Density and population size of mammals introduced on a land-bridge island in southeastern Brazil

Rabies in free-ranging capybaras (Hydrochoerus hydrochaeris) on Anchieta Island, Ubatuba, Brazil

Between December 2019 and January 2020, three cases of rabies were reported in free-ranging capybaras on Anchieta Island, Ubatuba-SP, Brazil. This 8.28 km² island is located 540 m offshore from the mainland. Two of the capybaras exhibited signs of hindlimb paralysis, and one was found dead. Rabies was diagnosed using the direct fluorescent antibody test (dFAT), while RT-qPCR and phylogenetic analysis of nucleotide sequences confirmed the presence of the vampire bat rabies virus (RABV) strain. Although no visible bat bite marks were found on the capybaras, vampire bats are known to inhabit the island. Other wildlife tested negative for rabies during this period, and no further rabies outbreaks have been observed since. Environmental changes and human activities, such as the disturbance of bat roosting sites, may have contributed to the incident. The detection of rabies in capybaras suggests a potential spillover from a vampire bat reservoir. Further investigation is needed to determine whether capybaras act as dead-end hosts or play a role in maintaining the rabies transmission cycle.

Terrestrial food web complexity in Amazonian forests decays with habitat loss

The conversion of natural ecosystems into human-modified landscapes (HMLs) is the main driver of biodiversity loss in terrestrial ecosystems.^1,2,3 Even when species persist within habitat remnants, populations may become so small that ecological interactions are functionally lost, disrupting local interaction networks.^4,5 To uncover the consequences of land use changes toward ecosystem functioning, we need to understand how changes in species richness and abundance in HMLs^6,7,8 rearrange ecological networks. We used data from forest vertebrate surveys and combined modeling and network analysis to investigate how the structure of predator-prey networks was affected by habitat insularization induced by a hydroelectric reservoir in the Brazilian Amazonia.⁹ We found that network complexity, measured by interaction diversity, decayed non-linearly with decreasingly smaller forest area. Although on large forest islands (>100 ha) prey species were linked to 3-4 potential predators, they were linked to one or had no remaining predator on small islands. Using extinction simulations, we show that the variation in network structure cannot be explained by abundance-related extinction risk or prey availability. Our findings show that habitat loss may result in an abrupt disruption of terrestrial predator-prey networks, generating low-complexity ecosystems that may not retain functionality. Release from predation on some small islands may produce cascading effects over plants that accelerate forest degradation, whereas predator spillover on others may result in overexploited prey populations. Our analyses highlight that in addition to maintaining diversity, protecting large continuous forests is required for the persistence of interaction networks and related ecosystem functions.

Unpaved roads are not adequate surrogates of true transects for sampling agoutis

The distance sampling is one of the most widely used techniques for estimating abundance and density, particularly for mammals. Managers/researchers sometimes sample unpaved roads assuming that these do not violate important assumptions. However, relatively few studies have attempted to address this, simultaneously comparing behavior between roads and transects, a key issue as behavior can potentially affect detection. Here, we used distance sampling to compare abundance and behavior of agoutis between transects and unpaved roads. We sampled an isolated agouti population during two contrasting seasons. Road densities (347–432 agoutis/km

Past and estimated future impact of invasive alien mammals on insular threatened vertebrate populations

Invasive mammals on islands pose severe, ongoing threats to global biodiversity. However, the severity of threats from different mammals, and the role of interacting biotic and abiotic factors in driving extinctions, remain poorly understood at a global scale. Here we model global extirpation patterns for island populations of threatened and extinct vertebrates. Extirpations are driven by interacting factors including invasive rats, cats, pigs, mustelids and mongooses, native species taxonomic class and volancy, island size, precipitation and human presence. We show that controlling or eradicating the relevant invasive mammals could prevent 41–75% of predicted future extirpations. The magnitude of benefits varies across species and environments; for example, managing invasive mammals on small, dry islands could halve the extirpation risk for highly threatened birds and mammals, while doing so on large, wet islands may have little benefit. Our results provide quantitative estimates of conservation benefits and, when combined with costs in a return-on-investment framework, can guide efficient conservation strategies.

