Effective conservation management requires an understanding of the source and direction of the many interactions that occur within ecological communities. Without this understanding, management interventions such as control or eradication of introduced species can have unexpected and undesirable outcomes. One of the challenges for wildlife managers is to garner relevant information for their site of management. In this paper we describe how images of mammals captured on remote cameras can be used to uncover behavioral interactions that can in turn help to identify and prioritize areas for more explicit research or management. Our cameras were set repeatedly at four sites over three years in Tasmania, Australia, and we used a series of generalized linear mixed models to interpret relative changes in count data of three species of small mammals: the introduced black rat Rattus rattus, and the native long-tailed mouse Pseudomys higginsi and swamp rat Rattus lutreolus velutinus. We also included two potential predators, the introduced feral cat Felis catus and the native Tasmanian devil Sarcophilus harrisii. We found that counts of the two species of native small mammals were correlated positively with each other, that swamp rats had a negative effect on black rats, and that black rats had a negative effect on the long-tailed mouse. Devils were important effects in most small mammal models. Despite their effect probably being underestimated by the remote camera survey method, feral cats were included in models for the long-tailed mouse. On the basis of the inclusion of native and both species of introduced mammals in long-tailed mouse models, we propose that the long-tailed mouse is a priority for further research. This research should clarify the competitive dominance and predatory pressure exerted by the black rat and feral cat, respectively, on this species, and also the potential for management of either introduced species to increase the impact of the other. We conclude that remote cameras can help to uncover cryptic or unsuspected interactions within ecological communities, and hence provide an informed basis for developing targeted research questions to increase the effectiveness of wildlife management.
Context Feral cats (Felis catus) threaten biodiversity in many parts of the world, including Australia. Low-level culling is often used to reduce their impact, but in open cat populations the effectiveness of culling is uncertain. This is partly because options for assessing this management action have been restricted to estimating cat activity rather than abundance. Aims We measured the response, including relative abundance, of feral cats to a 13-month pulse of low-level culling in two open sites in southern Tasmania. Methods To do this we used remote cameras and our analysis included identification of individual feral cats. We compared estimates of relative abundance obtained via capture–mark–recapture and minimum numbers known to be alive, and estimates of activity obtained using probability of detection and general index methods, pre- and post-culling. We also compared trends in cat activity and abundance over the same time period at two further sites where culling was not conducted. Key results Contrary to expectation, the relative abundance and activity of feral cats increased in the cull-sites, even though the numbers of cats captured per unit effort during the culling period declined. Increases in minimum numbers of cats known to be alive ranged from 75% to 211% during the culling period, compared with pre- and post-cull estimates, and probably occurred due to influxes of new individuals after dominant resident cats were removed. Conclusions Our results showed that low-level ad hoc culling of feral cats can have unwanted and unexpected outcomes, and confirmed the importance of monitoring if such management actions are implemented. Implications If culling is used to reduce cat impacts in open populations, it should be as part of a multi-faceted approach and may need to be strategic, systematic and ongoing if it is to be effective.
Land-based mammals were surveyed in a mosaic of dry sclerophyll forests and pasture on a sheep-grazing property on Bruny Island, Tasmania, using a range of methods in August 2010. This is the first mammal survey of a sheep-grazing property in Tasmania and the first large-scale survey of mammals on Bruny Island. Ten species were recorded comprising seven native and three introduced species. The Little Forest Bat, Vespadelus vulturnus , and the Black Rat, Rattus rattus , were recorded for the first time on Bruny Island, although both are probably long-term residents. No mammal species listed as rare or threatened under Tasmanian or Australian legislation were found on the property. Large numbers of Eastern Quolls, Dasyurus viverrinus , Brushtail Possums, Trichosurus vulpecula , Tasmanian Pademelons, Thylogale billardierii , and Bennetts Wallabies, Macropus rufogriseus , were recorded in a range of dry sclerophyll forests and in pasture. Longnosed Potoroos, Potorous tridactylus , were recorded widely on the property in native vegetation with relatively thick ground cover. Eastern Quoll capture rates were highest in pasture areas and in Eucalyptus ovata forest. Brushtail Possums, Long-nosed Potoroos, Tasmanian Pademelons and Bennetts Wallabies were virtually unrecorded from E. tenuiramis forest and woodlands. Given the level of survey effort and their potential to occur on the property it was remarkable that no Tasmanian Bettong, Bettongia gaimardi , Eastern Barred Bandicoot, Perameles gunnii , Southern Brown Bandicoot, Isoodon obesulus , or introduced House Mouse, Mus musculus , were recorded. We found that camera trapping was more cost-efficient than cage trapping for detecting the presence of mammals on "Murrayfield". Recommendations for ongoing management and monitoring of mammals are provided.
