Pygmy sloth

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Pygmy sloth
Bradypus pygmaeus.jpg

Pygmy sloth ( Bradypus pygmaeus )

Systematics
Order : Tooth arms (pilosa)
Subordination : Sloths (folivora)
Superfamily : Megatherioidea
Family : Three-toed sloth (Bradypodidae)
Genre : Three-toed sloth ( Bradypus )
Type : Pygmy sloth
Scientific name
Bradypus pygmaeus
Anderson & Handley , 2001

The dwarf sloth ( Bradypus pygmaeus ) is a described in 2001 Faul species from the family of three-toed sloth (Bradypodidae). The species is on the island Escudo de Veraguas , the off the northern coast of Panama in the province of Bocas del Toro is, endemic . There it lives mainly in the coastal mangrove forests , but little is known about the way of life. It is very likely that the pygmy sloth was created through island dwarfing at the end of the Last Cold Age , when the sea level rose and thus cut off the ancestors of today's representatives from their close relatives on the mainland. The pygmy sloth population is considered critically endangered.

features

General

The pygmy sloth is very similar to the brown-throated sloth shown here , but is significantly smaller.

The pygmy sloth is very similar to the brown-throated sloth ( Bradypus variegatus ), but is much smaller and thus a typical case of island dwarfing . It reaches a total length of 48.5 to 53 cm, with the short tail taking between 4.5 and 6 cm, and a weight of 2.5 to 3.5 kg. In terms of body weight, it is therefore about 40% smaller than the brown-throated sloth, and in terms of body dimensions about 15% smaller. The face is yellow-brownish to brownish and has a dark eye band around which the fur appears slightly orange. The hair on the head and shoulders is long and shaggy and sometimes forms a kind of hood around the short facial hair. The ears are small, a maximum of 1 cm long, and cannot be seen from the outside. The throat has an agouti to gray-brown tint. Males are characterized by an orange spot on the back with a dark central stripe. The fur is (hanging in the trees) parted like all sloths as an adaptation to their way of life from the belly away. Like all three-toed sloths , the pygmy sloth also has three-pronged feet with long claws in front and behind. The rear foot is between 9.4 and 11 cm long.

Skull and dentition features

The skull is gracefully built and between 6.7 and 7.2 cm long and on the cheekbone between 3.8 and 4.6 cm, but only a maximum of 2.2 cm wide behind the eyes. Typically the zygomatic arch is not completely closed, but has a narrow, long extension in the front section that is directed downwards. Two weak parasagittal ridges are also formed on the parietal bone . The rostrum is short and the frontal bone is slightly swollen. In the upper jaw there are 5 teeth per half of the jaw, in the lower jaw 4, a total of 18. The front ones are smaller and chisel-like in shape, and can sometimes be completely absent in the upper jaw, while the rear ones resemble molars . The upper row of teeth is almost 2.5 cm long. The skeletal features that distinguish the pygmy sloth from the mainland forms include a larger entrance to the carotid canal on the petrous bone , a larger external auditory canal and a thinner and more curved crown process on the lower jaw.

distribution

The distribution area of ​​the pygmy sloth is the small island Escudo de Veraguas (red point).

The species is endemic to the 4.3 km² island of Escudo de Veraguas , which is about 17.6 km off the north coast of Panama in the Bocas del Toro province . The island is densely forested, 10 to 12 hectares of which is occupied by the red mangrove on the northern and northeastern coastal areas, around 400 hectares are covered with tropical rainforests . The pygmy sloth is largely limited to the mangrove forests, but observations have shown that individual animals penetrated up to 200 m into the rainforest or stayed only there, but in the vicinity of the mangroves. The species has not yet been directly detected in the forests of the island's interior, but according to recent studies it is assumed that it also occurs there in part. The total inhabited area is so far given as 1.3 to 1.5 km², which corresponds to the total distribution of the red mangrove on Escudo de Veraguas.

