Domestic mink, which are bred in fur farms, have 19.6% smaller brains, 8.1% smaller hearts, and 28.2% smaller spleens than wild mink.[14][15] The feet are broad, with webbed digits.[10] It generally has eight nipples, with one pair of inguinal teats and three pairs of abdominal teats.[11] The adult male's penis is 2.2 in (5.6 cm) long, and is covered by a sheath. The baculum is well-developed, being triangular in cross section and curved at the tip.[12]