Radio‐tracking and mark recapture methods were used to characterize the spatial organization and temporal activity patterns of free‐ranging platypuses in southern Victoria. The study area supported an estimated 1.3‐2.1 adult or subadult animals per kilometre of stream in the three summers sampled. The individual home ranges of 15 radio‐tagged animals comprised 0.33‐2.28 km of stream; animals foraging exclusively in the stream had significantly longer ranges (mean=1.40 km) than animals which also foraged in associated pond habitats (mean=0.64km). Home ranges of grown females overlapped with those of neighbouring grown females, subadult and adult males, and juveniles (
Radiotracking and live‐trapping were used to describe spacing patterns of Dasyurus geoffroii along the Murray River in Western Australia. Both sexes are essentially solitary, and occupy numerous dens which define stable core areas. Female core areas typically showed little or no mutual overlap, suggesting that females are intrasexually territorial. As an exception to this, a non‐dispersing daughter may share her mother's core area and successfully rear young there. Transient females were rarely encountered, and vacant female core areas were eventually occupied by juveniles known to have been born on the study area. Male core areas were much larger than those of females, and overlapped broadly with those of other males as well as females. In captivity, females deposit scent by cloacal dragging in response to odours left by foreign conspecifics, and both sexes tend to defecate at sites already containing faeces. In the wild, faecal aggregations occurred throughout the areas used by Dasyurus, but were especially well developed in places where animal movements were likely to be concentrated, such as paths and river crossing points.
Radio-telemetry was used to monitor movements and burrow usage by O. anatinus living in the Yarra River catchment, about 20 km east-north-east of the central business district of Melbourne, Victoria. The home ranges of six adult or subadult animals were 2.9–7.3 km (mean ± s.d. = 4.6 ± 1.6 km) long, with individuals travelling up to 10.4 km (males) and 4.0 km (females) in a single overnight period. The mean home-range length of adult/subadult animals was significantly greater than that of juveniles (1.4–1.7 km, mean ± s.d. = 1.55 ± 0.2 km, n = 2). The animals utilised two drainage channels as well as 11.8 km of natural waterways, including the Yarra River (5 km), Mullum Mullum Creek (4 km) and Diamond Creek (2.8 km). Several animals travelled repeatedly below one-lane and two-lane bridges, confirming that these structures are not inherent barriers to platypus movement. In total, 57 platypus burrows were described, including 26 along the river, 29 along the creeks and 2 along drains. The horizontal distance from the water’s edge to burrow chambers was 0.4–3.7 m (mean ± s.d. = 1.5 ± 0.9 m, n = 41), with burrows found only in banks extending ≥ 0.5 m above the water. Platypus burrows occurred significantly more often than expected along undercut banks and in association with moderate-to-dense vegetation overhanging the water, and significantly less often at sites where banks had a convex profile at water level. As well, the amount of cover provided along the bank by shrubs/small trees and the ground layer of vegetation was significantly greater than expected at platypus burrows along the river. These attributes are believed to help conceal burrow entrances from predators as well as reduce burrow damage through erosion.
An understanding of animal population dynamics relies on identifying life-history attributes associated with population growth and determining how these are affected by environmental variables. We analysed platypus population processes over a 10-year period through mark–recapture studies conducted in three spatially independent stream systems located in the suburbs of Melbourne, Australia. The three populations were collectively characterised by a slightly male-biased adult sex ratio (1.15 : 1) and relatively low reproductive success (<0.5 juvenile captured annually per adult female). An estimated 16% of core residents disappeared annually and 18% of marked juveniles were recaptured as adults. However, some demographic parameters (reproductive success, frequency of non-core adult captures) varied significantly among populations. Estimates of annual core population size in the three systems varied asynchronously, with different trajectories in population size potentially reflecting habitat differences (amount of urban development, reliability of surface flow) as well as variation in spatial isolation and catchment history (implementation of stream rehabilitation programs, occurrence of severe floods). Across all three populations, significant variability in annual reproductive success was explained by linear relationships with the amount of rainfall recorded in the five months before breeding (positive) and after juveniles emerge from nesting burrows (negative).
The extent of mammalian movements often varies with size, sex and/or reproductive status. Fyke nets were set along streams and rivers near Melbourne (southern Victoria) from the mid-1990s to 2007, and in the Wimmera River catchment (western Victoria) from 1997 to 2005, to assess how far platypus of different age and sex classes travelled between captures and over longer periods. The mean distance between consecutive captures of adults did not vary significantly as intervals increased from 1–3 months to >3 years, suggesting that most individuals occupied stable ranges. However, adult females travelled, on average, only 35% as far between captures as males in southern Victoria, and 29% as far in the Wimmera. Up to half of this difference may be explained by variation in size-related metabolic requirements. Immature males and females respectively moved 61% and 53% as far, on average, as their adult equivalents, although two young males dispersed >40 km. Adults incrementally occupied up to 13.9 km of channel in the case of a male (based on six captures over 67 months) and 4.4 km of channel in the case of a female (based on five captures over 127 months).
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