Space use and interactions of two introduced mesopredators, European red fox and feral cat, in an arid landscape

Abstract

Introduced mammalian predators are drivers of species decline and extinction globally. The successful management and control of introduced mammalian predators is dependent on some knowledge of space use and movements in order to target a population and monitor outcomes. In Australia, these tasks are made complex as there is more than one significant introduced mammalian predator, namely the European red fox Vulpes vulpes and feral cat Felis catus, the landscapes are vast, and individual-level interactions between predators are little studied. The impact of these two introduced predators is large and a significant factor in the extinction of many of the country's small-to medium-sized mammals, either regionally or globally. In a three-year study, we used high-frequency location data, the deployment of the latest GPS tracking technologies, and recent advances in statistical modeling to examine how these two species distributed themselves in space, the degree to which individual distributions overlapped, intraand interspecific interactions, and temporal patterns of activity in an arid landscape. In the absence of an apex predator, the two introduced mesopredators showed large differences in how they distribute themselves across the landscape and interact with conspecifics. The red fox mostly occupies defined territories, while most feral cats roam apparently independent of each other with occasional periods of frequent interaction with conspecifics of either sex. Intraspecific attraction was strongest in cats, while interspecific avoidance was observed in both directions. The home ranges of feral cats that were range-resident were 3-3.5 times larger than foxes in the same landscape. Notably, we observed long-distance movements in feral cats and some were displaced up to 164 km from their point of release. A greater portion of the feral cat population were non-sedentary and therefore likely less amenable to local control efforts than foxes. Given the different patterns of distribution in time and space, the reliable monitoring of population trends or estimates of abundance will necessarily differ in extent, intensity, or duration for the same level of precision and/or require a different method for monitoring each population.

Visitation of artificial watering points by the red fox (Vulpes vulpes) in semiarid Australia

“…For each of 10 collars (2 collars in year 1; 5 collars in year 2; 3 collars in year 3), accuracy was assessed from 106 location attempts (i.e., the equivalent of two full days of data collection) using the same collection schedule as collars placed on active foxes (see Roshier & Carter, 2021 for additional detail). All fixes in the primary dataset (n = 95,413) were managed in Movebank (Kranstauber et al, 2011).…”

“…value) and elevations >200 meters above mean sea level and negative values of mean sea level, noting that the terrain is generally flat and elevations range from approximately 30-100 m across the study area. We then removed location fixes for which the rate of movement from the previous fix was >5 m/s and/or the turning angle was F I G U R E 1 Location of Scotia Wildlife Sanctuary within Australia (a), plus known artificial watering points on and around Scotia (blue circles) and GPS location fixes (gray dots, n = 93,969) for 22 foxes tracked from 2015 to 2017 (b) between 166° and 194° (see Roshier & Carter, 2021 for additional detail).…”

“…3.6.2, R Core Team, 2020) to model an animal's home range. We determined whether individuals were range resident or nonsedentary by fitting a semivariance function to the data (see Roshier & Carter, 2021 for additional detail). Only data from those individuals that were range resident were used to model rates of movement and directionality using step-selection functions.…”

“…). Four foxes (1 ♂, a Data fromRaupach et al (2009Raupach et al ( , 2012.TA B L E 1TA B L E 2 Summary of tracking data for foxes at Scotia Wildlife Sanctuary (2015-2017), including whether the individual was range resident (yes/no) and the area of home range (afterRoshier & Carter, 2021) and records of visitation to putative, artificial watering points a Figures in parenthesis are the number of watering points visited.…”

Long-Distance Movements of Feral Cats in Semi-Arid South Australia and Implications for Conservation Management

“…These control efforts over a vast area have enabled successful faunal recovery and reintroduction projects [26,27]. However, even on this scale the threats associated with the long-distance movements of feral cats, as previously reported [14,[28][29][30], exceed the scale of the cat management area.…”