Invasive vertebrates can decimate native species living on islands. Using a model of global extirpation patterns, McCreless et al. identify the types of invasive species most harmful to natives and predict when controlling or eradicating the invasive species is likely to succeed as a conservation strategy.

Seasonal variation in the fate of seeds under contrasting logging regimes

Seed predators and dispersers may drive the speed and structure of forest regeneration in natural ecosystems. Rodents and ants prey upon and disperse seeds, yet empirical studies on the magnitude of these effects are lacking. Here, we examined the role of ants and rodents on seed predation in 4 plant species in a successional gradient on a tropical rainforest island. We found that (1) seeds are mostly consumed rather than dispersed; (2) rates of seed predation vary by habitat, season, and species; (3) seed size, shape, and hardness do not affect the probability of being depredated. Rodents were responsible for 70% of seed predation and were negligible (0.14%) seed dispersers, whereas ants were responsible for only 2% of seed predation and for no dispersal. We detected seasonal and habitat effects on seed loss, with higher seed predation occurring during the wet season and in old-growth forests. In the absence of predators regulating seed-consumer populations, the densities of these resilient animals explode to the detriment of natural regeneration and may reduce diversity and carrying capacity for consumers and eventually lead to ecological meltdown.

Community ecology of euglossine bees in the coastal Atlantic forest of São Paulo state, Brazil

The Atlantic Forest stretches along Brazil's Atlantic coast, from Rio Grande do Norte State in the north to Rio Grande do Sul State in the south, and inland as far as Paraguay and the Misiones Province of Argentina. This biome is one of the eight biodiversity hotspots in the world and is characterized by high species diversity. Euglossini bees are known as important pollinators in this biome, where their diversity is high. Due to the high impact of human activities in the Atlantic Forest, in the present study the community structure of Euglossini was assessed in a coastal lowland area, Parque Estadual da Serra do Mar--Núcleo Picinguaba (PESM), and in an island, Parque Estadual da Ilha Anchieta (PEIA), Ubatuba, São Paulo State, Brazil. Sampling was carried out monthly, from August 2007 to July 2009, using artificial baits with 14 aromatic compounds to attract males. Twenty-three species were recorded. On PEIA, Euglossa cordata (L.) (Hymenoptera: Apidae) represented almost two thirds of the total species collected (63.2%). Euglossa iopoecila (23.0%) was the most abundant species in PESM but was not recorded on the island, and Euglossa sapphirina (21.0%) was the second most frequent species in PESM but was represented by only nine individuals on PEIA. The results suggest that these two species may act as bioindicators of preserved environments, as suggested for other Euglossini species. Some authors showed that Eg. cordata is favored by disturbed environments, which could explain its high abundance on Anchieta Island. Similarly, as emphasized by other authors, the dominance of Eg. cordata on the island would be another factor indicative of environmental disturbance.

Densidade, tamanho populacional e conservação de primatas em fragmento de Mata Atlântica no sul do Estado de Minas Gerais, Brasil

Este trabalho teve como objetivo estimar a densidade e o tamanho populacional de quatro espécies de primatas [Alouatta clamitans Cabrera, 1940; Callicebus nigrifrons (Spix, 1823); Callithrix aurita (É. Geoffroy, 1812); Cebus nigritus (Goldfuss, 1809)] que ocorrem em um fragmento de Mata Atlântica de aproximadamente 350 ha, localizado no município de Pouso Alegre, estado de Minas Gerais e reunir subsídios para a conservação dessas espécies na região. O levantamento populacional foi realizado através do método de amostragem de distâncias em transecções lineares (Distance Sampling). Os dados foram coletados entre os meses de abril e agosto de 2008 a partir de quatro transecções implantadas na área de estudo. Os cálculos de densidade e tamanho populacional foram realizados empregando-se o programa Distance 5.0. As densidades foram estimadas em 23,83 ± 9,78 ind./km² para Callicebus nigrifrons, 14,76 ± 5,92 ind./km² para Callithrix aurita e 7,71 ± 2,13 ind./km² para Cebus nigritus. O tamanho populacional foi estimado em 83,0 ± 34,0 indivíduos para C. nigrifrons, 52,0 ± 20,8 indivíduos para Callithrix aurita e 27,0 ± 7,4 indivíduos para Cebus nigritus. Com relação ao bugio (A. guariba clamitans), constatou-se que apenas um grupo com seis indivíduos sobrevive na área. Conclui-se que, no caso de continuarem isoladas, essas populações têm poucas chances de sobrevivência no futuro frente aos riscos de eventos estocásticos. A criação de corredores ecológicos conectando a área de estudo aos outros fragmentos em seu entorno e a translocação de indivíduos de outras áreas da Mata Atlântica para esta região poderão constituir alternativas para garantir a viabilidade dessas populações em longo prazo. Para tanto, é necessário que se consolide uma política pública no município de Pouso Alegre voltada à criação, ampliação e gestão de Unidades de Conservação, e ao incentivo para a adoção de práticas produtivas sob critérios de sustentabilidade no entorno dessas áreas de interesse ecológico.

