The effects of anthropogenic noise on communications between humpback whale mother-calf pairs
PRINCIPAL INVESTIGATOR: Whitlow Au
Co-INVESTIGATORS: Adam Pack
Graduate Trainee: Jessica Chen
Humpback whales in Hawaiʻi are a major attraction to whale watching tours. Humpback whales have recently been reassessed by the National Oceanic and Atmospheric Administration, which administers to marine species in the US. Humpbacks in the Hawaiʻi distinct population segment were deemed recovered and were removed from the Endangered Species List. However, all whales and dolphins are increasingly threatened by anthropogenic noise in the oceans. Few studies have examined the sounds made by baleen whale mothers and calves. We are studying the sounds made by humpback whale mothers and calves by using suction cup tags and a hydrophone array. The tags continuously record sound and movement data from the tagged animal. These recordings capture calls made by mothers and calves that have rarely been recorded, allowing for characterization of calls such as frequency of vocalizations and sound levels. The array is used to localize on the sound producing animal, to determine which one is vocalizing. Data from the tags and array, in conjunction with behavioral observations, allow us to learn about the sounds used by humpback mothers and calves to communicate with each other and determine if certain behaviors are correlated with particular sounds. In addition, boat noise recorded by the tag or array while near the whales will provide more information on the possible effects of boat noise on the whales. The levels of noise that can disrupt communications between humpback mothers and calves can be estimated. So far, data suggests that mother-calf vocal communications are rare and quiet, therefore potentially more susceptible to masking by other sounds in the ocean. This kind of information allows management agencies to better protect humpback whales so that they can continue to be an inspiring ambassador species for education and protection of our coastal and ocean communities.