Vangunu giant rat
| Vangunu giant rat | ||||||||||||
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| Uromys vika | ||||||||||||
| Lavery & Judge , 2017 |
The Vangunu giant rat ( Uromys vika ) is a rodent species from the genus of the mosaic- tailed giant rats ( Uromys ). Like all giant mosaic rats, it is relatively large for an Old World mouse, its weight is estimated to be up to 500 grams and its head-torso length is estimated to be around 30 cm. Exact dimensions are not available because the species is only known from a single, poorly preserved specimen. The Vangunu giant rat is endemic to the Solomon Islands of Vangunu , where it was found in the primary forest of the lowlands. She lives onRose apple trees of the species Dillenia salomonensis , in whose branches and tree hollows it builds nests.
The holotype , on the basis of which the species was first scientifically described in 2017 by Tyrone Lavery and Hikuna Judge , was caught during tree felling work on Vangunu in 2015. Investigations of their tooth structure and genetic material indicate that the Vangunu giant rat belongs to the subgenus Cyromys , which is otherwise restricted to the neighboring Guadalcanal . Nothing is known about the population of the species. The primary forest she inhabits extends over a maximum area of 81 km² and is declining due to the wood harvest. The Vangunu giant rat is therefore proposed for the critically endangered category of the IUCN list of threatened species .
features
The Vangunu giant rat is a relatively large rat. Their skull length is around 50 mm and thus reaches the dimensions customary for their group. Since so far only a half-decayed specimen was available for investigations, no reliable statements can be made about head-trunk length , tail length and other important dimensions. Because most of the existing dimensions are in the range of the closely related naked tail rat Solomys salebrosus , it is likely that the Vangunu giant rat weighs around 290–460 g and has a head-to-trunk length of 225–328 mm.
The species has back hairs 16 mm long and yellow-brownish-gray in color. The top hairs are up to 18 mm long. In terms of dentition, U. vika differs from other representatives of the subgenus Cyromys by a very short upper row of teeth and a very short foramen incisivum . In addition, its zygomatic plate hardly protrudes. The mosaic tail typical of the genus is almost completely hairless. Its mosaic scales have a tiny hump in the middle, which is surrounded by fleshy tissue; they are arranged in rings around the tail. The hind feet of the species are relatively broad, only thinly haired on the upper side and have strong, strongly curved claws, which indicates a very long tail.
distribution and habitat
The Vangunu giant rat is so far only known from two sightings and one specimen caught in 2015, all of which come from the Solomon island of Vangunu. Since Vangunu was connected to the neighboring islands of New Georgia , Kolombangara and Gatokae during the last Ice Age , there is a possibility that previously unknown deposits also exist there. All finds of the species come from rose apple trees of the species Dillenia salomonensis , from which the animals fled while felling trees. These trees are limited to the lowland rainforest of the Solomon Islands, but are common there. The upper limit of distribution of the species is estimated to be 400 m above sea level , analogous to the distribution of D. salomonensis . In total, the forests around the place where the species was found extend to about 81 km².
Way of life
Little is known about the way the Vangunu giant rat lives. The animals build nests in the ferns that grow in the crowns of Dillenia salomonensis , but also inhabit tree hollows. Signs of gnawing on canarium nuts ( C. indicum and C. salomonense ) indicate the possibility that the Vangunu giant rat feeds on them; but they could also come from other large rats.
Taxonomy and systematics
Reports from residents of Vangunu and biogeographical considerations suggested the existence of the Vangunu giant rat for mammalogy. Between the known species of Uromys on Guadalcanal and New Britain ( U. neobritannicus ) and New Guinea ( U. caudimaculatus ) there is a geographical gap with a suitable habitat of around 900 km, which, however, was not part of the range of the genus for a long time. At the same time, reports of a large rat from Vangunu that feed on coconuts and that live on old plantation islands such as Boluchupa and Mahoro off the coast of Vangunu have been known from Vangunu at least since the 1990s . When Tyrone Lavery learned of the existence of such a rat during a visit in 2010, he and his team made several attempts to document the animals using photo traps, live traps, field observations and the search of tree hollows. However, all of these efforts were unsuccessful. Only a piece of excrement containing canarium remains and rodent hair was brought to light in 2011. In addition, since the knowledge of native species among the population declines over the generations, it could not be assumed with certainty that they were not rather domestic rats ( Rattus rattus ).
In 2015, lumberjacks finally caught an animal that was escaping from a felled D. salomonensis tree and seriously injured it. It died shortly thereafter and was buried for conservation purposes until it was taken into custody by the Hikuna Judge ten days later . Hardly any soft tissues were preserved at this point. The state of preservation made it difficult to examine the animal, but Lavery and Judge could, based on the material available to them, assume a previously undescribed species. In 2017 they finally published their first description . As epithet they chose vika , the usual on Vangunu names for the animals.
U. vika classifies the details of the dental apparatus as well as DNA examinations as being related to the Uromys species U. rex , U. imperator and U. porculus that occur on Guadalcanal and are grouped together in the subgenus Cyromys . Uromys , along with Vangunu and Guadalcanal, is only known from the southern Solomon Islands, while the closely related genera Solomys and Melomys occur only in the northern part of the archipelago. This suggests that both groups reached the Solomon Islands independently and split up into different species locally. U. vika would therefore be part of an ecologically very diverse radiation on the southern Solomon Islands, which originated from an ancestor of New Guinea or New Britain who apparently did not find any other rodents in the southern Solomon Islands. The exact relationship between U. vika and other Austro-Papuan rats has not yet been clarified.
Endangerment status
In the absence of more precise inventory and distribution data, no assessments of the threat status are available for Uromys vika . However, since the species has only rarely been sighted in recent years and the forest area around the location of the holotype is relatively small at 81 km² and is also in decline, Tyrone Lavery and Hikuna Judge see a classification in the IUCN category critically endangered (from Threatened with extinction) as justified. In particular, the commercial logging on Vangunu is a source of danger for the species.
literature
- Tim Flannery : Mammals of the South-West Pacific & Moluccan Islands. Reed Books, Chatswood 1995, ISBN 0-7301-0417-6 .
- Tyrone H. Lavery, Hikuna Judge: A new species of giant rat (Muridae, Uromys) from Vangunu, Solomon Islands . In: Journal of Mammalogy . Online first, 2017, p. 1-13 , doi : 10.1093 / jmammal / gyx116 . (on-line)
Web links
- Emma Young: Giant, tree-dwelling rat discovered in Solomon Islands , Nature News, September 27, 2017