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Rhynchocyon udzungwensis

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA MACROSCELIDEA MACROSCELIDIDAE

Scientific Name: Rhynchocyon udzungwensis
Species Authority: Rathbun & Rovero, 2008
Common Name(s):
English Grey-faced Sengi, Grey-faced Elephant-shrew, Gray-faced Sengi
Taxonomic Notes: This recently described species is the fourth in the genus Rhynchocyon, and its description by Rovero et al. (2008) followed the taxonomy established by Corbet and Hanks (1968). A recent study has confirmed that R. udzungwensis is taxonomically distinct from the surrounding R. cirnei based on nuclear DNA loci (Lawson et al. 2013).  The common name "sengi" is being used in place of elephant-shrew by many biologists to try and dissociate the Macroscelidea from the true shrews (family Soricidae) in the order Soricomorpha. See the Afrotheria Specialist Group web site and www.sengis.org for additional information.

Assessment Information [top]

Red List Category & Criteria: Vulnerable D2 ver 3.1
Year Published: 2015
Date Assessed: 2013-11-25
Assessor(s): Rovero, F. & Rathbun, G.B.
Reviewer(s): Taylor, A.
Contributor(s): Doggart, N.
Justification:
The Grey-faced Sengi is listed as Vulnerable D2 because it occurs at only two locations (Mwanihana and Ndundulu-Luhomero) which, although fully protected, are vulnerable to stochastic drought-driven fires and increased human-induced fires, which could cause a rapid decline in its habitat. A rapid loss of habitat could result in a need to reassess its status to Endangered or Critically Endangered. In addition to natural fires, increasing human population pressure immediately outside the protected forests could cause unpredictable increases in fires and other types of disturbance such as pole and tree cutting (Museo Tridentino di Scienze Naturali 2007, Rovero et al. 2012). Moreover, since the species occurs mainly in moist montane forest (Rovero et al. 2008), predicted effects of global climate change will likely further reduce its habitat; whilst this is unlikely to represent an imminent threat, in the longer term it may become a determinant factor (e.g. Sekercioglu et al. 2008). Recently published information on distribution and habitat associations (Rovero et al. 2013) indicate no change is needed in the Red List status, despite an estimated increase in area of occupancy of 30% in one of the two forests where the species was already known to occur. This increase is mostly considered to be suboptimal habitat (see Habitat and Ecology section).
History:
2008 Vulnerable

Geographic Range [top]

Range Description: Endemic to the Udzungwa Mountains of Tanzania (Kilombero District, Morogoro Region and Kilolo District, Iringa Region), where it occurs solely in two forests, namely Ndundulu-Luhomero forest (north-western Udzungwa) and Mwanihana forest (northeastern Udzungwa). Within these forests, locations recorded by Rovero et al. (2013) indicate that the species is found in montane and upper montane forest throughout Ndundulu-Luhomero, whilst it occupies only the northern part of Mwanihana forest (north of Sonjo valley), above 400 m in elevation, which is where large areas of sub-montane and montane forest are found. The area of occupancy for R. udzungwensis, including all the closed-canopy, sub-montane and montane forest habitat, is estimated to be 390 km² (Rovero et al. 2013). This estimation is based on the spatial distribution of known and inferred sites of occurrence, based on sightings, camera-trap photos and live-trapping (Rovero et al. 2013). The extent of occurrence is estimated to be 810 km2. This includes a 25-km stretch of wooded grassland that separates the two forests from where R. udzungwensis has been recorded, and is not likely to occur.

The extensive zoological surveys that have been conducted in the Udzungwa Mountains and adjacent highland forests indicate that it is unlikely that the species will be found in forests other than Mwanihana and Ndundulu-Luhomero in the Udzungwa Mountains. However, further research is required to accurately define the margins of its distribution, especially in Mwanihana forest.
Countries:
Native:
Tanzania, United Republic of
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Rovero et al. (2008) estimate the population abundance at 15,000-24,000 individuals, with an extrapolated density of 50–80 individuals/km2 over the known area of occupancy. The density range was considered to be realistic by Rovero et al. (2008) based on sighting rates obtained during survey walks, which were compared with data from other species of Rhynchocyon. Rovero et al. (2013) estimated for the Mwanihana forest that the proportion of sites confirmed positive to sengi presence of the total sites sampled was 0.55.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Rhynchocyon udzungwensis occurs in different forest types, but always within moist, sub-montane and montane evergreen to upper montane closed-canopy forest, including bamboo thickets (Rovero et al. 2008, 2013). The canopy of sub-montane and montane forest typically is 25–50 m high, while that of the upper montane forest is 10–25 m. The forest floor vegetation varies from relatively open areas covered in leaf litter to more densely covered with clumps of grasses, herbs and tree seedlings.

