Summit rat

Summit rat
	on a pitcher of Nepenthes rajah
Conservation status
	; Least Concern (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Muridae
Genus:	Rattus
Species:	R. baluensis
Binomial name
	Rattus baluensis; (Thomas, 1894)

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]

References

^ ^a ^b Aplin, K. (2016). "Rattus baluensis". IUCN Red List of Threatened Species. 2016: e.T19323A22443731. doi:10.2305/IUCN.UK.2016-2.RLTS.T19323A22443731.en. Retrieved 17 November 2021.
^ 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
^ ^a ^b Camacho-Sanchez, Miguel; Leonard, Jennifer A. (2020). "Mitogenomes Reveal Multiple Colonization of Mountains by Rattus in Sundaland". Journal of Heredity. 111 (4): 392–404. doi:10.1093/jhered/esaa014. PMC 7423070. PMID 32485737.
^ Camacho-Sanchez, Miguel; Quintanilla, Irene; Hawkins, Melissa T. R.; Tuh, Fred Y. Y.; Wells, Konstans; Maldonado, Jesus E.; Leonard, Jennifer A. (2018-04-26). "Interglacial refugia on tropical mountains: Novel insights from the summit rat (Rattus baluensis), a Borneo mountain endemic". Diversity and Distributions. 24 (9): 1252–1266. Bibcode:2018DivDi..24.1252C. doi:10.1111/ddi.12761. ISSN 1366-9516.
^ ^a ^b Miguel 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 ONE 6(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 Ecology 27(4): 347–353. doi:10.1017/S0266467411000162