Most nipples on a mammal

The most nipples known for a mammal is 36 (18 pairs), which is a maximum total recorded from two very different species. One is a superficially hedgehog-like spiny insectivorous mammal native to Madagascar and known as the tailless or common tenrec (Tenrec ecaudatus). About the size of a Chihuahua, it produces up to 31 babies in a single litter – itself a record among mammals. The other species is a rodent native to many countries on mainland Africa, but most notably Nigeria, and is known as the Natal multimammate rat (Mastomys natalensis). Notoriously, it is the principal natural reservoir in Nigeria of the Lassa fever virus.

The tailless tenrec and the Natal multimammate rat are both placental mammals, but the marsupial species with most nipples is the shrewish or red-sided short-tailed opossum (Monodelphis sorex), native to southern Brazil, southern Paraguay and northern Argentina. Inhabiting humid Atlantic forests, it has 25–27 nipples, arranged with five central nipples and the remainder arranged in lateral lines. Despite possessing such a large number, however, this marsupial is itself tiny, with a head-and-body length of only 11–13 cm (4.3–5.1 in), a tail length of 6.5–8.5 cm (2.5–3.3 in), and a weight of just 48 g (1.7 oz).