Bioacoustics Research Program

Little is known about migration patterns and seasonal distribution away from coastal summer feeding habitats of many pelagic baleen whales. Recently, large-scale passive acoustic monitoring networks have become available to explore migration patterns and identify critical habitats of these species. North Atlantic minke whales (Balaenoptera acutorostrata) perform seasonal migrations between high latitude summer feeding and low latitude winter breeding grounds. While the distribution and abundance of the species has been studied across their summer range, data on migration and winter habitat are virtually missing. Acoustic recordings, from 16 different sites from across the North Atlantic, were analyzed to examine the seasonal and geographic variation in minke whale pulse train occurrence, infer information about migration routes and timing, and to identify possible winter habitats.

Abstract Stridulatory sound-producing behavior is widespread across catfish families, but some are silent. To understand why,
we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during
disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior
serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between
vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process.
Most silent species had reduced processes with exclusively smooth, convoluted, or honeycombed surfaces very similar to
spine-locking surfaces, or they had novel surfaces (beaded, vacuolated, cobwebbed). Most callichthyids had ridges but many were
silent during disturbance. All doradid, most auchenipterid and most mochokid species were vocal and had ridges or knobs.
Within the Auchenipteridae, vocal species had spines with greater weight and serration development but not length. Silent
auchenipterids had thin, brittle, distally segmented spines with few microscopic serrations on only one margin and a highly reduced
dorsal process lacking any known vocal morphology. Silent auchenipterids are derived and pelagic, while all vocal genera
are basal and benthopelagic. This is the first phylogenetic evidence for stridulation mechanism loss within catfishes. Phylogenetic
mapping of vocal ability, spine condition, and ecotype revealed the repeated presence of silence and vocal taxa, short and long
spines, and ecotype shifts within clades. The appearance and loss of vocal behavior and supporting morphologies may have facilitated
diversification among catfishes [Current Zoology 56 (1): 73–89 2010].
Key words Bioacoustic, Defense mechanisms, Historical biology, Stridulation
Studies of sound-producing behavior in catfishes
(Teleostei: Siluriformes) highlight the importance of
sound signals in reproductive and agonistic behavioral
contexts (Kaatz, 2002; Fine and Ladich, 2003). Pfeiffer
and Eisenberg (1965) hypothesized that catfishes with
weaponized pectoral spines produce disturbance sounds
as a form of acoustic aposematism, but an experimental
study of one species did not support this hypothesis
(Bosher et al., 2006). Disturbance sounds are produced
when a catfish is physically restrained in a way similar
to an interspecific or predatory attack and can indicate
the presence of stridulation signaling in undisturbed
intraspecific contexts (Kaatz, 1999). Heyd and Pfeiffer
(2000) observed that chemical alarm signals were
weakened or absent from species that were vocal during
disturbance. These findings suggest that disturbance
could function as a