Primeiro relato de predação de um jacaré-coroa (Paleosuchus trigonatus) por uma lontra (Lontra longicaudis)

aa Acta Amazonica Acta Amaz. 0044-5967 1809-4392 Instituto Nacional de Pesquisas da Amazônia RESUMO Lontra longicaudis é um predador semi-aquático com dieta principal a base de peixes e crustáceos, mas que oportunisticamente pode predar mamíferos, aves e répteis. Na Amazônia, essa espécie ocorre em simpatria com Paleosuchus trigonatus, uma das menores espécies de crocodilianos, apresentando como possível meio de defesa uma pele extremamente rígida, o que faz com que adultos tenham poucos predadores. Aqui nós relatamos o primeiro caso documentado de predação de P. trigonatus por L. longicaudis. The Neotropical otter, Lontra longicaudis (Olfers, 1818), is, along with the giant otter, Pteronura brasiliensis (Gmelin, 1788), one of two species of otter living in Brazil. Lontra longicaudis has a wide distribution in Central and South America (Sánchez and Gallo-Reynoso 2007; Rheingantz et al. 2014). This species can reach between 1.2 and 1.7 m in total length and weigh between 5 and 15 kg (Cheida et al. 2011). As they have a semi-aquatic habit, Neotropical otters depend strongly on water bodies, especially for foraging and feeding activities, and are usually found close to rivers, streams, lakes, ponds, estuaries, mangroves, swamps and along coastlines (Cheida et al. 2011; Rheingantz et al. 2014). This species also lives in habitats ranging from rocky shores to deciduous and perennial forests, tropical and temperate forests, and coastal savannah swamps (Cheida et al. 2011). Although Cheida et al. (2011) consider that the presence of otters is linked to the local availability of resources, Rheingantz et al. (2014) point out that the species can be found in environments with significant levels of anthropic impact. Four species of crocodilians are sympatric with Neotropical otters in the central Amazon, including the smooth-fronted caiman, Paleosuchus trigonatus (Schneider, 1801) (Magnusson and Lima 1991; Morales-Betancourt et al. 2013). Paleosuchus trigonatus are among the smallest living crocodilians, reaching up to 2.3 m in total length, though males rarely exceed 1.7 m and most females are less than 1.4 m in total length (Magnusson and Lima 1991; Morales-Betancourt et al. 2013). Individual P. trigonatus have a small home range, spending most of the time in terrestrial shelters, close to small watercourses in adjacent forests and flooded areas. This species rarely moves away from these places (Magnusson and Lima 1991; Marioni et al. 2022). Diet studies indicate that 58% of their prey is terrestrial (Villamarín et al. 2017), a number linked to the fact that smooth-fronted caiman spend much of their life in the terrestrial environment (Magnusson and Lima 1991). Although it is a cryptic species, population density studies have indicated that P. trigonatus has the highest biomass per km² of any large predator in the central Amazon (Magnusson and Lima 1991). In September 2022 (dry season in the central Amazon), during birdwatching activity, AJS saw a smooth-fronted caiman (P. trigonatus) being attacked by an otter (L. longicaudis), in a stream approximately 5 m wide and 1 m average depth, with margins laterally unvegetated for approximately 3 m. The site (3°24’12.380”S, 64°42’26.284”W) consists of secondary vegetation in a stretch of buriti palmtrees (Mauritia flexuosa L.f.) surrounded by shrubs, where the stream crossed a dirt road. The site was approximately 1 km from a paved road, in an urban area of Tefé municipality, Amazonas state, Brazil, 600 km west from the state capital, Manaus (Figure 1). Figure 1 A - Location of the study area in the Brazilian Amazon (darker grey); B - Study area showing the location of the predation event on the outskirts of the