Sloth Species Research Articles

Variations in dietary patterns of living sloths revealed by finite element analysis of jaws.

Although extinct sloths exhibited a wide range of dietary habits, modes of locomotion, and occupied various niches across the Americas, modern sloths are considered quite similar in their habits. The dietary habits of living sloths can be directly observed in the wild, and understanding the mechanical behavior of their jaws during chewing through finite element analysis (FEA) provides a valuable validation tool for comparative analysis with their extinct counterparts. In this study, we used FEA to simulate the mechanical behavior of sloth mandibles under lateral mastication loads, using it as a proxy for oral processing. Our research focused on the six extant sloth species to better understand their diets and validate the use of FEA for studying their extinct relatives. We found that all living sloths have the predominancy of low-stress areas in their mandibles but with significant differences. Choloepus didactylus had larger high-stress areas, which could be linked to a reduced need for processing tougher foods as an opportunistic generalist. Bradypus variegatus and Choloepus hoffmanni are shown to be similar, displaying large low-stress areas, indicating greater oral processing capacity in a seasonal and more competitive environment. Bradypus torquatus, Bradypus pygmaeus, and Bradypus tridactylus exhibited intermediary processing patterns, which can be linked to a stable food supply in more stable environments and a reduced requirement for extensive oral processing capacity. This study sheds light on extant sloths' dietary adaptations and has implications for understanding the ecological roles and evolutionary history of their extinct counterparts.

FIRST REPORT OF CHEMICAL IMMOBILIZATION AND PHYSIOLOGICAL PARAMETERS FOR FREE-RANGING MANED SLOTH (BRADYPUS TORQUATUS), USING A COMBINATION OF KETAMINE AND MEDETOMIDINE.

The maned sloth (Bradypus torquatus) is an endemic and endangered species of two Brazilian states, with much unknown biological information needed to direct conservation actions. Other sloth species have been studied regarding anesthesia; however, there is a lack of anesthesia research for the maned sloth. Anesthetic data were collected from 12 free-range maned sloths that were immobilized for a field examination. Individuals were anesthetized using a combination of ketamine (4.0 mg/kg) and medetomidine (0.03 mg/kg), and antagonized with atipamezole (0.1 mg/kg). Time to induction and recovery were recorded and compared with sex and age classes. After the induction and until antagonist administration, physiological parameters (rectal temperature, heart rate, respiratory rate, and oxygen saturation) were recorded every 10 min during anesthesia and were statistically evaluated over time. Induction was fast (3.21 ± 0.76), but recovery was longer (113.3 ± 18) when compared to other studies. Induction and recovery times were not different across sex or age classes. Rectal temperature, heart rate, and oxygen saturation remained stable throughout the procedure. Respiratory rate significantly decreased over time, from 18.25 ± 7.03 to 13.17 ± 3.66 movements per minute. Our results indicate that the described combination of ketamine and medetomidine is a safe and effective choice for anesthesia of maned sloths.

What, where, and how: a spatiotemporally explicit analysis of the drivers of habitat loss within the range of maned three‐toed sloths (Bradypus torquatus and Bradypus crinitus)

Abstract The first step towards understanding the conservation situation and informing conservation decision‐making is to identify the habitat loss drivers. However, for nearly all tropical biota, there is a glaring lack of information on the spatiotemporal patterns of anthropogenic drivers. Our objective was to analyse the spatial and temporal distribution of the main anthropogenic drivers of habitat loss for Bradypus torquatus and Bradypus crinitus, two endangered and endemic species to the Brazilian Atlantic Forest. We used land‐use information associated with seven major IUCN‐based threats to sloths, covering a three‐generation time window (1988–2020), to quantify the current area occupied, temporal changes, heterogeneity, and intensity of drivers across species distributions. We found that cattle farming and ranching dominate the range of both species (from 49% to 56%) and cover an area larger than the remaining native forest. Other drivers also represent important spatial and temporal features of land conversion across species distributions. Driven mainly by livestock expansion, both sloth species have experienced a significant loss of forest cover (Bradypus torquatus – 659098.70 ha; Bradypus crinitus – 139013.20 ha) in the Brazilian Atlantic forest. Overall, Bradypus torquatus showed a higher rate of deforestation than forest regeneration, whereas forest gains outweighed habitat loss for Bradypus crinitus. Our results show that a substantial area of native forest – essential for strictly arboreal species – is being continuously replaced by cattle ranching and agricultural activities, which may lead to population isolation and decline, threatening the long‐term population viability.

