Figure 2.

Behavioural audiograms of eight small rodents, collected from the literature. The ‘microtype rodent’ audiograms are those of Mus musculus and Sigmodon hispidus (Heffner & Masterton, 1980), Neotoma floridana and Onychomys leucogaster (Heffner & Heffner, 1985), Rattus norvegicus (Heffner et al. 1994), Phyllotis darwinii and Acomys cahirinus (Heffner et al. 2001). The audiogram of the gerbil Meriones unguiculatus, the only one of the eight to lack microtype ossicles and to have inflated ear cavities, is taken from Ryan (1976). Note that Meriones has much more acute hearing (lower thresholds) at frequencies below about 4 kHz, but its high‐frequency hearing is still reasonably good. All of these rodents are in the ‘mouse‐related clade’; Acomys, Mus and Rattus, like the gerbil, are placed in the family Muridae.