Carnivore coexistence without competition: giant otters are more nocturnal around dens than sympatric neotropical otters.

Nocturnal activity of tropical otters is rarely reported. To date no studies have documented den use by sympatric giant (Pteronura brasiliensis) and neotropical otters (Lontra longicaudis). We used camera-traps to monitor den use by sympatric otters along an equatorial Amazonian river. Camera-traps provided evidence that giant otters were more nocturnal around dens than sympatric neotropical otters. Nocturnal activity was recorded in 11% of giant otter photos (n = 14 of 125 photos), but was recorded only once for neotropical otters. Den use by giant and neotropical otters overlapped spatially and temporally but not concurrently. We hypothesize that previously reported nocturnal activity in neotropical otters is facilitated by the absence or low density of giant otters. Our results also underscore the need to use complementary techniques together with den counts for monitoring otters as sympatric species can use the same dens.

Human disturbances and the daytime activity of sympatric otters along equatorial Amazonian rivers.

Background: Previous studies suggest coexistence between sympatric neotropical (Lontra longicaudis) and giant otters (Pteronura brasiliensis) maybe facilitated by temporal and spatial differences in activity. Yet, to date there has been no systematic evaluation of activity of these species in sympatry. Here we use extensive multi-year field data to compare temporal and spatial patterns in the diurnal activity of sympatric giant and neotropical otters to answer three questions: Do temporal patterns in daytime river use change in relation to seasonal river levels (low, rising, high and declining river levels), do they change due to human disturbances (boats and fishing nets) and do patterns in neotropical otter activity change due to the presence of the larger sized giant otter? Methods: Direct observations of both species were recorded using standardized boat surveys along 218 km of rivers over 53 months during nine years (2011-2013 and 2015-2020). Complementary techniques (Generalized Additive Models, Kernel density estimates and non-parametric tests,) were used to compare diurnal activity patterns along rivers subdivided into 41 river reaches. Results: The presence of giant otters decreased threefold from 67% of the least disturbed reaches (few boats no fishing nets) to 18% of the most disturbed reaches with many boats and fishing nets. In contrast neotropical otter presence nearly doubled from 44% of the least disturbed to 73% of the most disturbed reaches with fewest giant otter detections. Both species were observed across all daytime hours but were observed rarely on the same day. There was no evidence to suggest simultaneous use of the same reach. When species were detected on the same day, they were separated spatially (median distance between species 12.5 km) and temporally (median time difference 3.0 hours). There was little change in activity of either species among seasons. Giant otters were less active in river reaches with fishing nets and boat use, whereas neotropical otter activity did not appear to be strongly affected by these activities. Conclusions: Our findings support evidence that diurnal activity in both otter species is flexible, with daytime activity changing due to human disturbances in the case of giant otters.

Amblyomma sculptum ticks on a giant otter from the Brazilian Pantanal / Carrapatos Amblyomma sculptum em uma ariranha no Pantanal Brasileiro

The giant otter (Pteronura brasiliensis) is a semiaquatic carnivore and a top predator in the trophic chain, considered a sentinel of freshwater ecosystems. Ticks are common ectoparasites of worldwide distribution and potential vectors of diseases. In this study, we report the ectoparasitism by ticks on a giant otter carcass found during monitoring activity at the Negro River, that holds a viable population of this endangered species in the Brazilian Pantanal. A total of three tick specimens were collected: two adults were identified as Amblyomma sculptum and a nymph as Amblyomma spp. There is a lack of information about the health of free-ranging giant otters and this report contributes to elucidate some of the host-parasite relationships, although much more research is needed to expand the knowledge about which kinds of pathogens are circulating in the species, especially among those transmitted by ticks.(AU)

A ariranha (Pteronura brasiliensis) é um carnívoro semiaquático e um predador de topo na cadeia trófica, considerada sentinela dos ecossistemas de água doce. Os carrapatos são ectoparasitos comuns com distribuição mundial e potenciais vetores de doenças. Neste estudo, foi relatado o ectoparasitismo por carrapatos em uma carcaça de ariranha encontrada durante atividade de monitoramento no Rio Negro, no Pantanal brasileiro, que abriga uma população viável desta espécie ameaçada de extinção. Um total de três espécimes de carrapatos foram coletados: dois adultos foram identificados como Amblyomma sculptum e uma ninfa como Amblyomma spp. Há uma lacuna de informações sobre a saúde das ariranhas de vida livre e este relato contribui para elucidar algumas das relações parasita-hospedeiro, embora ainda seja necessária mais pesquisa para ampliar o conhecimento sobre quais tipos de patógenos estão circulando na espécie, especialmente entre os transmitidos por carrapatos.(AU)

Improving Trapping Efficiency for Control of American Mink (Neovison vison) in Patagonia.

