Southwestern Brazilian Amazonia Research Articles

A new nurse frog from Southwestern Amazonian highlands, with notes on the phylogenetic affinities of Allobates alessandroi (Aromobatidae)

ABSTRACT Few studies have focused on the diverse fauna of southwestern Brazilian Amazonia. This region, spared from large-scale human occupation until the second half of the twentieth century, has been threatened by expanding agriculture, logging, and mining. Here, we describe a new nurse frog (Allobates, Aromobatidae) from the open highland habitats of Serra dos Pacaás Novos, one of the few large remnants of relatively intact native vegetation in the Brazilian state of Rondônia. The new species is diagnosed by its metallic orange dorsal colouration, weakly expanded discs on hands, and presence of two subarticular tubercles on Finger IV. A phylogenetic analysis based on DNA sequence data recovered the new species as more closely related to nurse frogs from the Madeira and Tapajós River basins; this pattern may reflect a history of dispersal uphill from a lowland ancestor. Our results also indicate that the generic assignment of Allobates alessandroi (Grant and Rodriguez, 2001), a high-elevation species from the Andes of Peru, needs to be reassessed; we discuss the phylogenetic affinities of this species based on morphological attributes. http://www.zoobank.org/urn:lsid:zoobank.org:act:79131D82-B1B6-455D-AD9A-676D7E0783BC

Anatomical review o Eira Barbara (Carnivora, Mustelidae) from the Quaternary of Southwestern Brazilian Amazonia

Most species of mustelids currently found in South America descend from North American immigrants that arrived during the Great American Biotic Interchange, following the rise of the Isthmus of Panama. However, previous works indicate that the genus Eira arrived in South America before this event, through an island bridge in Central America. The tayra Eira barbara (Mustelidae, Carnivora), the only species of the genus, currently has a wide geographic distribution, from Mexico to northern Argentina. Here, we redescribe a fossil of E. barbara collected close to the Municipality of Marechal Thaumaturgo, Acre State, Brazil. The southwestern Brazilian Amazonia is mostly characterized by the older sediments of Solimoes Formation (Neogene deposits), although on the riverbanks of the Upper Jurua River a typical Quaternary vertebrate fauna is also found, mainly represented by fossil mammals. The specimen UFAC PV-36 is a right hemimandible with the p4 preserved in situ, and it was compared to fossil and extant specimens of E. barbara, as well as with other carnivorans. The review of the fossil record shows that this taxon is restricted to the Quaternary of Brazil, in the states of Bahia, Minas Gerais and Acre, and of Argentina, in the Entre Rios Province. In this way, our study contributes to a better understanding of the origin and distribution of the genus in the Quaternary of South America.

Predation of Boana boans (Anura, Hylidae) by an opportunistic frugivorous primate

ABSTRACT Although relatively common among omnivorous primates, anurophagy is still poorly documented in frugivorous species. Here we report the predation of a giant gladiator treefrog (Boana boans) by a large arboreal frugivore, the gray woolly monkey (Lagothrix lagotricha cana). The predation event occurred in a stretch of riparian forest located in a fragmented region in Cacoal, Rondônia state, in southwestern Brazilian Amazonia. Anurans can be a profitable, non-contested, and relatively easily acquired alternative resource for gray woolly monkeys, helping to fulfill their demand for protein, especially in periods of fruit scarcity. This new record broadens the knowledge on the natural history and predators of the giant gladiator frog.

