Three-toed sloth

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Three-toed sloth
Brown-throated sloth (Bradypus variegatus)

Brown-throated sloth ( Bradypus variegatus )

Systematics
Superordinate : Sub-articulated animals (Xenarthra)
Order : Tooth arms (pilosa)
Subordination : Sloths (folivora)
Superfamily : Megatherioidea
Family : Three-toed sloth
Genre : Three-toed sloth
Scientific name of the  family
Bradypodidae
JE Gray , 1821
Scientific name of the  genus
Bradypus
Linnaeus , 1758

The three-toed sloths ( Bradypus ) are the only genus within the Bradypodidae family and represent one of the two lines of sloths (Folivora) that still exist today . The name three-toed sloth , which is sometimes given to these animals, is misleading, as The two-toed sloths ( Choloepus ), the second, recent line, also have three toes on their hind feet. The three-toed sloths live in the subtropical to tropical areas of Central and South America, where they mainly inhabit rainforests . There they lead a solitary life in the crowns of the trees, to which they are adapted through individual body features. They feed mainly on leaves, a very low-energy vegetable diet. The animals are best known for their low metabolic rate and the associated energy-saving lifestyle. From a systematic point of view, the three-toed sloths are compared to all other groups of sloths, both alive today and extinct, but nothing is known about their tribal history due to the lack of fossil records. There are four species today: the pygmy sloth , the collar -necked sloth , and the white -throated and brown-throated sloth , with the first two being threatened.

description

Habitus

White-throated sloth ( Bradypus tridactylus )

The body of the three-toed sloth is adapted to a way of life hanging upside down in the trees. They reach a head-torso length of 40 to 80 cm and a weight of 3 to 10 kg, so they are about the same size as their two-fingered relatives ( Choloepus ). The head of the three-toed sloth is small and round, the nose protrudes slightly from the face. The eyes are small and directed forward, the ears, which are also small, remain hidden in the fur. The limbs are long and sturdy, with the front extremities exceeding the rear by about one and a half times in length, which is a special adaptation to the way of life in the trees. They end in hands and feet with three rays each, which are about the same length and have sharp, hook-shaped claws . In a rudimentary shortened form, however, the first and fifth rays are still attached to the corresponding inner and outer sides. In contrast to the tailless two-toed sloths, the animals have a short tail , two to eleven centimeters long . The fur of the body is usually gray-brown to gray in color, but some species have a pronounced face and back coloring, the latter especially in males in the form of yellow or orange spots.

Skull and dentition features

Skull and lower jaw of a three-toed sloth

The skull of the three-toed sloth is rather short with an average length of 6.9 cm, even shorter than that of the two-toed sloth. This is caused, among other things, by the length of the frontal bone , which is greatly reduced and only reaches around 50% of that of the two-toed sloth. Typically for sloths in general, the upper jaw is elongated, but the middle jawbone is significantly shortened. This is also not in contact with the nasal bone . The extremely shortened skull is a derived feature of the three-toed sloth and is not found in any other known sloth form. Furthermore, the zygomatic arch is not completely formed. On the zygomatic bone , in addition to the insertion of the zygomatic arch, there is another bone outgrowth pointing diagonally back and down. In the three-toed sloth, the zygomatic arch extension extends further upwards and exceeds that of the two-toed sloth in both relative and absolute length dimensions. Further differences can be found in the ear region, where the three-toed sloth has a tympanic bladder , in contrast to its more recent relatives with a tympanic ring .

