Summit rat

The summit rat, Rattus baluensis, is a species of rodent in the family Muridae that is found only on Mount Kinabalu and Mount Tambuyukon in Malaysia. It has been recorded at altitudes of 2,040 to 2,477 metres on Tambuyukon and 2,670 to 3,426 metres on Kinabalu, and it is most abundant in high altitude dwarf forest and montane scrubland. The two mountain populations were joined in the Holocene but are now genetically isolated, although they are only 18 km apart. Genetic analysis places its origin in a local population of Rattus tiomanicus from northern Borneo some 300,000 to 400,000 years ago. It has a mutualistic relationship with the giant pitcher plant Nepenthes rajah, whose traps it visits to feed on sweet secretions and in which it defecates, as does the treeshrew Tupaia montana.