city of Tefé, Amazonas state, downriver of the confluence of the Solimões and Japurá rivers. At approximately 08:00 a.m., an adult Neotropical otter was observed leaving the stream and entering the riparian forest. Shortly afterwards, at a nearby point, bubbles and movement were observed in the watercourse, then the otter emerged dragging a smooth-fronted caiman, whose throat it was biting (Figure 2). The total length of each animal was similar (around 1 m). It was not recorded whether the attack began on land or in the water. While immobilized, the caiman made death roll attempts, both on and below the water surface. The otter emerged without the caiman, before diving and recovering it shortly after that. Some 5 minutes after the initial sighting, the caiman was dead and carried into the forest by the otter (Figure 3). After this, visual contact was lost. Figure 2 Adult individual of Lontra longicaudis attacking a subadult Paleosuchus trigonatus in a stream in the municipality of Tefé, Amazonas state, Brazil. Credit: Anselmo J Silva. Figure 3 Adult individual of Lontra longicaudis carrying a predated subadult Paleosuchus trigonatus out of the stream into the riparian forest in the municipality of Tefé, Amazonas state, Brazil. Credit: Anselmo J Silva. Otters usually catch their prey under water, subsequently eating it on the water surface, or on land (Cheida et al. 2011). Neotropical otters are considered opportunistic predators and specialists in aquatic prey which moves slowly and has limited capacity to escape (Pardini 1998; Quadros and Monteiro-Filho 2001; Rheingantz et al. 2017). Fish and crustaceans are the most common prey of Neotropical otter (Pardini 1998; Quadros and Monteiro-Filho 2001), although they may also opportunistically feed on small mammals, birds, and reptiles (Passamani and Camargo 1995; Platt and Rainwater 2011; Santiago-Plata et al. 2013), as well as insects, amphibians and mollusks (Quadros and Monteiro-Filho 2001; Casariego-Madorell et al. 2008; Carvalho-Junior et al. 2010; Rheingantz et al. 2011). Otter diets may be more diverse in less stable environments or when main prey density is low (Rheingantz et al. 2017). The diversity and abundance of fish assemblages in Amazonian streams, including otter prey species, is influenced by vegetation type and riverbed substrate, in addition to seasonal changes promoted by variation in water level and rainfall (Espírito-Santo et al. 2009; Kemenes and Forsberg 2014). The stream where the predation occurred was shallow and narrow during the dry season, in addition to being approximately 8 km away from the largest water body (Tefé lake), which may have reduced the abundance of larger fish. Changes in the water level of streams also influence niche partitioning by some species of predators, as reported for P. palpebrosus and P. trigonatus by Marioni et al (2022). With the reduction in water level of the stream, L.longicaudis, besides having fewer prey options, probably had increased home-range overlap with P.trigonatus (Magnusson and Lima 1991; Marioni et al. 2022), increasing the chance of interspecific interactions. Juvenile and subadult smooth-fronted caimans are potentially predated by felids, birds of prey, constricting snakes, other crocodilians, rodents, and freshwater turtles. However, adult animals supposedly have few predators (Morales-Betancourt 2013). According to reproductive biology studies of P. trigonatus, animals around 1 m in total length are still subadults, but close to sexual maturity (Magnusson and Lima 1991; Marioni et al. 2022). As one of the smallest and most terrestrial of crocodilians, one of their forms of defense consists of a high density of osteoderms on their skin and large irregular scales, which form a rigid carapace (English 2017). However, the otter attacked