| Rhynchocyon[1] | |
|---|---|
.jpg) | |
| Rhynchocyon petersi | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Macroscelidea |
| Family: | Macroscelididae |
| Genus: | Rhynchocyon Peters, 1847 |
| Type species | |
| Rhynchocyon cirnei Peters, 1847 | |
| Species | |
Rhynchocyon chrysopygus | |
Rhynchocyon is a genus ofelephant shrews in the familyMacroscelididae.[1] Members of this genus are known colloquially asgiant sengis.[2]They are a ground-dwelling mammal, significantly larger than their relatives in the orderMacroscelidea that live primarily in dense forests across eastern Africa.Habitats range from easternAfrica's coastal forests,Rift Valley highlands, and theCongo basin. The species is widely threatened, with two of four assessed by theInternational Union for Conservation of Nature's Red List of Threatened Species.Habitat fragmentation from the growth of human settlements and activities are the primary threats to their populations. The genus contains the following five species and several subspecies:[3][4][5]
| Cladogram of living Rhynchocyon species[4] |
The giant sengis areendemic to Africa, and usually live in lowlandmontane and dense forests,[6] often "avoiding" edges of forest patches.[7][8] These dense forests play a role in their shelter and reproduction, as they provide the ecological niche in which sengis exploit. They are typically active in the day (diurnal), spending their nights hidden in the shelters that they build the morning prior.[9] After a few nights of use, sengis tend to abandon their shelters to create new ones elsewhere.[9] They typically build their shelters at ground level,[10] requiring dryleaf litter.[11] The primary structure of a nest forR. udzungwensis, for example, consists of the excavation of a cup-like indentation in the soil, layered with leaves, and then covered with looser leaves as a roof covering.[12] They usually construct their nests at the base of trees.[12] They also use hollowed, fallen trees or trunks to retreat in shelter,[13] especially when faced with predation. Sengis respond to disturbances by staying still or making loud thumping noises on the forest floor.[9] In instances of predation, the giant sengi uses a half-bound gait to rapidly run away.[9]
Other Macroscelidea species are known tobask in the sun, as a method ofthermoregulation to save energy.[13] Giant sengis do not bask—and it is most likely due to their adaptation to shadedcanopy forest environments.[13]
Sengis live inmonogamous pairs, defendinghectare-sized territories.[14][10] Pairs spend little time together except when the female is inestrous.[13] Mating occurs quickly and offspring grow quickly with minimal parental investment—none of which is paternal.[13]
%2c_Cossypha_natalensis%2c_at_Ithala_Game_Reserve%2c_Kwa_Zulu-Natal%2c_South_Africa_(39023328225).jpg)
It has been observed that the genus has acommensal relationship with a variety of ground-foraging birds throughout its ranges. Both theRed-capped robin-chat andWhite-chested alethe often follow the giant sengis as they forage, in attempt at capturing prey that is disturbed while they shuffle through leaf litter looking for prey.[15] They eat primarily insects such as beetles,termites,ants, andcentipedes, using theirproboscises to dig them from the soil and its tongue to lick them up.[16] Their facial morphology limits their diets to tiny invertebrates, and unlike other members of Macroscelidea, do not supplement their diet with foods such as nuts or small fruits.[13]
Each species exhibits distinct and varying coat patterns and colors. Species and subspecies found in denser forests exhibit darker coloration and patterns while open woodland species exhibit lighter, chequers. The darker speciesR. petersi,R. chrysopygus, andR. udzungwensis still containvestigial chequers, but are masked by the blended dark fur between them. This makes coat patterns an unreliable indicator of species delineation though useful for identification.[12][17] The species are described as follows:
.jpg)
The genus' taxonomic status has been difficult to determine due to the very close similarities between populations. Up to ten species have been recognized, but over time they have been regrouped into four species.[4] Recently,R. cirnei, the species with the most subspecies, has hadR. c. stuhlmanni separated into its own species based on updated molecular data.[4]
