Habitat preferences of Rattus rattus (ship rats) across composite urban landscapes
Predator Free Wellington is pioneering a world-first multispecies elimination in an urban environment. This was previously achieved only on offshore islands and in fenced sanctuaries. There is plenty of research on Ship rat behaviour in urban city centres. What makes Wellington unique is the combination of manmade and natural areas. We know from the mahi on Miramar Peninsula that Ship rats are more abundant in certain habitats. However, their specific ecological preferences across varied peopled landscapes are largely unknown.
Learning more about Ship rat behaviour
This research sought to learn more by:
- Understanding ship rat preferences in six different habitat types. This research area was in and around Oruaiti Reserve, part of our Phase 1 project area. The habitat types were:
- Developed urban – heavily modified urban landscapes: concrete, buildings, houses and manicured gardens
- Coastal scrub – early-successional coastal plants mostly native, up to 1.5m
- Mid-regeneration native – multi-stemmed young trees up to 3m, mostly early-mid successional native species
- Capy Ivy – dominated by Cape Ivy, a dense and tangled vine between 2-5m with fleshy leaves
- Mixed vegetation – unmanaged gardens or messy fragmented vegetation, with some urban infrastructure
- Exotic pine – pine plantation or wilding pines with minimal understory, predominantly open.
- Using these insights to help inform habitat-based elimination techniques.
What we learned from this research:
- Ship rats were detected across all of the assessed habitat types, but their presence varied significantly depending on the type of habitat.
- Ship rats were most commonly detected in the coastal scrub habitat type, followed by Cape Ivy. These habitats presented the most favourable conditions.
- There was a moderate abundance of rats in the mid-regeneration native habitat, followed by the mixed vegetation habitat.
- Developed urban and exotic pine habitats had an equally low presence of rats.
Our conclusions from this research:
- Dense vegetation creates a favourable habitat. Habitat-specific food sources and low levels of human disturbance are also significant.
- Natural habitats were favoured more than manmade. However, the area studied was a high socioeconomic level.
- This study was unable to find a habitat preference of native versus non-native vegetation.
Our recommendation:
We recommend that elimination projects operating in composite urban environments assess the habitat before installing a habitat-based grid of devices. The network can then focus on favourable habitat.
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This research was conducted in 2023 by Eleanor Dewar, a postgraduate student researcher of Te Pūkenga Open Polytechnic, in collaboration with Predator Free Wellington Ltd.