The lower jaw has a massive, well-ossified symphysis that is not drawn forward like a spatula as in the two-toed sloth. Compared to these, the ascending articular branches extend significantly further upwards and lie prominently above the occlusal plane. As with all sloths, the dentition is greatly reduced and structured differently from that of most other higher mammals . Basically, the three-toed sloths lack incisors and canines , they have a total of 18 teeth, five on each side of the upper jaw and four on each side of the lower jaw. The foremost teeth are significantly smaller and shaped like a chisel or stake and flattened at the front and back, also a characteristic that differs from the other sloths. The rear teeth connect directly and are not separated from the foremost by a diastema, as in the two-toed sloths . Overall, they resemble the molars, but can not be precisely assigned to the molars and premolars of other mammals . They have a rounded or rectangular shape and grow throughout life. A special feature is the lack of tooth enamel . In the closed mouth, the molars are directly opposite each other, in contrast to the alternating position in two-toed sloths

Skeletal features

Skeleton of a three-toed sloth

Some peculiarities are in the area of ​​the spine . Based on the foremost, rib-bearing thoracic vertebrae , three-toed sloths have 8 to 10 vertebrae between this and the head, all of which were originally interpreted as cervical vertebrae . Some researchers see only thoracic vertebrae in the rearmost one to three additional cervical vertebrae, which have shifted in front of the shoulder girdle and do not have any joints for the ribs , which was recognized, among other things, by the ossification stages of the vertebrae in embryos . This adjustment allows the animals greater head mobility, up to 270 ° vertically and 330 ° horizontally, to reach more food sources. Also based on the first rib-bearing thoracic vertebra, two-toed sloths only have 5 to 7 cervical vertebrae, which means that their necks are significantly shorter. Furthermore, a total of 14 pairs of ribs are formed in the three-toed sloth, which is significantly fewer than in their recent relatives (23 to 24). The forward displacement of the ribless thoracic vertebrae as part of the cervical spine resulted in a backward displacement of the shoulder girdle and thus also of the forelegs. This also partially changed the muscle structure, as the levator scapulae and the rhomboideus minor muscles , which normally play an important role in stabilizing the shoulder blade during locomotion, are no longer connected to the occiput. Especially in the area of ​​the forelimbs, there were also some changes in both the skeletal and muscular anatomical areas, which represent a special adaptation to the head-hanging and tree-dwelling way of life, whereby in contrast to ground-living mammals, the drive for locomotion comes from the forelegs.

hide

Brown-throated sloth in the branches with greenish shimmering fur

The body is covered by a dense fur, which is composed of two layers: At the bottom there is a soft undercoat made of colorless and translucent hair with a diameter of up to 0.05 mm, above it a shaggy, thick (about 0.4 mm in Diameter) outer hair that gives the animals their color. With the exception of the ring-necked sloth ( Bradypus torquatus ), male animals have a so-called speculum on their backs , a spot where no outer hair is formed and the undercoat shines through. A special characteristic of the hair of the sloth is the absence of the medulla. In contrast to most other mammal species, the hair is parted away from the belly in order to allow the rainwater to drain off better. The top coat has partly transverse breaks in which water collects , especially in the rainy season, and provides a habitat for algae . The most common algae forms include red algae of the genus Rufusia and green algae such as Dictyococcus and Chlorococcum . Due to the algae, the fur often has a greenish hue under certain lighting conditions, an effect that is particularly evident in the rainy season. This partly serves as a camouflage for the animals.

Utterances and sensory performances

In general, three-toed sloths make very few sounds. Therefore, only a few sounds are known, most of which contain whistles. The best known is the piercing ai or ai-ai of the white-throated sloth , which is usually expelled in extreme danger and to which it owes its other trivial name . The ear of the three-toed sloth is designed for a rather low frequency range between 0.3 and 30 kHz, which is mainly due to the structure of the cochlea . Adult animals are mainly activated by sounds of 2 to 8 kHz, which the young animals also take advantage of when they are separated from the mother. Since the three-toed sloths lack the ciliary muscle , the sense of sight is underdeveloped and the animals are nearsighted . Furthermore, the cornea is strongly convexly curved and the eye lens is very thick, which means that the field of view is only slightly resolved. However, the eyesight of the young is better than that of the adult.

distribution

Distribution map of the three-toed sloth

The three-toed sloths live in the subtropical to tropical areas of the American continent , their range extends from Central America , with the northern border in Honduras , to South America in central Brazil . They live exclusively in tropical rainforests , mountain cloud forests and the tropical coastal rainforests ( Mata Atlântica ), which means that animals are absent in the highlands of the Andes and in the more open Llanos regions along the Orinocos . Since they cannot tolerate cold temperatures, they are also not found in wooded regions in the south of the continent. The range partially overlaps with that of the two-toed sloth , especially in Central America and in northern and western South America. The representatives of this group of sloths are more sensitive to the cold due to the lack of undercoat and have a higher thermoneutrality (24 ° C) than the three-toed sloths (18 ° C).

