Editing American black bear (section)

=== Reproduction and development ===
Sows usually produce their first litter at the age of 3 to 5 years,{{sfn|Brown|1993|loc=Ch. "Behaviour and Activities"}} with those living in more developed areas tending to get pregnant at younger ages.<ref name="life">{{cite web |url=https://www.sciencedaily.com/releases/2008/09/080930135301.htm |title=Urban Black Bears "Live Fast, Die Young" |publisher=Sciencedaily.com |date=October 1, 2008 |access-date=February 21, 2011 |archive-date=February 23, 2011 |archive-url=https://web.archive.org/web/20110223145458/http://www.sciencedaily.com/releases/2008/09/080930135301.htm |url-status=live }}</ref> The breeding period usually occurs in the June–July period, though it can extend to August in the species' northern range. The breeding period lasts for two to three months. Both sexes are promiscuous. Males try to mate with several females, but large, dominant ones may violently claim a female if another mature male comes near.<ref name="Lariviere" /> Copulation can last 20–30 minutes.<ref>{{cite journal |last1=Ludlow |first1=Jeanne C. |title=Observations on the Breeding of Captive Black Bears, Ursus americanus |journal=Bears: Their Biology and Management |date=1976 |volume=3 |pages=65–69 |doi=10.2307/3872755 |jstor=3872755 |citeseerx=10.1.1.552.1405 }}</ref> Sows tend to be short-tempered with their mates after copulating.

The fertilized eggs undergo delayed development and do not implant in the female's womb until November. The gestation period lasts 235&nbsp;days, and litters are usually born in late January to early February. Litter size is between one and six cubs, typically two or three.<ref name="North American Bear Center – Reproduction">{{cite web |title=Reproduction |url=http://www.bear.org/website/bear-pages/black-bear/reproduction.html |archive-url=https://web.archive.org/web/20101217155959/http://www.bear.org/website/bear-pages/black-bear/reproduction.html |url-status=dead |archive-date=2010-12-17 |publisher=North American Bear Center}}</ref> At birth, cubs weigh {{convert|280|–|450|g|lb|abbr=on}} and measure {{convert|20.5|cm|in|abbr=on}} in length. They are born with fine, gray, down-like hair and their hind quarters are underdeveloped. They typically open their eyes after 28–40&nbsp;days and begin walking after 5 weeks. Cubs are dependent on their mother's milk for 30&nbsp;weeks and will reach independence at 16–18&nbsp;months. At 6 weeks, they attain {{convert|900|g|lb|abbr=on}}, by 8 weeks they reach {{convert|2.5|kg|lb|abbr=on}} and by 6 months they weigh {{convert|18|to|27|kg|lb|abbr=on}}. They reach sexual maturity at 3 years and attain their full growth at 5 years.{{sfn|Brown|1993|loc=Ch. "Behaviour and Activities"}}