Ryukyu long-tailed giant rat

Ryukyu long-tailed giant rat Temporal range: Late Pleistocene–Recent PreꞒ Ꞓ O S D C P T J K Pg N ↓
Stuffed specimen. Exhibit in the National Museum of Nature and Science, Tokyo, Japan.
Conservation status
Endangered  (IUCN 3.1) [1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Muridae
Genus:	Diplothrix
Species:	D. legata
Binomial name
Diplothrix legata (Thomas, 1906)
Synonyms [1] [2]
Diplothrix legatus Lenothrix legataThomas, 1906

The Ryukyu long-tailed giant rat or Ryukyu rat (Diplothrix legata), also known as the rodent in the family Muridae. It is the only extant species in the genus Diplothrix and is endemic to the central Ryukyu Islands of Japan (Amami-oshima, Tokuno-shima, and Okinawa-jima). Its natural habitat consists of temperate forests.

Description

The Ryukyu long-tailed giant rat is the largest rodent endemic to the central Ryukyu Islands and the largest arboreal murid native to Japan. The body length of both sexes is estimated to be over 56 centimetres at sexual maturity. ^{[3] [4]}

D. legata has experienced a population bottleneck in the past and, as a result, may have evolved pleomorphic sperm head morphology (a wide variety of sperm-head shapes), although more studies are needed to explore this variation. The size of its sperm is also relatively larger than that of other rodents. ^[5]

Behaviour

This species is nocturnal and arboreal. Its diet includes both plants, such as fruits, and animals, including invertebrates like butterflies, beetles, and slugs (of the genus Meghimatium sp.). Plant items were found in similar amounts in the stomach contents of males and females, whereas more animal items were found in the stomachs of females.

D. legata may serve as an important seed disperser across the central Ryukyu Islands, which lack the typical dispersers like primates, squirrels, and large birds. ^[6]

Dental microwear texture analysis suggests a seasonal dietary shift from soft-bodied invertebrates in summer to tougher foods such as acorns in winter. ^[7]

This species is believed to have its breeding season between September and February. ^[3] Videos of nesting individuals reveal that nesting material, including branches and leaves, were carried into the nest box between October and February. From February to March, the calls of newborns could be heard, with multiple overlapping calls suggesting a litter of several pups. However, nest predation on young rats by habu pit vipers appears to be high, with no newborns being observed leaving the nest. ^[4]

Conservation

The species is threatened by habitat loss, predation by feral cats (with studies finding that the rat contributed 23% of feral cat's diet on Amami-Oshima), ^[8] and introduced nematode and helminth parasites. ^{[9] [10]}

References

1. Ishii, N. (2016). "Diplothrix legata". IUCN Red List of Threatened Species . 2016 e.T6671A22459891. doi: 10.2305/IUCN.UK.2016-2.RLTS.T6671A22459891.en . Retrieved 16 November 2021.
2. Diplothrix legata. pir.uniprot.org
3. Okano, Tsukasa; Nakata, Katsuhi; Nakaya, Yumiko; Nagamine, Takashi; Onuma, Manabu (2015). "Reproductive traits of the Ryukyu long-furred rat (Diplothrix legata) on Okinawa-jima Island". Journal of Veterinary Medical Science. 77 (6): 637–642. doi:10.1292/jvms.14-0277.
4. Higashi, Teppei; Kobayashi, Shun (2025-01-20). "Record of the Nesting Process of the Ryukyu Long-Furred Rat Diplothrix legata (Rodentia: Muridae) and Newborn Predation by the Habu Snake Protobothrops flavoviridis (Squamata: Viperidae)". Mammal Study. 50 (2). doi:10.3106/ms2024-0042. ISSN   1343-4152.
5. Okano, Tsukasa; Onuma, Manabu (2015-09-01). "Morphological Variation in the Sperm Head of Ryukyu Long-Furred Rat, Diplothrix legata". Mammal Study. 40 (3): 193–196. doi:10.3106/041.040.0307. ISSN   1343-4152.
6. Kobayashi, Shun; Sato, Yukuto; Izawa, Masako (2024-10-16). "Omnivorous Food Habits of the Endangered Ryukyu Long-Furred Rat Diplothrix legata (Muridae) Estimated Using the DNA Metabarcoding Method". Mammal Study. 50 (2). doi:10.3106/ms2024-0007. ISSN   1343-4152.
7. Kubo, Mugino O.; Araki, Kaito; Winkler, Daniela E.; Kondo, Kei; Hayashi, Shoji (2025-04-02). "Feeding Ecology of the Amami Rabbit (Pentalagus furnessi) and the Ryukyu Long-Furred Rat (Diplothrix legata) Inferred from Dental Microwear Texture Analysis". Mammal Study. 50 (2). doi:10.3106/ms2024-0040. ISSN   1343-4152.
8. Shionosaki, K.; Yamada, F.; Ishikawa, T.; Shibata, S. (2015). "Feral cat diet and predation on endangered endemic mammals on a biodiversity hot spot (Amami–Ohshima Island, Japan)". Wildlife Research. 42 (4): 343. Bibcode:2015WildR..42..343S. doi:10.1071/WR14161.
9. Okano, T.; Haga, A.; Mizuno, E.; Onuma, M.; Nakaya, Y.; Nagamine, T. (2014). "Angiostrongylus cantonensis (Nematoda: Metastrongylidae) in the Ryukyu Islands Tree Rat (Diplothrix legata)". Journal of Wildlife Diseases. 50 (2): 322–325. doi: 10.7589/2013-03-050 . PMID   24499332.
10. Tokiwa, T.; Yoshimura, H.; Ito, K.; Chou, S.; Yamamoto, M. (2020). "Alien parasitic infections in the endangered Ryukyu long-furred rat (Diplothrix legata) on Amami-Oshima Island, Japan". Parasitology International. 76 102058. doi:10.1016/j.parint.2020.102058. PMID   31958570.

• Musser, G. G.; Carleton, M. D. (2005). "Superfamily Muroidea". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 894–1531. ISBN   978-0-8018-8221-0. OCLC   62265494.