Differencial efficiency of two sampling methods in capturing non-volant small mammals in an area in eastern Amazonia / Diferenças na eficiência entre dois métodos de amostragem para capturar pequenos mamíferos não-voadores em uma área na Amazônia oriental

ABSTRACT This study was the first to evaluate the efficiency of trapping methods in the study of small mammals in the Carajás National Forest, southeastern Brazilian Amazon. It is an area with a unique vegetation type (metalofilic savannah or Canga). The aims of this study were to compare the efficiency of two trapping methods (i.e. live-traps and pitfalls), the bait types used, and evaluate if trapping success varied seasonally. We used four sampling grids, each with six parallel transects. The trap effort for live-traps and pitfalls was 51,840 trap*nights and 10,800 bucket*nights, respectively. We used three types of bait: a paste of peanut butter and sardines, bacon, and bananas. We placed one type of bait in each trap, alternating between points. We recorded 26 species of small mammals, 11 from the order Didelphimorphia and 15 from the order Rodentia. Pitfalls captured a higher number of species compared with live-traps. The capture rate, the mortality rate and the quantity of juveniles and adults did not differ significantly between methods. Capture rate for pitfalls differed significantly between seasons. The majority of species were captured by a single method. Species were equally attracted to the traps regardless of the type of bait used. Some of our results differed significantly from other studies in Amazonia and such variation should be taken into account when designing survey methods for Amazonian small mammals.

RESUMO Este estudo foi o primeiro a avaliar a eficiência de métodos de captura de pequenos mamíferos não-voadores na Floresta Nacional de Carajás, sudeste da Amazônia brasileira. É uma área que apresenta características fitofisionômicas exclusivas (savana metalófila ou Canga) e sofre pressão da atividade mineradora. Os objetivos desse estudo foram comparar a eficiência de dois métodos de captura e de três tipos de iscas, bem como se a eficiência dos métodos variou sazonalmente. Nós usamos quatro grades de amostragem, cada uma com seis trilhas paralelas. Capturas com armadilhas de gaiola (live-traps) e armadilhas de caída (pitfall traps) foram realizadas durante três estações secas e três úmidas. O esforço total de captura foi de 51.840 armadilhas*noite e 10.800 baldes*noite para live-traps e pitfalls, respectivamente. Três tipos de isca (pasta de amendoim com sardinha, bacon e banana) foram usadas de forma alternada em todas as armadilhas. Nós registramos 26 espécies de pequenos mamíferos, 11 da ordem Didelphimorphia e 15 da ordem Rodentia. Pitfalls capturaram mais espécies que live-traps. As taxas de captura e de mortalidade e a proporção de jovens e adultos não diferiram entre os métodos. O sucesso de captura diferiu sazonalmente apenas para pitfalls. A maioria das espécies foi capturada preferencialmente ou exclusivamente por um dos dois métodos. As espécies foram igualmente atraídas por todos os tipos de iscas. Nossos resultados diferiram de outros obtidos na Amazônia, o que deve ser levado em consideração em desenhos amostrais para pequenos mamíferos na região.

Diversity and Impacts of Mining on the Non-Volant Small Mammal Communities of Two Vegetation Types in the Brazilian Amazon.

The Carajás National Forest contains some of the largest iron ore deposits in the world. The majority of the minerals are found below a plant community known as Savana Metalófila, or "Canga", which represents only 3% of the landscape within the Carajás National Forest (CNF). The aim of our study was to understand the diversity of community of non-volant small mammals in the two predominant vegetation types: Ombrophilous Forest and Canga, and to examine how mining impacts these communities. Sampling was conducted from January 2010 to August 2011 in 11 sampling sites divided by the total area of Canga and 12 sampling sites in the forest, totalizing 23 sites. Of these, 12 sites (Canga and Forest) were considered impacted areas located close to the mine (<< 900 meters) and 11 sites (Canga and Forest), serving as controls, which were at least 7,000 meters from the mine. We recorded 28 species, 11 from the Order Didelphimorphia and 17 from the Order Rodentia. The two forest types shared 68.42% of the species found in the CNF. A gradient analysis (Non-metric multidimensional scaling) revealed that the first axis clearly separated the non-flying small mammal communities by vegetation type. Occupancy models showed that the detectability of species was affected by the distance from the mining activities. Of all the small mammals analyzed, 10 species were positively affected by the distance from mining in areas impacted (e.g. more likely to be detected farther from mining areas) and detectability was lower in impacted areas. However, three species were negatively affected by the distance from mining, with higher detectability in the impacted areas, and seven species showed no effect of their proximity to mining operations. To date, there are no studies in Brazil about the impact of mining on mammals or other vertebrates. This study reveals that the effect of mining may go beyond the forest destruction caused by the opening of the mining pits, but also may negatively affect sensitive wildlife species.

Some laelapine mites (Acari: Laelapidae) ectoparasitic on small mammals in the Galapagos Islands, including a new species of Gigantolaelaps from Aegialomys galapagoensis.

