Population biology of the ship rat and Norway rat in Pureora Forest Park, 1983–87

Abstract

Populations of ship rats (Rattus rattus) and Norway rats (R. norvegicus) were sampled over the five years 1983-87 at Pureora Forest Park, by Fenn and rat kill-traps every three months. Fenn and rat traps recorded similar capture rates in comparable habitats, although Fenns caught more heavy and fewer young rats. Ship rats (n = 1793 collected) were more abundant, heavier and larger in native forest, regardless of logging history, than in exotic forest of any age. Young ship rats (age classes 1-3) were most abundant in unlogged interior native forest, and in autumn and winter after summer and autumn breeding. Capture rates declined after peaking in 1985, probably due to reduced recruitment of young rats following lower pregnancy rates in adult females. The irregular annual seasonal cycle of reproduction and abundance observed at Pureora is the same as that described for non-commensal ship rat Z00035

Tree-climbing capabilities of Norway and ship rats

“…For example, 26% of all radio-tracking fixes recorded by Hooker & Innes (1995) in complex forest were in vegetation of the 0Á2-m height class, 56% in the 2Á8-m height class and 18% in the over 8-m height class; similarly, 87% of fixes recorded by Perry et al (2009) were in the subcanopy and canopy. In such 3D environments, ship rats can avoid or rapidly escape from Norway rats, permitting local sympatry wherever there is enough food both above and on the ground (Innes et al 2001). The hood of a pest-proof fence, 2 m above the ground and a good place for hunting nocturnal insects, was a veritable highway for ship rats (Connolly et al 2009), from which they were perfectly positioned for immediate access into the sanctuary through any breach in the fence caused by a falling tree.…”

Biology and Impacts of Pacific Island Invasive Species. 11.Rattus rattus,the Black Rat (Rodentia: Muridae)

“…In a study on South Island, New Zealand, Alterio et al (1999) found that abundances of R. rattus ranged from 1.8 to 5.6 individuals/100 trap-nights. In a 5-yr study of R. rattus in North Island, New Zealand, Innes et al (2001) found that abundances were 1 -20 individuals/100 trap-nights (mean ca. 8 -10).…”

Denning behaviour of ship rats (Rattus rattus) on Taukihepa, a seabird breeding island

“…Very little is known about ship rat ecology on seabird islands, as most research in New Zealand has been carried out in mainland forest habitats (Daniel 1972;Dowding & Murphy 1994;innes et al 2001;harper et al 2005). Population ecology of island rodents differs from that of mainland populations (Gliwicz 1980;Polis et al 1997), so it is surprising that more research has not been conducted on islands.…”

“…This study and the small amount of research on den site selection in non-commensal ship rats has revealed a variable fine-scale spatial ecology, influenced by habitat structure, food quantity and dispersion, sexual activity and possibly relatedness (Dowding & Murphy 1994;hooker & innes 1995;cox et al 2000), with larger-scale effects including predation risk and inter-specific competition (innes et al 2001;harper et al 2005;harper 2006;harper & Veitch 2006). Our results emphasise the importance of underground activity of ship rats on Taukihepa, and showed that radio-tracked rats moved and denned freely underground despite a dense population of sooty shearwater adults sitting on eggs and newly hatched chicks.…”