If you’ve ever seen those cute little striped furballs scurrying around your backyard or garden, you were likely looking at a chipmunk. Chipmunks are small rodents that are closely related to squirrels, and they can be found across most of North America.
If you’re short on time, here’s a quick answer to your question: Chipmunk breeding season lasts from early spring through mid summer, so baby chipmunks (called kits or pups) are usually born between March and August depending on the climate.
Chipmunk Breeding Season
Early Spring Mating
Chipmunks emerge from hibernation in early spring, usually in March or April, when temperatures begin to warm up. This signals the start of their breeding season. Male chipmunks wake up first and start preparing for mating by cleaning out their burrows. Females emerge a few weeks later.
Once the females wake up, the male chipmunks compete for their attention through mating rituals like chasing each other around. The dominant males mate with multiple female partners. Mating typically occurs in early spring, with most babies born in late April or May.
The exact timing depends on the local climate and elevation.
Pregnancy and Gestation Period
After successful mating, the female chipmunk is pregnant for about 30-31 days before giving birth. Their gestation period is around one month long. During this time, the pregnant female works hard to build an underground nest in preparation for the arrival of her babies.
She digs burrows that are up to 30 feet long and lines the nest with soft plant material like leaves, grass, moss, and bark to keep the newborns warm and safe. The nest chamber is typically 8 to 10 inches underground.
Building a secure birthing nest is crucial to protecting the vulnerable newborn chipmunks.
Baby Chipmunk Birth Season
Most baby chipmunks are born in late spring, between April and June. The average chipmunk litter contains 4 to 5 babies, though they may have as many as 8. The babies are called kits or pups. They are born hairless, blind, and totally dependent on their mother.
For the first 6 to 8 weeks, the kits remain protected in the underground burrow, nursing and growing stronger. Around mid-summer, the kits open their eyes, develop fur, and start venturing out of the nest.
By late summer, around 10 to 12 weeks old, the young chipmunks are ready to fully emerge and start foraging on their own.
The breeding season allows chipmunk babies to be born at the optimal time when food is abundant. With spring underway, there are plenty of nuts, seeds, fruits, and vegetation for the mothers to eat while nursing and for the kits to eat as they wean off milk and transition to solid foods.
The presence of ample food in summer and early fall allows the young chipmunks to quickly grow, develop, and build up fat reserves before entering their first winter hibernation.
Raising Baby Chipmunks
Caring for Kits in the Den
After a 30-32 day gestation period, baby chipmunks known as “kits”, are born in the mother’s underground den. The average litter size is 4 or 5 kits. The kits will remain in the den for the first six to eight weeks of life, relying exclusively on their mother’s milk and care while their eyes open, their fur grows in, and they develop the strength and coordination to emerge from the burrow.
The mother chipmunk spends nearly 100% of her time underground caring for the helpless kits during this period. She nurses, cleans, and protects the kits until their eyes open and they develop more independence. The father chipmunk does not assist with rearing the young.
By about six weeks old, the kits will begin eating insects and seeds brought to them by their mother to supplement nursing.
Weaning and Emerging from the Den
At around eight weeks old, the kits are ready to emerge from the den and begin transitioning from their mother’s milk to other foods. They will play near the den entrance, venturing further out each day to forage on their own.
They are still nursing some at this stage but become fully weaned over the next few weeks as they gain complete independence.
The kits remain vulnerable as they learn to survive on their own. Having multiple kits in the litter helps ensure the survival of the species since some young often do not make it through weaning. By late summer, the now fully mature young chipmunks will leave their mother’s territory to establish their own territory before winter settles in.
Identifying Baby Chipmunks
Size Difference from Adults
One of the most obvious ways to identify baby chipmunks is by their small size. Newborn chipmunks weigh just 2 to 5 grams, about the size of a grape. They are born hairless and with their eyes closed. Within a couple weeks of being born, baby chipmunks grow fur and open their eyes, but they still only weigh 10 to 15 grams, similar in size to a large walnut.
It takes nearly 2 months for baby chipmunks to reach adult size, weighing around 50 to 65 grams when fully grown, similar in size to a golf ball. So if you spot a tiny chipmunk that can fit in the palm of your hand, it’s likely a baby.
In addition to their miniature size, baby chipmunks have proportionately larger heads and feet compared to their body size. Their tails are also stubbier and less bushy than adult chipmunks. So if you see an especially tiny chipmunk with big paws, a large head, and a short skinny tail, there’s a good chance it’s a baby.
Fur Color and Markings
Another way to identify infant chipmunks is by their fur color and markings. Baby chipmunks are born with a pale gray coat. Within a couple weeks, their fur turns reddish-brown or grayish-brown. The characteristic stripes of chipmunks don’t appear until the babies are around 6 to 8 weeks old.
At first, the stripes are faint and incomplete, but they become more defined and blackish in color as the babies mature.
In comparison, adult chipmunks tend to have more sharply defined black and white stripes running from head to tail. So if you notice a chipmunk with blurry, light brown stripes, it’s likely a juvenile.
However, fur color can vary somewhat between different species and geographic regions, so body size and proportions are a more reliable indicator.
| Age | Size | Fur Color and Markings |
|---|---|---|
| Newborn | 2-5 grams, hairless, eyes closed | Pinkish gray |
| 2 weeks | 10-15 grams | Reddish brown, faint stripes appear |
| 6-8 weeks | 20-30 grams | Grayish brown, stripes more defined |
| Adult | 50-65 grams | Sharply defined black and white stripes |
Interacting with Baby Chipmunks
Leaving Kits Alone
When you come across baby chipmunks, known as kits, it’s best to leave them alone. Kits are highly dependent on their mothers for survival in their first few weeks. If you notice kits outside of the burrow, don’t assume they have been abandoned.
The mother chipmunk likely stashed them there temporarily while she gathers food. She will return to nurse and care for the youngsters every few hours. Attempting to rescue healthy kits often does more harm than good.
According to wildlife experts, kits found alone outside may appear orphaned, but their mother is likely nearby. She is probably waiting for potential predators to leave before collecting them. If the kits are quiet, uninjured, and sheltered, the best course of action is to leave the area so the mother feels safe returning.
Any human scent or contact could cause her to abandon the nest. Healthy baby chipmunks should never be taken from the wild. Their survival rates are extremely low without the nurturing only a mother chipmunk can provide.
Avoiding Danger to Babies
There are a few key things you can do to avoid endangering baby chipmunks around your home. First, look before you mow or use heavy landscaping equipment from spring through fall when kits may be stashed in burrows or vegetation.
Accidentally striking a nest could orphan the litter or injure the mother at a critical time. Next, cap any open pipes or window wells kits may fall into and not be able to escape. Finally, keep pets like dogs and cats away from areas frequented by chipmunks.
Even supervised pets could frighten a mother chipmunk away or lead predators right to her helpless offspring.
When it comes to protecting baby chipmunks, an ounce of prevention is worth a pound of cure. Something as simple as mowing higher could make all the difference for a hidden litter. Since chipmunk mothers routinely leave babies unattended to find sustenance, our best course of action is simply to leave found kits be.
Assuming they appear healthy, the mother will return in time. With some thoughtful precautions, we can coexist safely with these tiny spring surprises and their nests.
Conclusion
Now you know all about when chipmunks give birth and raise their young kits. The breeding, pregnancy, and birthing timeline spans early spring through mid summer across most chipmunk habitats.
Understanding their reproduction cycle and how to identify baby chipmunks can help you coexist safely with these cute backyard critters.