Gender Determination by PCR Assay for The Sex-Determining Region Y(SRY) Gene Amplification in Linnaeus’s Two-Toed Sloth (Choloepus Didactylus)

In Linnaeus’s two-toed sloths (Choloepus didactylus), there is no distinct sexual dimorphism. It is an obstacle for gender determination from the external genitalia, especially in newborns or young sloths. Hence, easy, rapid, and reliable genetics-based methods for gender identification of the sloths are needed to continue captive breeding more successfully. In this study, a PCR-based technique that allows gender determination of two-toed sloths by using a sex-determining region Y (SRY) gene marker was described. The hair samples from young (suspect gender) and adult sloths (known gender) were used in genetic analysis. Initially, genomic DNA was isolated from hair root samples using Roche high pure PCR template preparation kit. The SRY primers were specifically designed based on the NCBI and Ensembl databases, and they were verified with the BLAST program concerning the two-toed sloth genome. PCR amplification with the SRY-specific primers was carried out by a programmable thermal cycler device using FastStart High Fidelity PCR System, Roche dNTPack. The samples were then electrophoresed on 2% agarose gels and were visualized by a gel documentation and analysis system. A specific band in the electrophoresis pattern is diagnostic for a male individual with a partial SRY region. Hence, the analysis demonstrated that the samples belonged to a male two-toed sloth. Two-toed sloth species are commonly preferred animals in zoos. Gender determination is inevitable for these animals in captivity to be raised successfully and healthily. Molecular genetic techniques allow high efficiency in taxonomic evaluations and gender identification in species that do not display sexual dimorphism. The PCR assay described here may be helpful for a rapid genetic analysis that can be widely used in gender determination for two-toed sloths.

FATAL GASTRIC DILATATION AND VOLVULUS IN THREE CAPTIVE JUVENILE LINNAEUS'S TWO-TOED SLOTHS (CHOLOEPUS DIDACTYLUS).

Linnaeus's two-toed sloth (Choloepus didactylus) is one of two extant neotropical species of the family Megalonychidae. Despite their being commonly kept under managed care, the digestive physiology of sloths remains poorly understood. Gastrointestinal disease has been reported as a primary or contributing cause of morbidity and mortality in captive two-toed and three-toed (Bradypus spp.) sloths. Gastric dilatation due to gas accumulation ("bloat") has been reported in sloths; however, a literature search failed to yield any published mention of gastric volvulus in any sloth species. Following an inquiry sent to the electronic mailing lists of the American Association of Zoo Veterinarians, the European Association of Zoo and Wildlife Veterinarians, and the LatinVets community, three cases of fatal gastric dilatation and volvulus (GDV) were identified in one male and two female Linnaeus's two-toed sloths from institutions in the United States, Canada, and Germany. All cases occurred in juvenile sloths <1 yr of age. Two animals were primarily hand reared, whereas one was reared primarily by its dam. Two animals were found dead with no overt premonitory signs, whereas one animal died following a 3-wk course of waxing and waning clinical signs consistent with gastric gas accumulation. In all cases, GDV was diagnosed on postmortem examination. Similar to other species, the condition is likely subsequent to a combination of host- and husbandry-related contributing factors. Further research into sloth husbandry is required in order to take an evidence-based approach to their management.

Iteratively mapping ancient DNA to reconstruct highly divergent mitochondrial genomes: An evaluation of software, parameters and bait reference