Close genetic relatedness indicates that thecommon ancestor of the genus lived around 7.9 million years ago (Ma).[19] There are, however, fossil taxa push this time further into theOligocene.[19]Miorhynchocyon [it] meswae dates from the Meswa Bridge fossil site in Kenya dates to 22.5 Ma.[19]Oligorhynchocyon songwensis [it] from theNsungwe Formation in Tanzania dates to 25 Ma.[19] Other fossils of the subfamily Rhynchocyoninae are found between 18 and 23 Ma[19] such asM. clarki andM. rusingae from about 20 Ma from Songhor fossil site in Kenya.[20] This large gap between estimated divergence time of the genus indicates thatM. meswae andO. songwensis species are likely stem taxa of the entire group.[21] Because ofRhynchocyon's canopy forest and dense leaf litter requirements, the ancestors of the genus may have experienced selective pressures to become more greatly adapted to forest environments as theMiocene experienced a large expansion of grasslands.[21] Several other extinct genera of the family Rhynchocyonidae have been described:Brevirhynchocyon [it] andHypsorhynchocyon.[22]Eorhynchocyon (E. rupestris) is the oldest fossil species similar to giant sengis, but containing intermediate traits to those ofElephantulus andPetrodromus.[22]
Various classification issues still exist, with several undetermined questions left unresolved:[4]
Mitochondrial DNA sequencing was conducted on a single specimen (dubbed the Boni giant sengi) from the Dodori and Boni national reserves in Kenya,[4] as there was suspicion that there may be another species present based on specimen capture, sightings, andcamera trap images.[23]
The pelage pattern differs significantly fromR. chrysopygus,[4] as it does not have the bright yellow patch on its rump. It also does not possess the same pelage traits asR. petersi—the Boni giant sengi has dark brown and black skin on its ears and tail whereasR. petersi has orange skin. It's face is griseous yellow-brown and the black fur on its rump does not extend to the middle of the back like it does inR. petersi. The single captured specimen weighs about 600 grams, lighter thanR. udzungwensis, but heavier thanR. petersi. It also has no noticeable chequers, though the dark fur patterns obscures these in all dark-colored giant sengis.[23] A unique feature not found among other giant sengis is the prominent crest of hair along the nape of the neck.[5] Despite the pelage differences, initial DNA comparisons found it nearly identical toR. chrysopygus.[4] A later DNA comparison supported a designation of a new subspecies,Rhynchocyon chrysopygus mandelai as it diverges in pelage and is allopatric toR. chrysopygus.[5]
_Distribution-2024.png)
R. chrysopygus,R. cirnei, andR. petersi areallopatrically distributed; with the more recently discoveredR. udzungwensis and subspeciesR. cirnei reichardi exhibitingparapatric distributions.[24] Some introgression (hybridization) has taken place betweenR. udzungwensis andR. cirnei reichardi as detected bymtDNA.[24]R. p. adersi is rare and unique in its distribution, being found isolated on the islands of theZanzibar Archipelago.[25]R. c. reichardi is typically found in the Rift Valley highlands of Tanzania, Zambia, and Malawi, withR. c. hendersoni found in the highlands of northern Malawi.[4]
BothR. c. hendersoni andR. c. shirensis are known at higher elevations, similar to that ofR. udzungwensis; howeverR. udzungwensis is unique in its larger body size[12] (being the largest giant sengi known[26]).Bergmann's rule suggests that specialized ecological factors such as climate and temperature would favor larger bodies like that ofR. udzungwensis, though the latter two species do not share this trait.[12] For comparison,R. udzungwensis occurs in greater abundance at elevations above 1000 meters,[24] has a body mass of 710 grams and a brain mass of 7131 milligrams,[26] whileR. petersi occurs at greater abundance at elevations between 0 and 2000 meters, has a body mass of 471 g, and a brain mass of 5400 mg.[26]
Estimated of population size and density vary and can be difficult to determine. However, measurements of the species populations has been undertaken.R. chrysopygus, in protected areas, is about 150 individuals per square kilometer (about 14–20,000 individuals);[2]R. petersi is between 19 and 80 individuals per square kilometer;R. udzungwensis has an estimated 15,000–24,000 individuals.R. udzungwensis has a tiny distribution (restricted to submontane and montane forest in the Ndundulu–Luho-mero and Mwanihana forests) compared to the other species but resides in land.[12]
| Species | Localities | Elevation range (meters) |
|---|---|---|
| Rhynchocyon chrysopygus chrysopygus | Kenya (Arabuko-Sokoke Forest)[2] | 30–360 m[27] |
| Rhynchocyon chrysopygus mandelai | Kenya (Boni National Reserve andDodori National Reserve)[23] | |
| Rhynchocyon cirnei cirnei | Mozambique (north ofZambezi River);Malawi,Zambia andTanzania (highlands withinRift Valley); Tanzania (south ofRufiji River)[28] | 0–2100 m[28] |
| Rhynchocyon cirnei reichardi | Tanzania, Malawi, and Zambia (highlands)[4] | 290–1800 m[24] |
