Physical constraints of cultural evolution of dialects in killer whales.

J Acoust Soc Am. 2016 Nov;140(5):3755.

Filatova OA¹, Samarra FI², Barrett-Lennard LG³, Miller PJ⁴, Ford JK⁵, Yurk H⁶, Matkin CO⁷, Hoyt E⁸.

Author information

• ¹Department of Vertebrate Zoology, Faculty of Biology, Moscow State University, Moscow 119991, Russia.
• ²Marine and Freshwater Research Institute, Skúlagata 4, 101 Reykjavík, Iceland.
• ³Vancouver Aquarium Marine Science Centre, Vancouver, British Columbia V6B 3X8, Canada.
• ⁴Sea Mammal Research Unit, Scottish Oceans Institute, University of St. Andrews, St. Andrews, Fife KY168LB, Scotland.
• ⁵Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Road, Nanaimo, British Columbia V9T1K6, Canada.
• ⁶JASCO Research Ltd., 2305-4464 Markham Street, Victoria, British Columbia V8Z7X8, Canada.
• ⁷North Gulf Oceanic Society, Homer, Alaska 99603, USA.
• ⁸Whale and Dolphin Conservation, Park House, Allington Park, Bridport, Dorset DT65DD, United Kingdom.

Abstract

Odontocete sounds are produced by two pairs of phonic lips situated in soft nares below the blowhole; the right pair is larger and is more likely to produce clicks, while the left pair is more likely to produce whistles. This has important implications for the cultural evolution of delphinid sounds: the greater the physical constraints, the greater the probability of random convergence. In this paper the authors examine the call structure of eight killer whale populations to identify structural constraints and to determine if they are consistent among all populations. Constraints were especially pronounced in two-voiced calls. In the calls of all eight populations, the lower component of two-voiced (biphonic) calls was typically centered below 4 kHz, while the upper component was typically above that value. The lower component of two-voiced calls had a narrower frequency range than single-voiced calls in all populations. This may be because some single-voiced calls are homologous to the lower component, while others are homologous to the higher component of two-voiced calls. Physical constraints on the call structure reduce the possible variation and increase the probability of random convergence, producing similar calls in different populations.