Way of life

Little is known about the way of life of the pygmy sloth. Like all three-toed sloths, it is likely to feed primarily on leaves and lead an energy-saving lifestyle to compensate for the low nutritional value of its food. The red mangrove itself, ant trees and flowers of guavas have so far been proven as food plants . The species is both in the trees and on the ground. According to observations, individual animals cover up to 200 m and use an action area of 0.25 ha on average, but this can only be regarded as a minimum value due to the lack of long-term studies. In addition, like other three-toed sloths, the pygmy sloth is a skilled swimmer. It is also less distinctly diurnal than its mainland relatives, possibly related to the lack of a predatory threat . The reproductive behavior has not yet been investigated, but individual females with singular young animals have been spotted. As with the other species of sloth, green algae nest in the fur and are deposited in transverse cracks in the thick hair. Often the head, neck, upper back, and upper sections of the forelegs are covered in algae. So far, only one species of algae has been identified with Trichophilus welckeri . In addition, 37 other species of creatures have been found that live in the fur of the pygmy sloth, including mushrooms , ciliates , apicomplexa and dinoflagellates . It is the highest number of eukaryotes that has been observed in sloths to date.

Systematics

Internal systematics of recent sloths according to Delsuc et al. 2004
  Pilosa  

 Vermilingua (anteaters) 


  Folivora (sloths)  
  Choloepodidae  

 Choloepus (two-toed sloth)


  Bradypodidae  

 Bradypus (three-toed sloth)




Template: Klade / Maintenance / Style

The pygmy sloth is a species from the genus of the three-toed sloth ( Bradypus ), to which three other species belong. These, in turn, are part of the monotypical family of the Bradypodidae today , which, within the subordination of the sloths (Folivora), is either compared to all other groups of sloths as a sister group according to skeletal anatomical features or is assigned to the superfamily of the Megatherioidea according to molecular genetic studies and protein analyzes . The next related group within the sloth that is still alive today is that of the two-toed sloth ( Choloepus ) from the Choloepodidae family . The sloths, in turn, are more closely related to the anteaters (vermilingua) and together form the order of the tooth arms (pilosa). The splitting off of the line of the sloths from the anteaters began according to molecular genetic studies in the late Paleocene about 58 million years ago. The two genera Bradypus and Choloepus , which are still alive today, separated in the Oligocene around 29 million years ago.

Internal systematics of the genus Bradypus according to Gibb et al. 2015
  Bradypus  

 Bradypus torquatus


   

 Bradypus pygmaeus


   

 Bradypus tridactylus


   

 Bradypus variegatus





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Within the genus of the three-toed sloth, the brown-throated sloth ( Bradypus variegatus ) is generally accepted as the closest related species. This is widespread in Central and South America and also occurs on some islands off the coast of Panama, such as Colón , Cayo Nancy and Bastimentos . The individuals of the individual populations resemble the pygmy sloth in a certain way in their fur pattern and are also significantly smaller in body size than those of the populations on the mainland. The island of Escudo de Veraguas is much further away from the mainland than the other islands. Rising sea water after the end of the last glacial period separated it from the mainland about 8,900 years ago. The island of Colón, home of today's brown-throated sloth, however, came into being in this way only 5200 years ago - and thus at a much later date. The ancestors of the pygmy sloth were separated from the other groups of the brown-throated sloth for much longer and were therefore subject to greater island dwelling - over an estimated 1500 generations until today - than the ancestors of the sloths of the islands closer to the mainland. Despite the noticeably smaller body proportions compared to the brown-throated sloth from the mainland, the sloths of the other islands off the coast of Panama are all assigned to this species. This means that the range of the pygmy sloth is limited to Escudo de Veraguas. Contrary to the assumed origin scenario for the pygmy sloth, molecular genetics studies from 2015 show that the species split off from the line of the brown and white-throated sloth ( Bradypus tridactylus ) in the Miocene around 8 million years ago . There are no fossil records of the pygmy sloth.