Way of life

Social behavior and activities

The three-toed sloths live in the canopy of trees ( arboreal ), their way of life is characterized by a head-hanging lifestyle and a nutrient-poor diet, which leads to an extremely energy-saving lifestyle. They eat and sleep in the trees, and mating and giving birth also take place there. The movements are extremely slow both vertically and horizontally in the trees, estimates of the maximum speed are a maximum of 4 to 5 m per minute (0.25 to 0.35 km per hour). In the course of a day, however, a maximum of 133 m, but mostly less than 36 m, are covered to search for food. The animals only come on the floor to urinate and defecate, which is necessary on average every 8 days due to the low metabolic rate . A tree change to forage often takes place through the branches, less often through the ground, and takes place on average every three days. On the ground, the three-toed sloth move awkwardly, crawling forward with the forearms and the soles of the hind legs. However, they can swim well.

The animals are solitary animals that do not seek any contact with conspecifics other than mating. They inhabit an area averaging 2 to 5 hectares in size; in their natural environment, the population density is 0.09 to 8 individuals per hectare, depending on the region. In contrast to the two-toed sloths, which are mainly nocturnal, these animals have no fixed activity times, the few hours that they do not spend asleep or resting can lie both during the day and at night.

Diet and Metabolism

Three-toed sloth eating

The diet of the three-toed sloth consists of more than 94% almost exclusively of leaves ( folivor ), occasionally supplemented by fruits and flowers , which are mostly plucked from trees and, to a lesser extent , from lianas. Mostly young leaves are part of the menu, less often older ones. The animals often prefer the leaves of ant trees ( Cecropia ), but also of figs ( Ficus ) and clitoria . In general, three-toed sloths eat the leaves of numerous food plants, but individual individuals specialize in a few plant species, mostly 5 to 8, which make up between 50 and 80% of the diet. The young animals learn this specialization from the mother animal. The long tongue and lips help with the ingestion of food, as do the hands, which push the food into the correct position. The construction of the lower jaw with the high side branches and the arrangement of the chewing muscles cause the three-toed sloths to chew their food predominantly with vertical and forward and backward chewing movements.

The metabolic rate of the three-toed sloth is 40 to 45% lower than that of mammals of comparable size, and it takes a long time to digest food. An enlarged digestive tract, the stomach reaches about a third of the body weight when full, contrasts with a low muscle mass. The low metabolism also means that the muscle contraction is 3 to 4 times slower than that of a similarly large house cat . The body temperature of the three-toed sloth is lower and more variable than that of most other mammals. It is around 34 ° C and can drop sharply during sleep, during cooler times of the day and in damp weather, which also saves energy. To compensate, these animals, like many reptiles , often bask in the sun. Their energy-saving way of life also includes long rest periods, which last up to 20 hours a day, a little more than that of the two-toed sloth. However, the length of the sleep and rest phases are distributed throughout the year and depend on the seasons , but this is different for the individual species: During more active times, three-toed sloths only spend around 60% of the day sleeping and resting while it is in less active 80 to 90% are. In some wild populations of the three-toed sloths, an average sleep time of around 9.6 hours per day was determined by means of EEG measurements ; in total, the active time is only about 10% of what another mammal of the same size produces in a comparable period of time.