A collection of laelapine mites from small mammals in the Galapagos Islands are identified and their host distributions reviewed. Two species of native rodents, Aegialomys galapagoensis and Nesoryzomys narboroughii, were infested only with laelapine species typical of Neotropical oryzomyine rodents; Rattus rattus was infested with Laelaps nuttalli, a host-specific ectoparasite endemic to Old World Rattus. A synopsis of Gigantolaelaps Fonseca is provided and we describe a new laelapine mite, Gigantolaelaps aegialomys n. sp., from the pelage of the rodent A. galapagoensis on Santa Fe Island. The new species has strong morphological affinities with a subgroup of Gigantolaelaps associated with a group of semiaquatic oryzomyine rodents ( Holochilus, Nectomys, Sooretamys, Pseudoryzomys , Oryzomys palustris). The other nominal species of this group, Gigantolaelaps mattogrossensis (Fonseca, 1935) and Gigantolaelaps goyanensis Fonseca, 1939 , are characterized by 10 setae on Tibia IV, large metapodal shields, and spiniform setae on Coxae I. Gigantolaelaps aegialomys is distinguished from these species by a lack of clearly spiniform setae on Coxa I, with setiform distal seta longer than the proximal; metapodal shields about the same size as the stigma; less than 100 µm separating the first pair of sternal setae.

A method for testing the host specificity of ectoparasites: give them the opportunity to choose

Host-choice experiments were carried out with rodent and bat ectoparasites on Ilha Grande, state of Rio de Janeiro, Brazil. We constructed experimental chambers that enclosed three different rodent or bat host species, and then introduced a selected set of ectoparasitic arthropods. When given the opportunity to choose among host species, the ectoparasites showed a strong tendency to select their primary hosts, and reject novel host species. These kinds of simple experiments can be valuable tools for assessing the ability of ectoparasites to locate and discern differences between host species, and make choices about which hosts to infest, and which hosts to avoid.

Laelapine mites (Acari: Laelapidae) associated with small mammals from Amazonas, Brazil, including a new species from marsupials.

An intensive survey of ectoparasitic arthropods associated with small mammals in upland forests near Manaus, Brazil, provides information on the taxonomy and host distribution of laelapine mites in the Amazonian Region. We identified 5 genera and 21 species of these mites by comparison with representative museum specimens, the taxonomic literature, and, when possible, the original type specimens. These mites are host specific, with associations ranging from strict monoxeny (18 species) to oligoxeny (1 species) and pleioxeny (2 species). Marsupials were infested with species of Androlaelaps, echimyid rodents with Tur, and sigmodontine rodents with Gigantolaelaps, Laelaps, and Mysolaelaps. Androlaelaps bergalloi, a new species of Laelapinae, is described from the pelage of the marsupial Monodelphis brevicaudata.

A method for testing the host specificity of ectoparasites: give them the opportunity to choose.

Host-choice experiments were carried out with rodent and bat ectoparasites on Ilha Grande, state of Rio de Janeiro, Brazil. We constructed experimental chambers that enclosed three different rodent or bat host species, and then introduced a selected set of ectoparasitic arthropods. When given the opportunity to choose among host species, the ectoparasites showed a strong tendency to select their primary hosts, and reject novel host species. These kinds of simple experiments can be valuable tools for assessing the ability of ectoparasites to locate and discern differences between host species, and make choices about which hosts to infest, and which hosts to avoid.

A new species of neotropical laelapine mite (Acari: Parasitiformes, Laelapidae) from the marsupial Monodelphis americana.

Androlaelaps ilhacardosoi, a new species of Laelapinae, is described from the pelage of a 3-lined marsupial, Monodelphis americana, collected on Ilha Cardoso, São Paulo State, Brazil. The description is based on the female, and the systematics of laelapine mites associated with neotropical marsupials is discussed.

Ecology and host specificity of laelapine mites (Acari: Laelapidae) of small mammals in an Atlantic forest area of Brazil.

Mesostigmatic mites of the Laelapinae Berlese, 1892 (Acari: Laelapidae) are nidicolous arthropods that commonly occur in the fur of Neotropical small mammmals. In this 2-yr study, the laelapine acarofauna associated with the small mammal community in an area of Atlantic forest on Ilha Grande, Rio de Janeiro State, was examined, including observations on patterns of host specificity, mite dispersal, ecology, and food habits. A total of 1,347 laelapines was sampled from the pelage of 6 species of small mammals (Marmosops incanus, Nectomys squamipes, Oryzomys russatus, Rhipidomys n. sp., Oxymycterus dasytrichus, and Trinomys dimidiatus), all of which occurred exclusively in monoxenous associations with their hosts. No evidence of a blood meal was observed in the gut of the mites. With the exception of the 2 species of Tur, mite populations on hosts were entirely or nearly restricted to adult females. These results, together with some morphological characteristics of laelapines, reinforce the hypotheses that Neotropical laelapine mites are not ectoparasitic, and that females disperse by phoresy.