01454nas a2200145 4500008004100000245003800041210003800079520104400117100001901161700002501180700001801205700002001223700001801243856004701261 2004 eng d00aEocene evolution of whale hearing0 aEocene evolution of whale hearing3 a

The origin of whales (order Cetacea) is one of the best-documented examples of macroevolutionary change in vertebrates1,2,3. As the earliest whales became obligately marine, all of their organ systems adapted to the new environment. The fossil record indicates that this evolutionary transition took less than 15 million years, and that different organ systems followed different evolutionary trajectories. Here we document the evolutionary changes that took place in the sound transmission mechanism of the outer and middle ear in early whales. Sound transmission mechanisms change early on in whale evolution and pass through a stage (in pakicetids) in which hearing in both air and water is unsophisticated. This intermediate stage is soon abandoned and is replaced (in remingtonocetids and protocetids) by a sound transmission mechanism similar to that in modern toothed whales. The mechanism of these fossil whales lacks sophistication, and still retains some of the key elements that land mammals use to hear airborne sound.

1 aNummela, Sirpa1 aThewissen, J., G. M.1 aBajpai, Sunil1 aHussain, Taseer1 aKumar, Kishor uhttp://www.nature.com/articles/nature0272001130nas a2200145 4500008004100000022001400041245005500055210005500110260001600165300001400181490000700195520071300202100002200915856004700937 2004 eng d a1063-771000aSome results of studying the acoustics of dolphins0 aSome results of studying the acoustics of dolphins cJan-05-2004 a343 - 3490 v503 a

An experimental study of the echolocation ability of dolphins (Tursiops truncatus) is performed in the presence of correlated and uncorrelated broadband noise acting on their organs of hearing. It is shown that, under such conditions, the echolocating pulses of a dolphin become noticeably modified: in the absence of noise, standard broadband pulses are produced, while in the presence of noise, the pulses acquire an oscillatory character (become narrowband). Sounds and air pressure that occur inside the respiratory tract of a dolphin when the animal produces whistles and pulsed signals are studied. Data testifying in favor of the pneumatic origin of sounds generated by dolphins are obtained.

1 aRomanenko, E., V. uhttp://link.springer.com/10.1134/1.173950301746nas a2200121 4500008004100000245013300041210006900174520120600243653005701449100002701506700002501533856006601558 2004 eng d00aAcoustic monitoring on a humpback whale ( Megaptera novaeangliae) feeding ground shows continual singing into late spring0 aAcoustic monitoring on a humpback whale iMegaptera novaeangliaei3 a

Singing by males is a major feature of the mating system of humpback whales, Megaptera novaeangliae (Borowski). Although a few songs have been opportunistically recorded on the whales' high–latitude feeding grounds, singing in these regions was thought to be only sporadic. We report results from the first continuous acoustic monitoring of a humpback whale feeding ground (off Cape Cod, MA, USA) in spring. Using autonomous sea–floor recording systems, we found singing on a daily basis over the entire 25 day monitoring period, from 14 May to 7 June 2000. For much of the period, song was recorded 24 h per day. These results, combined with evidence for aseasonal conceptions in whaling catch data, suggest that the humpback whale breeding season should no longer be considered as confined to lower–latitude regions in winter. Rather, we suggest breeding extends geographically and temporally onto feeding grounds into at least spring and early summer. Singing at these times represents either low–cost opportunistic advertising by (perhaps relatively few) males to court females that failed to conceive during the winter, and/or possibly an intrasexual display.

10ahumpback whale; song; mating systems; North Atlantic1 aClark, Christopher, W.1 aClapham, Phillip, J. uhttps://royalsocietypublishing.org/doi/10.1098/rspb.2004.2699