Another consequence of the low metabolic rate is that defecation is only necessary every one to two weeks. To do this, the animals leave the trees and climb to the ground. They dig a hole with their short tails and empty their intestines. This process is very dangerous for the three-toed sloth, as around half of all adult animals are preyed on by predators . For a long time it was unclear why the animals take the arduous way to the ground instead of defecating in the usual hanging manner. Originally it was partly assumed that the behavior developed evolutionarily in that the fertilization of the trees in this way reduced the number of necessary trips to other trees. Recent studies have shown a different picture. The fur of the three-toed sloth is a habitat for several species of insects, including beetles and butterflies . There is a special relationship to the moths, especially from the genera Cryptoses and Bradipodicola , which are also called "sloth moths" and of which up to 120 individuals can appear on a three-toed sloth. When a three-toed sloth climbs on the ground to defecate, the moth leaves its host's fur and lays its eggs in the excrement. The larvae feed on it and after metamorphosis look for a new sloth host. There is a symbiotic relationship between the three-toed sloth and the moth, as the latter release nitrogen and phosphorus compounds into the fur, which in turn promote the growth of the algae living in the fur . While grooming, the three-toed sloths eat the algae and thereby receive important supplements that they would otherwise not get due to their very low-energy leaf diet. The higher concentration of algae in the fur also partially increases the camouflage effect of the three-toed sloth in the branches.

Reproduction

In contrast to the two-toed sloths, the three-toed sloths reproduce more seasonally, which may be due to the different diets of the two sloth representatives. Overall, the reproductive behavior of the three-toed sloth has so far only been insufficiently researched. The animals are sexually mature at around three years of age. Mating takes place in the typical hanging way of life. Then the male withdraws and leaves the rearing of the offspring to the females alone. After a gestation period of around six months, a single, 190 to 300 g heavy and 14 to 20 cm large young animal is born. Most of the time the births occur at the end of the rainy season and the beginning of the dry season, which means that the young animal can be raised during a rather low-stress period. Sloths do not build nests for their young, but carry them on their stomachs for the first few weeks of life. The young animal eats its first solid food at around one to two weeks. It is weaned after around four to eight weeks, but stays with its mother for some time. The interval between two births is about a year. The life expectancy of these animals is not known. The oldest three-toed sloth found was twelve years old but still capable of reproduction. However, experts assume that this corresponds roughly to that of the two-toed sloth, some of which can live up to 30 years.

Predators and survival strategies

The predators of the three-toed sloths mainly include larger and smaller cats such as the jaguar , long-tailed cat and ocelot , but also birds of prey such as the harpy and giant snakes such as the anacondas . The animals are mainly protected by their camouflage color and their only slight and slow movements.

Systematics

Internal systematics of the sloths according to Presslee et al. 2019 (based on protein analysis)
 Folivora  
  Megalocnoidea  

 Acratocnidae (†) 


   

 Parocnidae (†) 



   
  Megatherioidea  


 Nothrotheriidae (†) 


   

 Megatheriidae (†) 



   

 Megalonychidae (†) 


   

 Bradypodidae




  Mylodontoidea  

 Scelidotheriidae (†) 


   

 Choloepodidae


   

 Mylodontidae (†) 






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The megalocnoid is subdivided according to Delsuc et al. 2019

Internal systematics of the sloths according to Varela et al. 2019 (based on skeletal anatomical features)
 Folivora  
  Eufolivora  
  Megatherioidea  


 Megatheriidae (†)


   

 Nothrotheriidae (†)



   

 Megalonychidae (including two-toed sloths)



 Mylodontoidea  


 Mylodontidae (†)


   

 Orophodontidae (†)



   

 Scelidotheriidae (†)




   

 Bradypodidae



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The three-toed sloths ( Bradypus ) form a genus from the monotypic family of Bradypodidae within the suborder of the sloths (Folivora). The sloths, together with the anteaters (vermilingua), form the closer kinship group of the tooth arms (pilosa), an order within the superordinate order of the secondary animals (xenarthra), which in turn represent one of the four main lines of the higher mammals . With the help of molecular genetic studies, a split of the sloths from the common line with the anteaters in the end of the Paleocene could be determined about 58 million years ago.

