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Behavior and Feeding Habits

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Rhynchocyon are solitary, diurnal, nest-building animals (Kingdon 2015; Rathbun 2009). They prefer forest floors that are well drained and covered with a dense layer of leaf litter, which is used to build 1 m-wide leaf-mound shelters piled on top of shallow body-sized recesses in the soil (Kingdon 2015). The nests are built in the early morning when the litter is damp, limp and easily compressed without causing loud noises, avoiding detection from predators (Kingdon 2015; Rathbun 2016). At night the nests are used for sleeping and during the day they are rarely occupied, except when used as a nursery (Kingdon 2015; Rathbun 2009). It is believed that each individual maintains an average of 10 or more of these nests within its home range, which averages 1.7 ha (17,000 square meters or 4.2 acres) (Kingdon 2015).

Rhynchocyonfeed on insects, including larvae, termites, ants, beetles, spiders, myriapods (e.g., centipedes and millipedes), and earthworms (Kingdon 2015). Their hypsodont dentition, which refers to high-crowned shaped teeth found in animals that eat high fiber diets such as horses and cows, suggests an earlier ancestor ate an herbivorous diet (Merriam Webster 2016; Rathbun 2009). Giant sengis forage through the leaf litter and soil using their paws and flexible snout (Kingdon 2015; Rathbun 2009). A proboscis can extend past the mouth and the long tapered tongue can extend several millimeters past the tip of the snout (Kingdon 2015). Giant sengis collect food items into their under-slung mouths, which open downward, using a rapid flicking motion of the tongue (Rathbun 2009). They have strong hind legs making them excellent at rapid movement and avoiding predators (Kingdon 2015). They have a compact skull and low profile stance helping them occupy little space in their nests and facilitating a ready to flee sleep position (Kingdon 2015).

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Comprehensive Description

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The giant sengi (Rhynchocyon) is a genus of elephant shrew (sengi) (Corbet and Hanks 1968; Rathbun 2009). Sengi is the Bantu word for shrew and is the preferred naming by conservationists (Mangat 2015). Within the Rhynchocyon genus are the largest and most colorful sengis, members of the family Macroscelididae, order Macroselidea, and class Mammalia (Corbet and Hanks 1968; Rathbun 2009). Sengis were first named elephant shrews for their elongated nose, which resembles a small elephant’s trunk, and their seeming, but false, similarity to shrews (Understanding Evolution 2008). Based on genetic and molecular data, sengis and elephants are both members of the superorder Afrotheria, meaning that sengis are technically more closely related to elephants than shrews (BBC Nature Wildlife 2014; Understanding Evolution 2008). Giant sengis are endemic to central and eastern Africa and live in a variety of forests and woodlands that typically have a dense canopy and a thick layer of leaf litter covering the ground (Corbet and Hanks 1968; Rathbun 2009).

There are four established species of giant sengis: R. chrysopygus (golden-rumped sengi), R. cirnei (chequered sengi), R. petersi (black-and-rufous sengi), and R. udzungwensis (grey-faced sengi)(Rathbun 2009). R. udzungwensis was discovered in 2008 in two isolated forests in the northern Udzungwa Mountains of Tanzania, while the other three species were first observed by Western scientists at the end of the eighteenth-century (Rovero et al. 2008). Each of these species has distinct geographical ranges: R. chrysopygus is limited to Kenya; R. cirnei is can be found in the Democratic Republic of the Congo, Uganda, Tanzania, Mozambique, Malawi, and Zambia (there is also one unconfirmed sighting in the Central African Republic); R. petersi can be found in Kenya and Tanzania, and R. udzungwensis is limited to Tanzania (Corbet and Hanks 1968; Rathbun 2009). A potential fifth species called Mandela’s giant sengi (or Boni giant sengi) was identified in 2010 in the dried evergreen thickets of the Boni and Raas Kaamboni forests near the Kenyan coastal border with Somalia (Andanje et al. 2010). Mandela’s giant sengi is named in honor of the African leader and peacemaker Nelson Mandela because its habitat spans the border of conflicted nations (Kingdon 2015). It has not been fully described and does not yet have a specific scientific name (R. sp. nov.), but is listed among the species of Rhynchocyon in recent publications in order to highlight its narrow range, unique natural history, and sensitivity to environmental changes caused by ecological or human factors (Baillie and Butcher 2012; Kingdon 2015; Mangat 2015).