Home range, population density, and foraging behaviour of the Yellow-breasted Warbling-Antbird (Hypocnemis subflava) in forest fragments in southwestern Brazilian Amazonia

ABSTRACTHypocnemis subflava is endemic to southwestern Amazonia, where it prefers habitats dominated by bamboo. We estimated the home range size and population density of this species, and described its foraging behaviour and occurrence in bamboo. We collected data within 1 – ha plots located in three different 16-ha grids. The mean home range of the species was 0.65 ± 0.26 ha (mean ± SE). The population density was 0.44–0.75 individuals per hectare and 0.22–0.37 pairs per hectare within the different study plots. The birds foraged primarily in bamboo leaves (65%), using ‘reach’ and ‘sally’ movements, and foraging was most frequent at a height of 1.1–2 m. Logistic regression analysis indicated that the probability of occurrence of the species increases with the density of culms and percentage bamboo cover per ha. The home range of H. subflava is one of the smallest yet reported for a thamnophilid species, while the density of the bamboo-dwelling populations among the highest recorded for any Amazonian thamnophilid, including other bamboo forest specialists. The high degree of habitat specificity of H. subflava for bamboo-dominated environments makes the species vulnerable to the loss of its preferred habitat in the region.

Insights into the development of a juvenile harpy eagle’s hunting skills

ABSTRACT The post-fledging period is of paramount importance for raptors, since this is when a juvenile develops its hunting skills and gains the abilities required in adulthood and independence through dispersal. Little is known however, about this stage in the lives of raptors such as harpy eagles, Harpia harpyja. Between March 2016 and July 2017, we recorded three predation attempts on groups of primates by a wild juvenile harpy eagle in southwestern Brazilian Amazonia, including the first predation of an adult squirrel monkey, Saimiri ustus. These sequential records give insights into the gradual development of hunting skills during the post-fledging period, similar to what has been reported for other birds of prey. We hypothesize that a link between developing flight skills, decreasing parental food provisioning and increasingly successful captures triggers adulthood and independence in harpy eagles.

Reproductive and feeding biology of the common lancehead Bothrops atrox (Serpentes, Viperidae) from central and southwestern Brazilian Amazonia

ABSTRACT The pitviper Bothrops atrox is a widely distributed and medically important snake in Amazonia. Given that the reproductive and feeding biology of snakes varies geographically, we aimed to characterize the natural history of individuals from the central and southwestern portions of the biome. We analyzed museum-preserved specimens collected in the region between the metropolitan areas of the Brazilian cities of Manaus and Porto Velho. We took morphometric measurements and performed the analysis of gonads and digestive tracts of 109 individuals. Females attain sexual maturity with larger body sizes. Adults of the species show pronounced sexual dimorphism in body size, with females being larger. The reproductive cycle, especially in males, appears to be synchronized with regional rainfall, which markedly differed across the biome. The pitvipers had a generalist diet, consuming a wide range of prey such as centipedes, frogs, lizards, snakes and mammals. We provide the first record of predation of the snake Imantodes cenchoa (Dipsadidae) by B. atrox. There was an ontogenetic shift in the diet: smaller individuals fed mainly on ectothermic prey (centipedes, frogs, lizards and snakes), while adults tended to incorporate endothermic prey (mammals) to their food repertoire.

Birds and bats captured in a managed forest in Southwestern Brazilian Amazonia: Results and recommendations from a short-term study

Understanding the activity pattern and the height of capture of birds and bats can help to optimize the sampling of both groups. Our aimed was to determine the rates of capture at different times of day/night, and the overlap in the height of capture; classify the trophic guilds, and check variation in the capture rates of the birds and bats. We conducted the study in the Antimary State Forest, in March, 2017. We set mist-nets at the same location during five consecutive days, and were open between 06:00 h and 00:00 h. The birds presented a bimodal activity pattern, as well as bats. Bats were captured at higher levels than birds. Most of the birds captured were insectivores, where as most of the bats were frugivores. Neither group presented a clear pattern of variation in capture rates. Therefore, the first hours of the morning are fundamental for the capture of birds. For bats, we would recommend the captures only after 17:00 h. Mist-nets should be set at ground level for birds, whereas for bats, they should be set above a height of 0.5 m. Thus, the captures should be optimized.