The position of the Bradypodidae within the sloth is assessed differently. In a classic view based on features of the skeletal anatomy , the three-toed sloths form the sister taxon to all other groups of sloths, both recent and fossil. The main reasons for this were the structure of the middle ear with an ossified tympanic bladder , which is not found in other sloths. Differences could also be determined in the further skull morphology and in the structure of the teeth. However, this contradicts molecular genetic and protein-based analyzes from 2019, which refer the three-toed sloths with the Megatheriidae , the Nothrotheriidae and the Megalonychidae - all three groups include extinct, sometimes huge ground-fawns - to the superfamily of the Megatherioidea .

The closest related recent group within the sloths are the two-toed sloths ( Choloepus ) from the Choloepodidae family. In the past, the three- and two-toed sloths were thought to be closely related, they were even grouped together in the Bradypodidae family to extinct ground-dwelling sloths. However, the external similarities are based in part on convergent evolution , the tree-dwelling sloths are a paraphyletic group, since the two-toed sloths are more closely related to the Mylodontidae than to the three-toed sloths, according to genetic studies from 2019 . The two-toed sloths are therefore classified in the superfamily of the Mylodontoidea . According to the molecular genetic data, the two current genera of the sloth had already separated in the Oligocene around 30 million years ago.

There are four types in two sub-genera:

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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  • Subgenus Bradypus Linnaeus , 1758
  • Subgenus Scaeopus Peters , 1864

The genus Bradypus split up relatively early, supported by molecular genetic data. The collar-necked sloth first separated itself from the common lineage with the other three-toed sloths in the Lower Miocene around 19 million years ago; the other three species formed their own lines during the Miocene and in the transition to the Pliocene 12 to 5.7 million years ago. The sequence is not entirely clear, however, since depending on the analysis, the pygmy sloth branched off either very early or later. The species itself may not have differentiated itself until around 10,000 years ago on the island of Escudo de Veraguas off the north coast of Panama through island dwelling. There are no fossil records of the three-toed sloth.

The subgenus Scaeopus differs from Bradypus by the uniform color of fur, with the exception of a darker mane, which is also only typical for this subgenus, and the lack of the speculum s (color spot) on the back of the male animals. The clear deviations paired with the early splitting off of the collar sloth from the other three-toed sloths would, according to more recent studies from 2019 , advocate an independent genus Scaeopus . According to further genetic research, the Andean brown-throated sloth population could be a distinct species.

The genus Bradypus was named in 1758 by Linnaeus , who, in addition to Bradypus tridactylus, also included Bradypus didactylus , distinguishing the species based on the number of finger rays on the forefeet. The latter species is now counted among the two-toed sloths. Linnaeus gave Americae meridionalis arboribus as the type locality for Bradypus tridactylus , it was not until 1911 that Oldfield Thomas established Suriname as the actual type locality. In the earlier editions of Linnaeus' Systema Naturae he had counted the sloths among the primates , he obtained most of his information from Albert Seba's Thesaurus from 1734. The generic name Bradypus comes from the Greek language and is derived from βραδύς ( bradys "slow") and πούς ( poús "foot"), so it refers to the slow movements of animals. The current name of the Bradypodidae family goes back to John Edward Gray , who used it for the first time in 1821 (as "Bradypidae") and united both the three- and two-toed sloths in it.

Three toed sloths and humans

Historical

Since their discovery by the Europeans, sloths have enjoyed a very bad reputation, which is also reflected in their name. They were considered indolent, despicable creatures. There are also Indian legends in which the supposed lack of drive of these animals is expressed. However, since these perspectives refer to both families of sloths, further information on this topic can be found in the article Sloths .

threat

Brown-throated sloth on an ant tree

Due to their more specialized diet, three-toed sloths are more difficult to keep in human care than their two-toed relatives, and most of the animals kept in zoos are two-toed sloths. Only imprecise information can be given about the threat level of these animals. As inhabitants of tropical rainforests, they are undoubtedly affected by the deforestation, and they are also hunted for their meat, but this practice is declining. The collared sloth, which only occurs in the rainforests of south-east Brazil, is listed by the IUCN as "endangered" ( vulnerable ). This region is one of the most densely populated regions in Brazil and is therefore heavily subject to clearing. It is estimated that only two percent of the original area is left, which has a worrying effect on the animal species present there. Bradypus pygmaeus is considered " critically endangered " because of its small distribution area . The other two species have a larger range and are not considered endangered.