the least protected areas of the caiman body, such as the throat and side of the neck. More recent research has suggested that this dense ossification may actually be an adaptation of dwarf crocodilian species to equatorial environments, functioning mainly as a calcium reserve and for thermoregulation (Clarac et al. 2024). As an additional defense strategy, they can perform the death roll when they are captured, as was observed during the current event. A death roll consists of spinning around the long axis of the own body, a behavior used by crocodilians to divide their prey into smaller fractions, or to injure or escape from a rival or predator during conflict (Drumheller et al. 2019). There are reports of otter predation on smaller reptiles, such as adult iguanas (Pereira et al. 2020), juvenile turtles (Platt and Rainwater 2011) and juvenile spectacled caiman (Medina-Barrios and Morales-Betancourt 2015), however, this is the first record of Neotropical otter predation on a large subadult smooth-fronted caiman. Our observation includes the Neotropical otter as potential predator of subadult and adult P. trigonatus, and highlights the need for further studies on the interaction between sympatric predators in Amazonian environments. ACKNOWLEDGMENTS The authors are grateful to Pedro Nassar, for his support in recognizing the place of occurrence, and Darlene Gris, for identifying the phytophysiognomy. REFERENCES Carvalho-Júnior, O.; Macedo-Soares, L.C.P.; Brirolo, A.B. 2010. Annual and interannual food habits variability of a Neotropical otter (Lontra longicaudis) population in Conceição Lagoon, south of Brazil. IUCN Otter Specialist Group Bulletin 27: 24-32 Carvalho O. Júnior Macedo-Soares L.C.P. Brirolo A.B. 2010 Annual and interannual food habits variability of a Neotropical otter (Lontra longicaudis) population in Conceição Lagoon, south of Brazil IUCN Otter Specialist Group Bulletin 27 24 32 Casariego-Madorell, M.A.; List, R.; Ceballos, G. 2008. Tamaño poblacional y alimentación de la nutria de río (Lontra longicaudis annectens) en la costa de Oaxaca, México. Acta Zoológica Mexicana 24: 179-199. Casariego-Madorell M.A. List R. Ceballos G. 2008 Tamaño poblacional y alimentación de la nutria de río (Lontra longicaudis annectens) en la costa de Oaxaca, México Acta Zoológica Mexicana 24 179 199 Cheida, C.; Nakano-Oliveira, E.; Fusco-Costa, R.; Rocha-Mendes, F.; Quadros, J. 2011. Ordem Carnivora. In: Reis, N.R.; Peracchi, A.L.; Pedro, W.A.; Lima, I.P. (Eds.). Mamíferos do Brasil. 2nd ed. Universidade Estadual de Londrina, Londrina. p.235-272. Cheida C. Nakano-Oliveira E. Fusco-Costa R. Rocha-Mendes F. Quadros J. 2011 Ordem Carnivora Reis N.R. Peracchi A.L. Pedro W.A. Lima I.P. Mamíferos do Brasil 2nd ed Universidade Estadual de Londrina Londrina 235 272 Clarac, F.; Campos, Z.; Marquis, O. 2024. The extended osteoderm shield in Paleosuchus sp.: A dwarf crocodylian adaptation to the equatorial forest ecosystem? Comptes Rendus Palevol 23: 161-170. Clarac F. Campos Z. Marquis O. 2024 The extended osteoderm shield in Paleosuchus sp.: A dwarf crocodylian adaptation to the equatorial forest ecosystem? Comptes Rendus Palevol 23 161 170 Drumheller, S.K.; Darlington, J.; Vliet, K.A. 2019. Surveying death roll behavior across Crocodylia. Ethology, Ecology and Evolution 31: 329-347. Drumheller S.K. Darlington J. Vliet K.A. 2019 Surveying death roll behavior across Crocodylia Ethology, Ecology and Evolution 31 329 347 English, L.T. 2017. Variation in crocodilian dorsal scute organization and geometry with a discussion of possible functional implications. Journal of Morphology 279: 154-162. English L.T. 2017 Variation in crocodilian dorsal scute organization and geometry with a discussion of possible functional implications Journal of Morphology 279 154 162 