References

  • Nairobi, Kenya: African Wildlife Foundation. Available: http://www.awf.org/wildlife-conservation/elephant-shrew. (Accessed: Dec. 4, 2016)
  • Understanding Evolution. 2008. The new shrew that’s not. University of California Museum of Paleontology. Berkeley, CA. Available: http://evolution.berkeley.edu/evolibrary/news/080301_elephantshrew. (Accessed: Dec. 9, 2016).

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Ecological associations, population biology and conservation

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Natural predators consist of large birds of prey and snakes, yet predation is generally low for giant sengis likely due to their ability to construct well-hidden nests (Kingdon 2015). Dogs from nearby populated areas also prey on Rhynchocyon (Kingdon 2015). Rhynchocyon live in restricted or fragmented forests that are threatened by logging practices and clearing for agricultural and urban development (Rathbun 2009; Rathbun 2016). Hunting giant sengis for survival food may also threaten the sengi in some areas (Rathbun 2016).

Evolutionarily, Rhynchocyon and the “micro-niches” they occupy have changed little over the past 30 million years, suggesting long-term ecosystem stability (Kingdon 2015). While each individual characteristic of the giant sengi is not particularly unique, it is the collection of them found in a single mammal that makes the giant sengis exceptional (Rathbun 1979; Rathbun 2009). In particular, the sengi represents an unusual combination of miniaturized antelope and anteater in what has been defined as the “micro-cursorial adaptive syndrome” (Rathbun 1979). According to Version 2016-2 of the IUCN Red List of Threatened Species R. chrysopygus is endangered, R. cirnei are near-threatened, R. petersi are of least concern, and R. udzungwensis is vulnerable (IUCN 2016). R. chrysopygus is considered a global conservation priority by the Zoological Society of London (ZSL) due to its threatened status and evolutionary uniqueness (ED) (Mangat 2015). ZSL applied its scoring system to all over 5,000 mammal species and R. chrysopygus ranked 46th (Mangat 2015).

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Physical Description

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Rhynchocyon individuals are morphologically similar, weighing 350-700 g (1.0-1.5 lbs) and having head-body and tail lengths of up to 31 cm and 25 cm (12 inches and 9.8 inches), respectively (Rathbun 2016). They have long legs and a long, naked, white-tipped tail (Kingdon 2015). Their long and flexible nose is especially adapted for foraging for insects on the forest floor (Rathbun 2009). Rhynchocyon have short and sleek fur with each species having a distinct color pattern (Kingdon 2015; Rathburn 2016). A pungent smell is emitted from a gland behind the anus, which is used to mark their territory (Kingdon 2015). Males and females are physically indistinguishable, except that females have longer, sharper canine teeth (Kingdon 2015).

Each species with the genus has distinct body color patterns. R. chrysopygus has a golden colored rump, grizzled gold forehead that is in contrast with its dark reddish-brown body color (Corbet and Hanks 1968). R. udzungwensis has a black rump that gradually becomes rich russet on the shoulders and thorax. It is marked by two rows of red-orange spots on each flack and has a greyish face (Rovero et al. 2008; Kingdon 2015). Mandela’s giant sengi has a black rump with two paired lines along each side of a mahogany dorsal stripe that starts at the ears as a deep red crest and that becomes narrower until it reaches the tail (Kingdon 2015). Its face is a tawny color. R. cirnei has a checkered pattern of longitudinal dark bands on an agouti-grizzled background with pale (almost white) spots or flecks (Corbet and Hanks 1968; Kingdon 2015). R. petersi has a rufous head and shoulders, while the rest of the body is black. The tails of all Rhynchocyon species have a conspicuously white section near the tip (Corbet and Hanks 1968; Rathbun 2016).