Subsistence Hunting with Mixed-Breed Dogs Reduces Hunting Pressure on Sensitive Amazonian Game Species in Protected Areas

SummaryHunting is a major threat to wildlife, and the use of dogs for subsistence hunting may significantly impact wildlife. I assessed the impacts of hunting with dogs by comparing the assemblages of species hunted by the Huni Kuin with and without dogs in indigenous lands in southwestern Brazilian Amazonia. I also assessed whether Huni Kuin agreements on hunting with dogs can be effective for conservation. Huni Kuin hunters with dogs rely on a different assemblage of prey than those without dogs; the former strategy targets mainly fast-reproducing, resilient species, whereas the latter method kills several sensitive or threatened species. Hunting with dogs is also limited to disturbed mixed landscapes near villages because the dogs are used to protect crops and are not allowed into forests in order to prevent them from becoming lost. Additionally, compared to hunting without dogs, hunting with dogs results in an equivalent amount of meat with the use of less effort and ammunition. Moreover, hunting with dogs is not associated with an increase in the distance of prey from villages. Therefore, there is no conservation-related reason to prohibit hunting with mixed-breed dogs in subsistence communities. Nevertheless, community agreements mediate local conflicts caused by the social inequalities related to hunting with dogs.

A new caimanine (Crocodylia, Alligatoroidea) species from the Solimões Formation of Brazil and the phylogeny of Caimaninae

ABSTRACTThe Miocene deposits of South America are notable for their diverse crocodyliform fauna, of which the giant caimanine Purussaurus is a well-known example. This contribution describes a new caimanine, Acresuchus pachytemporalis, gen. et sp. nov., based on an almost complete skull and mandible from the late Miocene Solimões Formation of the southwestern Brazilian Amazonia. This new taxon is based on a unique combination of characters, of which the presence of an upturned posterolateral margin of the squamosal throughout the entire lateral margin of the bone (a ‘horn’), with a dorsoventral expansion in the posterior portion of the eminence, stands out. We conducted a phylogenetic analysis of Eusuchia, which showed the new taxon as sister to Purussaurus. This placement allows discussion about the evolution of gigantism in the Acresuchus-Purussaurus clade, which reveals several characters that may be related to gigantism. Additionally, Acresuchus was probably a medium-sized generalist caimanine that had an ecological niche similar to the extant Melanosuchus niger. Until now, crocodyliforms that had such niches were unknown from the Solimões Formation.

Narrating the First Dogs: Canine Agency in the First Contacts with Indigenous Peoples in the Brazilian Amazon

ABSTRACTNarratives addressing the presence of European domestic dogs (Canis familiaris) in the encounters between Indians and non-Indians in the conquest of the Central and South American lowlands often portray those animals as terrible and bloodthirsty weapons. From the settlers’ perspective, dogs were formidable instruments in the subjugation of the native peoples they came across at various times over more than 500 years of American colonialization. But the indigenous narratives of these first contacts with dogs may exhibit distinct perspectives that view dogs not only as weapons, instruments, or tools of conquest but rather as agents or actors smoothing contact and establishing peaceful relations between Indians and non-Indians. This article explores the narratives of the first dogs encountered by two native populations in southwestern Brazilian Amazonia—the Puruborá and the Karitiana in the state of Rondônia—to demonstrate the canine agency behind the interethnic meetings in this region, where dogs were largely absent until the arrival of the Europeans and their descendants beginning in the sixteenth century. First contacts between Indians and non-Indians are complex inter-specific events, and may extend beyond only two participants (a group of non-Indians and a native people) to include at least three parties, since the actions and dispositions of dogs play a crucial role in the development of human interactions. Recollections of the first dogs encountered by the Puruborá and Karitiana point precisely toward recognizing the importance of the animal's presence as an actor, far beyond a mere instrument.

Establishing baseline biodiversity data prior to hydroelectric dam construction to monitoring impacts to bats in the Brazilian Amazon.

