When Do Squirrels Mate? The Two Seasons and the Chases

Grey squirrels breed twice a year, in midwinter and midsummer. What the frantic spiral chases mean, and why babies appear in your attic in February.

By Zakaria September 21, 2026 4 min read Save to Pinterest

A grey squirrel clinging partway up a broad tree trunk, looking upward into the canopy — Photo: Dominic Nelson, CC BY-SA 4.0, via Wikimedia Commons

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Squirrels breed twice a year, in midwinter and midsummer — which is why the chases start in January, and why something is scratching in the attic by late February.

The short answer

Eastern grey and fox squirrels breed twice a year, from December to February and again from May to July. Gestation is about 44 days, so litters of two to four kits arrive in late February to March and in July to August. The spiralling chases seen in January and June are several males following a female who is receptive for less than a day. Males leave after mating and take no part in raising young. Red squirrels usually manage only one litter a year. The winter season is why pregnant females move into attics in December and January.

Two seasons: Dec–Feb and May–July
44 days gestation — kits in late Feb–March, and July–August
The chases are courtship, not fighting. She is receptive under a day
Males leave. The female raises the litter alone
Winter breeding is why attics get occupied in December and January

The calendar

Breeding seasons by species

Species	Seasons	Litters born
Eastern grey	Dec–Feb, May–July	Late Feb–Mar, Jul–Aug
Fox squirrel	Dec–Feb, May–June	Feb–Mar, Jul
Red squirrel	Late winter–spring, usually once	Mar–May
Flying squirrel	Spring, late summer	Apr–May, Aug–Sep
Ground squirrels	Once, after emerging from hibernation	Spring

Timing shifts a few weeks with latitude, and with the previous autumn’s nut crop — a good mast year brings females into condition earlier and produces more and larger litters. A bad one can cut a population to a single season.

The chases

The part everyone sees. From a distance it reads as a fight; it is not.

A female is receptive for less than a day, once per season
She advertises it by scent and by calling
Several males detect it and converge, sometimes from a considerable distance
The spiralling chase up, around and down trunks is the males competing for position while she leads
Aggression is brief. Staying with her matters more than driving the others off
Peaks in January and June, and is impossible to miss in a bare winter canopy

It is not squirrels playing, and not squirrels fighting

Both explanations circulate. What you are watching in January is a breeding chase — a single female and the males that found her.

The giveaway is the number: one animal in front, several behind, all moving in the same direction at speed.

After mating

Mating is brief, repeated with more than one male, and a single litter commonly has multiple fathers.

The male then leaves entirely. He builds nothing, feeds nothing and defends nothing. The female:

Prepares a nest — a tree cavity by preference, a leaf drey otherwise
Carries for about 44 days
Gives birth to two to four kits, blind, deaf, hairless, about an inch long
Nurses alone, leaving only to feed herself

The first three months

Age	Stage
Birth	Blind, deaf, hairless, ~1 in
2 weeks	Fur coming in
4 weeks	Eyes open
6–7 weeks	First trips out of the nest
10–12 weeks	Weaned
3–4 months	Independent

Females often move a litter — carrying kits one at a time by the scruff — if the nest is disturbed, infested with fleas, or found by a predator. A squirrel crossing a lawn with something in its mouth in March is usually doing exactly that.

Why this matters for your roof

The winter season puts pregnant females looking for cavities in December and January. An attic is warm, dry, high, and nothing can climb to it — from a squirrel’s point of view it is the best tree in the neighbourhood.

Do not seal an entry hole in late winter

Block it in February and you may be sealing a litter inside the roof. They die there, and you will then have a second problem in the walls, along with a frantic mother chewing new holes to get back in.

Check for young before closing anything. Do exclusion work in autumn, between the two seasons, when no litter is in residence.

The workable order:

Autumn — proof the roof. Cut back branches within ten feet, cap vents, mesh soffits and fascia gaps, repair rotten boards
Late winter, if you are already too late — get a professional to check for kits, and use a one-way exclusion door once the young are mobile
Never trap and remove a nursing female and leave her litter behind

Population, and why it is slower than it sounds

Two litters of two to four looks like an explosion. It is not:

First-year mortality is high — commonly over half, sometimes far more
Young females often manage only the summer litter in their first year
A poor mast year suppresses breeding outright
Predation, cars, disease and hard winters take the rest

A squirrel that survives its first year can live six or more in the wild. Most do not get there, and that is the number the two seasons are compensating for.

Common questions

When do squirrels mate?

Eastern grey squirrels have two breeding seasons a year. The first runs from roughly December through February and the second from May through July, which puts litters on the ground in late February to March and again in July to August. Fox squirrels follow much the same calendar. Red squirrels usually manage only one litter, in late winter or spring, and flying squirrels breed in spring and again in late summer. Exact timing shifts a few weeks with latitude and with how good the previous autumn's nut crop was.

Why are squirrels chasing each other around trees?

That is mating behaviour, and it is the most visible part of the whole process. A female is receptive for less than a day, so when she comes into oestrus several males detect it and follow her, and the spiralling chase up and down trunks is them competing for position while she leads. It looks like fighting and is mostly not — genuine aggression between the males is brief and secondary to keeping up with her. Chases peak in January and again in June.

When do squirrels have babies?

About 44 days after mating, so late February through March from the winter season and July through August from the summer one. A litter is typically two to four kits, born blind, deaf and hairless in a tree cavity or a leaf drey. They open their eyes at around four weeks, first venture out at six to seven, and are weaned by ten to twelve weeks. That February timing is exactly why attic noises start in late winter and why the young are so often heard before they are seen.

How do squirrels mate?

The female signals receptivity by scent and by calling, and males gather and follow her through the canopy in the chase everyone notices. Mating itself is brief, repeated, and not exclusive — a single litter commonly has more than one father. Afterwards the male leaves entirely: he contributes nothing to the nest or the young, and the female raises the litter alone, which is why a nest disturbance in spring is always a female's problem to solve.

How many times a year do squirrels breed?

Twice, for grey and fox squirrels in most of their range, though a young female in her first year often manages only the summer litter and a poor food year can reduce the whole population to one. Red squirrels typically breed once. Two litters of two to four kits is the upper end of what a healthy female produces annually, and mortality in the first year is high enough that populations grow far more slowly than the arithmetic suggests.

Why do squirrels get into attics in winter?

Because the winter mating season puts pregnant females looking for nest sites in December and January, and an attic is a warm, dry, predator-proof tree cavity as far as a squirrel is concerned. This is the single most common reason squirrels appear in a roof, and it is also why exclusion work has to be timed carefully — sealing an entry point in February can trap a litter inside. Check for young before closing anything, and do the proofing in autumn instead.

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An eastern gray squirrel gripping the bark of a tree trunk

Backyard Animals · Sep 6, 2026