RESUMEN

Autonomous recorders are frequently used for examining vocal behaviour of animals, and are particularly effective in remote habitats. Southern right whales are known to have an extensive acoustic repertoire. A recorder was moored at the isolated sub-Antarctic Auckland Islands for a year to examine whether the acoustic behaviour of southern right whales differed seasonally and throughout the day at their main calving ground in New Zealand. Recordings were made in each month except June, and vocalizations were audible in all months with recordings except January. A total of 35 487 calls were detected, of which upcalls were the most common (11 623). Call rate peaked in August (288 ± 5.9 [s.e.] calls/hour) and July (194 ± 8.3). Vocal behaviour varied diurnally with highest call rates detected at dusk and night, consistent with the concept that upcalls function primarily as contact calls. Zero-inflated model results confirmed that seasonal variation was the most important factor for explaining differences in vocal behaviour. An automated detector designed to expedite the analysis process for North Atlantic right whales correctly identified 80% of upcalls, although false detections were frequent, particularly when call rates were low. This study is the first to attempt year-round monitoring of southern right whale presence in New Zealand.

RESUMEN

Sounds produced by Irrawaddy dolphins, Orcaella brevirostris, were recorded in coastal waters off northern Australia. They exhibit a varied repertoire, consisting of broadband clicks, pulsed sounds and whistles. Broad-band clicks, "creaks" and "buzz" sounds were recorded during foraging, while "squeaks" were recorded only during socializing. Both whistle types were recorded during foraging and socializing. The sounds produced by Irrawaddy dolphins do not resemble those of their nearest taxonomic relative, the killer whale, Orcinus orca. Pulsed sounds appear to resemble those produced by Sotalia and nonwhistling delphinids (e.g., Cephalorhynchus spp.). Irrawaddy dolphins exhibit a vocal repertoire that could reflect the acoustic specialization of this species to its environment.

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RESUMEN

The pipistrelle bat Pipistrellus pipistrellus is the most widespread in Europe, and is often the most abundant bat species in northern and central Europe. P. pipistrellus has traditionally been considered as one species throughout Europe. Here we show that: (i) the echolocation calls of pipistrelles fall into two distinct frequency bands in Britain, with frequencies containing most energy averaging 46 kHz and 55 kHz; (ii) roosts consist of bats which use only one form of echolocation; (iii) small but significant differences in average gross morphology exist between the phonic types; and (iv) the two phonic types occur in sympatry over much of Britain. Recordings made from European populations show that bimodal echolocation is also typical of continental pipistrelles, with only one phonic type found in some areas, two types in sympatry in others. The sympatric occurrence of two phonic types, the lack of mixing of types between colonies, and the morphological divergence between phonic types suggests that P. pipistrellus may actually consist of at least two cryptic sibling species. The evolution of bimodal echolocation in bats is discussed, and a model involving disruptive selection is presented to show how sympatric speciation may occur.

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