Bengal slow loris

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Bengal slow loris[1]
CITES Appendix I (CITES)[3]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Strepsirrhini
Family: Lorisidae
Genus: Nycticebus
Species:
N. bengalensis
Binomial name
Nycticebus bengalensis
(Lacépède, 1800)
Range of the Bengal slow loris
Synonyms[4][5]
  • Lori bengalensis Lacépède, 1800
  • Nycticebus cinereus Milne-Edwards, 1867
  • Nycticebus tardigradus typicus Lydekker, 1905
  • Nycticebus tenasserimensis Elliot, 1913
  • Nycticebus incanus
    Thomas
    , 1921

The Bengal slow loris (Nycticebus bengalensis) or northern slow loris is a

Indochina. Its geographic range is larger than that of any other slow loris species. Considered a subspecies of the Sunda slow loris (N. coucang) until 2001, phylogenetic analysis suggests that the Bengal slow loris is most closely related to the Sunda slow loris. However, some individuals in both species have mitochondrial DNA sequences that resemble those of the other species, due to introgressive hybridization. It is the largest species of slow loris, measuring 26 to 38 cm (10 to 15 in) from head to tail and weighing between 1 and 2.1 kg (2.2 and 4.6 lb). Like other slow lorises, it has a wet nose (rhinarium), a round head, flat face, large eyes, small ears, a vestigial tail, and dense, woolly fur. The toxin it secretes from its brachial gland (a scent gland
in its arm) differs chemically from that of other slow loris species and may be used to communicate information about sex, age, health, and social status.

The Bengal slow loris is

marks its territory with urine, and sleeps during the day by curling up in dense vegetation or in tree holes. It is a seasonal breeder, reproducing once every 12–18 months and usually giving birth to a single offspring. For the first three months, mothers carry their offspring, which reach sexual maturity
at around 20 months. The Bengal slow loris can live up to 20 years.

The species is listed as endangered on the

locally extinct in several regions. It is found within many protected areas throughout its range, but this does not protect them from rampant poaching and illegal logging
. Critical conservation issues for this species include enhancing protection measures, stricter enforcement of wildlife protection laws, and increased connectivity between fragmented protected areas.

Taxonomy and phylogeny

An old drawing of a Bengal slow loris sitting on a branch with another moving between branches in the background
The Bengal slow loris was long considered a subspecies until it was recognized as a distinct species in 2001.

Nycticebus bengalensis, commonly known as the Bengal slow loris or northern slow loris,[6] is a strepsirrhine primate in the slow loris genus, Nycticebus. Formerly considered a subspecies of the Sunda slow loris (N. coucang), it was recognized as a distinct species in 2001 by taxonomist and primatologist Colin Groves.[1] It is difficult to distinguish from the other species in its genus.[6]

To help clarify species and subspecies boundaries, and to establish whether

introgressive hybridization, as the tested individuals of these two taxa originated from a region of sympatry in southern Thailand. The precise origin of one of the N. coucang individuals was not known.[7] This hypothesis was corroborated by a 2007 study that compared the variations in mitochondrial DNA sequences between N. bengalensis and N. coucang, and suggested that there has been gene flow between the two species.[8]

Anatomy and physiology

The Bengal slow loris has large eyes, a round head, and short ears, as shown in this illustration from the mid-19th century.

The Bengal slow loris is the largest species of slow loris, weighing 1 to 2.1 kg (2.2 to 4.6 lb),

toilet-claw" that the animal uses for scratching and grooming, while the other nails are straight.[12]

In addition to being smaller than the Bengal slow loris, the sympatric Sunda slow loris also differs in its coloring: it does not have the pale areas of the head, nape, and shoulders, and its overall color is a tawny- or golden-brown.[10] The pygmy slow loris (N. pygmaeus) is much smaller, with a skull length less than 55 mm (2.2 in).[5] It also lacks the dark dorsal stripe of the Bengal slow loris,[14] has dark brown fur, and longer ears.[15]

The Bengal slow loris has a small swelling on the ventral side of its elbow called the brachial gland, which secretes a pungent, clear oily toxin that the animal uses defensively by wiping it on its

dominance.[18]

Behavior and ecology

bastard myrobala
tree to obtain exudates, an important food source—especially in winter seasons.

The preferred habitats of the Bengal slow loris range across

subtropical regions, and include evergreen and semi-evergreen rainforests with forest edges and continuous, dense canopies.[6] It can also be found in bamboo groves.[19] It prefers habitats with larger diameter, tall trees with a large crown depth (defined as the length along the main axis from the tree tip to the base of the crown); these areas are typically associated with greater food abundance, and decreased risk of predation.[20] Because of its preference for dense forests, it acts as a good indicator of the ecosystem's health.[6]

The species acts as an important

katydids and crickets),[23] gum, snails, small birds, and reptiles, it is primarily frugivorous.[6] Lianas of the flowering plant genus Bauhinia are a commonly-used food source.[20]

A nocturnal animal, the Bengal slow loris has excellent night vision, enhanced by a tapetum lucidum—a layer of tissue in the eye that reflects visible light back through the retina. It sleeps during the day curled up in a ball in dense vegetation or in tree holes. Males and females mark their territory with urine.[23] The species is known to live in small family groups.[6] Animals may practice social grooming.[23]

Reproduction

The Bengal slow loris is not a seasonal breeder, unlike the pygmy slow loris.[8] Females in an estrous cycle attract males with a loud whistle. Females reproduce every 12–18 months and have a six-month gestation.[23] Because they are not seasonal breeders, females could become pregnant when their offspring are approximately 6 months old, making possible for females to produce two offspring per year.[8] Females typically give birth to a single offspring, although twins rarely occur.[23] This differs from the sympatric pygmy slow loris, which commonly has twins.[8] The mother carries her young about three months before they become independent, although they may be temporarily left on branches while the mother searches for food.[23] Sexual maturity is reached at approximately 20 months of age.[6] The species is known to live up to 20 years.[6]