References

  • Andanje, S., B. R. Agwanda, G. W. Ngaruiya, R. Amin, and G. B. Rathbun. 2010. Sengi (elephant-shrew) observations from northern coastal Kenya. Journal of East African Natural History 99:1-8.
  • Baillie, J. and E. Butcher. 2012. Priceless or worthless? The world’s most threatened species. Zoological Society of London, United Kingdom. 84.
  • BBC Nature Wildlife. 2014. Elephant shrews. Available: http://www.bbc.co.uk/nature/life/Elephant_shrew. (Accessed: Dec. 11, 2016).
  • Corbet, G. B. and J. Hanks. 1968. A revision of the elephant-shrews, Family Macroscelididae. Bulletin of the British Museum of Natural History, Zoology 16:47-111.
  • Hedges, S. B. 2001. Afrotheria: Plate tectonics meets genomics. PNAS 98:1-2.
  • IUCN. 2016. The International Union for Conservation of Nature’s Red List of Threatened Species. Version 2016-2. Available: www.iucnredlist.org. (Accessed: Dec.5, 2016).
  • Kingdon, J. 2015. The Kingdon field guide to African mammals (2nd ed.). Bloomsbury Publishing. London, England. 80-85.
  • Mangat, R. 2015. Elephant shrew facing extinction. The East African Magazine. Available: http://www.theeastafrican.co.ke/magazine/Elephant-shrew-facing-extinction-/434746-2606250-10wt3xz/index.html. (Accessed: Dec.5, 2016).
  • Merriam-Webster. 2016. Medical Definition of Hyposodont. Available: https://www.merriam-webster.com/medical/hypsodont. (Accessed: Dec. 9, 2016).
  • Rathbun, G. B. 1979. The social structure and ecology of elephant-shrews. Advances in Ethology 20:1-75.
  • Rathbun, G. B. 2009. Why is there discordant diversity in sengi (Mammalia: Afrotheria: Macroscelidea) taxonomy and ecology? African Journal of Ecology 47:1-13.
  • Rathburn, G. B. 2016. Sengis (Elephant Shrews). Available: www.sengis.org. (Accessed: Dec. 5, 2016).
  • Rovero, F., G. B. Rathbun, A. Perkin, T. Jones, D. O. Ribble, C. Leonard, R.R. Mwakisoma, and N. Doggart. 2008. A new species of giant sengi or elephant-shrew (genus Rhynchocyon) highlights the exceptional biodiversity of the Udzungwa Mountains of Tanzania. Journal of Zoology 274:126-133.
  • Understanding Evolution. 2008. The new shrew that’s not. University of California Museum of Paleontology. Berkeley, CA. Available: http://evolution.berkeley.edu/evolibrary/news/080301_elephantshrew. (Accessed: Dec. 9, 2016).
  • African Wildlife Foundation. 2016. What we do: wildlife conservation: elephant shrew. Nairobi, Kenya: African Wildlife Foundation. Available: http://www.awf.org/wildlife-conservation/elephant-shrew. (Accessed: Dec. 4, 2016)

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Brief Summary

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A possibly new species, the Boni Giant Sengi, has not yet been formally described, but regardless of whether it is recognized as a full species, its highly restricted distribution and threats to its existence from major planned development in the area have led to its listing as critically endangered by the International Union for Conservation of Nature (IUCN).

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Rhynchocyon

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Rhynchocyon is a genus of elephant shrew (or sengi) in the family Macroscelididae.[1] Members of this genus are known colloquially as the checkered elephant shrews[3] or giant sengis.[4] It contains the following five species:[5]

Ecology

The giant sengis are endemic to Africa, and usually live in lowland montane and dense forests,[6] often "avoiding" edges of forest patches.[7][8] They eat primarily insects such as beetles, termites, ants, and centipedes, using their proboscises to dig them from the soil and its tongue to lick them up.[9] 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.[10]

They typically build ground level nests for shelter[11] requiring dry leaf litter.[12] The primary structure of a nest for R. udzungwensis, for example, consists of the excavation of a cup-like indentation in the soil, layered with leaves, and the covered with looser leaves as a roof covering.[13] They usually construct their nests at the base of trees.[13] They also use hollowed, fallen trees or trunks to retreat in shelter.[10]

