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Little is known of owls in south-western Australia compared with the owls of southern and eastern Australia. Surveys of forest owls in the south-west are almost completely lacking. This study sought to determine the abundance and detectability of owls immediately around the Peel–Harvey Estuary in south-western Australia. The southern boobook (Ninox boobook) and the masked owl (Tyto novaehollandiae) were the only owls detected (n = 23 and n = 1 respectively), although the nocturnal tawny frogmouth (Podargus strigoides) was detected from unelicited calls on three occasions. Southern boobooks were found to be common in this area though they are reported to be in decline in south-eastern and inland Australia. Their detectability was significantly greater in August (late winter) than at other times through unelicited calls; otherwise, there were no detections in winter. A variety of small mammals were detected during the surveys, including: a little red flying-fox (Pteropus scapulatus), a western ringtail possum (Pseudocheirus occidentalis), 19 southern brown bandicoots (Isoodon obesulus), 4 common brushtail possums (Trichosurus vulpecula), 21 rabbits (Oryctolagus cuniculus), a black rat (Rattus rattus), 2 red foxes (Vulpes vulpes) and 22 microbats.
Nest predation is the main cause of hatch failure for many turtle populations. For loggerhead turtles (Caretta caretta) nesting at the Wreck Rock rookery, adjacent to Deepwater National Park in south-east Queensland, yellow-spotted goannas (Varanus panoptes) are the main nest predator. However, no studies have documented the space use of goannas in costal habitat adjacent to a sea turtle nesting beach. Here we used Global Positioning System data loggers to evaluate the spatial ecology of adult yellow-spotted goannas in order to discover their potential interaction with sea turtle nests. Male yellow-spotted goannas had larger home ranges, spent a greater proportion of their time in the beach dune area where sea turtles nest, and their home ranges overlapped with more sea turtle nests compared with females. Both males and females had a bimodal activity pattern, with peaks in activity in the early morning and mid to late afternoon. Examination of space-use patterns indicates that it is the larger male yellow-spotted goannas that are the main predators of sea turtle nests at the Wreck Rock beach-nesting aggregation. Hence, by inference, it is probable that large male yellow-spotted goannas are responsible for opening nests at other Australian mainland sea turtle beaches, and if a goanna-specific management strategy is implemented to control predation it is these large males that should be targeted.
Describing the population trends of threatened species over time is central to their management and conservation. The green and golden bell frog (Litoria aurea) is a formerly common species of south-eastern Australia that has declined to ∼40 populations in New South Wales, and experienced a substantial contraction of its geographic range. We aimed to determine whether an unmanaged population at the northern end of its range had declined across a 17-year period. We estimated population size at the beginning and end of this period, using several population models to fully characterise this population. Different modelling approaches gave different population estimates. Based on a similar number of survey occasions the adult male segment of the population was estimated using the Popan model at 112.0 (±13.5, s.e.; 95% CI: 85.5–138.8) in 1998/99 and 95.2 (±17.6; 60.8–129.7) in 2015/16. With the inclusion of maturing subadults following the practice of earlier studies, the population was estimated at 163.6 (±25.9; 112.8–214.5) males in 2015/16. These estimates represent an index of a larger population because the largest wetland was subsampled. Our data provide no evidence of a declining population. Our study highlights the need to understand the implications of using different population models and two age-classes to estimate population parameters.
We conducted a morphometric analysis of 279 Crocodylus johnstoni, using specimens from the McKinlay River (n = 265) and Arnhem Land (n = 14), to meet the management need for predicting body size of C. johnstoni from isolated body parts. The results also allow reconstruction of C. johnstoni dimensions for comparison with other crocodilian species. We detected sexual dimorphism in some body measurements from the McKinlay River, and geographic variation in the morphology of McKinlay River and Arnhem Land populations, but differences were slight. There is pronounced allometric growth in C. johnstoni in the immediate post-hatching phase, largely due to elongation of the snout after exiting the confines of the egg. We compared the size, shape and relative growth of C. johnstoni with that of other crocodilian species for which equivalent data are available, but particularly the other Australian crocodile, Crocodylus porosus. C. porosus has a proportionately longer tail and a shorter but wider snout than C. johnstoni, and we discuss possible ecological correlates of these and other differences.
Hybridisation between animals that breed once (e.g. dingoes) and twice (e.g. domestic dogs) annually may produce offspring that breed either way. This question was investigated by determining the breeding seasonality of female dingo–dog hybrids in south-east Queensland, Australia, through evaluating macroscopic and histological features of 71 female reproductive tracts. All animals were sourced from urban areas where levels of hybridisation are generally high. Most animals trapped in summer were pups less than 6 months of age. A peak of uterus diameter and weight coincided with a peak of corpus luteum in winter. The follicular phase was characterised by growing follicles, ∼1–3 mm wide, in late summer and autumn. Only two of the animals (1.4%) showed out-of-season reproductive cycles: one was found with corpus luteum in summer and another in autumn. Our data clearly show that hybrids have a single annual breeding season in winter, exhibiting the same breeding seasonality as dingoes. Our findings are similar to those found in the New Guinea singing dog. Future studies should be conducted to understand and exploit the mechanism and drivers of the breeding seasonality of dingo–dog hybrids to develop more effective management of their populations.
We investigated relationships between Pseudomys pilligaensis and other small mammal species in terms of their population fluctuations and habitat selection during a population irruption of P. pilligaensis. Antechinus flavipes showed only seasonal fluctuations in numbers, suggesting that it did not respond to the same environmental factors as P. pilligaensis. A. flavipes consistently selected areas with less sand in all phases of the irruption of P. pilligaensis, resulting in a clear separation from P. pilligaensis except in the Peak phase of the latter’s irruption. Numbers of Mus domesticus fluctuated similarly to P. pilligaensis until the latter’s irruption peak in April 2000. However, M. domesticus disappeared after July 2000 from our sites. M. domesticus seemed to occupy the area only temporarily when seeds were abundant. In the Increase and Peak phases of the irruption of P. pilligaensis, M. domesticus occupied core habitats characterised by more sand and shrub, and less litter, while in the Low phase P. pilligaensis occupied the core habitats that M. domesticus used to occupy. This may suggest that M. domesticus was excluded from core habitats through competition with P. pilligaensis in the Low phase of the latter’s irruption. However, since increased anthropogenic disturbance might create conditions that M. domesticus prefers, it is important to assess carefully any impacts of such disturbance on P. pilligaensis.
The platypus (Ornithorhynchus anatinus) occupies a wide range of aquatic habitats, feeding mainly on benthic macroinvertebrates. In this study, we investigated how flow affects platypus reproduction in the unregulated upper Shoalhaven River in rural New South Wales. In a mainly dry period, the population occurred at relatively high density (12.4 animals km–1) and was strongly female-biased (84% of resident animals); mean annual loss and recruitment of resident females were respectively estimated to be 12% and 14%. Percentage lactation was 17–71% (n = 23 years), and annual reproductive success (defined as the mean number of juveniles captured per adult/subadult female from February to April) varied from 0 to 1.5 juveniles female–1 (n = 21 years). A significant positive linear relationship was evident between percentage lactation and antecedent discharge in the five months before breeding (March–July) and a positive curvilinear relationship was evident between percentage lactation and mean litter size. Conversely, reproductive success was compromised by high poststorm discharge in the period when juveniles are confined to a nesting burrow, especially from late November to early January. The relationships identified in our study between flow and reproduction also appear to apply to platypus populations occupying urban streams in Victoria, suggesting that they may be widely relevant to this species.