Choosing the appropriate method to detect and monitor wildlife species is difficult if the species is rare or cryptic in appearance or behaviour. We evaluated the effectiveness of the following four methods for detecting red foxes (Vulpes vulpes) on the basis of equivalent person hours in a rural landscape in temperate Australia: camera traps, hair traps (using morphology and DNA from hair follicles), scats from bait stations (using DNA derived from the scats) and spotlighting. We also evaluated whether individual foxes could be identified using remote collection of their tissues. Genetic analysis of hair samples was the least efficient method of detection among the methods employed because of the paucity of samples obtained and the lack of follicles on sampled hairs. Scat detection was somewhat more efficient. Scats were deposited at 17% of bait stations and 80% of scats were amplified with a fox-specific marker, although only 31% of confirmed fox scats could be fully genotyped at all six microsatellite loci. Camera trapping and spotlighting were the most efficient methods of detecting fox presence in the landscape. Spotlighting success varied seasonally, with fox detections peaking in autumn (80% of spotlighting transects) and being lowest in winter (29% of transects). Cameras detected foxes at 51% of stations; however, there was limited seasonality in detection, and success rates varied with camera design. Log-linear models confirmed these trends. Our results showed that the appropriate technique for detecting foxes varies depending on the time of the year. It is suggested that wildlife managers should consider both seasonal effects and species biology when attempting to detect rare or elusive species.
We present evidence that Devil Facial Tumour Disease (DFTD) is an emerging disease that is now widespread and constitutes a serious threat to the Tasmanian devil Sarcophilus harrisii. This species, the world’s largest extant marsupial carnivore, is endemic to Tasmania. DFTD is a cancerous disease found exclusively in wild devil populations, and appears to be consistently fatal to afflicted individuals. We draw on data from a wide range of sources and locations across Tasmania, acquired through trapping, spotlighting and public observation, to assess the impact and distribution of this disease. The dramatic tumours characteristic of DFTD were first reported in 1996. There were no reports of these signs in any of more than 2020 individuals trapped previously. Since 1996, DFTD has been histologically confirmed in individuals from 41 separate sites, covering 32930km2 (51%) of mainland Tasmania. From the few sites for which timing of DFTD emergence can be estimated, there is evidence for geographical spread of the disease. Of 147 devils with DFTD-like signs, at least 140 were sexually mature. Proportion of animals displaying signs at any one site reached up to 83% (15/18) of trapped adults. Spotlighting surveys and trapping indicated a significant local association between population decline and date of first report of DFTD. In the region where the disease was first reported, mean spotlighting sightings declined by 80% from 1993–1995 to 2001–2003. On the basis of the threat posed by DFTD, the devil has been listed as a threatened species in Tasmania, and nominated for listing at national level.
The diet and food requirements of free-living Pedra Branca skinks (Niveoscincus palfreymani) were studied on Pedra Branca Island, the only known location for this vulnerable, endemic species. While discarded fish remains and regurgitate from seabirds are utilised as food by the skinks during summer, invertebrates represent the most important prey. Isotope turnover rates indicate that feeding is negligible over winter and that significant amounts of non-food water are turned over during summer, either by drinking rainwater or as pulmo-cutaneous water exchange. An assessment is made of the seasonal and annual food requirements of individual skinks and the population.