The platypus diet is typically dominated by various bottom-dwelling (or “benthic”) aquatic insects such as caddis fly and mayfly larvae, water bugs, water beetles, dragonfly and damselfly larvae, and larval midges and blackflies. Other prey items include freshwater shrimps, snails, “pea shell” mussels, seed-shrimps (or ostracods) and worms (Faragher et al. 1979; Grant 1982; McLachlan-Troup et al. 2010; Marchant and Grant 2015; Hawke et al. 2022). The best available evidence suggests that the platypus is a fairly non-selective feeder that eats virtually whatever small invertebrates it encounters (Marchant and Grant 2015). Although freshwater crayfish (or “yabbies”) are often listed as an important platypus food source on many websites, crayfish DNA was rarely detected in a platypus dietary study conducted in New South Wales and Victoria based on DNA metabarcoding of cheek pouch contents (Hawke et al. 2022). However, small burrowing crayfish have been found to be an important part of the platypus diet in a Tasmanian lake (Munks et al. 2000), and trout eggs were often consumed along the Thredbo River when fish were spawning in winter (Grant 1982). The bits of algae occasionally found in platypus cheek pouches are believed to be ingested accidentally rather than as food (Faragher et al. 1979; Grant 1982).
The platypus’s ability to prey on fish or other vertebrates is restricted by its lack of true teeth as an adult. A young platypus is equipped with a set of shallow-rooted premolar and molar teeth located at the back of the bill, but these fall out around the time that a juvenile begins to eat solid prey. The teeth are replaced by rough grinding pads which grow continuously to offset natural wear – a very handy feature given that abrasive material such as sand may often enter the platypus’s mouth accidentally when prey items are snapped up from the bottom (Grant 1989).
Remains of a small frog (which may have been eaten as carrion) have been recovered from a platypus cheek pouch in the upper Shoalhaven River in New South Wales (Faragher et al. 1979; Grant 1982), and elvers (young eels) may be killed and eaten when they are migrating in great numbers up a river (as shown at left). Platypus have also been known to dine on small goldfish after killing them in captivity (Krueger et al. 1992).
Reflecting the fact that the platypus diet consists of small, soft-bodied prey items that are masticated quite finely even before they are swallowed, the platypus’s stomach is small and lacks the ability to secrete digestive enzymes or hydrochloric acid (Harrop and Hume 1980; Ordoñez et al. 2008). However, the platypus’s stomach does contain Brunner’s glands, which produce a mucus-rich secretion to help lubricate the intestinal walls and assist efficient nutrient uptake there (Krause 1971).
Because the platypus is a relatively small, warm-blooded animal, it needs a lot of food to serve as fuel. Studies in captivity have shown that animals must consume the daily equivalent of around 15-28% (Krueger et al. 1992) or up to 21% (Thomas et al. 2017) of their body weight to maintain good physical condition. Similarly, the average daily food intake of animals occupying a Tasmanian lake has been estimated to be 19% of body mass (Munks et al. 2000). Not surprisingly, the energy requirements of lactating females increase substantially as their offspring grow. For example, daily food consumption of a mother in captivity was found to increase from around 14% of her body weight in the first month of lactation to slightly more than 36% in the final month of lactation (Thomas et al. 2020).
Photos courtesy of https://www.mdfrc.org.au/bugguide/resources/howtouse.htm (macroinvertebrates) and Peter Broomhall (platypus eating an elver)
LITERATURE CITED
Faragher R A, Grant TR and Carrick FN (1979) Food of the platypus (Ornithorhynchus anatinus) with notes on the food of brown trout (Salmo trutta) in the Shoalhaven River, NSW. Australian Journal of Ecology 4, 171-179.
Grant TR (1982) Food of the platypus, Ornithorhynchus anatinus (Monotremata: Ornithorhynchidae), from various water bodies in New South Wales. Australian Mammalogy 5, 235-236.
Grant TR (1989) Ornithorhynchidae. Pp.436-450 in Fauna of Australia Volume 1B Mammalia (DW Walton and BJ Richardson, eds) Australian Government Publishing Service: Canberra.
Harrop CJF and Hume ID (1980) Digestive tract and digestive function in monotremes and nonmacropod marsupials. Pp. 63-77 in Comparative Physiology: Primitive Mammals (K Schmidt-Nielsen, L Bolis and CR Taylor, eds) Cambridge University Press: New York.
Hawke T, Bino G, Shackleton ME, Ross AK and Kingsford RT (2022) Using DNA metabarcoding as a novel approach for analysis of platypus diet. Scientific Reports 12, 2247.
Krause WJ (1971) Brunner’s glands of the duckbilled platypus (Ornithorhynchus anatinus). American Journal of Anatomy 132, 147-165.
Krueger B, Hunter S and Serena M (1992) Husbandry, diet and behaviour of platypus Ornithorhynchus anatinus at Healesville Sanctuary. International Zoo Yearbook 31, 64-71.
Marchant R and Grant TR (2015) The productivity of the macroinvertebrate prey of the platypus in the upper Shoalhaven River, New South Wales. Marine and Freshwater Research 66, 1128-1137.
McLachlan-Troup TA, Dickman CR and Grant TR (2010) Diet and dietary selectivity of the platypus in relation to season, sex and macroinvertebrate assemblages. Journal of Zoology 280, 237-246.
Munks SA, Otley HM, Bethge P and Jackson J. (2000) Reproduction, diet and daily energy expenditure of the platypus in a sub-alpine Tasmanian lake. Australian Mammalogy 21, 260-261.
Ordoñez GR, LaDeana WH, Warren WC, Grützner F, López-Otín and Puenta XS (2008) Loss of genes implicated in gastric function during platypus evolution. Genome Biology 9, R81.
Thomas JL, Handasyde K, Temple-Smith P and Parrott ML (2017) Seasonal changes in food selection and nutrition of captive platypuses (Ornithorhynchus anatinus). Australian Journal of Zoology 65, 319-327.
Thomas JL, Parrott ML, Handasyde KA and Temple-Smith P (2020) Maternal care of platypus nestlings (Ornithorhynchus anatinus). Australian Mammalogy 42, 283-292.