•The platypus is a semi-aquatic mammal, endemic to waterways of eastern Australia. Understanding spatial and temporal patterns of platypus occupancy within alpine and sub-alpine waterways is limited, particularly for low-order, high altitude or streams typically snowed over in winter.
•We tested platypus occupation using eDNA at 43 sites across Kosciuszko National Park (KNP). 18 sites were sampled over a two-year period (2021-23) with seasonal sampling periods in November-December and April-May. Stream orders varied from 2 to 8 with altitude from 300 m to 1750 m.
•Platypus were detected in waterways at high altitudes and lowstream orders not previously recorded. However, platypus occupation remained relatively localized at sites with lower altitude, high stream-orders and closer to dams, during both sampling seasons. During the autumn, platypus occupancy of higher altitude and low stream-order waterways was more likely. This seasonal use of alpine streams that are subject to large variation in abiotic conditions, may suggest a relationship to platypus metabolic requirements and foraging efficiency trade-offs. Increases in spatio-temporal occupation during spring may be attributed to breeding and territorial behaviour of males, or dispersing juveniles.
•Evidence for variability of occupation across spatial and temporal scales in alpine waterways has implications for population connectivity across KNP and the importance of maintaining healthy habitat for platypus in areas lesser known to be utilised. Understanding platypus distribution across alpine catchments is pertinent for their conservation, as water resource development and habitat modification from feral pest activity and hydrologic alterations may reduce connectivity between populations across their distribution.