The behavioural ecology of R. udzungwensis appears similar to congeneric species (Rathbun 1979). For example, five nests were examined by Rovero et al. (2008), each had an oval cup excavated in the soil lined with layered leaves and loose leaves piled on top to form an indistinct dome surrounded by thick leaf litter on the forest floor. Four of the five nests were situated at the base of trees.

Only in northern Mwanihana forest does the species occur in deciduous to semi-deciduous lowland habitat, which may be sub-optimal (Rovero et al. 2013). Rovero et al. (2013) found that level of occupancy was best predicted by the forest habitat type, with interior, closed-canopy forest supporting highest estimated occupancy. Terrain slope and distance to the nearest park boundary were less important covariates, but nevertheless were still among the variables retained by the best models. Camera-trapping rate (photographic events by day) was significantly correlated with sub-canopy tree coverage. Combined, these habitat features were considered optimal by the authors to reduce predation risk (vegetation cover), and for nest-building and/or foraging on invertebrates in the thicker leaf litter on gentle slopes.
Systems: Terrestrial

Threats [top]

Major Threat(s): The main threat to this species is from habitat loss as a result of forest fires. These fires are causing a slow reduction in forest area, particularly in the Ndundulu – Luhomero forest.  In addition, with the distribution of sengis in Mwanihana forest extending lower than it was believed earlier (Rovero et al. 2013), the threat of forest destruction from fires set by people now extends to the lower edges of this forest.

An analysis of changes in forest and woodland areas for the period 1970-2000 was carried out for the Udzungwa Mountains by the Forestry and Beekeeping Division of the Ministry of Natural Resources and Tourism (2006; see also Burgess et al. 2007). The study was based on analysis of remotely sensed images of land cover and ground-truthing. For the present assessment, the analysis was applied to the extent of occurrence of R. udzungwensis (courtesy of Jenny Hewson, Center for Applied Biodiversity Science, Conservation International). The results reveal that Ndundulu-Luhomero forest has faced a reduction of 2.71% between 1970 and 2000, Mwanihana forest has faced a reduction of 0.52%, and the woodland area between these two forests was degraded by 56%. Habitat loss in this area is mainly attributed to human-induced or natural fires. Fires appear to have caused major degradation of the woodland (including the low elevation, deciduous forest in Mwanihana) along with evergreen forest loss that mainly occurred at the edges and interior clearings. As R. udzungwensis appears to be restricted to forest interiors (Rovero et al. 2013), the gradual reduction in total forest area will reduce the habitat available to the species.

Whilst there is no evidence of hunting by the local people, the ethnic tribe living in the western Udzungwa plateaux (called the Wahehe) are known to routinely practice subsistence hunting, including of the Giant Sengi Rhynchocyon cirnei (Nielsen 2006). This species occurs widely in the Udzungwa Mountains including areas near the Wahehe villages located to the west of the Ndundulu-Luhomero forest (T. Jones pers. comm.). Therefore, in addition to the predicted habitat reduction, with the growth and expansion of human population around protected areas in the Eastern Arc Mountains (Schipper and Burgess 2004), threats to the very localized R. udzungwensis are likely to increase.

Conservation Actions [top]

Conservation Actions: The known range falls entirely within two protected areas: the Udzungwa Mountains National Park (including Mwanihana forest and the eastern part of the Ndundulu-Luhomero forest) and the Kilombero Nature Reserve (including the remaining, western part of the Ndundulu-Luhomero forest). Both the Udzungwa Mountains National Park and Kilombero Nature Reserve are designated for the protection of biodiversity and no utilization of animals for food or trade is permitted in either protected area. The National Park has a management plan that is being implemented with a regular operating budget. The National Park also has a community education and outreach plan. Rates of disturbance are low relative to other Eastern Arc Mountains. The Kilombero forest consists of three Forest Reserves that were upgraded to a Nature Reserve in 2008. This Nature Reserve has a management plan, but the operating budget is insufficient to support many management activities, and there is a lack of personnel and ranger posts.

Citation: Rovero, F. & Rathbun, G.B. 2015. Rhynchocyon udzungwensis. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 30 August 2015.
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