Activity of the Insectivorous Bat Pteronotus parnellii Relative to Insect Resources and Vegetation Structure

Riparian areas often are assumed to be necessary sites for foraging by insectivorous bats because of high insect availability and ease of movement and echolocation in the forest. However, effects of vegetation clutter and insect availability on bat activity have not been compared between riparian and nonriparian areas. We used autonomous recorders to evaluate the effects of vegetation structure, insect mass, and assemblage composition on the activity of the aerial insectivorous bat Pteronotus parnellii along stream channels and nonriparian areas in a tropical rainforest in central Brazilian Amazonia. We quantified vegetation clutter using horizontal photographs, captured nocturnal insects with light traps, and recorded bat activity for 110 nights (1,320 h) in 22 sampling plots. Pteronotus parnellii was more active in sites with dense understory vegetation, which were more common away from riparian zones. Bat activity was related to insect availability (mass and composition), independent of the habitat type. Ability to detect insects on vegetation and avoid obstacles should not restrict the activity of P. parnellii in cluttered sites. This suggests that mass and species composition of insects had stronger influences on habitat use than did vegetation clutter. Pteronotus parnellii probably selects cluttered places as feeding sites due to the availability of higher quality prey. © 2015 American Society of Mammalogists

Mammalia, Chiroptera, Phyllostomidae, Lampronycteris brachyotis (Dobson, 1879): first record in Acre, Brazil

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Efeito da obstrução gerada pela densidade da vegetação do sub-bosque sobre morcegos frugívoros e animalívoros catadores (Chiroptera: Phyllostomidae) na Amazônia Central, Brasil

Cluttered vegetation structure demands maneuverable fight for bats. Based on wing morphology, it has been suggested that animalivorous bats have better flight performance in cluttered areas than others trophic guilds. I related density of understory vegetation as a measure of clutter to species composition of Phyllostomidae bats assemblages. I expected find a great contribution of animalivores bats to species composition in mature-forest sites with denser understory. The study was carried out in Purus-Madeira interfluves, along BR-319 highway where eight sample units at least 40 km apart and constituted for ten permanents plots were sampled. I employed ordination techniques and generalized linear models to make inferences about habitat use by phyllostomid bats along a clutter gradient. With a capture effort of 3,840 nets-hour, 511 bats of 4 families (Emballunoridae, Phyllostomidae, Vespertilionidae and Thyropteridae) and 27 species were captured, of which 12 were frugivores (n=414 captures) and 10 animalivores (n=70 capturas). The number of species was reduced from 16 to 7 along a gradient of vegetation obstruction among 53% to 73%. This negative effect occurred for both trophic guilds. Assemblages showed a nested pattern along the clutter gradient, with animalivorous bats tending to occur in sites with denser vegetation. The filter effect on body size alone was not sufficient to explain the structure of bat assemblages in relation to clutter. The effect of clutter differed between foraging guilds. Differences in availability and distribution of food resources in forest sites with different degrees of clutter may affect the proportion of different guilds that use cluttered sites.Locais onde a vegetação florestal é fechada demandam dos morcegos maior capacidade de manobrar durante o voo. Baseado na morfologia das asas, sugere-se que morcegos animalívoros catadores apresentam melhor desempenho de voo em ambientes obstruídos do que outras guildas tróficas. Eu relacionei a densidade da vegetação do sub-bosque, como uma medida de obstrução do espaço, e a composição de espécies em assembléias de morcegos Phyllostomidae. Em florestas primárias, nos sítios com sub-bosque mais denso, eu esparava encontrar uma maior contribuição de morcegos animalívoros na composição de espécies. Realizei o estudo no Interflúvio dos Rios Purus e Madeira, ao longo da rodovia BR-319 onde oito unidades amostrais distantes no mínimo 40 km e compostas por dez parcelas permanentes foram amostradas. Empreguei técnicas de ordenação e modelos lineares generalizados, para realizar inferências sobre o uso de ambientes com diferentes níveis de obstrução por morcegos Phyllostomidae. Após 3.840 horas-rede, 511 morcegos de 4 famílias (Emballunoridae, Phyllostomidae, Vespertilionidae e Thyropteridae) e 27 espécies foram capturadas, dos quais 12 espécies foram frugívoras (n=414 capturas) e 10 espécies foram animalívoras (n=70 capturas). Ao longo de um gradiente de obstrução cuja amplitude variou de 53% a 73%, o número de espécies foi reduzido de 16 para 7 sete espécies registradas, respectivamente. O efeito negativo da obstrução ocorreu em ambos os morcegos animalívoros e frugívoros. A ocorrência das espécies nos sítios apresentou estrutura aninhada e morcegos animalívoros contribuíram mais para a composição de espécies em sítios com sub-bosque mais denso. O efeito de filtro sobre o tamanho corporal não foi suficiente para explicar a estrutura de comunidades de morcegos em função da obstrução do espaço. A relação das espécies com a obstrução foi dependente do hábito alimentar. Diferenças na disponibilidade e distribuição de frutos e presas animais em sítios com diferentes graus de obstrução podem afetar a proporção de espécies de diferentes guildas alimentares que usam sítios com vegetação densa na floresta

