Otter females are called bitches or sows, and their offspring are called pups. The collective nouns for otters are bevy, family, lodge, romp (being descriptive of their often playful nature) or, when in water, raft. The feces of otters are typically identified by their distinctive aroma, the smell of which has been described as ranging from freshly mown hay to putrefied fish; these are known as spraints. The gestation period in otters is about 60 to 86 days. The newborn pup is cared for by the bitch, dog and older offspring. Bitch otters reach sexual maturity at approximately two years of
Mammal scheme used, are the [[Primate]]s including the [[ape]]s, [[monkey]]s and [[lemur]]s; the [[Cetartiodactyla]] including [[whale]]s and [[even-toed ungulates]]; and the [[Carnivora]] which includes [[cat]]s, [[dog]]s, [[weasel]]s, [[bear]]s, [[Pinniped|seals]] and allies. According to "[[Mammal Species of the World]]", 5,416 species were identified in 2006. These were grouped into 1,229 [[genus|genera]], 153 [[family (biology)|families]] and 29 orders. In 2008, the [[International Union for Conservation of Nature]] (IUCN) completed a five-year Global Mammal Assessment for its [[IUCN Red List]], which counted 5,488 species. According to a research published in the "[[Journal of Mammalogy]]" in 2018, the number of recognized mammal species is 6,495