literature

  • Bernhard Grzimek: Grzimeks animal life. Encyclopedia of the Animal Kingdom. Augsburg, 2001 ISBN 3-8289-1603-1 .
  • Gene Montgomery: The Evolution and Ecology of Armadillos, Sloths and Vermilinguas. Smithsonian Institute Press, Washington DC, 1985 ISBN 0-87474-649-3 .
  • Ronald Nowak: Walker's Mammals of the World. Johns Hopkins University Press, Baltimore, 1999 ISBN 0-8018-5789-9 .
  • Jonathan N. Pauli: Bradypodidae (Three-toed sloths). In: Don E. Wilson, Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 118-132 ISBN 978-84-16728-08-4 .

Individual evidence

  1. ↑ a b c d e f g Alfred L. Gardner: Family Bradypodidae Gray, 1821. In: Alfred L. Gardner (Ed.): Mammals of South America, Volume 1: Marsupials, Xenarthrans, Shrews, and Bats. University of Chicago Press, 2008, ISBN 978-0-226-28240-4 , pp. 158-164.
  2. ^ Virginia Hayssen: Bradypus variegatus (Pilosa: Bradypodidae). In: Mammalian Species. 42, (1), 2010, pp. 19-32.
  3. ↑ a b Virginia Hayssen: Bradypus tridactyla (Pilosa: Bradypodidae). In: Mammalian Species. 839, 2009, pp. 1-9.
  4. ↑ Virginia Hayssen: Bradypus torquatus (Pilosa: Bradypodidae). In: Mammalian Species. 829, 2009, pp. 1-5.
  5. ↑ Virginia Hayssen: Bradypus pygmaeus (Pilosa: Bradypodidae). In: Mammalian Species. 812, 2008, pp. 1-4.
  6. ↑ a b c d e f g h i Jonathan N. Pauli: Bradypodidae (Three-toed sloths). In: Don E. Wilson, Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 118-132 ISBN 978-84-16728-08-4 .
  7. ^ A b c d Virginia L. Naples: Cranial osteology and function in the tree sloths. Bradypus and Choloepus. In: American Museum Novitates. 2739, 1982, pp. 1-21.
  8. ↑ Sergio F. Vizcaíno: The teeth of the “toothless”: novelties and key innovations in the evolution of xenarthrans (Mammalia, Xenarthra). In: Paleobiology. 35 (3), 2009, pp. 343-366.
  9. Jump up ↑ Lionel Hautier, Vera Weisbecker, Marcelo R. Sánchez-Villagra, Anjali Goswami, Robert J. Asher: Skeletal development in sloths and the evolution of mammalian vertebral patterning. In: PNAS. 107 (44), 2010, pp. 18903-18908 ( pnas.org ).
  10. ↑ Hideki Endo, Osamu Hashimoto, Hajime Taru, Keisuke Sugimura, Shin-ichi Fujiwara, Takuya Itou, Hiroshi Koie, Masato Kitagawa, Takeo Sakai: Comparative Morphological Examinations of the Cervical and Thoracic Vertebrae and Related Spinal Nerves in the Two-Toed Sloth. In: Mammal Study. 38 (3), 2013, pp. 217-224.
  11. ^ John A. Nyakatura and Martin S. Fischer: Functional morphology of the muscular sling at the pectoral girdle in tree sloths: convergent morphological solutions to new functional demands? In: Journal of Anatomy. 219, 2011, pp. 360-374.
  12. ↑ a b c d e f D. P. Gilmore, CP Da Costa, DPF Duarte: Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses. In: Brazilian Journal of Medical and Biological Research. 34 (1), 2001, pp. 9-25 ( scielo.br ).
  13. ^ A b c Desmond Gilmore, Denia Fittipaldi Duarte, Carlos Peres da Costa: The physiology of two- and three-toed sloth. In: Sergio F. Vizcaíno, WJ Loughry (Ed.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 130-142.
  14. ↑ a b Mariella Superina, Tinka Plese, Nadia Moraes-Barros, Agustín Manuel Abba: The 2010 Sloth Red List Assessment. In: Edentata. 11 (2), 2010, pp. 115-134.
