Where My Cubs At?


Why Katmai’s first spring cubs show up when they do…

by David Kopshever, SCA Media Intern for Katmai National Park

ABOVE: 128 and her three COYs walk along the Valley Road. Photo by NPS/Tammy Carmack.

When sows with yearlings and older cubs first begin to show up around Brooks Camp (and on the Bear Cams) each year, some may wonder, “Where are all the spring cubs?” Sows with spring cubs, or cubs of the year (COYs,) are generally the last bears to leave their dens. After emerging they tend to spend their first few weeks around the den site, allowing the COY to slowly explore a bright new world. Sows with spring cubs also tend to avoid unnecessarily visiting areas where other adult bears may be lurking, to avoid the possibility of infanticide. The survival rate for COY’s is around 50%. However, newborn cub development and physiology has adapted in some interesting ways to help give our favorite furry critters a good shot at survival.

After giving birth in the depths of winter, usually during January or February, the sow and cub remain warm in their den for the next two to four months. At birth, a brown bear cub is incredibly small, weighing just one pound and measuring about 9 inches long. That same bear may multiply its weight well over 1,000 times from newborn to adult. Humans would weigh over 6,000 pounds if we shared the same weight increase.

This is what a newborn brown bear cub looks like (NPS illustration).

Nearly bald, completely blind, and very vulnerable, the newborn cub continues to develop in the den – its second womb. Its eyes will remain closed for nearly one month, though almost immediately after birth the newborn cub navigates its way to its mother’s teat, where it suckles on some of the most nutritious baby food on the planet. Bear milk contains roughly 35% fat and over 10% protein. In comparison, human milk contains about 3% fat and less than 1% protein.

The rich milk allows the cub to grow at an astonishing rate. A few months after birth, the cub emerges from the den weighing up to ten pounds. During their first year out of the den, fueled by its mother’s  milk and whatever scraps of salmon it can scrounge, spring cubs can double their weight every two months. By the time they retire to the den with their mother at the end of fall, a healthy COY will weigh as much as eighty pounds.

Brown bears have developed these adaptations for one simple reason: it gives them the best chance at survival. While visitors, staff and cam viewers patiently (or impatiently) await the arrival of the cutest little bears around, newborn cubs are already hard at work putting on the weight and learning the skills necessary to grow into successful adult bears.

409 Beadnose and one of her COYs stand on the bank of Brooks River. Photo by NPS/Tammy Carmack.

This post originally appeared on Katmai National Park’s Terrane Blog and was adapted for SCA by its author. 

David Kopshever is a recent graduate of the University of Montana, where he studied English and creative writing. His passion for wilderness, wildlife, and storytelling has led him to Katmai National Park, where he works alongside interpretive rangers to educate the public about the brown bears of Brooks Camp. As an SCA Digital Media Intern, David manages the park’s websites and social media pages, and conducts live online events for the public, sharing the life stories of the Brooks River bears.