They are typically active in the day (diurnal), spending their nights sheltered. Other Macroscelidea species are known to bask in the sun as a method of thermoregulation to save energy.[10] Giant sengis do not bask—and it is most likely due to their adaptation to shaded canopy forest environments.[10]

Sengis live in monogamous pairs, defending hectare-sized territories.[14][11] Pairs spend little time together except when the female is in estrous.[10] Mating occurs quickly and offspring grow quickly with minimal parental investment—none of which of is paternal.[10]

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 species R. petersi, R. chrysopygus, and R. udzungwensis still contain vestigial chequers, but are masked by the blended dark fur between them. This makes coat patterns an unreliable indicator of species delineation.[13] The species are described as follows:

  • R. chrysopygus exhibits a bright yellow patch of fur on its rump with very little black coloration at all. R. chrysopygus has a unique dermal shield (a specialized thickening of skin) on its rump.[13]
  • R. petersi has mostly orange-rufous coloration on its feet, ears, tail, chest, and on its face. Black fur extends from its rump and thighs up to its shoulders.[13]
  • R. udzungwensis has black feet, ears and a tail. Its face is griseous grey with its lower rump and thighs are black. The chest is pale yellow.[13]
  • R. cirnei and its subspecies feature six dark-colored stripes and spots (chequers) on its back.[13] They contain little to no black fur, are lighter in color, and differ markedly by their lack of orange-rufous coloration found on its coastal relatives R. petersi, R. chrysopygus, and R. udzungwensis.[2] The subspecies R. c. macrurus exhibits a clinal variation different from coastal populations towards inland populations.[13][15]
  • R. stuhlmanni exhibits a similar coloration and pattern as R. cirnei differing notably by its white tail.[2]

Taxonomy, distribution, and speciation

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.[2] Recently, R. cirnei, the species with the most subspecies, has had R. c. stuhlmanni separated into its own species based on updated molecular data.[2]

R. chrysopyguus, R. cirnei, and R. petersi are allopatrically distributed; with the more recently discovered R. udzungwensis and subspecies R. cirnei reichardi exhibiting parapatric distributions.[16] Some introgression (hybridization) has taken place between R. udzungwensis and R. cirnei reichardi as detected by mtDNA.[16]

Estimated of population size and density vary and can be difficult to determine. However, measurements of the species populations has been undertaken. R. chrysopyguus, in protected areas, is about 150 individuals per square kilometer (about 20,000 individuals); R. petersi is between 19–80 individuals per square kilometer; R. udzungwensis has an estimated 15,000–24,000 individuals. R. udzungwensis has a tiny distribution compared to the other species but resides in a protected forest.[13]