The pygmy sloth was first described scientifically in 2001 by Robert P. Anderson and Charles O. Handley . The holotype (specimen number USNM 579179) is an adult, skin-and-skull female, collected by Handley and Penny Nelson on Escudo de Veraguas Island in March 1991. The holotype is kept in the National Museum of Natural History in Washington, DC The Latin species name pygmaeus means something like "dwarf".

Danger

The pygmy sloth is listed as " critically endangered " in the IUCN's Red List due to its small distribution area - its home island measures only around 4.3 km² - and in a new list it is even among the hundred most threatened species counted. During a three-week observation in 2011, a total of 79 animals were registered, most of which were in mangrove trees, rarely only a short distance from them. The size of the total population is unknown; it was originally estimated at less than 500 specimens with an average density of 5.8 to 7.4 animals per hectare in the mangrove forests. Due to the distribution of the species in the tropical rainforests of the island, which has been observed since 2012, experts now assume a total of 500 to 1500 animals. The home island is uninhabited, but fishermen, farmers and other people visit it from time to time and hunt the animals for food or catch them to sell as pets. Further dangers are the extraction of wood as building and fuel material as well as the development of the island for tourism, likewise the presence of house cats is likely to have an influence on the population. At the moment the pygmy sloth enjoys little public attention. Originally unprotected, Escudo de Veraguas is now part of the indigenous territory of Ngöbe-Buglé and is itself a protected landscape area, which has been reopened for economic development since 2012. It is therefore recommended to upgrade the island's protection status.

literature

  • Robert P. Anderson and Charles O. Handley, Jr: A new species of three-toed sloth (Mammalia: Xenarthra) from Panamá, with a review of the genus Bradypus. Proceedings of the Biological Society of Washington 114, 2001, pp. 1-33.
  • Virginia Hayssen: Bradypus pygmaeus (Pilosa: Bradypodidae). Mammalian Species 812, 2008, pp. 1-4.
  • Jonathan N. Pauli: Bradypodidae (Three-toed sloths). In: Don E. Wilson and Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 118-132 (p. 131) ISBN 978-84-16728-08-4 .
  • DE Wilson, DM Reeder, Mammal Species of the World , Johns Hopkins University Press, 2005.