Ground-Vegetation Clutter Affects Phyllostomid Bat Assemblage Structure in Lowland Amazonian Forest

<div><p>Vegetation clutter is a limiting factor for bats that forage near ground level, and may determine the distribution of species and guilds. However, many studies that evaluated the effects of vegetation clutter on bats have used qualitative descriptions rather than direct measurements of vegetation density. Moreover, few studies have evaluated the effect of vegetation clutter on a regional scale. Here, we evaluate the influence of the physical obstruction of vegetation on phyllostomid-bat assemblages along a 520 km transect in continuous Amazonian forest. We sampled bats using mist nets in eight localities during 80 nights (3840 net-hours) and estimated the ground-vegetation density with digital photographs. The total number of species, number of animalivorous species, total number of frugivorous species, number of understory frugivorous species, and abundance of canopy frugivorous bats were negatively associated with vegetation clutter. The bat assemblages showed a nested structure in relation to degree of clutter, with animalivorous and understory frugivorous bats distributed throughout the vegetation-clutter gradient, while canopy frugivores were restricted to sites with more open vegetation. The species distribution along the gradient of vegetation clutter was not closely associated with wing morphology, but aspect ratio and wing load differed between frugivores and animalivores. Vegetation structure plays an important role in structuring assemblages of the bats at the regional scale by increasing beta diversity between sites. Differences in foraging strategy and diet of the guilds seem to have contributed more to the spatial distribution of bats than the wing characteristics of the species alone.</p></div

Map of the study area showing the eight sampling modules along the 520-km section of the BR-319 highway, Central Amazonia.

<p>Map of the study area showing the eight sampling modules along the 520-km section of the BR-319 highway, Central Amazonia.</p

Relationship between rank values (mean number of captures weighted by vegetation clutter of each module) and wing morphology (wing load and aspect ratio) of 21 bat species captured along the BR-319 highway, Central Amazonia.

<p>Relationship between rank values (mean number of captures weighted by vegetation clutter of each module) and wing morphology (wing load and aspect ratio) of 21 bat species captured along the BR-319 highway, Central Amazonia.</p

Relationship between bat abundance and the gradient of vegetation clutter.

<p>The horizontal order of the sampling modules was based on the gradient in vegetation clutter. The vertical order of species was based on the average number of captures weighted by vegetation clutter of each module, as indicated by rank values. Species with higher rank values are placed near the top of the graph. Black squares represent gleaning animalivorous bats, white squares canopy frugivores, grey squares understory frugivores, and hatched squares the nectarivore.</p

Bats captured in eight modules along the BR-319 highway, Central Amazonia, Brazil.

<p>Bats captured in eight modules along the BR-319 highway, Central Amazonia, Brazil.</p

Richness and abundance of bats captured at the edge and within a forest fragment in Acre, Brazil

As a consequence of deforestation, forest fragmentation is a reality that is increasingly present in the western part of the state of Acre, Brazil. The objective of this study was to evaluate variations in the richness and abundance of bats in an urban forest fragment of approximately 150ha, which is located in Rio Branco (AC). Collections were performed in two places: two points that were 200m from the edge and two that were 20m from the edge. Mist-nets were opened four hours after sundown during three nights/month. The Shannon-Wiener diversity index (H’) and the Jaccard Similarity index (J) were used for comparative analysis. On 48 nights (November/2005 to July/2007), 85 individual bats of 15 species were captured, with greater richness and abundance of chiropters within the fragment. The similarity index of species was low (J=0.44), indicating habitat preference. The diversity index (H’=2.091) was similar to that of previous studies in the Amazon, especially in Brazil, with lower diversity at the edge (H’=1.864) than inside the fragment (H’=2.047). Carollia perspicillata (n=32) and Artibeus lituratus (n=13) were responsible for 57.6% of the total captured. The characteristics of the matrix and the adaptation of the bats to the mist-nets explained the observed values