| Rhynchocyon cirnei hendersoni | Northern Malawi (highlands)[4] | Similar toR. udzungwensis[24] |
| Rhynchocyon cirnei shirensis [avk;nl] | Southern Malawi (Shire Valley)[4] | Similar toR. udzungwensis[24] |
| Rhynchocyon petersi | Tanzania (Eastern Arc Mountains, West and EastUsambara,Nguru,NguuUluguru mountains,North andSouth Pare mountains, and coastal fragmented forests from Rabai Hills and Diani Forest toRufiji River.[29][3] | 0–2020 m[3][29] |
| Rhynchocyon petersi adersi | Zanzibar Archipelago (onlyUnguja Island andUzi Island) andMafia Archipelago (onlyMafia Island).[25][29][30] | Undetermined, though they are restricted to Zanzibar's and Mafia Island's highest elevations of 119 and 53 meters respectively. |
| Rhynchocyon stuhlmanni | Democratic Republic of Congo (between theCongo andUbangi Rivers); Uganda (western forests surroundingLake Albert,Mabira Central Forest Reserve east ofKampala)[28] | |
| Rhynchocyon udzungwensis | Udzungwa Mountains of Tanzania in theKilombero District of theMorogoro Region and theKilolo District of theIringa Region (specifically, the Ndundulu-Luhomero and Mwanihana forests within the ).[31] | 350–2300 m[24][31] |
All species in the genus are threatened by habitat destruction (primarilydeforestation).Forest fragmentation from human activities have created a patchwork of forestnational parks andpreserves. This has resulted in an uneven and variable level oflegal protection.[3][13][17][32]
.png)
Species particularly threatened are those with greatly restricted distributions such asR. udzungwensis andR. chrysopygus. Often, restricted ranges are habitats that are protected forests and preserves that are bordered by human settlements.R. chrysopygus for example, resides mostly in theArabuko-Sokoke Forest as well as in patchy, fragmented forests between the Arabuko-Sokoke Forest andMombasa.[2] The Arabuko-Sokoke Forest provides only 395.4 km2 of suitable habitat, with an additional 30 km2 available in non-forest, isolated,scrub anddegraded woodland fragments.[7] Between 1993 and 1996,R. chrysopygus populations declined from 20,000 to 14,000.[33] Tiny forest fragments putR. chrysopygus at greater risk of localized extinction due to agricultural clearing, harvesting of trees, and fires.[2] One fragment population was assessed in 2008 and found only 20 individuals remained.[34]
To illustrate the severe reduction of habitat over time,R. chrysopygus used to occupy uninterruptedcoastal forests that spanned from Mombasa all the way to the Tana River.[7] Eighty percent has been deforested, with only the Arabuko-Sokoke Forest remaining as the largest portion.[7]R. chrysopygus uses about 328 km2, with decreasing presence and activity the closer they are to theforest edges.[7] Different types of habitats exist within this forest:Cynometra thickets,Brachystegia woodlands, and mixed forest (historically dominated byAfzelia quanzensis, a heavily logged tree species[35]).[7]R. chrysopygus heavily favorsCynometra forests as well are mixed forest areas that have maintained plenty ofA. quanzensis.[7] The greatest issue facingR. chrysopygus from forest reduction is that removing trees eliminates tree-trunk hollows, thick leaf litter, and coveredcanopy—all critically important for survival and reproduction.[36] These factors, alongside hunting andsubsistence trapping,[37] are why it is listed as Endangered by the IUCN.[2] Human-driven pressures have not declined, with continuedlogging, hunting, and even a 2015 proposal to extract fossil fuels from parts of the forest.[7][38]
WithR. chrysopygus being listed by the IUCN Red List as Endangered, a strategic plan was developed for 2002–2027 for the Arabuko-Sokoke Forest, where the sengis were monitored for a three-year period.[2] The forest is managed by two institutions: the Forest Department and the Kenya Wildlife Service as well as being listed as a National Monument as part of the Coast Forest Conservation Unit's efforts.[2] This designation prevents human encroachment and development, but does not necessarily protect the biodiversity within.[2]
R. cirnei is listed as Least Concern with the IUCN,[28] though this has limited specifics about the various subspecies. Range maps give an inaccurate visualization of the distribution, as the species is restricted to isolated montane forest patches, lowland forests, woodlands with closed tree canopies, andriparian thickets.[28] In Mozambique, it is realistically only found in small, suitable forests areas.[39] In the Central African Republic, only a single specimen ofR. cirnei (which would technically now beR. stuhlmanni) has been found to the west of theUbangi River, indicating an exaggerated distribution.[28] Distributions within the Eastern Arc Mountains are patchy, and are threatened due to decreasing forested areas, fragmentation, and the reduction of habitat quality from human activity.[28]
