Diet and dietary selectivity of the platypus in relation to season, sex and macroinvertebrate assemblages

Abstract

The diet of the platypus Ornithorhynchus anatinus was studied by examination of material collected from the cheek pouches of animals captured while foraging in streams in Kangaroo Valley, NSW, Australia. Platypuses consumed benthic invertebrates from 55 families in 16 orders, with virtually no prey being derived from the terrestrial environment. We also sampled invertebrates in pool, riffle and stream edge habitats to identify where prey were obtained. Invertebrates in the diet were most similar to those collected along stream edges and in pools compared with the faster-flowing riffles, suggesting that platypuses focused their foraging activities largely in these deeper water habitats. Although there was no seasonality in the assemblage structure of macroinvertebrates, the diet of platypuses varied between seasons, notably between winter and summer, suggesting that some dietary selectivity is seasonal. Dietary differences between the sexes were not detected. Overall, our results suggest that some dietary selection occurs in the platypus with respect to both foraging habitat and season. Seasonal selectivity may reflect different metabolic demands on platypuses at different times of the year. In contrast, habitat selectivity may reflect difficulty of prey access and risk of prey escape in fast-flowing riffles, higher energy costs and risk of predation associated with exploiting this habitat, and prey avoidance responses that are more rapid in the shallow riffles than in the deeper water pools and stream edges. These alternatives await evaluation by future research.

Comparison of diet and prey selectivity of the Pyrenean desman and the Eurasian water shrew using next-generation sequencing methods

“…Specialization on particular microhabitats in streams is also known for other semi-aquatic mammals. For instance, the platypus Ornithorhynchus anatinus does not allocate an equal foraging effort to benthic macroinvertebrates across all habitats, its preference going to pools and littoral margins rather than riffles (McLachlan-Troup et al, 2010). The overall low selectivity, active selection or avoidance of different taxa, together with the distinct trophic niche we observed in the whole study area in G. pyrenaicus and N. fodiens, suggest that they use distinct foraging micro-habitats (Castién and Gosálbez, 1999) within the stream and riparian mosaic.…”

Urban stormwater runoff limits distribution of platypus

“…; McLachlan‐Troup et al . ). The loss of these preferred platypus prey items from streams receiving urban stormwater runoff (e.g.…”

Use of implanted acoustic tags to assess platypus movement behaviour across spatial and temporal scales

“…Such shifts have previously been observed in platypuses foraging in several locations, attributed to resource variability when energy requirements increase with seasonal regulation of body temperature, as well as territoriality during the breeding season (around September) 13 , 17 , 63 – 65 . Uncertainty still exists over quantity, composition and variation of platypus diet and differentiation between summer and winter periods 66 , 67 . Emerging stable isotope analysis in platypuses 68 and DNA-based identification of macroinvertebrate prey items 69 will undoubtedly improve our understanding of seasonal changes in dietary composition.…”