Human-wildlife conflicts with crocodilians, cetaceans and otters in the tropics and subtropics

Conservation of freshwater biodiversity and management of human-wildlife conflicts are major conservation challenges globally. Human-wildlife conflict occurs due to attacks on people, depredation of fisheries, damage to fishing equipment and entanglement in nets. Here we review the current literature on conflicts with tropical and subtropical crocodilians, cetaceans and otters in freshwater and brackish habitats. We also present a new multispecies case study of conflicts with four freshwater predators in the Western Amazon: black caiman (Melanosuchus niger), giant otter (Pteronura brasiliensis), boto (Inia geoffrensis) and tucuxi (Sotalia fluviatilis). Documented conflicts occur with 34 crocodilian, cetacean and otter species. Of the species reviewed in this study, 37.5% had conflicts frequently documented in the literature, with the saltwater crocodile (Crocodylus porosus) the most studied species. We found conflict severity had a positive relationship with species body mass, and a negative relationship with IUCN Red List status. In the Amazonian case study, we found that the black caiman was ranked as the greatest ‘problem’ followed by the boto, giant otter and tucuxi. There was a significant difference between the responses of local fishers when each of the four species were found entangled in nets. We make recommendations for future research, based on the findings of the review and Amazon case study, including the need to standardise data collection.

El bufeo colorado en algunas novelas amazónicas peruanas

El bufeo colorado (Inia geoffrensis) es el delfín rosado que vive en los ríos de la cuenca amazónica y es el protagonista de una de las más difundidas narraciones de la tradición oral de las poblaciones indígenas y ribereñas de la zona, para las que posee facultades metamórficas. El bufeo, de hecho, puede transformarse en un hombre de rasgos occidentales, un “gringo” alto, muchas veces rubio y con los ojos claros y, frecuentemente, se indica como el padre de los niños de los que se ignora la paternidad. En este trabajo se traza una panorámica de su presencia en algunas novelas ambientadas en la selva, para demostrar cómo los autores —en la mayoría de los casos— aprovechan este relato exclusivamente para perpetuar estereotipos sobre la selva vista como “infierno verde” y sobre la sexualidad de sus habitantes. En contraste, se enseñarán dos casos, los de las novelas Paiche de César Calvo de Araújo y La virgen del Samiria de Róger Rumrrill, en los que se deconstruye el mito y se apunta a una descripción más objetiva de la selva. En estas dos obras, en efecto, los autores explican de manera explícita la carga metafórica del relato, desvelan la violencia que se halla detrás de su creación, lo contextualizan y explican sus funciones en el ámbito social, contribuyendo de esta manera a un acercamiento más equilibrado al mundo amazónico.

Highly divergent herpesviruses in threatened river dolphins from Brazil

River dolphins are a highly threatened polyphyletic group comprised of four odontocete families: Iniidae, Pontoporiidae, Lipotidae, and Platanistidae, the first two endemic to South America. To address the knowledge gap regarding infectious agents in this cetacean group, we surveyed the presence of herpesviruses by PCR in skin and/or blood samples of live-captured Amazon (Inia geoffrensis, n = 25) and Bolivian (Inia boliviensis, n = 22) river dolphins of the Amazon basin and in selected tissue samples of franciscanas (Pontoporia blainvillei, n = 27) stranded or bycaught in southeastern Brazil. Additionally, available franciscana tissue samples were examined by histopathology. Herpesvirus DNA was amplified in 13 Bolivian river dolphins (59.1%, 95% CI 38.5–79.6%) and 14 franciscanas (51.9%, 95% CI 33.0–70.7%). All Amazon river dolphins were herpesvirus-negative. Two different herpesviruses were found in Bolivian river dolphins: a previously known gammaherpesvirus detected in blood and/or skin samples of all positive individuals and a novel alphaherpesvirus in the skin of one animal. A new gammaherpesvirus was found in several franciscana samples—the first herpesvirus recorded in Pontoporiidae. Intranuclear inclusion bodies consistent with herpesvirus were observed in the lymph node of one franciscana. The high divergence among the obtained herpesviruses and those previously described can be explained by viral-host coevolution, and by the fact that these populations are fairly isolated.