Individual evidence

  1. ↑ a b c d e Virginia Hayssen: Bradypus pygmaeus (Pilosa: Bradypodidae). Mammalian Species 812, 2008, pp. 1-4
  2. ↑ a b c d e f Robert P. Anderson and Charles O. Handley, Jr: A new species of three-toed sloth (Mammalia: Xenarthra) from Panamá, with a review of the genus Bradypus. Proceedings of the Biological Society of Washington 114, 2001, pp. 1-33
  3. ↑ a b c Jonathan N. Pauli: Bradypodidae (Three-toed sloths). In: Don E. Wilson and Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 118-132 (p. 131) ISBN 978-84-16728-08-4
  4. ↑ a b c d e f g Bryson Voirin: Biology and conservation of the pygmy sloth, Bradypus pygmaeus. Journal of Mammalogy , 2015; DOI: 10.1093 / jmammal / gyv078
  5. ↑ a b c Sam Kaviar, Jakob Shockey and Peter Sundberg: Observations on the Endemic Pygmy Three-Toed Sloth, Bradypus pygmaeus of Isla Escudo de Veraguas, Panamá. PlosOne 7 (11), 2012, p. E49854 ( [1] )
  6. ^ A b Robert P. Anderson, Nadia Moraes-Barros and B. Voirin: Bradypus pygmaeus. Edentata 11, 2010, p. 117
  7. ^ Bryson Voirin, Madeleine F. Scriba, Dolores Martinez-Gonzalez, Alexei L. Vyssotski, Martin Wikelski, and Niels C. Rattenborg: Ecology and Neurophysiology of Sleep in Two Wild Sloth Species. Sleep 37 (4), 2014, pp. 753-761
  8. ↑ Milla Suutari, Markus Majaneva, David P Fewer, Bryson Voirin, Annette Aiello, Thomas Friedl, Adriano G Chiarello and Jaanika Blomster: Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association with Trichophilus welckeri (Chlorophyta , Ulvophyceae). BMC Evolutionary Biology 10, 2010, p. 86
  9. ↑ a b Frédéric Delsuc, Sergio F Vizcaíno and Emmanuel JP Douzery: Influence of Tertiary paleoenvironmental changes on the diversification of South American mammals: a relaxed molecular clock study within xenarthrans. BMC Evolutionary Biology 4 (11), 2004, pp. 1-13
  10. ↑ Timothy J. Gaudin: Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence. Zoological Journal of the Linnean Society 140, 2004, pp. 255-305
  11. ↑ Luciano Varela, P. Sebastián Tambusso, H. Gregory McDonald and Richard A. Fariña: Phylogeny, Macroevolutionary Trends and Historical Biogeography of Sloths: Insights From a Bayesian Morphological Clock Analysis. Systematic Biology 68 (2), 2019, pp. 204-218
  12. ↑ Frédéric Delsuc, Melanie Kuch, Gillian C. Gibb, Emil Karpinski, Dirk Hackenberger, Paul Szpak, Jorge G. Martínez, Jim I. Mead, H. Gregory McDonald, Ross DE MacPhee, Guillaume Billet, Lionel Hautier and Hendrik N. Poinar : Ancient mitogenomes reveal the evolutionary history and biogeography of sloths. Current Biology 29 (12), 2019, pp. 2031-2042, doi: 10.1016 / j.cub.2019.05.043
  13. ↑ Samantha Presslee, Graham J. Slater, François Pujos, Analía M. Forasiepi, Roman Fischer, Kelly Molloy, Meaghan Mackie, Jesper V. Olsen, Alejandro Kramarz, Matías Taglioretti, Fernando Scaglia, Maximiliano Lezcano, José Luis Lanata, John Southon, Robert Feranec, Jonathan Bloch, Adam Hajduk, Fabiana M. Martin, Rodolfo Salas Gismondi, Marcelo Reguero, Christian de Muizon, Alex Greenwood, Brian T. Chait, Kirsty Penkman, Matthew Collins and Ross DE MacPhee: Palaeoproteomics resolves sloth relationships. Nature Ecology & Evolution 3, 2019, pp. 1121-1130, doi: 10.1038 / s41559-019-0909-z
  14. ↑ a b c Gillian C. Gibb, Fabien L. Condamine, Melanie Kuch, Jacob Enk, Nadia Moraes-Barros, Mariella Superina, Hendrik N. Poinar and Frédéric Delsuc: Shotgun Mitogenomics Provides a Reference Phylogenetic Framework and Timescale for Living Xenarthrans. Molecular Biology and Evolution 33 (3), 2015, pp. 621-642
  15. ↑ Mariella Superina and Agustín Manuel Abba: Bradypus variegatus. Edentata 11, 2010, pp. 124-125
  16. ↑ Robert P. Anderson and Charles O. Handley, Jr: Dwarfism in insular sloths: biogeography, selection, and evolutionary rate. Evolution 56, 2002, pp. 1045-1058
  17. ↑ Manuel Ruiz-García, Diego Chacón, Tinka Plese, Ingrid Schuler and Joseph Mark Shostell: Mitogenomics phylogenetic relationships of the current sloth's genera and species (Bradypodidae and Megalonychidae). Mitochondrial DNA Part A 29 (2), 2018, pp. 281-299, doi: 10.1080 / 24701394.2016.1275602
  18. ^ A b Robert P. Anderson, Nadia Moraes-Barros and B. Voirin: Bradypus pygmaeus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. ( [2] ); last accessed on January 5, 2014
  19. ^ IUCN information sheet, engl.

Web links

Commons : Pygmy Sloth  - Collection of images, videos and audio files