May through mid-August or during winter hibernation.

An attic bat colony — hire a licensed NH Wildlife Control Operator, who may perform exclusion only, never extermination

A bat found in a bedroom or any bare-hand contact — a rabies concern; contact NH DHHS Bureau of Infectious Disease Control at 603-271-4496 and a doctor, and do not release the bat

A bat active and struggling by day in cold weather — a possible white-nose syndrome victim

Guano or urine staining plus a dusk emergence pattern at a gap — signs of an active roost worth documenting before the legal window opens

Wildlife & Exclusion

Free inspection and same-day wildlife & exclusion service across southern New Hampshire. NH-licensed #782664. Bat work should always go through a licensed NH Wildlife Control Operator working within the legal window — never DIY removal out of season.

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Learn more about this pest

Common Questions

Frequently asked

Sources & references

NH Fish & Game — Homeowners and Bats
maternity moratorium mid-May–mid-Aug, mid-August exclusion window
NH Fish & Game — Bats of New Hampshire
hibernacula temperature/humidity, hibernating vs. migrating species
NH Fish & Game — White-nose Syndrome
WNS history, hibernacula population decline
NH Fish & Game — SWAP Little Brown Bat
Wildlife Control Operator exclusion-only rule, maternity window
UNH Cooperative Extension — Bats in New Hampshire
maternity exclusion ban, WNS population decline
U.S. Fish & Wildlife Service — Northern Long-Eared Bat
federal endangered status effective March 31, 2023
Federal Register — Northern Long-Eared Bat Final Rule (87 FR 73488)
WNS caused 97–100% declines across 79% of range
NH DHHS — Infectious Disease Control
rabies exposure protocol, Bureau of Infectious Disease Control contact

Editorial disclaimer: This content is provided for informational purposes only and does not constitute pest control advice. Every property is unique — consult a licensed professional for guidance specific to your situation. Anchor Pest Services is licensed in New Hampshire (#782664).

Written & reviewed by

Verified

Daniel Brady

NH-Licensed Pesticide Applicator · License #782664 (NHDAMF, RSA 430)

Daniel Brady is the New Hampshire–licensed applicator behind Anchor Pest Services, a family-owned pest control company serving the Manchester area since 2017.

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Last updated Jul 2026

Anchor Pest Services

Whatever the season — we handle the timing for you.

Same-day service across Southern New Hampshire. NH-licensed #782664, family-owned since 2017. We track the local calendar so you don't have to guess the right window.

Get a Free Inspection (603) 785-0118

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Keep Exploring

When Do Bats Leave the Attic? NH Legal Timing Guide

The short of it

When are they active — the whole year at a glance

Winter behavior

A year in the life

Spring

Summer

Fall

Winter

Bats in southern New Hampshire

Timing your treatment

Frequently asked

Sources & references

Whatever the season — we handle the timing for you.

Your next step

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Where Do Bats Go In The Winter?

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Natural Bird & Bat Control in NH: The Legal Limits That Matter

What Pests Are Actually Active in June in New Hampshire?

When Do Bats Leave the Attic? NH Legal Timing Guide

The short of it

When are they active — the whole year at a glance

Winter behavior

A year in the life

Spring

Summer

Fall

Winter

Bats in southern New Hampshire

Timing your treatment

Frequently asked