Density and Abundance Estimation of Amazonian River Dolphins: Understanding Population Size Variability

The dolphins Inia geoffrensis—boto and Sotalia fluviatilis—tucuxi are threatened cetaceans inhabiting river ecosystems in South America; population numbers are still lacking for many areas. This paper provides density and abundance estimations of boto and tucuxi in 15 rivers sampled during the past nine years as part of a multinational research alliance. Visual boat-survey data collection protocols and analyses have been developed since 2012 (based on Distance Sampling methods) and recently reviewed (2019) to improve robustness and comparability. Differences across the sampled rivers and the analyzed river basins (Amazon and Orinoco) pointed to a density/population size gradient with lower densities and abundances observed in the Orinoco basin (0.9–1.5 ind./km²), passing through the eastern Amazon basin (2–5 ind./km²), and the largest numbers found at the central Brazilian Amazon (lower Purus River—2012 (14.5 boto/km², N = 7672; 17.1 tucuxi/km², N = 9238)). However, in other parts of the central Amazon, the density of dolphins was smaller than expected for high productive whitewater rivers (1–1.7 ind./km² in the Japurá and Solimões rivers). We attributed these differences to specific features of the basin (e.g., hydro-geomorphology) as well as to the cumulative effects of anthropogenic activities.

Aggression towards neonates and possible infanticide in the boto, or Amazon river dolphin (Inia geoffrensis)

Recent observed attacks by male Amazon river dolphins on conspecific calves, together with post-mortem examinations, indicate that infanticide occurs in this species but that not all attacked calves are killed. If mortality occurs, it might therefore be an inadvertent consequence of the behaviour rather than the motive for it. Our observations suggest that males who commit infanticide are unlikely to gain direct fitness benefits. Evidence does not fit the sexual selection hypothesis. Aggression towards calves usually ‘drew a crowd’ and may represent socio-sexual display or simply be a form of social pathology, as found in other infanticidal mammals.

The biosonar of the boto: evidence of differences among species of river dolphins (Inia spp.) from the Amazon

Echolocation clicks can reflect the anatomy of the vocalizing animal, enabling the distinction of species. River dolphins from the family Iniidae are formally represented by one species and two subspecies (Inia geoffrensis geoffrensis and I. g. humboldtiana). Additionally, two other species have been proposed (I. boliviensis and I. araguaiaensis) regarding its level of restricted distribution and morph-genetics differences. For the Committee on Taxonomy of the Society for Marine Mammalogy, the specific status of the proposed species relies on further knowledge on morphology, ecology, and genetics. Given that species-specific status is required for conservation efforts, we described and compared the echolocation clicks of Inia spp., searching for specific differences on their vocalizations. The sounds were captured with a Cetacean Research ™ C54XRS (+3/−20 dB, −185 dB re: 1V/μPa) in Guaviare River (Orinoco basin), Madeira River (Madeira basin), Xingu River (Amazon Basin), and Araguaia River (Tocantins-Araguaia basin). We found significant differences in all analyzed parameters (peak frequency, 3 dB bandwidth, 10 dB bandwidth and inter-click interval) for all species and subspecies. Differences in acoustical parameters of clicks are mainly related to the animal’s internal morphology, thus this study may potentially support with information for the species-level classification mostly of I. araguaiaensis (the Araguaian boto). Classifying the Araguaian boto separately from I. geoffrensis has important implications for the species in terms of conservation status, since it is restricted to a highly impacted river system.

Osteomorphological Features of the Carcass of Inia geoffrensis (Cetacea: Iniidae)

Osteological studies can have implications that allow direct biological inferences to be made, such as locomotion, as well as indirect ones, such as species distribution, evolution and ecology. This study was aimed at describing some osteological traits of Inia geoffrensis (Blainvillei, 1817), Macapá/AP. A nearly complete carcass was found in a local forest. Information about the killing was collected through community reports. After collecting bones and information, the carcass was taken to the Laboratory of Zoology at the Federal University of Amapá for cleaning and examination. The cleaning process was carried out following the step-by-step maceration protocol and measurements of bones were taken with a measuring tape (2 m) and ruler (50 cm), except for cervical vertebrae, which were measured with a caliper (15 cm). To find the limbs in the carcass, an identification guide and a bone chart of aquatic mammals were used. Based on the observed data, the animal was a female, determined by the genital cleft. Examination of the occipital bone revealed an adult with complete bone fusion, obliterated sutures on the external surface of the skull. The carcass was nearly complete, with the entire face measuring 55 cm. Further studies are needed on environmental education about cetaceans, local awareness with the assistance of inspectors and competent authorities for the conservation of freshwater dolphins in the region and studies on carcasses for the maintenance of the species.