The baculum is a heterotrophic skeletal element-in other words, it’s not attached to the skeleton-that has a rough base and a deep groove giving it a V-shape in cross-section it serves to maintain an erection during intercourse. Like most mammals (including dogs, cats, hedgehogs, bats, rodents and non-human primates), dog foxes have a bony structure in the penis called a baculum (or ‘os penis’ - left). It seems that foxes undergo significant increases in testes size, and invest relatively more energy resources into producing sperm-making tissues, because there’s a high demand for sperm given the brief period during which this species can breed. The greatest quantities of mature sperm are produced during December and January, after which sperm production reduces sperm may be present in the epididymis until April (some studies have found sperm in every month) but will have deteriorated to such an extent as to be largely useless. Dog foxes begin the entry to breeding condition in August, as the production of sperm resumes following a hiatus during the late spring and summer months – accordingly, the testes have increased in size by around six-fold come December (from 1-2 grams to 7-8 grams).

Stuck to dogs knot