Population structure and movements of introduced rats in an Hawaiian rainforest

Abstract

We studied populations of introduced rats in three areas in Hawaiian rainforests as part of a larger study to determine the factors limiting endangered bird populations. Species composition among 1 264 rats live trapped was Black Rats Rattus rattus 60.8%, Polynesian Rats R. exulans 38.1 %, and Norway Rats R. norvegicus 1.0%. Capture rates did not differ among the three study areas or four seasonal periods for any of the species. Males comprised 53.0% of 921 Black Rats and 55.3% of 783 Polynesian Rats that were sexed. Juvenile rats comprised 26.2% of Black Rats and 31.7% of Polynesian Rats captured and weighed. Black and Polynesian Rats reproduced throughout the year, but the highest proportion of juveniles in the population was captured in September-November and the lowest proportion in April-June. Mean home range size was 3.6 ha for four Black Rats (three males and one female) and 3.0 ha for three Polynesian Rats (two males and one female). All daytime nests of Black Rats found were above ground, generally in cavities within tree canopies. Mean annual rat activity in tree canopies as measured with tracking tunnels was 43% (range 21?80%). Of 44 rats captured in trees, 43 were Black Rats and one was a Polynesian rat.

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

“…Relative to other invasive Rattus spp. and Mus musculus, R. rattus uses a much greater proportion of the arboreal habitat ( Lindsey et al 1999, Shiels 2010, and R. rattus prefers forests over open, heath, and scrub macrohabitats in Australia (Cox et al 2000). Preference of R. rattus for arboreal habitats is further supported by its numeric dominance over other coexisting rodents in most insular forests in the Pacific (Tamarin and Malecha 1971, Daniel 1973, Clark 1981, Sugihara 1997, Yabe et al 2010).…”

“…Rattus rattus does not seem to be limited by an upper temperature level, or at least this has not been investigated. Thus, R. rattus is abundant and spans most terrestrial communities, from arid lowland and montane ecosystems (Tamarin and Malecha 1971, Clark 1981, Amarasekare 1994, Harris and Macdonald 2007, Chimera and Drake 2011 to lowland and montane rain forests (Daniel 1973, Sugihara 1997, Lindsey et al 1999, Wegmann 2009). Even in highly disturbed environments, such as Eniwetok Atoll, which suffered numerous nuclear explosions, R. rattus survived in densities of approximately 20 individuals/ ha 10 yr after the last nuclear test (Fall et al 1971).…”

How elevation affects ship rat (Rattus rattus) capture patterns, Mt Misery, New Zealand

“…Furthermore, male ship rats have been recorded moving distances of up to 790 m in a night in beech forest (Pryde et al 2005), so should be capable of living in the forest and commuting into the alpine zone. Overseas, while ship rats tend to be more abundant in temperate locations (Horskins et al 1998;Lindsey et al 1999;Wegmann et al 2008), they are also present in cold climatic zones like Macquarie Island where mean annual temperature is 4.9°C (Australian Government Bureau of Meteorology, unpubl. data).…”

“…Ship rats (Rattus rattus) are habitat generalists, capable of occupying a wide range of habitats, although they tend to be more abundant in temperate regimes than cold temperate regions (Horskins et al 1998;Lindsey et al 1999;Wegmann et al 2008). Ship rats are present in high elevation forest (1600-2000 m a.s.l.…”

Excluding Nontarget Species from Brown Tree Snake, Boiga irregularis (Reptilia: Colubridae), Bait Stations: Experimental Tests of Station Design and Placement

“…Previous studies have found roof rats to be efficient climbers, with higher recapture rates and bait take occurring above ground than on the ground (Tobin et al 1997, Nelson et al 2002, Spurr et al 2007. The Polynesian rat is considered less arboreal than the roof rat (Lindsey et al 1999) but is known to nest and feed in trees (Daniel 1969, McCartney 1970, Williams 1973, Moors et al 1992. Norway rats are also considered less arboreal than roof rats (Atkinson 1985, Key andWoods 1996).…”