Taxonomy, status and distribution of the Azorean bat (Nyctalus azoreum)

Abstract

The taxonomic status of the Azorean bat (Nyctalus azoreum Thomas 1901) was assessed, by a principal components analysis of measurements of the external morphology of the bat, together with specimens of the closest related Nyctalus species from mainland Europe (Nyctalus leisleri). This analysis confirms the recent suggestion, based on a similar analysis of skull morphology, that the Azorean bat represents a good species, distinguished from N. leisleri by its smaller size—forearm lengths for N. azoreum in range 35·7–42·0 mm (n= 14). compared with 42·0−45·8 mm (n = 8) for N. leisleri. The status and distribution of the Azorean bat was assessed by a survey conducted in the islands in September and October 1988. We assessed the presence or absence of bats, in 62(1′ latitude × 1′ longitude) plots at the west end of the island of Sao Miguel. The study area covered 6% of the total land area of the archipelago and contained representative areas of all the major island habitat types. A less intensive survey throughout four other islands, literature review and information from other sources revealed that the bat is probably distributed throughout the entire archipelago, with the possible exception of Flores and Corvo. Bats were active both in the day and at night. At night, bats were mostly active in coastal villages where they were closely associated with street lighting. During the day, most hats were active in the inland areas near to Caldeira lakes. The maximum number of bats observed simultaneously active in the day was six whilst at dusk swarms of up to 55 (± 5) bats were observed together. At night, bats were also active over approximately 1·5 × the area they occupied in the day. By assuming the bat is found throughout the archipelago, and that our study area was representative, we estimated the maximum population to be between 1750 (from daylight activity) and 23,650 (from nocturnal activity). This latter estimate implies a population density throughout the archipelago of around 0·1 bats per hectare.