Its bacula was, on average, 9.1 inches (23.3 centimeters) long - significantly larger than the penis bones of much bigger bears. Male polar bears, the biggest bears on Earth today, typically weigh 1,100 lbs. (500 kg), but their penis bone averages about 7.3 inches (18.6 cm) long, the researchers say.
The length of the penis bone could reveal details not only about the sexual behavior of Indarctos arctoides, but also the species' ecological habits and mating system.
Based on the size of baculum, the researchers think the bear likely had fewer but longer periods of intercourse than other mammals. A long baculum, the study researchers say, could have served as a physical support during mating, helping to keep the female's reproductive tract open and in an optimal position for fertilization during these sporadic dalliances.
Indarctos arctoides may have also had relatively large individual ranges and possibly a lower population density, giving rise to fewer sexual encounters, the researchers say.