AbstractIntroduction: 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.
Aiello, A. (1985). Sloth hair: unanswered questions. In G. G. Montgomery (ed). The Evolution of Armadillos, Sloths, and Vermilinguas (pp. 213-218). Washington, D.C., USA: Smithsonian Institution Press.
Bailey, T. N. (1974). Social organization in a bobcat population. The Journal of Wildlife Management, 38(3),435-446.
Chiarello A.G. (2008) Sloth ecology: an overview of field studies. In S. Vizcaíno & W. Loughry (eds.). The biology of the Xenarthra (pp. 269–280). Gainesville, FL: University Press of Florida.
Clauss, M. (2004). The potential interplay of posture, digestive anatomy, density of ingesta and gravity in mammalian herbivores: Why sloths do not rest upside down. Mammal Review, 34(3), 241-245.
Dünner, C., & Pastor, G. (2017). Manual de manejo, medicina y rehabilitación de perezosos. Chile: Fundación Huálamo.
Hayssen, V. (2009). Bradypus tridactylus (Pilosa: Bradypodidae). Mammalian Species, 839, 1-9. DOI: 10.1644/839.1
Hayssen, V. (2011). Choloepus hoffmanni (Pilosa: Megalonychidae). Mammalian Species, 43(873), 37-55. DOI: 10.1644/873.1
Hunt, A. P., & Lucas, S. G. (2018). The Record of Sloth Coprolites in North and South America: Implications for Terminal Pleistocene Extinctions. New Mexico Museum of Natural History and Science Bulletin, 79, 277-298.
Liberg, O. (1980). Spacing patterns in a population of rural free roaming domestic cats. Oikos, 32(3),336-349.
Montgomery, G. G., & Sunquist, M. E. (1975). Impact of Sloths on Neotropical Forest Energy Flow and Nutrient Cycling. Ecological Studies, 69–98. DOI:10.1007/978-3-642-88533-4_7
Pauli, J. N., Mendoza, J. E., Steffan, S. A., Carey, C. C., Weimer, P. J., & Peery, M. Z. (2014). A syndrome of mutualism reinforces the lifestyle of a sloth. Proceedings of the Royal Society B: Biological Sciences, 281(1778), 20133006. DOI: 10.1098/rspb.2013.3006
Peery, M. Z., & Pauli, J. N. (2014). Shade‐grown cacao supports a self‐sustaining population of two‐toed but not three‐toed sloths. Journal of Applied Ecology, 51(1), 162-170. DOI: 10.1111/1365-2664.12182
Ramírez, O., Vaughan, C., Herrera, G., & Guries, R. (2011). Temporal and spatial resource use by female three-toed sloths and their young in an agricultural landscape in Costa Rica. Revista de Biologia Tropical, 59(4), 1743-1755.
Slater, G. J., Cui, P., Forasiepi, A. M., Lenz, D., Tsangaras, K., Voirin, B., ... & Greenwood, A. D. (2016). Evolutionary relationships among extinct and extant sloths: the evidence of mitogenomes and retroviruses. Genome Biology and Evolution, 8(3), 607-621. DOI: 10.1093/gbe/evw023
Sunquist, M. E., & Montgomery, G. G. (1973). Activity patterns and rates of movement of two-toed and three-toed sloths (Choloepus hoffmanni and Bradypus infuscatus). Journal of Mammalogy, 54(4), 946-954. DOI: 10.2307/1379088
Suutari, M., Majaneva, M., Fewer, D. P., Voirin, B., Aiello, A., Friedl, T., ... & Blomster, J. (2010). 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(1), 1-12. DOI: 10.1186/1471-2148-10-86
Vaughan, C., Ramírez, O., Herrera, G., & Guries, R. (2007). Spatial ecology and conservation of two sloth species in a cacao landscape in Limón, Costa Rica. Biodiversity and Conservation, 16(8), 2293-2310. DOI: 10.1007/s10531-007-9191-5
Voirin, B., Kays, R., Wikelski, M., & Lowman, M. (2013). Why Do Sloths Poop on the Ground? In M. Lowman, S. Devy, & T. Ganesh (eds). Treetops at Risk (pp. 195-199). Springer, New York, NY.
Waage, J. K., & Best, C. (1985). Arthropod associates of sloths. In G. G. Montgomery (ed). The Evolution of Armadillos, Sloths, and Vermilinguas (pp. 297-311). Washington, D.C., USA: Smithsonian Institution Press.
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