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Motivated by the reported dearth of debris discs around M stars, we usesurvival models to study the occurrence of planetesimal discs around them.These survival models describe a planetesimal disc with a small number ofparameters, determine if it may survive a series of dynamical processes andcompute the associated infrared excess. For the WISE satellite, we demonstratethat the dearth of debris discs around M stars may be attributed to the smallsemi-major axes generally probed if either: 1. the dust grains behave likeblackbodies emitting at a peak wavelength coincident with the observed one; 2.or the grains are hotter than predicted by their blackbody temperatures andemit at peak wavelengths that are shorter than the observed one. At these smalldistances from the M star, planetesimals are unlikely to survive or persist fortime scales of 300 Myr or longer if the disc is too massive. Conversely, oursurvival models allow for the existence of a large population of low-massdebris discs that are too faint to be detected with current instruments.However, our interpretation becomes less clear and large infrared excesses areallowed if only one of these scenarios holds: 3. the dust grains are hotterthan blackbody and predominantly emit at the observed wavelength; 4. or areblackbody in nature and emit at peak wavelengths longer than the observed one.Both scenarios imply that the parent planetesimals reside at larger distancesfrom the star than inferred if the dust grains behaved like blackbodies. In allscenarios, we show that the infrared excesses detected at 22 and 70 micronsfrom AU Mic are easily reconciled with its young age. We elucidate theconditions under which stellar wind drag may be neglected when considering dustpopulations around M stars. The WISE satellite should be capable of detectingdebris discs around young M stars with ages on the order of 10 Myr.

Debris discs around M stars: non-existence versus non-detection