  15. ^ Alberto Galvao de Moura Filho, Sara Espe Huggins, Salustiano Gomes Lines: Sleep and awaking in the Three-toed Sloth, Bradypus tridactylus. In: Comparative Biochemistry and Physiology. 76A (2), 1983, pp. 345-355.
  16. ^ A b c Adriano Garcia Chiarello: Sloth ecology. An overview of field studies. In: Sergio F. Vizcaíno, WJ Loughry (Ed.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 269-280.
  17. ^ A b Jonathan N. Pauli, Jorge E. Mendoza, Shawn A. Steffan, Cayelan C. Carey, Paul J. Weimer, M. Zachariah Peery: A syndrome of mutualism reinforces the lifestyle of a sloth. In: Proceedings of the Royal Society. B 281, 2014, p. 20133006, doi: 10.1098 / rspb.2013.3006 .
  18. ↑ Leyn Castro-Vásquez, Marlon Meza, Tinka Plese, Sergio Moreno-Mora: Activity Patterns, Preference and Use of Floristic Resources by Bradypus variegatus in a Tropical Dry Forest Fragment, Santa Catalina, Bolívar, Colombia. In: Edentata. 11 (1), 2010, pp. 62-69.
  19. ^ Adriano G. Chiarello: Activity budgets and ranging patterns of the Atlantic forest maned sloth Bradypus torquatus (Xenarthra: Bradypodidae). In: Journal of Zoology (London). 246, 1998, pp. 1-10.
  20. ↑ Niels C. Rattenborg, Bryson Voirin, Alexei L. Vyssotski, Roland W. Kays, Kamiel Spoelstra, Franz Kuemmeth, Wolfgang Heidrich, Martin Wikelski: Sleeping outside the box: electroencephalographic measures of sleep in sloths inhabiting a rainforest. In: Biology Letters. 4 (4), 2008, pp. 402-405 ( rsbl.royalsocietypublishing.org ).
  21. ^ GG Montgomery, ME Sunquist: Impact of sloths on Neotropical forest energy flow and nutrient cycling. In: FB Golley, E. Medina (Ed.): Tropical Ecology Systems: Trends in Terrestrial and Aquatic Research. Ecology Studies 11, Springer-Verlag, New York 1975, pp. 69–111.
  22. ↑ Bernardo B. Dias, Luis Alberto Dias dos Santos, Paula Lara-Ruiz, Camila Righetto Cassano, Laurenz Pinder, Adriano G. Chiarello: First observation on mating and reproductive seasonality in maned sloths Bradypus torquatus (Pilosa: Bradypodidae). In: Journal of Ethology. 27, pp. 97-103.
  23. ↑ Erica Taube, Joël Keravec, Jean-Christophe Vié, Jean-Marc Duplantier: Reproductive biology and postnatal development in sloths, Bradypus and Choloepus: review with original data from the field (French Guiana) and from captivity. In: Mammal Review. 31 (3), 2001, pp. 173-188.
  24. ^ Paula Lara-Ruiz, Adriano Garcia Chiarello: Life-history traits and sexual dimorphism of the Atlantic forest maned sloth Bradypus torquatus (Xenarthra: Bradypodidae). In: Journal of Zoology. 267, 2005, pp. 63-73.
  25. ↑ a b c 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, Ross DE MacPhee: Palaeoproteomics resolves sloth relationships . In: Nature Ecology & Evolution. 3, 2019, pp. 1121-1130, doi: 10.1038 / s41559-019-0909-z .
  26. ↑ a b c 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, Hendrik N. Poinar: Ancient mitogenomes reveal the evolutionary history and biogeography of sloths. In: Current Biology. 29 (12), 2019, pp. 2031-2042, doi: 10.1016 / j.cub.2019.05.043 .