Espírito‐Santo, H.M.V.; Magnusson, W.E.; Zuanon, J.; Mendonca, F.P.; Landeiro, V.L. 2009. Seasonal variation in the composition of fish assemblages in small Amazonian forest streams: evidence for predictable changes. Freshwater Biology 54: 536-548. Espírito‐Santo H.M.V. Magnusson W.E. Zuanon J. Mendonca F.P. Landeiro V.L. 2009 Seasonal variation in the composition of fish assemblages in small Amazonian forest streams: evidence for predictable changes Freshwater Biology 54 536 548 Kemenes, A.; Forsberg, B. R. 2014. Factors influencing the structure and spatial distribution of fishes in the headwater streams of the Jaú River in the Brazilian Amazon. Brazilian Journal of Biology 74: 23-32. Kemenes A. Forsberg B. R. 2014 Factors influencing the structure and spatial distribution of fishes in the headwater streams of the Jaú River in the Brazilian Amazon Brazilian Journal of Biology 74 23 32 Magnusson, W.E.; Lima, A.P. 1991. The ecology of a cryptic predator, Paleosuchus trigonatus, in a tropical rainforest. Journal of Herpetology 25:41-48. Magnusson W.E. Lima A.P. 1991 The ecology of a cryptic predator, Paleosuchus trigonatus, in a tropical rainforest Journal of Herpetology 25 41 48 Marioni, B.; Magnusson, W. E.; Vogt, R. C.; Villamarín, F. 2022. Home range and movement patterns of male dwarf caimans (Paleosuchus palpebrosus and Paleosuchus trigonatus) living in sympatry in Amazonian floodplain streams. Neotropical Biodiversity 8: 156-166. Marioni B. Magnusson W. E. Vogt R. C. Villamarín F. 2022 Home range and movement patterns of male dwarf caimans (Paleosuchus palpebrosus and Paleosuchus trigonatus) living in sympatry in Amazonian floodplain streams Neotropical Biodiversity 8 156 166 Medina-Barrios, O.D.; Morales-Betancourt, D. 2015. Evento de depredación de Caiman crocodilus fuscus por Lontra longicaudis (Carnivora: Mustelidae) en el río Palomino, departamento de La Guajira, Colombia. Mammalogy Notes, 2: 19-21. Medina-Barrios O.D. Morales-Betancourt D. 2015 Evento de depredación de Caiman crocodilus fuscus por Lontra longicaudis (Carnivora: Mustelidae) en el río Palomino, departamento de La Guajira, Colombia Mammalogy Notes 2 19 21 Morales-Betancourt, M. A.; Lasso, C. A.; De La Ossa, J.; Fajardo-Patino, A. 2013. Biologia y conservacion de los Crocodylia de Colombia. 8th. ed. Instituto de Investigacion de Recursos Biologicos Alexander von Humboldt (IAvH), Bogotá. 336p. Morales-Betancourt M. A. Lasso C. A. De La Ossa J. Fajardo-Patino A. 2013 Biologia y conservacion de los Crocodylia de Colombia 8th. ed Instituto de Investigacion de Recursos Biologicos Alexander von Humboldt (IAvH) Bogotá 336 Pardini, R. 1998. Feeding ecology of the Neotropical river otter Lontra longicaudis in an Atlantic Forest stream, south-eastern Brazil. Journal of Zoology 245: 385-391. Pardini R. 1998 Feeding ecology of the Neotropical river otter Lontra longicaudis in an Atlantic Forest stream, south-eastern Brazil Journal of Zoology 245 385 391 Passamani, M.; Camargo, S. 1995. Diet of the river otter Lutra longicaudis in Furnas Reservoir, south-eastern Brazil. IUCN Otter Specialist Group Bulletin 12: 32-34. Passamani M. Camargo S. 1995 Diet of the river otter Lutra longicaudis in Furnas Reservoir, south-eastern Brazil IUCN Otter Specialist Group Bulletin 12 32 34 Pereira, K.D.L.; Teixeira, J.V.; Silva, E.M.D.J.N.; Ribeiro, M.V. 2020. Predation attempted on Iguana iguana (Squamata, Iguanidae) by Lontra longicaudis (Carnivora, Mustelidae). Herpetology Notes 13: 491-493. Pereira K.D.L. Teixeira J.V. Silva E.M.D.J.N. Ribeiro M.V. 2020 Predation attempted on Iguana iguana (Squamata, Iguanidae) by Lontra longicaudis (Carnivora, Mustelidae) Herpetology Notes 13 491 493 Platt, S.; Rainwater, T. 2011. Predation by Neotropical otters (Lontra longicaudis) on turtles in Belize. IUCN Otter Specialist Group