largest extant terrestrial carnivorans. The standard method of evaluating the size of bears is by measuring their skulls. Most North American hunting organizations and management agencies use calipers to measure the length of the skull (back of sagittal crest on the back of the skull to the front tooth), and the width (maximum width between the zygomatic arches — "cheek bones"). The total skull size is the sum of these two measurements. The largest bear ever killed in North America was from Kodiak Island, with a total skull size of , and eight of the top 10 brown bears listed in the Boone and Crockett record book are from Kodiak. The average skull size of Kodiak bears that were killed by hunters in the first five years of the 21st century was for boars, and for sows. Also, an individual named Teddy, which portrayed a killer bear in the movie Grizzly, stood tall on hind legs and was the largest bear in captivity at the time. Distribution and density This brown bear population only occurs on the islands of the Kodiak Archipelago (Kodiak, Afognak, Shuyak, Raspberry, Uganik, Sitkalidak, and adjacent islands). The Kodiak bear population was estimated to include 3,526 bears in 2005, yielding an estimated archipelago-wide population density of 270 bears per 1000 km2 (700 per 1000 sq.mi). During the past decade the population has been slowly increasing. Life history Reproduction and survival Kodiak bears reach sexual maturity at age five, but most sows are over nine years old when they successfully wean their first litter. The average time between litters is four years. Sows continue to produce cubs throughout their lives, but their productivity diminishes after they are 20 years old. Mating season for Kodiak bears is during May and June. They are serially monogamous (having one partner at a time), staying together from two days to two weeks. As soon as the egg is fertilized and divides a few times, it enters a state of suspended animation until autumn when it finally implants on the uterine wall and begins to grow again. Cubs are born in the den during January or February. Weighing less than at birth with little hair and closed eyes, they suckle for several months, emerging from the den in May or June, weighing . Typical litter sizes on Kodiak are two or three cubs, with a long-term average of 2.4 cubs per litter.