The modification of Amazonian rivers by the construction of megaprojects of hydroelectric dams has widely increased over the last decade. Robust monitoring programs have been rarely conducted prior to the establishment of dams to measure to what extent the fauna, and its associated habitats may be affected by upcoming impacts. Using bats as models, we performed analyses throughout the area under the influence of the Santo Antônio hydroelectric dam, Southwestern Brazilian Amazonia before its construction to estimate how the fauna and its associated habitats would be affected by the upcoming impacts. We surveyed bats in 49 plots distributed along the areas going to be inundated by the dam and those remaining dry. As predictors for the species distribution, we tested the variables of vegetation structure and topography. Species composition largely differed between the dry plots and the plots located in areas that will be flooded, and this was strongly associated with the variables of forest basal area and elevation. Vegetation-related variables also had strong influence on the guilds distribution. The flooding of lower elevations areas is expected to negatively affect the species number and abundance of frugivorous species. In contrast, it is likely that animalivores will be less vulnerable to dam-induced flooding, since they were abundant in the areas not expect to be inundated. We urge for the implementation of studies to predict impacts caused by large hydroelectric dams, including tests of the influence of the local conditions that shape diversity to avoid massive losses of the biota, and to build preventive monitoring and management actions.

A new rodent (Caviomorpha: Dinomyidae) from the upper Miocene of southwestern Brazilian Amazonia

Recently, the fossil record of rodents from southwestern Brazilian Amazonia has been reviewed with regards to its diversity as well as its ecological relationships. In the reviews, the necessity to report new specimens collected with stratigraphic control was stated. Here, a new dinomyid specimen collected during a 2015 expedition to the Niterói locality, Acre River, is reported. The material is a fragment of skull with the right P4–M1 and the left P4–M2 preserved. The cheek teeth are protohypsodont, a characteristic employed to differentiate Potamarchinae dinomyids from the euhypsodont dinomyids Eumegamyinae and Tetrastylinae. The occlusal surface of the cheek teeth is composed of lophs with interruptions, showing little wear, which suggests that the specimen is not fully ontogenetically developed. The specimen has a unique combination of characters (protohypsodont and pentalophodont cheek teeth, with the leading edges of similar thickness to the trailing edges, and presence of a groove on the bottom of the infraorbital foramen) not present in other known dinomyids, which led us to erect a new taxon. The abundant and diverse fossil record of protohypsodont dinomyids suggests that an important radiative event may have occurred during the middle–late Miocene of northern South America.http://zoobank.org/urn:lsid:zoobank.org:pub:E082C3C6-47B6-4D83-9009-A64879AAFC7Ahttp://www.zoobank.org/NomenclaturalActs/16235A7B-A261-445E-8DD4-940AB21DCB06

Land-uses and tropical log production of Rondonia State in Southwestern Brazilian Amazonia

Land-uses and tropical log production of Rondonia State in Southwestern Brazilian Amazonia

New crocodylian remains from the Solimões Formation (lower Eocene–Pliocene), State of Acre, Southwestern Brazilian Amazonia

The Solimoes Formation (lower Eocene–Pliocene), southwestern Brazilian Amazonia, is one of the most abundant deposits of reptiles from the Cenozoic of Brazil. Eight species of Crocodylia have been described from this formation, including taxa of all the three main extant clades: Gavialoidea (Gryposuchus and Hesperogavialis), Alligatoroidea (Caiman, Mourasuchus and Purussaurus) and Crocodyloidea (Charactosuchus). Here, we describe crocodylian fossil remains collected in 1974 by RadamBrasil Project. Specimens were described and identified to the possible lowermost systematic level. With the exception of the osteoderms, the associated postcranial elements were not identified. It is concluded that at least in one location there may have been co-occurrence of four different morphotypes (Gavialoidea indet., Purussaurus sp., Mourasuchus sp. and taxa of the Brevirostres clade, but not pertaining to Purussaurus or Mourasuchus), suggesting that they could have been contemporaneous, with habitat and niche partitioning

