Abstract
The Australian water rat, Hydromys chrysogaster, preys on a wide variety of aquatic and semiaquatic arthropods and vertebrates, including fish. A frequently observed predatory strategy of Hydromys is sitting in wait at the water's edge with parts of its vibrissae submersed. Here we show that Hydromys can detect water motions with its whiskers. Behavioural thresholds range from 1.0 to 9.4 mm s−1 water velocity, based on maximal horizontal water velocity in the area covered by the whiskers. This high sensitivity to water motions would enable Hydromys to detect fishes passing by. No responses to surface waves generated by a vibrating rod and resembling the surface waves caused by struggling insects were found.
Highlights
Many aquatic and semiaquatic mammals use their vibrissae to obtain information by directly touching and investigating unknown objects (Dehnhardt 1990, 1994; Dehnhardt and Kaminski 1995; Dehnhardt and Dücker 1996; Dehnhardt et al 1998b; Catania et al 2008)
The present study shows that the Australian water rat H. chrysogaster can sense, like the harbour seal P. vitulina (Dehnhardt et al 1998a, 2001) and the California sea lion Zalphus californianus (Gläser et al 2011), water motions with its vibrissae
Response thresholds with the hydrodynamic stimuli being detected on 50% of stimulus trials presented to Hydromys are only a few millimetres per second
Summary
Many aquatic and semiaquatic mammals use their vibrissae to obtain information by directly touching and investigating unknown objects (Dehnhardt 1990, 1994; Dehnhardt and Kaminski 1995; Dehnhardt and Dücker 1996; Dehnhardt et al 1998b; Catania et al 2008). Harbour seals (Phoca vitulina) use their vibrissae to detect minute subsurface water motions (Dehnhardt et al 1998a). Harbour seals (Dehnhardt et al 2001; Wieskotten et al 2010) and California sea lions (Gläser et al 2011) can even follow the hydrodynamic trail left behind by a moving object. Many aquatic and semiaquatic mammals associated with fresh water habitats have vibrissae which they might use to. Wolf Hanke and Sabine Meyer should be considered co-first authors.
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