Distribution

The species has the largest geographic range of all slow loris species

Pegu; populations in Laos have been recorded in the north, central, and southern portions of the country.[6]

The Bengal slow loris is

southern peninsula of Thailand. In 2001, Groves reported the existence of hybrids between these two species in this region.[8]

Conservation

Listed as "

Wildlife Protection Act of 1972,[13][24] and in June 2007, it was transferred, along with all other slow loris species, to CITES Appendix I, which forbids international commercial trade.[26]

The most severe threats facing the species are the

Slash and burn agriculture has also resulted in the destruction of its habitat, and road construction is another factor in its decline. Hunting has been found to be most severe when nearby urban human populations increase.[6] Enhancing protection measures, enforcing current wildlife protection laws, and improving the connectivity between protected areas are factors considered critical to ensure the survival of this species.[11][27]

The species is commonly sold as a pet and to zoos throughout Southeast Asia. In Cambodia, it was reported in 2006 as one of the most common mammals found in shops and stalls, found in the hundreds and selling for US$0.85 to US$6.25. In the same year, it was found selling for US$2.50 to US$6.30 at bazaars in China (Mengla County in Yunnan Province) and US$70 in Thailand. The Bengal slow loris is used in traditional medicine in all of these countries, selling for US$15 in Vietnam, and is also eaten in Vietnam.[6] The animal is predominantly used to prepare treatments for women after childbirth, stomach problems, healing wounds and broken bones, and in the treatment of sexually transmitted diseases. Primary users are wealthy to middle-class women in urban areas.[28]

Habitat and population trends

Throughout its geographic range, slow lorises are in serious decline. Their habitat has been seriously degraded, and growing human populations will add increasing pressure. In countries like Bangladesh, only 9% of the original forest cover was still present in 2000. In northeastern Cambodia, forests are being cleared at an increasing rate, with a loss of 6% of the natural forest between 1999 and 2000. Within those same years, Myanmar and Thailand lost 14% and 26% of their natural forest, respectively. In Vietnam, only 30% of the original forest cover remains due to the deforestation caused by the

Quảng Nam Province and parts of the highlands, and the same is expected in Song Thanh and Kon Cha Rang nature reserves.[6]

In India, dense forest canopy has been depleted by as much as 55% in some areas and is rapidly disappearing. As early as 1987, the Indo-China region had reportedly lost 75% of the natural habitat for slow lorises. In 1992, the population size was estimated between 16,000 and 17,000 individuals, based on available habitat; however, recent publications report that few individuals remain due to a reduced geographic range. The Bengal slow loris may be restricted to a few isolated populations and is in serious threat of becoming locally extinct in parts of Assam and Meghalaya. In Arunachal Pradesh, its population is declining and under threat.[6][25]

Gibbon Wildlife Sanctuary in Assam.[25]

Since the 1990s, China's forests have declined significantly. In

References

  1. ^ a b Groves 2005, pp. 122–123.
  2. ^ . Retrieved 19 November 2021.
  3. ^ UNEP-WCMC. "CITES species database: Nycticebus bengalensis". UNEP-WCMC Species Database. Retrieved 3 February 2011.[permanent dead link]
  4. ^ Groves 2005, p. 122.
  5. ^ a b c Groves 2001, p. 99.
  6. ^ a b c d e f g h i j k l m n o p q r s Management Authority of Cambodia (3–15 June 2007). Notification to Parties: Consideration of Proposals for Amendment of Appendices I and II (PDF). Netherlands: CITES. p. 31. Archived from the original (PDF) on 28 February 2011. Retrieved 9 January 2011.
  7. ^ Chen et al. 2006, pp. 1197–1198.
  8. ^
    S2CID 35725257
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  9. ^ a b Nekaris et al. 2010, p. 157.
  10. ^ a b Osman Hill 1953, p. 160.
  11. ^
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  12. ^ a b Smith et al. 2008, pp. 159–160.
  13. ^ a b c d e Swapna, N.; Gupta, Atul; Radhakrishna, Sindhu (2008). "Distribution survey of Bengal Slow Loris Nycticebus bengalensis in Tripura, northeastern India" (PDF). Asian Primates Journal. 1 (1): 37–40. Archived from the original (PDF) on 2011-07-27.
  14. ^ Smith et al. 2008, p. 159.
  15. ^ Osman Hill 1953, p. 162–163.
  16. ^ Hagey, Fry & Fitch-Snyder 2007, p. 253.
  17. ^ Hagey, Fry & Fitch-Snyder 2007, p. 263.
  18. ^ Hagey, Fry & Fitch-Snyder 2007, p. 269.
  19. ^ Francis 2008, p. 261.
  20. ^
    S2CID 31261833
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  21. ^ Nekaris et al. 2010.
  22. S2CID 23726143
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  23. ^ a b c d e f Smith et al. 2008, p. 160.
  24. ^ a b Nandini, Rajamani; Kakati, Kashmira; Ved, Nimesh (2009). "Occurrence records of the Bengal Slow Loris (Nycticebus bengalensis) in northeastern India" (PDF). Asian Primates Journal. 1 (2): 12–18. Archived from the original (PDF) on 2012-03-03.
  25. ^
    ISSN 0974-7907
    .
  26. S2CID 45718454. Archived from the original
    on 24 July 2011. Retrieved 9 January 2011.
  27. .
  28. (PDF) from the original on 2020-12-02. Retrieved 2020-01-27.

Literature cited