Grizzly Bear Gestation Period: How Long Is a Grizzly Bear Pregnant?

How long is a grizzly bear pregnant?

A grizzly bear carries her cub for an average of 235 days, or about 7 months and 3 weeks. Counting from the breeding date, birthing is normal anywhere from day 180 to day 250.

Key checkpoints across the 235-day grizzly bear gestation, measured in days from breeding:

Estimate your grizzly bear's birthing date

Enter the breeding date for an estimated birthing date at 235 days.

Grizzly bear gestation stages, month by month

Signs a grizzly bear is pregnant

• Mating seen in late spring or early summer
• Heavy autumn feeding and a large build-up of fat
• Pregnancy cannot be seen from outside during delayed implantation
• Hormone tests in managed care can suggest pregnancy, but are less reliable than in many species

Signs of approaching birthing

• The female entering her den, sometimes earlier than males
• Spring emergence with cubs is often the first confirmation in the wild
• Contact your vet if labour stalls, if the animal strains without progress, or if there is abnormal discharge before birthing begins.

What affects grizzly bear gestation length

• From mating to birth, a grizzly bear pregnancy usually lasts around six to eight months, but most of that time is a pause called delayed implantation.
• Grizzlies mate from roughly May to July. The embryo does not implant until late autumn, around when the female enters her den.
• Implantation only goes ahead if the female has built up enough fat over summer and autumn. A thin bear may not give birth that winter at all.
• Once the embryo implants, active development takes only about two months, so cubs are born tiny, at roughly 0.5 kg, in January or February while the mother is in the den.
• Litters are usually one to three cubs, most often two. The cubs nurse in the den and come out with their mother in spring.
• Cubs stay with their mother for around two to three years, so females typically breed only every three years or more.

Grizzly bear gestation chart

Every fifth breeding date across the year with the matching birthing date, calculated at 235 days. Find the row closest to the date the grizzly bear was served; because normal gestation spans 180 to 250 days, plan for a window of a few days either side. Filter by month, or print the chart for the barn wall or breeding record: navigation, buttons and adverts are hidden on paper.

Sources for grizzly bear gestation figures

Figures on this page are drawn from U.S. Fish and Wildlife Service and National Park Service grizzly bear information, and published research on bear reproduction and delayed implantation, and checked against the references below. Averages describe healthy animals under normal management; individual animals vary, and nothing here replaces advice from your vet.

• U.S. Fish and Wildlife Service — grizzly bear recovery information
• National Park Service — bear biology pages for parks such as Yellowstone
• Association of Zoos and Aquariums (AZA) — species husbandry and animal care manuals
• Smithsonian's National Zoo & Conservation Biology Institute — species fact sheets
• Published zoological studies of captive births