Abstract The ability to obtain ancient DNA (aDNA) from extinct species has greatly improved our ability to study their evolutionary histories. Most aDNA studies focus on mitochondrial DNA for both population‐level and species‐level insights, due to its relatively high abundance and increased obtainability. Although several approaches are available to assemble mitogenomes, high levels of DNA damage and non‐target contaminating DNA make many approaches unsuitable for aDNA. Further complicating matters for most extinct species is the lack of a sufficiently closely related extant relative to act as a reference. Iterative mapping can assemble mitogenomes without using a close reference sequence, and has been applied to aDNA from various extinct species. Despite its widespread use, the accuracy of the reconstructed assemblies is yet to be comprehensively assessed. Here, we investigated the influence of (i) mapping software (Burrows–Wheeler Alignment [BWA], MITObim and NOVOplasty), (ii) parameters and (iii) bait reference phylogenetic distance on assembly accuracy using two simulated datasets: spotted hyena and various mammalian bait references; southern cassowary and various avian bait references, and two empirical datasets: extinct cave hyena; two extinct sloth species. Specifically, we assessed the accuracy of results through three parameters: pairwise distance to a reference conspecific mitogenome, number of incorrectly inserted base pairs and total length of the assembly. We found large discrepancies in the accuracy of reconstructed assemblies using different mapping software, parameters and bait references. Results also varied depending on the dataset, thereby making broad, generalised conclusions difficult. However, the overall most accurate results were obtained with either BWA using a minimum mapping quality of 20 and relaxed mismatch parameters (‐n 0.001 ‐o 2), or MITObim using a mismatch value of 3 or 5. We also show accuracy could be further improved by combining results from multiple bait references. Our study provides information on how divergent mitogenomes are best reconstructed from aDNA. By obtaining the most accurate reconstruction possible, one can be more confident as to the reliability of downstream analyses, and the evolutionary inferences made from them.

Taxonomic revision of maned sloths, subgenusBradypus(Scaeopus), Pilosa, Bradypodidae, with revalidation ofBradypus crinitusGray, 1850

AbstractWe present a taxonomic revision of maned sloths, subgenus Bradypus (Scaeopus), a taxon endemic to the Brazilian Atlantic Forest and currently composed of a single species, the vulnerable Bradypus torquatus. Our review is based on coalescent species delimitation analyses using mitochondrial and nuclear DNA, morphological analyses, and field observations. Our integrative approach demonstrates that two species of maned sloth can be recognized: the northern maned sloth (Bradypus torquatusIlliger, 1811) occurring in the Brazilian states of Bahia and Sergipe, and the southern maned sloth (Bradypus crinitusGray, 1850), occurring in Rio de Janeiro and Espirito Santo states. The two species diverged in the Early Pliocene and are allopatrically distributed. We discuss the biogeographic pattern of the two maned sloth species, comparing it with other Atlantic Forest mammals. We also suggest that the conservation status of both maned sloths needs to be reassessed after this taxonomic rearrangement.

Slow science: how I'm protecting sloth species.

Slow science: how I'm protecting sloth species.

Inferring the paleoecology of the Late Pleistocene giant ground sloths from the Brazilian Intertropical Region

This paper provides diet interpretations for nine giant ground sloth species that lived in the Brazilian Intertropical Region, through the relative muzzle width technique and occlusal surface area (except Mylodonopsis ibseni). We propose that Eremotherium laurillardi, Ocnotherium giganteum, Mylodonopsis ibseni, Glossotherium phoenesis, Catonyx cuvieri, Valgipes bucklandi, Ahytherium aureum, and Australonyx aquae were adapted to had a mixed-feeder diet, having a great oral food processing, which could indicate an adaptation to need less from the fermentation on digestive tract, and similar, or even higher, metabolic requirements in comparison with ungulates of similar body mass. While, N. maquinense was adapted to a browser diet, and probably presented high fermetantion capability and low metabolic requirement, in comparison with all other giant ground sloth taxa.

Presence and Multi-Species Spatial Distribution of Oropouche Virus in Brazil within the One Health Framework.

Oropouche virus (OROV) is an emerging vector-borne arbovirus with high epidemic potential, causing illness in more than 500,000 people. Primarily contracted through its midge and mosquito vectors, OROV remains prevalent in its wild, non-human primate and sloth reservoir hosts as well. This virus is spreading across Latin America; however, the majority of cases occur in Brazil. The aim of this research is to document OROV’s presence in Brazil using the One Health approach and geospatial techniques. A scoping review of the literature (2000 to 2021) was conducted to collect reports of this disease in humans and animal species. Data were then geocoded by first and second subnational levels and species to map OROV’s spread. In total, 14 of 27 states reported OROV presence across 67 municipalities (second subnational level). However, most of the cases were in the northern region, within the tropical and subtropical moist broadleaf forests biome. OROV was identified in humans, four vector species, four genera of non-human primates, one sloth species, and others. Utilizing One Health was important to understand the distribution of OROV across several species and to suggest possible environmental, socioeconomic, and demographic drivers of the virus’s presence. As deforestation, climate change, and migration rates increase, further study into the spillover potential of this disease is needed.