R. c. macrurus is at greater risk due to its more restricted range along the coastal areas of Tanzania due to increased human pressures.[28]Mount Rungwe populations (technicallyR. c. reichardi are particularly at risk due to increase hunting in the region.[40] One population of concern is the extremely small isolated range ofR. cirnei (which would technically now beR. stuhlmanni) individuals in theMabira Forest east ofKampala.[28] This forest is only 300 km2 and has been the focus of political controversy due to plans to deforest a large portion of the reserve.[41] The species lacks any specific conservation efforts, but is found within various protected areas throughout its range.[28] Antelope and primate protection conservation efforts are likely to have unintentional benefits forR. cirnei.[28]
.png)
R. petersi is listed as Least Concern with the IUCN;[29] however, the species distribution is discontinuous due to human-caused habitat fragmentation that has created a mosaic of forest patches, parks, and reserves.[3] Because of this complex distribution, many forest patches have not been surveyed so presence is unclear—especially the case for non-protected, coastal forest fragments.[3] Notable and well-surveyed forests are those that are protected in forests (see Table 2).[3] Between these protected forest patches exist unsuitable habitat;[3] with coastal forest area fragments being particularly unsuitable due to extreme habitat degradation and severe isolation of remaining forest patches.[42] A few coastal forest exceptions exist: theSelous Game Reserve and theSaadani National Park are well-managed protected lands in whichR. petersi are commonly found, especially within the 20 km2 Zaraninge Forest within Saadani.[29] Since forest fragmentation is the greatest threat toR. petersi, conservation focuses on the local drivers of this process: agricultural expansion and logging for firewood, charcoal production, and woodcarving.[29] Hunting also plays a minor role in population declines, but is not thought to be a significant threat.[29]R. petersi is unique in that it has been successfully bred in zoos allowing for the possibility of breeding and reintroduction programs.[29]
| Mountain range | Surveyed protected land | Unsurveyed protected land |
|---|---|---|
| South Pare mountains | Chome Forest Reserve | Chambogo, Kwizu |
| North Pare mountains | Kamwalla II, Kindoroko, Minja, Mramba | Kiverenge |
| WestUsambara mountains | Magamba, Ambangulu | Shaguya, Mkussu, Baga II, Ndelemai, Mafi Hill, Bangalai, |
| East Usambara mountains | Nilo, Bamba Ridge, Kambai, Kwamarimba, Kwamgumi, Manga, Mgambo, Mtai, Segoma, | Longuza South, Bombo West |
| Nguu mountains | Nguru North, Kilindi | Derema, Mkuli, Pumila, Rudewa |
| Nguru mountains | Nguru South, Kanga, Mkindo | |
| Uluguru mountains | Uluguru North, Uluguru South, Mkangazi | Ruvu |
| R. petersi is not found inTaita Hills, or theMahenge,Malundwe,Ukaguru,Rubeho, andUdzungwa mountains and associated forest patches. | ||
.png)
Listed as Vulnerable with the IUCN Red List,R. udzungwensis has a highly restricted and small geographic range of about 810 km2.[31] Because the distribution is in two locations (the Ndundulu-Luhomero forest and the Mwanihana forest), its suitable habitat makes up only 390 km2,[32] with a 25 km region between the two forests being less-suitable wooded grassland.[31] Not all of theUdzungwa Mountains are protected,[43] puttingR. udzungwensis at greater risk from human pressures.[32] The greatest threat facing the species is uncontrolled forest fires[31] that cause loss of the required moist, montane canopy forests.[32] Between 1970 and 2000, 2.71% of the Ndundulu-Luhomero forest was reduced, with another 0.51% lost from the Mwanihana forest.[31] The land between the two forests has been significantly degraded as well, with human-caused fires as the greatest driver of habitat loss.[31]Hehe people are known to huntR. cirnei for food,[44] but it is unknown if they huntR. udzungwensis;[31] though it is expected to become a future threat due to human population expansion in the surrounding areas.[45] Since the two forests exist entirely within the Udzungwa Mountains National Park and Kilombero Nature Reserve,R. udzungwensis is protected from being used as food and for trade; though funding is low and ranger monitoring is limited.[31] The park has an educational outreach program as part of its management plan budget.[31]
{{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link){{citation}}: CS1 maint: numeric names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link){{citation}}: CS1 maint: multiple names: authors list (link)