Tropical Fossil Caviomorph Rodents from the Southwestern Brazilian Amazonia in the Context of the South American Faunas: Systematics, Biochronology, and Paleobiogeography

The fossil-bearing stratigraphic sections of the Solimoes Formation (southwestern Brazilian Amazonia) are exposed mainly along the Jurua, Purus, and Acre rivers, and in road cuts. These deposits have provided fossils of the four main lineages of Caviomorpha – Cavioidea, Erethizontoidea, Octodontoidea, and Chinchilloidea, contributing to the understanding on the evolution of tropical Neogene rodents. Herein, our knowledge about fossil rodents from this region is reviewed. New specimens are recorded, including taxa mentioned for this region for the first time, such as basal cavioids, Dolichotinae, Caviodon (Hydrochoeridae), and Drytomomys (Dinomyidae). Unfortunately, the deposits have no absolute ages, and based on palynological data and the biochronology of several taxa (mainly mammals), the encompassed fauna has been constrained to the late Miocene. However, some rodent lineages recorded here seem to be more related to older faunas, from the middle Miocene and Paleogene. Regarding the biogeographic and paleoenvironmental affinities, most of the Neogene rodents from the Acre region show more similarities to those from the Entre Rios, Argentina, and Urumaco, Venezuela, where wet environments were present during Neogene times. An increase in prospecting along southwestern Amazonian rivers looking for rodents (among other vertebrates) associated with methods to better constrain the ages of these faunal assemblages will contribute to a better understanding of the evolution of the tropical rodents as well as the stratigraphy and age of that portion of the basin.

Object-based classification of vegetation and terrain topography in Southwestern Amazonia (Brazil) as a tool for detecting ancient fluvial geomorphic features

Reconstructing the evolution of large tropical fluvial systems over the geological time is challenging, particularly in areas such as the Amazonian lowlands where basic geological and geomorphological data are still scarce relatively to the large dimension of the region. In such areas, remote sensing data are useful for detecting ancient morphological features that may reveal past fluvial dynamics. In this study, we explored object-based image analysis (OBIA) in the Madeira-Purus interfluve, Southwestern Brazilian Amazonia, integrating geospatial data including Landsat satellite multispectral images, the digital elevation model (DEM) acquired during the Shuttle Radar Topography Mission (SRTM), and stream channels digitized from topographic maps. This approach provided the basis to categorize automatically classes with contrasting vegetation and/or topographic characteristics within the dense tropical forest over an extensive and relatively flat forested area. The main goal was to use these classes as a surrogate for the recognition of ancient geomorphic features consisting mainly of paleochannels that may help reconstructing fluvial history in space and time. Landsat optical images with stream vector were appropriate to classify open vegetation areas that grow over paleochannels, but failed to identify these objects when they were located over forested areas. However, the digital elevation model (DEM) derived from the Shuttle Radar Topography Mission (SRTM) was successful to detect these objects even in forested areas. Topographic survey undertaken in the field increased the classification reliability by demonstrating true terrain variations along transects measured across the paleochannels. Based on this technique, networks of dendritic paleochannels were mapped and related to ancient tributaries of the Madeira River that had their courses flowing opposite to main modern streams. This denotes a significant change in fluvial dynamics over time, most likely resulting from tectonic tilting.

Forest fires in southwestern Brazilian Amazonia: Estimates of area and potential carbon emissions

