Counts of burrow entrances
Platypus mainly rest in burrows that have platypus-sized entrances opening near the edge of the water. Unfortunately, a number of factors preclude using counts of burrow entrances as a reliable index of platypus abundance:
Platypus burrow entrances are characteristically very difficult to detect – they can be located underwater and are often concealed by undercut banks or trees, overhanging shrubby vegetation or long grass (as shown at right), piles of miscellaneous woody debris, or even man-made structures such as concrete drains and boardwalks (Serena 1994; Gardner and Serena 1995; Serena et al. 1998; Thomas et al. 2019). For example, the entrances of only 6 of 57 known platypus burrows could be identified with reasonable certainty in a radio-tracking study conducted near Melbourne (Serena et al. 1998).
Apart from the mothers of small juveniles, a platypus normally will occupy several different burrows scattered across its home range in a period of just a few weeks (e.g. Serena 1994; Gardner and Serena 1995; Gust and Handasyde 1995; Thomas et al. 2019).
Burrows are occupied sequentially by different individuals over time (Serena 1994; Serena et al. 1998), and presumably may continue to exist for many years (even if a population becomes locally extinct) unless substantial bank erosion or compaction occurs.
There are currently no known grounds for clearly distinguishing a platypus burrow from a water-rat/rakali burrow – the two species are fairly similar in size, and in fact have been documented to occupy the same burrow sequentially (Serena 1994).
Gardner, J. L., and Serena, M. (1995). Spatial organisation and movement patterns of adult male platypus, Ornithorhynchus anatinus (Monotremata: Ornithorhynchidae). Australian Journal of Zoology 43, 91-103.
Gust, N. and Handasyde, K. (1995). Seasonal variation in the ranging behaviour of the platypus (Ornithorhynchus anatinus) on the Goulburn River, Victoria. Australian Journal of Zoology 43, 193-208.
Serena, M. (1994). Use of time and space by platypus (Ornithorhynchus anatinus: Monotremata) along a Victorian stream. Journal of Zoology 232, 117-131.
Serena, M., Thomas, J. L., Williams, G. A., and Officer, R. C. E. (1998). Use of stream and river habitats by the platypus, Ornithorhynchus anatinus, in an urban fringe environment. Australian Journal of Zoology 46, 267-282.
Thomas, J. L., Parrott, M. L., Handasyde, K. A., and Temple-Smith, P. (2019). Burrow use by juvenile platypuses (Ornithorhynchus anatinus) in their natal home range. Journal of Mammalogy 100, 1182-1190.