The summit rat (Rattus baluensis) is a species of
rodent in the family
Muridae. It is found only on
Mount Kinabalu and
Mount Tambuyukon,[2]Malaysia, and has been recorded at altitudes of 2,040 to 2,477 m on Mt. Tambuyukon and 2,670 to 3,426 m on Mt. Kinabalu.[1][3] They are most abundant in higher altitude dwarf forest and montane scrubland.[4] The rat populations from these two peaks were connected in the
Holocene. However, nowadays they are genetically isolated despite being 18 km apart.[5] With current predictions of Global warming, the suitable habitat for Rattus baluensis is expected to shift around 500 m upwards. This will put the population in
Mount Tambuyukon at risk. However, the population in
Mount Kinabalu will likely survive in its upper slopes.[5]
Genetic analysis situate its origin in a local population of Rattus tiomanicus from northern Borneo at around 300-400 thousand years ago.[3]
The summit rat has a
mutualistic relationship with a species of giant
pitcher plant, Nepenthes rajah. Like the treeshrew Tupaia montana, it defecates into the plant's traps while visiting them to feed on sweet, fruity secretions from glands on the pitcher lids.[6][7]
^Camacho-Sanchez M*, Hawkins MTR*, Tuh Yit Yuh F, Maldonado JE, Leonard JA. 2019. Endemism and diversity of small mammals along two neighboring Bornean mountains. PeerJ 7:e7858
https://doi.org/10.7717/peerj.7858
^
abMiguel Camacho-Sanchez, Irene Quintanilla, Melissa T. R. Hawkins, Fred Y. Y. Tuh, Konstans Wells, Jesus E. Maldonado and Jennifer A. Leonard. 2018. "Interglacial refugia on tropical mountains: novel insights from the summit rat (Rattus baluensis), a Borneo mountain endemic". Diversity and Distributions, 24: 1252-1266.
https://doi.org/10.1111/ddi.12761
^Greenwood, M., C. Clarke, C.C. Lee, A. Gunsalam & R.H. Clarke 2011. A unique resource mutualism between the giant Bornean pitcher plant, Nepenthes rajah, and members of a small mammal community. PLoS ONE6(6): e21114.
doi:
10.1371/journal.pone.0021114
^Wells, K., M.B. Lakim, S. Schulz & M. Ayasse 2011. Pitchers of Nepenthes rajah collect faecal droppings from both diurnal and nocturnal small mammals and emit fruity odour. Journal of Tropical Ecology27(4): 347–353.
doi:
10.1017/S0266467411000162