What Is a Baby Bear Called? Bear Cubs and Their Mothers

Cub, sow, boar: bear family names

Young bears of every species are called cubs. A female bear is a sow and a male bear is a boar, the same words used for pigs. Wildlife biologists often call cubs in their first year “cubs of the year,” and a bear in its second year a “yearling.” Young bears that have recently left their mothers but are not yet fully grown are called subadults.

The father plays no role. Bears are solitary and mate for only a few days or weeks in early summer, then go their separate ways, so a mother raises her cubs entirely alone.

Born in a winter den

Bear cubs are born in January or February in black and brown bears, and from November to January in polar bears, while the mother is in her winter den. This timing is possible because of delayed implantation: bears mate in late spring or early summer, but the embryo does not attach to the womb and start growing until autumn, and only if the mother has stored enough fat. Real development takes only about two months. You can read about the den itself in do bears hibernate?

Newborn cubs are tiny compared with their mothers. A black bear cub weighs about 280–450 g (10–16 oz) and is roughly 20 cm (8 in) long, and newborn brown bear cubs weigh about 350–510 g (12–18 oz). That is less than 1% of the mother’s weight, a smaller ratio than in almost any other placental mammal. The cubs’ eyes are closed, they have only fine, short hair, and they cannot walk.

Growing up in the den

For the first months of life, cubs do little but sleep and nurse. Bear milk is very rich in fat, and the mother produces it without eating or drinking anything herself. Black bear cubs open their eyes at about four to six weeks and start to walk at about five weeks.

By the time they leave the den in April or May, black bear cubs typically weigh about 2–5 kg (4–11 lb). Brown bear cubs leave the den at roughly 7–9 kg (15–20 lb) by early summer. The family often stays near the den for a few days while the cubs gain strength.

Learning to be a bear

Cubs do not inherit a list of foods or skills; they learn by following and copying their mother. Over their first summer and autumn they learn which plants, berries, nuts and insects are worth eating, where to find them in each season, how to dig, fish or catch fawns, and where to den. They also learn which places to avoid.

Black bear cubs nurse for about six to eight months, but they start eating solid food in their first summer. They spend their first winter in the den with their mother, then separate from her in late spring or early summer of their second year, at about 16–18 months. The mother then mates again and usually has her next litter the following winter, so most black bear sows breed every two years.

Brown bear cubs stay longer. In North America they remain with their mother for an average of about two and a half years, and some stay until they are four. That longer childhood means brown bear sows usually have a litter only every three or four years.

Dangers for bear cubs

Many cubs do not survive their first year. Starvation in poor food years, accidents, disease and predators all take a toll. Wolves, cougars, coyotes and bobcats can kill young black bear cubs, and spring floods sometimes drown newborn cubs in low-lying dens.

One of the biggest threats comes from adult male bears. Males sometimes kill cubs that are not their own, which brings the mother back into breeding condition. Mothers defend their cubs fiercely, and black bear cubs escape by scrambling up trees, where their mother sends them at the first sign of danger. Brown bear mothers, which often live in more open country with fewer trees, tend to rely more on standing their ground.

Across North America, roughly 60% of black bear cubs live to see their first birthday. Bears that survive cubhood can live for decades, as explained in how long do bears live?

Bear cubs and people

Spring and early summer are when people most often see bear cubs, and a cub alone is rarely truly alone: its mother is usually nearby and may be very protective. Never approach, follow or try to feed a cub. If you find a cub that seems to be orphaned or injured, keep away and contact your local wildlife agency rather than handling it yourself.