Two main challenges when controlling alien American mink (Neovison vison) in Patagonia are to maximize campaign efficacy and cost-effectiveness and to avoid trapping native species. We designed and tested new variants of collapsible wire box traps, compared the efficacy of a food-based bait and a scent lure and compared catch rates in different seasons of the year. We used the data to model the efficiency rate of the trapping and to determine the trapping effort required to remove 70-90% of the estimated discrete mink population. Between January 2018 and March 2021, we operated 59 trapping transects over 103 three-day trapping periods in southern Chile. Traps were first baited with canned fish, and afterwards with mink anal gland lure. We compared the efficacy of mink capture with that of our previous study. We trapped 196 mink (125 males, 71 females), with most captures in summer. The medium-sized GMV-18 trap caught more male mink, but the more compact GMV-13 caught fewer non-target rodents and no native mammals. The scent lure was more successful than the canned fish when the previous campaign's data were included in the analysis. There was also a significant improvement in the proportion of female mink trapped and reduced labour compared with our previous campaign that used larger traps, fish bait and 400-500 m trap spacings. We caught relatively more females than males after the third night of trapping on a transect. Our data analysis supports the use of the GMV-13 variant of wire cage trap as the best trap size: it is effective on female mink, small, cheap and easy to transport. Combined with mink anal scent lure, it reduces the possibility of trapping native species compared with other traps tested in Chile. As the most efficient method for removing at least 70% of the estimated discrete mink population within the area covered by each trap transect in southern Chile tested to date, we recommend trapping campaigns using GMV-13 during summer, with a 200-m trap spacing, for up to 6 days before moving traps to a new site, with a combination of three days with a female scent gland lure, followed by three days with a male scent gland lure.

First report of myiasis caused by Cochliomyia hominivorax in free-ranging giant otter (Pteronura brasiliensis) / Primeiro relato de miíase causada por Cochliomyia hominivorax em ariranha (Pteronura brasiliensis) de vida livre

Giant otters are territorial semi-aquatic mammals. It is common to find several individuals exhibiting wounds and scars due to intraspecific conflicts. Myiasis is a parasitic infestation on living tissues of vertebrates caused by dipterous larvae, that usually develops in freshly open wounds and can seriously threaten the host's health. Ectoparasites seem to be rare among giant otters and myiasis had not been recorded in this species until now. Here, is presented one record of myiasis in a free-ranging giant otter found dead in the Pantanal, Brazil. An ulcerative lesion was found in the frontoparietal region, from which 22 larvae were recovered and identified as Cochliomyia hominivorax. The low occurrence of ectoparasites in giant otters might reflect their semi-aquatic habits and their grooming behavior, which makes it difficult for parasites to remain on the skin. The injured otter probably got the larvae after an intraspecific fight. Agonistic encounters between groups of giant otters have been reported before and these fights can result in serious wounds or even death. It was hypothesized that the myiasis caused by C. hominivorax deteriorated the health of the infested giant otter, which prevented recovery and accelerated its death.(AU)

As ariranhas são mamíferos semiaquáticos habitantes do território brasileiro. É comum encontrar vários indivíduos apresentando feridas e cicatrizes devido a conflitos intraespecíficos. A miíase é uma infestação parasitária em tecidos vivos de vertebrados, causada por larvas de dípteros que, geralmente, se desenvolvem em feridas recém-abertas, podendo ameaçar seriamente a saúde do hospedeiro. Ectoparasitos parecem ser raros em ariranhas e, até o presente, não há relatos de miíase nesta espécie. Aqui, é apresentado um registro de miíase em uma ariranha de vida livre, encontrada morta no Pantanal, Brasil. Foi encontrada uma lesão ulcerativa na região frontoparietal, na qual foram recuperadas 22 larvas identificadas como Cochliomyia hominivorax. A baixa ocorrência de ectoparasitos em ariranhas pode refletir seus hábitos semiaquáticos e seu comportamento de limpeza, o que dificulta a permanência dos parasitos na pele. A ariranha ferida, provavelmente, se infestou com as larvas após uma briga intraespecífica. Encontros agonísticos entre grupos de ariranhas já foram relatados antes, e essas lutas podem resultar em ferimentos graves ou até mesmo em morte. Foi hipotetizado que a miíase causada por C. hominivorax deteriorou a saúde da ariranha infestada, o que impediu a recuperação e acelerou sua morte.(AU)

Occurrence of tayras (Eira barbara Linnaeus, 1758) with anomalous coloration in Cerrado remnants in the state of São Paulo, Brazil / Ocorrência de iraras (Eira barbara Linnaeus, 1758) com coloração anômala em remanescentes de Cerrado no estado de São Paulo, Brasil

Abstract: Coloration anomalies are mainly genetically-based disorders in which body pigmentation is either reduced (hypopigmentation) or produced in excess (melanism), in parts or the totality of the body. Cases of hypopigmentation have been documented in many neotropical mammals, including the tayra (Eira barbara Linnaeus, 1758). We expand the account of anomalous coloration occurrence presenting new registers of hypopigmented tayras in Brazil. Data was collected during a mammal survey carried out in three agricultural landscapes within the Cerrado domain in the northeast of the state of São Paulo. We obtained two kinds of records of hypopigmented tayras, one from direct sighting and the other from a camera-trap. We discuss the likely implications of this conspicuous coloration to tayras and highlight some possibilities of study.

Resumo: Colorações anômalas são desordens geralmente de origem genética, em que a pigmentação do corpo é reduzida (hipopigmentação) ou excessiva (melanismo), em partes ou totalmente. Casos de hipopigmentação já foram documentados em muitos mamíferos neotropicais, incluindo a irara (Eira barbara Linnaeus, 1758). Nós expandimos os relatos de ocorrência de colorações anômalas apresentando novos registros de iraras hipopigmentadas no Brasil. Dados foram coletados durante um levantamento de mamíferos em três paisagens agrícolas no domínio do Cerrado no nordeste do estado de São Paulo. Obtivemos dois tipos de registros de iraras hipopigmentadas, sendo um por avistamento e outro por armadilhas fotográficas. Nós discutimos possíveis implicações ecológicas dessa coloração em iraras e sugerimos novas possibilidades de estudos.