Bark-stripping of tankan orange, Citrus tankan, by the roof rat, Rattus rattus, on Amami Oshima Island, southern Japan.

Twig Cutting by the Black Rat, Rattus rattus (Rodentia: Muridae), on the Ogasawara (Bonin) Islands

“…Seeds and fruits are preferred food for black rats in general (Yabe 1979), but their availability changes seasonally. A total of only 14 rats was available for stomach-content analysis between July and December 2005 in Nishijima because snap traps were disturbed by hermit crabs.…”

“…Twig cutting in response to scarcity of preferred food is similar to reports of debarking by black rats and other rodents during food shortages. Black rats on an island off southern Japan ate phloem of tankan orange, Citrus tankan, as a supplement because of food shortage after an outbreak of the rats when they were inactive in breeding (Yabe 1998(Yabe , 1999. Kenward (1989) pointed out that the phloem of beech and sycamore trees has a low energy content, and that there is evidence against any link between debarking and food shortage in gray squirrels.…”

“…This information shows that black rats damage a wide range of endemic trees on the Islands by twig cutting. Several cases of debarking or suspected debarking by black rats have been reported in Hawai'i, Italy, and Japan (Scowcroft and Sakai 1984, Santini 1987, Yabe 1998, 1999, Kitahara and Sato 2000, but reports on twig cutting by black rats are limited. Watanabe et al (2003) observed a black rat on a tree and in a cage gnawing twigs of H. glaber.…”

“…Collected specimens were sexed and measured by a routine procedure. Stomachs of rats collected with snap traps were removed for examination of their contents under a stereoscopic microscope following the method of Yabe (1979). The percentage volume of food items in each stomach (excluding bait) was estimated, and the mean percentage volume of each food item was calculated across all stomachs examined.…”

Pattern of Twig Cutting by Introduced Rats in Insular Cloud Forests

“…The aim of the twig-cutting behavior is not clear, but it could supply nutrients (Hansson 1991, Yabe 1998, 1999, Yabe et al 2010 or water (Taylor 1970) in tree sap. The water-intake hypothesis was proposed on the grounds that the behavior occurred in the dry season, but this did not apply in Ogasawara (Figure 7).…”