Phylogeny and geographic distribution of species in the Rhynchocyon genus

References

  1. ^ a b Schlitter, D.A. (2005). "Genus Rhynchocyon". 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. 84–85. ISBN 978-0-8018-8221-0. OCLC 62265494.
  2. ^ a b c d e Carlen, E.J.; Rathbun, G.B.; Olson, L.E.; Sabuni, C.A.; Stanley, W.T.; Dumbacher, J.P. (2017). "Reconstructing the molecular phylogeny of giant sengis (Macroscelidea; Macroscelididae; Rhynchocyon)". Molecular Phylogenetics and Evolution. 113: 150–160. doi:10.1016/j.ympev.2017.05.012. PMID 28552433.
  3. ^ ITIS.gov
  4. ^ FitzGibbon, C.; Rathbun, G.B. (2015). "Rhynchocyon chrysopygus". IUCN Red List of Threatened Species. 2015: e.T19705A21287265. doi:10.2305/IUCN.UK.2015-2.RLTS.T19705A21287265.en. Retrieved 12 November 2021.
  5. ^ Hoffmann Michael; Rathbun Galen B.; Rovero Francesco; Perkin Andrew; Owen Nisha; Burgess Neil (2016). "The distribution of the genus Rhynchocyon in the Eastern Arc Mountains, with an emphasis on the Black-and-rufous Sengi, Rhynchocyon petersi". Afrotherian Conservation. 12: 3–8.
  6. ^ G. Rathbun. (1984). Elephant-shrews, Order Macroscelidea. In : MacDonald (ed), The Encyclopedia of Mammals. Facts on File Publications, New York: 730-735.
  7. ^ Rajan Amin, Bernard Agwanda, Tim Wacher, Bernard Ogwoka, Cedric Khayale, and Linus Kariuki (2020), "Habitat use of the endangered golden-rumped sengi Rhynchocyon chrysopygus", African Journal of Ecology, 59: 108–116, doi:10.1111/aje.12804, S2CID 225142032{{citation}}: CS1 maint: multiple names: authors list (link)
  8. ^ Francesco Rovero ,Emanuel Martin, Melissa Rosa, Jorge A. Ahumada, and Daniel Spitale (2014), "Estimating Species Richness and Modelling Habitat Preferences of Tropical Forest Mammals from Camera Trap Data", PLOS ONE, 9 (7): e103300, doi:10.1371/journal.pone.0103300, PMC 4108438, PMID 25054806{{citation}}: CS1 maint: multiple names: authors list (link)
  9. ^ J. Kingdon (1997), The Kingdon Field Guide to African Mammals, Academic Press, pp. 142–152
  10. ^ a b c d e f Galen B. Rathbun (2009), "Why is there discordant diversity in sengi (Mammalia: Afrotheria: Macroscelidea) taxonomy and ecology?", African Journal of Ecology, 47 (1): 1–13, doi:10.1111/j.1365-2028.2009.01102.x
  11. ^ a b G. B. Rathbun (1979), "The social structure and ecology of elephant-shrews", Journal of Comparative Ethology, 20: 1–77
  12. ^ Norbert J. Cordeiro; Nathalie Seddon; David R. Capper; Jonathan M. M. Ekstrom; Kim M. Howell; Isabel S. Isherwood; Charles A. M. Msuya; Jonas T. Mushi; Andrew W. Perkin; Robert G. Pople & William T. Stanley (2005), "Notes on the ecology and status of some forest mammals in four Eastern Arc Mountains", Journal of East African Natural History, 94 (1): 175–189, doi:10.2982/0012-8317(2005)94[175:noteas]2.0.co;2, S2CID 85816994
  13. ^ a b c d e f g h i F. Rovero, G. B. Rathbun, A. Perkin, T. Jones, D. O. Ribble, C. Leonard, R. R. Mwakisoma, and N. Doggart (2007), "A new species of giant sengi or elephant-shrew (genus Rhynchocyon) highlights the exceptional biodiversity of the Udzungwa Mountains of Tanzania", Journal of Zoology, 274 (2): 126–133, doi:10.1111/j.1469-7998.2007.00363.x{{citation}}: CS1 maint: multiple names: authors list (link)
  14. ^ C. D. Fitzgibbon & G. B. Rathbun (1994), "Surveying Rhynchocyon elephant-shrews in tropical forest", African Journal of Ecology, 32: 50–57, doi:10.1111/j.1365-2028.1994.tb00554.x
  15. ^ Corbet, G.B., Hanks, J., 1968. A revision of the elephant-shrews, family Macroscelididae. Bull. Br. Museum (Natural Hist.) Zool. 16, 45–111.
  16. ^ a b Lucinda P. Lawson; Cristiano Vernesi; Silvia Ricci & Francesco Rovero (2013), "Evolutionary History of the Grey-Faced Sengi, Rhynchocyon udzungwensis, from Tanzania: A Molecular and Species Distribution Modelling Approach", PLOS ONE, 8 (8): e72506, doi:10.1371/journal.pone.0072506, PMC 3754996, PMID 24015252

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Rhynchocyon: Brief Summary

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Rhynchocyon is a genus of elephant shrew (or sengi) in the family Macroscelididae. Members of this genus are known colloquially as the checkered elephant shrews or giant sengis. It contains the following five species:

Golden-rumped elephant shrew, Rhynchocyon chrysopygus Checkered elephant shrew, Rhynchocyon cirnei Black and rufous elephant shrew, Rhynchocyon petersi Stuhlmann's elephant shrew, Rhynchocyon stuhlmanni Grey-faced sengi, Rhynchocyon udzungwensis
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