Areas affected by forest fires that occurred in 2005 were mapped in the municipalities of Boca do Acre and Lábrea (in the southern part of Brazil’s state of Amazonas) and estimates were made of the loss of biomass and carbon stock and the committed emissions from increased tree mortality due to fire. Fire scars observed on Landsat-5 TM satellite images from 2004 to 2006 were visually interpreted and digitized; over 865.6km2 of forest affected by fire were mapped, the majority (2.9% of the total forest cover) concentrated along the southern edges of the municipalities, which border on the states of Rondônia and Acre. The greatest loss of biomass due to the increase in tree mortality was indicated by the survey made 4years after the fires: 4.5×106Mg total (above+below-ground) and 3.7×106Mg (only above-ground). Consequently, 2.2×106MgC (total) and 1.8×106MgC (above-ground) of potential carbon emissions were committed from the initial burn of forest biomass and from trees killed by the fire. Emissions occur both through oxidation of dead biomass by decomposition or through combustion in subsequent fire events. Our results indicate that fires can affect extensive tracts of forest and can emit significant amounts of carbon to the atmosphere in periods of drought. Fire plays a significant role as a threat to the biological balance of the forest and causes loss of biomass and emission of greenhouse gases that have critical implications for the future of forests in the Amazon.

Second record of the pale brown ghost bat Diclidurus isabella (Thomas, 1920) (Chiroptera, Emballonuridae) from Brazil and range extension into southwestern Brazilian Amazonia

AbstractWe present a new record of

Restricted natural hybridization between two species of litter frogs on a threatened landscape in southwestern Brazilian Amazonia

Natural hybridization between allopatric species following secondary contact has been poorly documented for Neotropical anurans inhabiting the Amazonian lowlands. We conducted a genetic survey across a contact zone between two species of litter frogs, Allobates hodli and Allobates femoralis (family Dendrobatidae), located on the left riverbank of the upper Madeira River, State of Rondonia, Brazil. We obtained tissue samples from 11 sampling sites on both riverbanks, covering approximately a 400 km long transect. We evaluated the genetic relationships between samples using haplotype networks and a distance-based phylogenetic tree obtained from a dataset of 16S rRNA mtDNA sequences. Estimates of genetic diversity, population structure, and the identification of sites where genetic admixture occurred were carried out by means of frequency-based methods and Bayesian inference on mtDNA and a set of four microsatellite loci, including samples collected throughout the study area. A reduced dataset including only microsatellite loci genotyped from samples on the left riverbank was applied in assignment tests for detecting levels of admixture at the contact zone and adjacent sampling sites, and for detecting and quantifying hybrid individuals. Our results suggest that genetic introgression between A. hodli and A. femoralis is restricted to the core area of the contact zone, where potential hybrids are less frequent than parental genotypes. Effects on the genetic variability of adjacent populations are only detected at sites located 1.5 km downstream and upstream of the core area, suggesting the existence of selection against hybrids, possibly mediated by postzygotic isolation mechanisms. The contact zone between A. femoralis and A. hodli is the first well delimited suture line between anuran species ever documented in the Brazilian Amazon. The settlement of two dams along the upper Madeira River poses an immediate threat to the gene flow and hybridization balance observed between the populations studied. Our results provided guidelines for a current monitoring program, aiming at the impacts of dams on this evolutionary system’s dynamics.

Habitat patch and matrix effects on small-mammal persistence in Amazonian forest fragments

Tropical forest mammal assemblages are widely affected by the twin effects of habitat loss and habitat fragmentation. We evaluated the effects of forest patch metrics, habitat structure, age of patch isolation, and landscape metrics on the species richness, abundance and composition of small mammals at 23 forest fragments (ranging in size from 43 to 7,035 ha) in a highly deforested 3,609-km2 landscape of southwestern Brazilian Amazonia. Using pitfall traps and both terrestrial and arboreal traplines of Sherman, Tomahawk and snap traps, we captured a total of 844 individuals over 34,900 trap-nights representing 26 species and 20 genera of small-mammals, including 13 rodent and 13 marsupial species. We also consider the effects of distance from forest edges on species occupancy and abundance. Overall small mammal abundance, species richness and species composition were primarily affected by the quality of the open-habitat matrix of cattle pastures, rather than by patch metrics such as fragment size. Ultimately, small mammal community structure was determined by a combination of both landscape- and patch-scale variables. Knowledge of the anthropogenic factors that govern small mammal community structure is of critical importance for managing the persistence of forest vertebrates in increasingly fragmented neotropical forest landscapes.