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Contribution of acoustic methods to the study of insectivorous bat diversity in protected areas from northern Venezuela

100%

Ochoa J. G., Farrell M. J. O., Miller B. W.

Acta Chiropterologica

2000

tom 02

nr 2

We present the results of an acoustic survey of aerial insectivorous bats conducted in four protected areas in northern Venezuela. These areas represent localities where the taxonomic composition of the bat communities was relatively well known. We conducted field surveys using the Anabat II detector and analysis system. We compared acoustic inventories with previous lists obtained with conventional sampling methods (principally mist nets). We identified 30 species acoustically (representing 15 genera of the families Emballonuridae, Noctilionidae, Mormoopidae, Vespertilionidae, and Molossidae) on the basis of vocal signatures. Nineteen of these were verified by capture and subsequent recording of released animals; the remainder were identified by comparison with verified vocalizations from other localities. An additional 11 unidentified but distinct taxa were recorded and are referred to here as ‘sonotypes’ (based on similarities in call structure to known species) representing eight genera of the families Emballonuridae, Vespertilionidae, and Molossidae. The short-term acoustic surveys nearly equaled or exceeded the known species richness at three of the four localities, and added two to nine species to previous lists from all locations; many of these bats correspond to taxa difficult to detect with conventional capture methods.

Geographic variation in the echolocation calls of the hoary bat ( Lasiurus cinereus)

100%

Farrell M. J. O., Corben C., Gannon W. L.

Acta Chiropterologica

2000

tom 02

nr 2

Use of bat detectors to perform inventories, determine activity, and assess differential use of habitats has become a generally accepted method. However, there has been vigorous disagreement as to the level of efficacy, primarily relating to the ability to distinguish certain species and groups of species. The primary explanation suggested for the inability to identify certain species is due to the magnitude of intraspecific variation resulting in overlap among species, presumably compounded by geographic variation. Lasiurus cinereus has been identified as exhibiting the greatest degree of geographic variation including recent findings of distinct variation between populations in Hawaii and Manitoba. We find that claims of geographic variation have not been proven because of small sample size and lack of adequate description of method, including the behavior of the bat and the context during which bats were recorded. Previous geographical comparisons of species have relied on standard statistical methods that do not allow a comprehensive examination of the range in variation of diagnostic call parameters. We present data from a broad range of sites throughout mainland United States and Hawaii, and compare a multivariate statistical approach with repertoire plots of characteristic frequency versus call duration. Although we demonstrated a statistical finding of geographic variation in L. cinereus, small sample size, context, and behavior could not be discounted as the proximal cause of observed variation. The perceived variation across the geographic range that we sampled did not affect our ability to identify the species by call structure. We suggest methods for future studies of geographic variation.

Ograniczanie wyników

2 Acta Chiropterologica

2 Farrell M. J. O.

1 Corben C.

1 Gannon W. L.

1 Miller B. W.

1 Ochoa J. G.

2 2000

Wyniki wyszukiwania

Contribution of acoustic methods to the study of insectivorous bat diversity in protected areas from northern Venezuela

Geographic variation in the echolocation calls of the hoary bat ( Lasiurus cinereus)