Bulletin 28: 4-10. Platt S. Rainwater T. 2011 Predation by Neotropical otters (Lontra longicaudis) on turtles in Belize IUCN Otter Specialist Group Bulletin 28 4 10 Quadros, J.; Monteiro-Filho, E.L.D.A. 2001. Diet of the Neotropical otter, Lontra longicaudis, in an Atlantic Forest area, Santa Catarina State, southern Brazil. Studies on Neotropical Fauna and Environment 36: 15-21. Quadros J. Monteiro E.L.D.A. Filho 2001 Diet of the Neotropical otter, Lontra longicaudis, in an Atlantic Forest area, Santa Catarina State, southern Brazil Studies on Neotropical Fauna and Environment 36 15 21 Rheingantz, M.L.; Waldemarin, H.F.; Rodrigues, L.; Moulton, T.P. 2011. Seasonal and spatial differences in feeding habitats of the Neotropical otter Lontra longicaudis (Carnivora: Mustelidae) in a coastal catchment of southeastern Brazil. Zoologia 28:37-44. Rheingantz M.L. Waldemarin H.F. Rodrigues L. Moulton T.P. 2011 Seasonal and spatial differences in feeding habitats of the Neotropical otter Lontra longicaudis (Carnivora: Mustelidae) in a coastal catchment of southeastern Brazil Zoologia 28 37 44 Rheingantz, M. L.; Menezes, J. F. S.; Thoisy, B. 2014. Defining Neotropical otter Lontra longicaudis distribution, conservation priorities and ecological frontiers. Tropical Conservation Science 7: 214-229. Rheingantz M. L. Menezes J. F. S. Thoisy B. 2014 Defining Neotropical otter Lontra longicaudis distribution, conservation priorities and ecological frontiers Tropical Conservation Science 7 214 229 Rheingantz, M. L.; Menezes, J. F. S.; Galliez, M.; Santos Fernandez, F. A. 2017. Biogeographic patterns in the feeding habits of the opportunist and semiaquatic Neotropical otter. Hydrobiologia 792: 1-15. Rheingantz M. L. Menezes J. F. S. Galliez M. Santos Fernandez F. A. 2017 Biogeographic patterns in the feeding habits of the opportunist and semiaquatic Neotropical otter Hydrobiologia 792 1 15 Sánchez, O.; Gallo-Reynoso, J.P. 2007. Evaluación del riesgo de extinción de Lontra longicaudis de acuerdo al numeral 5.7 de la NOM-059-SEMARNAT-2001. In: Sánchez, O.; Medellín, R.; Aldama, A.; Goettsch, B.; Soberón, J.; Tambutti, M. (Eds.). Método de Evaluación del Riesgo de Extinción de las Especies Silvestres en México. INE-SEMARNAT, México. p.61-89. Sánchez O. Gallo-Reynoso J.P. 2007 Evaluación del riesgo de extinción de Lontra longicaudis de acuerdo al numeral 5.7 de la NOM-059-SEMARNAT-2001 Sánchez O. Medellín R. Aldama A. Goettsch B. Soberón J. Tambutti M. Método de Evaluación del Riesgo de Extinción de las Especies Silvestres en México INE-SEMARNAT México 61 89 Santiago-Plata, V.M.; Valdez-Leal, J.D.; Pacheco-Figueroa, C.J.; Cruz-Burelo, F.; Moguel-Ordóñez, E.J. 2013. Aspectos ecológicos de la nutria Neotropical (Lontra longicaudis annectens) en el camino La Veleta en la Laguna de Términos, Campeche, México. Therya 4: 265-280. Santiago-Plata V.M. Valdez-Leal J.D. Pacheco-Figueroa C.J. Cruz-Burelo F. Moguel-Ordóñez E.J. 2013 Aspectos ecológicos de la nutria Neotropical (Lontra longicaudis annectens) en el camino La Veleta en la Laguna de Términos, Campeche, México Therya 4 265 280 Villamarín, F.; Jardine, T.D.; Bunn, S.E.; Marioni, B.; Magnusson, W.E. 2017. Opportunistic top predators partition food resources in a tropical freshwater ecosystem. Freshwater Biology 62: 1389-1400. Villamarín F. Jardine T.D. Bunn S.E. Marioni B. Magnusson W.E. 2017 Opportunistic top predators partition food resources in a tropical freshwater ecosystem Freshwater Biology 62 1389 1400 CITE AS: Franco, D. de L.; Coelho, A.G. de A.; Silva, A.J. da. 2024. First report of predation of a smooth-fronted caiman (Paleosuchus trigonatus) by a Neotropical otter (Lontra longicaudis). Acta Amazonica 54: e54bc23340. Data availability The data that support the findings of this study were published in this article.