  27. ↑ a b Luciano Varela, P. Sebastián Tambusso, H. Gregory McDonald, Richard A. Fariña: Phylogeny, Macroevolutionary Trends and Historical Biogeography of Sloths: Insights From a Bayesian Morphological Clock Analysis. In: Systematic Biology. 68 (2), 2019, pp. 204-218.
  28. ↑ a b Frédéric Delsuc, Sergio F Vizcaíno, Emmanuel JP Douzery: Influence of Tertiary paleoenvironmental changes on the diversification of South American mammals: a relaxed molecular clock study within xenarthrans. In: BMC Evolutionary Biology. 4 (11), 2004, pp. 1-13.
  29. ↑ a b c d Gillian C. Gibb, Fabien L. Condamine, Melanie Kuch, Jacob Enk, Nadia Moraes-Barros, Mariella Superina, Hendrik N. Poinar, Frédéric Delsuc: Shotgun Mitogenomics Provides a Reference Phylogenetic Framework and Timescale for Living Xenarthrans. In: Molecular Biology and Evolution. 33 (3), 2015, pp. 621–642.
  30. ^ A b Robert P. Anderson, Charles O. Handley, Jr: A new species of three-toed sloth (Mammalia: Xenarthra) from Panamá, with a review of the genus Bradypus. In: Proceedings of the Biological Society of Washington. 114, 2001, pp. 1-33.
  31. ↑ Timothy J. Gaudin: Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence. In: Zoological Journal of the Linnean Society. 140, 2004, pp. 255-305.
  32. ↑ Don E. Wilson, DeeAnn M. Reeder: Mammal Species of the World. Johns Hopkins University Press, Baltimore 2005, ISBN 0-8018-8221-4 ( [1] ).
  33. ↑ Nadia de Moraes-Barros, Juliana AB Silva, João Stenghel Morgante: Morphology, molecular phylogeny, and taxonomic inconsistencies in the study of Bradypus sloths (Pilosa: Bradypodidae). In: Journal of Mammalogy. 92 (1), 2011, pp. 86-100.
  34. ↑ a b Manuel Ruiz-García, Diego Chacón, Tinka Plese, Ingrid Schuler, Joseph Mark Shostell: Mitogenomics phylogenetic relationships of the current sloth's genera and species (Bradypodidae and Megalonychidae). In: Mitochondrial DNA Part A. 29 (2), 2018, pp. 281-299, doi: 10.1080 / 24701394.2016.1275602 .
  35. ↑ Manuel Ruiz-García, Diego Chacón, Tinka Plese, Joseph Mark Shostell: Molecular phylogenetics of Bradypus (Three-toed sloth, Pilosa: Bradypodidae, Mammalia) and phylogeography of Bradypus variegatus (Brown-throated three-toed sloth) with mitochondrial gene sequences . In: Journal of Mammalian Evolution. , 2019, doi: 10.1007 / s10914-019-09465-w .
  36. ^ Carl von Linné: Systema naturae. 10th edition, 1758, volume 1, p. 34 ( [2] ).
  37. ↑ Oldfield Thomas: The mammals of the tenth edition of Linnaeus; an attempt to fix the types of the genera and the exact bases and localities of the species. In: Proceedings of the Zoological Society of London. 1911, pp. 120-158.
  38. ^ Carl von Linné: Systema naturae. 1st edition, 1735, no page number ( [3] ).
  39. ^ Albert Seba: Locupletissimi rerum naturalium thesauri accurata descriptio, et iconibus artificiosissimis expressio, per universam physices historiam. Amsterdam, 1734, plate 34 and p. 53 ( [4] ).
  40. ↑ John Edward Gray: On the natural arrangement of vertebrose animals. In: London Medical Repository. 15, 1821, pp. 297-310 (304-305) ( [5] ).

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This article was added to the list of excellent articles on May 5, 2005 in this version .