Integrating climate, ecophysiology, and forest cover to estimate the vulnerability of sloths to climate change

AbstractGlobal change imposes multiple challenges on species and, thus, a reliable prediction of current and future vulnerability of species must consider multiple stressors and intrinsic traits of species. Climate, physiology, and forest cover, for example, are required to evaluate threat to thermolabile forest-dependent species, such as sloths (Bradypus spp.; Mammalia: Xenarthra). Here, we estimated future changes in the distribution of three sloth species using a metabolic-hybrid model focused on climate (climatic only, i.e., CO approach) and adding forest cover constraints to distribution of species (climate plus land cover, i.e., CL approach). We used an innovative method to generate estimates of physiological parameters for endotherms, validated with field data. The CF approach predicted a future net expansion of distribution of B. torquatus and B. variegatus, and a future net contraction of distribution of B. tridactylus. The inclusion of forest cover constraints, however, reversed the predictions for B. torquatus, with a predicted net distribution contraction. It also reduced expansion of B. variegatus, although still showing a large net expansion. Thus, B. variegatus is not predicted to be threatened in the future; B. tridactylus emerges as the species most vulnerable to climate change, but with no considerable forest losses, while B. torquatus shows the opposite pattern. Our study highlights the importance of incorporating multiple stressors in predictive models in general. To increase resilience of species to climate change, it is key to control deforestation in the Amazon for B. tridactylus, and to promote reforestation in the Atlantic Forest for B. torquatus.

Sloth's giant tick (Amblyomma varium) parasitizing free-ranging maned sloth (Bradypus torquatus) in the Atlantic Forest biome, Brazil.

Amblyomma varium is a neotropical tick popularly known as the sloth’s giant tick, during the adult stage is found almost exclusively on mammals of the Bradypodidae and Megalonychidae families of the superorder Xenarthra. The maned sloth (Bradypus torquatus) is the only sloth species in danger of extinction in Brazil. This species is arboreal and descends to the ground only to perform defecation behavior. This behavior can be the determining factor for infestation and infection by different parasitic agents, including A. varium. This study reported the occurrence of A. varium found parasitizing free-living maned sloths (B. torquatus) in the Atlantic Forest biome of Northeast and Southeast Brazil. A total of 36 individuals were evaluated and more than 50% of the individuals were parasitized by ticks of the species A. varium. This study confirmed the importance of B. torquatus as a host for adults and nymphs of A. varium and reported the variation in length of the spurs on coxa IV of A. varium males.

New species of the ground sloth Parocnus from the late Pleistocene-early Holocene of Hispaniola

Parocnus dominicanus sp. nov. represents a new species of megalonychid ground sloth from theAltagracia Province of southeastern Dominican Republic. Specimens of multiple individuals, including oneassociated partial skeleton, were recovered from two separate underwater caves in the Parque Nacional delEste through collaborations with museums and cave divers between 2009–2013. Parocnus dominicanus sp.nov. is distinguished by its small size compared to that of P. serus, with percent differences in limb elementlengths ranging from 13−24%. Numerous cranial and post-cranial elements also exhibit morphological characterstates that are not attributable to size variations. The recovery of multiple individuals within each localitydemonstrates a size dimorphism, possibly sexual, which parallels patterns exhibited by P. serus. The twospecies are also geographically distinct, with no examples of co-occurrence at any localities to date. Parocnusdominicanus sp. nov. and P. serus share character states that are distinct from those of the Cuban species, P.browni, and which suggest differential usage of the forelimb. The exact age of the specimens described here isunknown, however, Parocnus has been dated to the Holocene in Haiti.http://zoobank.org/urn:lsid:zoobank.org:pub:12E495D3-E261-4522-9854-D3B4C2D5FFB8

