High‐resolution mapping of rabbit (Oryctolagus cuniculus) densities for targeted conservation management

Abstract

Despite the staggering economic and ecological impacts of invasive animals, maps of their distribution are often only broad generalisations. Detailed knowledge about the spatial distribution of pest animals is crucial to efficiently reduce their numbers in open landscapes where no conservation fencing, or natural boundaries exist. Our case study tests a random but spatially balanced transect design to collect data on the distribution of the European rabbit (Oryctolagus cuniculus), a major destructive pest species in Australian ecosystems, and create distribution maps in relation to abiotic and biotic features. We surveyed an area of 650 km2 in the semi‐arid Flinders Ranges of South Australia using 95 transects (1.4 km length by 50 m width), that were placed with a method originally developed for surveying the ocean‐floor and applied for the first time in terrestrial ecosystems. According to a hurdle model fitted to our data set, the presence of rabbit warrens is influenced by geology, vegetation cover and the topographic wetness index, whereas the number of holes per warren depends on the ruggedness of the terrain, the vegetation cover and whether it has previously been destroyed. The model predicted the numbers of rabbit holes with up to 96.4% accuracy and at a previously unavailable resolution, providing a significant improvement in detail of the distribution of this feral animal. Synthesis and applications: A reliable, high‐resolution map of the distribution of rabbit densities was generated with surveying of less than 1% of the study area, information that can now be used to direct targeted conservation management efforts. This method is highly accurate and can still be improved in future studies.

Spatial niche separation of an invasive and a native mesopredator

“…F) The Topographic Wetness Index (TWI) estimates the relative wetness of parts of the landscape by the size of catchment and the slope (Gallant & Austin 2012b). In addition to these six environmental parameters, we used maps of the potential rabbit abundance derived from previous ground surveys across the study area (see Jansen et al (2023) for the detailed methods). For each GPS location of cats and quolls, we extracted the values of the six environmental parameters and potential rabbit abundance for the cell (25×25m) containing the GPS location.…”

“…In the IFRNP, these threats are connected. The open grassy plains in the IFRNP have the highest abundance of rabbits (Jansen et al 2023) and cats (Stobo-Wilson et al 2020), as well as high grazing and browsing pressure from a range of domestic, feral and native herbivores that severely reduces cover of ground vegetation. Structural complexity of the ground vegetation layer may indirectly influence quoll survival by providing hiding places and food sources as well as enabling them to evade detection or to escape from mammalian predators such as cats (McGregor et al 2015).…”

“…In the IFRNP, these threats are connected. The open grassy plains in the IFRNP have the highest abundance of rabbits (Jansen et al . 2023) and cats (Stobo-Wilson et al .…”