Diel patterns in underwater sounds produced by beluga whales and Pacific white‐sided dolphins at John G. Shedd Aquarium

Abstract

Diel patterns in underwater sounds from five beluga whales (Delphinapterus leucas) and five Pacific white‐sided dolphins (Lagenorhynchus obliquidens) housed at John G. Shedd Aquarium in Chicago, IL were studied. Underwater sounds were sampled systematically over 24‐h periods by using a battery‐operated cassette recorder and an Ithaco 605C hydrophone controlled by a digital timer, which activated every hour and then shut off after 2.5 min. Belugas had 14 sounds and Pacific white‐sided dolphins produced 5 sounds. For each species, the use of some sounds was correlated with other sounds. The diel pattern for both species was similar and mostly affected by the presence of humans. Sounds gradually increased after the staff and visitors arrived, peaked during the midday, gradually decreased as closing of the aquarium approached, and was minimal overnight. These data can help identify the best time of day to make recordings and perhaps could be used to examine social, reproductive, or health changes in these captive cetaceans.