Why sloths defecate on the ground: rejection of the mutualistic model

Introduction: Sloths are arboreal mammals that defecate on the ground, increasing the risk of predation. There are several hypotheses that try to explain why they undergo this risk. Objective: To critically review all the hypotheses and to propose a new hypothesis that is compatible with all known data. Methods: I verified the assumptions and implications of five hypotheses against the literature available February, 2021. Results: Previous hypotheses either lack reliable supporting data, or are contradicted by published data. Here I propose that defecation on the ground is an ancestral behavior that persists in all sloth species because there has not been enough natural selection against it. Conclusions: Current knowledge of sloth biology is compatible with the hypothesis that there has not been enough selective pressure for sloths to abandon defecation on the ground.

IDLY INFECTED: A REVIEW OF INFECTIOUS AGENTS IN POPULATIONS OF TWO- AND THREE-TOED SLOTHS (CHOLOEPUS SPECIES AND BRADYPUS SPECIES).

Two- and three-toed sloths (Choloepus spp. and Bradypus spp.) have become popular animals in American culture and in American zoos, where they are frequently used as animal ambassadors. Despite the increased focus on sloth species, the prevalence of infectious diseases in sloth populations and the associated clinical consequences are relatively unknown. This study reviewed all published literature from 1809 to 2019 that examined infectious agents in both captive and wild populations of either two- or three-toed sloths. Online databases were electronically searched for relevant manuscripts using strings of inclusion and exclusion terms, resulting in an initial identification of 5,364 articles. After removing duplications and conducting two relevance screenings, 57 manuscripts were included in the full review. A total of 1,769 individual two-toed sloths and 879 individual three-toed sloths were accounted for in the included studies, with evidence of infection or exposure to infectious agents in 647 (36.6%) and 222 (25.3%) individual two- and three-toed sloths, respectively. Approximately 74% of documented infections were cryptic fungal, parasitic, and viral infections. The remaining 26% of infections represent those that were associated with clinical signs of disease. The infectious agents reported were bacterial (84), parasitic (20), viral (9), and fungal (4). Significant knowledge gaps remain regarding clinical and subclinical infectious disease prevalence and impact in both free-ranging and captive sloths.

PATHOLOGIC FINDINGS IN 36 SLOTHS FROM BRAZIL.

Sloths are xenarthrans from Central and South America with a highly adapted morphophysiology. Five of the six known species of sloths are found in Brazil, among which Bradypus torquatus (maned three-toed sloth) is considered a vulnerable species by International Union for Conservation of Nature. Nevertheless, knowledge on health and disease of sloths is very scarce, thus this study aimed to describe macroscopic and microscopic findings in 36 Brazilian sloths. The most common findings included iron storage disorder, probable bacterial pneumonia, gastric and intestinal nematode parasitism, and a presumptive diagnosis of systemic mastocytosis.

RENAL EVALUATION IN CHOLOEPUS SPECIES.

Two species of sloths in the family Megalonychidae, Hoffmann's (Choloepus hoffmanni) and Linnaeus's (Choloepus didactylus) two-toed sloths, are commonly held in zoological institutions. Despite frequent published reports of urinary tract disease in these species, reports of diagnostics are mostly limited to descriptions of hematology and serum chemistry. In this study, repeated urinalysis, urinary chemistry, serum chemistry, and radiographs were collected opportunistically from six Hoffmann's and five Linnaeus's sloths. Proteinuria, bacteriuria, low urine specific gravity, and crystalluria were common in the absence of other signs of urinary tract pathology.

Sloths host Anhanga virus-related phleboviruses across large distances in time and space.

