An understanding of the factors that drive inter-population variability in home-range size is essential for managing the impacts of invasive species with broad global distributions, such as the feral domestic cat (Felis catus). The assumption that home-range sizes scale negatively with landscape productivity is fundamental to many spatial behaviour models, and inter-site variation in landscape productivity has often been invoked to explain the vast differences in feral cat home-range sizes among different regions. However, the validity of this explanation has not been tested or described. We used regression models to examine the ability of remotely sensed landscape productivity data, average body weight and population density to explain differences in the size of feral cat home ranges estimated across a diverse collection of sites across the globe. As expected for a solitary polygynous carnivore, female cats occupied smaller home ranges in highly productive sites, and range sizes of male cats scaled positively with those of females. However, the relationship between range size and productivity broke down at highly seasonal sites. Home-range size also scaled negatively with population density, but there was no clear relationship with average body weight. The relationships we describe should be useful for predicting home-range sizes and for designing effective feral cat control and monitoring programmes in many situations. More generally, these results confirm the importance of landscape productivity in shaping the spatial distribution of solitary carnivores, but the nature of the relationship is more complicated than is often appreciated.
The activity patterns and partitioning of time by four small mammal species, with a focus on the swamp rat (Rattus lutreolus) in north-eastern New South Wales, was investigated using camera trap data from two studies. Analysis was carried out on 1079 camera trap events over 1530 camera trap–nights or 36 720 h of camera trap deployment in the field. The activity patterns of Rattus lutreolus were distinctly diurnal with crepuscular peaks of activity but this differed between sites and when in the presence of competitors. The Hastings River mouse (Pseudomys oralis) and the bush rat (Rattus fuscipes) displayed typical bimodal patterns of nocturnal activity. Antechinus were mostly nocturnal but were occasionally active during the day. These data indicate that where species of Muridae co-occur, diurnal time partitioning by R. lutreolus may reduce competition for food resources. It also confirms the speculation that R. lutreolus displays diurnal behaviour, albeit dependent on the presence of other murids.
Abstract. Novel bait stations can be used as a targeted method of delivering bait by exploiting behavioural traits of the target species. On Muttonbird Island, New South Wales, the black rat (Rattus rattus) has been baited to aid the conservation of the island's wedge-tailed shearwater (Ardenna pacifica) colony, which may result in poisoning of the sympatric swamp rat (Rattus lutreolus). We aimed to design a bait station that R. rattus could reach, but that R. lutreolus could not. We found that 11 (92%) of 12 captive R. rattus reached the bait chambers by climbing a 50-cm vertical pipe, whereas only four (18%) of 22 R. lutreolus reached these bait stations. In a field trial on Muttonbird Island R. rattus entered the bait chamber on an average of 5.3 events per night of vertical bait station deployment, but R. lutreolus did not enter the stations. In a field trial on the mainland at a site with a high density of R. lutreolus, this species was detected in one vertical bait station five times, equating to an average of 0.017 events per night of vertical bait station deployment. We conclude that R. rattus readily climbs a 50-cm pipe to enter the bait station, whereas R. lutreolus rarely or never does on Muttonbird Island or at the mainland site.
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