Backfilled tunnels provide a novel and efficient method of revealing an elusive Australian burrowing mammal

Abstract

Itjaritjari, the southern marsupial mole (Notoryctes typhlops), is an extreme fossorial species that is very rarely encountered on the surface and has been regarded as a sand swimmer that leaves no reliable trace of its passage through the sand. Like many extreme fossorial species on other continents, itjaritjari is poorly known and is considered rare and threatened. In this study, surface tracks known to have been made by itjaritjari were followed underground where they became clearly defined, circular, sand-filled tunnels with a mean diameter of 39 mm. Trenches dug to expose vertical sections of dune revealed that backfilled tunnels of similar appearance and dimensions were common on dunes in the study areas, averaging 3.2 backfilled tunnels per vertical square meter. Loose sand, and thus opportunities for sand swimming, is confined to the surface in the Australian dune fields, which are well vegetated and characterized by lightly bonded sand. Rather than sand swim, itjaritjari carves tunnels and backfills as it goes, leaving clearly distinguishable and unique traces of its passage ("moleholes") that accumulate over years or decades. This finding provides a much needed means of investigating the distribution, abundance, and conservation of marsupial moles. The technique may have application in the study of several other elusive fossorial species on other continents that may backfill their tunnels, many of which are endangered.