Sloths are genetically and physiologically divergent mammals. Phleboviruses are major arthropod‐borne viruses (arboviruses) causing disease in humans and other animals globally. Sloths host arboviruses, but virus detections are scarce. A phlebovirus termed Anhanga virus (ANHV) was isolated from a Brazilian Linnaeus's two‐toed sloth (Choloepus didactylus) in 1962. Here, we investigated the presence of phleboviruses in sera sampled in 2014 from 74 Hoffmann's two‐toed (Choloepus hoffmanni, n = 65) and three‐toed (Bradypus variegatus, n = 9) sloths in Costa Rica by broadly reactive RT‐PCR. A clinically healthy adult Hoffmann's two‐toed sloth was infected with a phlebovirus. Viral load in this animal was high at 8.5 × 107 RNA copies/ml. The full coding sequence of the virus was determined by deep sequencing. Phylogenetic analyses and sequence distance comparisons revealed that the new sloth virus, likely representing a new phlebovirus species, provisionally named Penshurt virus (PEHV), was most closely related to ANHV, with amino acid identities of 93.1%, 84.6%, 94.7% and 89.0% in the translated L, M, N and NSs genes, respectively. Significantly more non‐synonymous mutations relative to ANHV occurred in the M gene encoding the viral glycoproteins and in the NSs gene encoding a putative interferon antagonist compared to L and N genes. This was compatible with viral adaptation to different sloth species and with micro‐evolutionary processes associated with immune evasion during the genealogy of sloth‐associated phleboviruses. However, gene‐wide mean dN/dS ratios were low at 0.02–0.15 and no sites showed significant evidence for positive selection, pointing to comparable selection pressures within sloth‐associated viruses and genetically related phleboviruses infecting hosts other than sloths. The detection of a new phlebovirus closely‐related to ANHV, in sloths from Costa Rica fifty years after and more than 3,000 km away from the isolation of ANHV confirmed the host associations of ANHV‐related phleboviruses with the two extant species of two‐toed sloths.

Hand rearing a Linné’s two‐toed sloth Choloepus didactylus at ZSL London Zoo

There is an increasing emphasis on the importance of ensuring the long‐term viability of taxa maintained in zoological collections. The captive population of Linné’s two‐toed sloth Choloepus didactylus is monitored and managed in European and American breeding programmes. However, although breeding success is increasing the population is still not sustainable. Hand rearing is one option in the ‘toolbox’ of measures that can be used to assist with achieving integrated conservation goals, despite being challenging and labour intensive. This paper describes the enforced, but successful, hand rearing of a two‐toed sloth from 26 days of age at ZSL London Zoo, UK. The feeding protocol, behaviour and development are reported, and growth‐rate data are presented. While presenting data for only one individual, the experience has provided practical information about hand‐rearing practice that may inform future interventions in the management of ex situ populations, and assist with rescue and rehabilitation efforts for this and related species in the field. This species is classified as Least Concern by the International Union for Conservation of Nature and Natural Resources (IUCN) Red List; however, these sloths are threatened by habitat loss. Two of the six extant species of sloths are assessed as threatened; Pygmy three‐toed sloth Bradypus pygmaeus (Critically Endangered) and the Maned three‐toed sloth Bradypus torquatus (Vulnerable).

On the presence of Megatherium Cuvier, 1796 (Xenarthra, Pilosa) in fossiliferous deposits of the Coastal Plain of Southern Brazil

The presence of the extinct sloth Megatherium americanum Cuvier in Pleistocene deposits of the Coastal Plain of the State of Rio Grande do Sul, southern Brazil, has been mentioned by several authors for decades, but formal descriptions of skeletal elements with unambiguous diagnostic features have never been published. The recent description of one dentary of the megatheriid Eremotherium laurillardi Lund from deposits in this area raised doubts about the taxonomic affinity of the materials assigned to M. americanum. The present work confirms the presence of the latter in the coastal plain of the state of Rio Grande do Sul (Santa Vitoria do Palmar County), from a partial skull collected in fluvial deposits of the Santa Vitoria Formation exposed on the banks of the Chui Creek, plus an incomplete dentary, one tibia, one astragalus found on the shoreline, and another tibia with the fibula fused proximally and distally retrieved from the bottom of the continental shelf by the research vessel “Atlântico Sul”. The fossils of both species of megatheriid sloths were found in the same deposits of Rio Grande do Sul (Chui Creek in the coastal plain and Pessegueiro Creek in the central area of the state), which is remarkable given that E. laurillardi is known mostly from the intertropical Americas, whereas M. americanum is restricted to the subtropical-temperate regions of South America. Such co-occurrence could indicate that both species were sympatric or be related to the mixing by fluvial processes of remains of animals that occupied the same areas at distinct times due to periodic latitudinal shifts of the climatic belts.