Herpetofauna em uma área de Floresta Atlântica na Ilha Anchieta, município de Ubatuba, sudeste do Brasil

Este trabalho teve como objetivo o estudo da diversidade da herpetofauna do Parque Estadual da Ilha Anchieta, município de Ubatuba, localizada no litoral norte do estado de São Paulo, enfocando os seguintes aspectos: diversidade, distribuição e padrões de atividade sazonal. Entre julho de 2005 e junho de 2006 foram realizadas viagens mensais à ilha, totalizando 55 dias de trabalhos de campo. Para a amostragem foram utilizados os métodos busca ativa, armadilhas de interceptação e queda, armadilhas de funil e coleta por terceiros, Busca ativa e armadilhas de interceptação e queda apresentaram melhor desempenho, e os demais métodos se mostraram complementares. Foram inventariadas 17 espécies de anfíbios anuros distribuídas em oito famílias, e oito espécies de répteis das quais cinco são espécies de lagartos de quatro famílias e três de serpentes de duas famílias. Como observado na grande maioria das pesquisas em áreas tropicais, a área de estudo apresentou relativamente baixa equabilidade, porém, diferente de outras comunidades estudadas, apresentou um maior número de espécies comuns em relação às espécies raras. A riqueza de anfíbios anuros foi mais alta nas fisionomias consideradas fechadas (mata latifoliada densa e mata latifoliada rala) em relação às abertas, enquanto que a riqueza de répteis foi mais representativa no campo antrópico (fisionomia considerada aberta). A análise de correlação demonstrou que a riqueza de anfíbios não foi significativa em relação aos elementos climáticos, enquanto a riqueza de répteis foi significativamente correlacionada às médias de temperaturas máxima e mínima. A presença de inúmeras peculiaridades reforça a importância da conservação do Parque Estadual da Ilha Anchieta.

Predação de ninhos artificiais em uma ilha na Mata Atlântica: testando o local e o tipo de ovo

Experimentos com ninhos artificiais são utilizados para testar hipóteses ecológicas e comportamentais que influenciam na predação de ninhos naturais. O tamanho do ovo, a textura da casca e a cor podem influenciar na taxa de predação, porém poucos estudos avaliam qual modelo de ovo é o mais adequado para simular a predação de ninhos em áreas tropicais. O objetivo deste trabalho foi comparar a predação de diferentes modelos de ovos (ovos de codorna, massa de modelar e canários) no solo e a 1,30 m de altura no sub-bosque. O experimento foi realizado Ilha Anchieta, Ubatuba, São Paulo, Brasil. Foi encontrada uma diferença significativa na taxa de predação entre os ovos de codorna (71,87%) e sintéticos (93,75%) e entre os ovos de codorna e de canário (100%) no solo. Entretanto, não houve diferença significativa entre os ovos sintéticos e de canário. Os ninhos no sub-bosque apresentaram um padrão diferenciado do solo quando se refere aos ovos de codorna (25%) e sintéticos (28,1%), mas houve diferenças significativas quando os ovos de canário foram comparados com os ovos sintéticos e de codorna. Nosso trabalho demonstrou que diferentes tipos de ovos sobre uma mesma pressão de mesopredadores apresentaram taxas de predação diferentes. Portanto, estudos que avaliam o sucesso reprodutivo da avifauna baseado na predação de ninhos artificiais devem considerar a utilização de diferentes tipos de ovos e estratos na vegetação.