Certain small mammals, such as hedgehogs, bats, and dormice, are called true hibernators because they spend most of the winter in a state similar to death, their body temperature approximating that of the environment.
On väikesi imetajaid, nagu siilid, nahkhiired ja unilased, kes magavad talveund. Nad veedavad suurema osa talvest tardumusseisundis, mil nende kehatemperatuur läheneb ümbritseva keskkonna temperatuurile.