International scientists confirm that the orca Morgan, rescued in Holland in 2010 and moved to Loro Parque in 2011 at the request of a Dutch judge, suffers a hearing loss that could be very severe and even absolute. This is the conclusion reached by the experts, having made multiple hearing tests that took place last week at the facilities of Orca Ocean.
The research team, composed of experts from the Netherlands Institute for Marine Resources and Ecosystem Study (IMARES), the National Foundation for Marine Mammals of the U.S.A., and also from the Office of Naval Research for the U.S. Armed Forces (U.S. Navy ), studied the hearing of several orca individuals at the park. As a result they found that in all of them they could record brain responses to sound stimuli, except for Morgan. This study confirms the suspicions of our trainers and veterinarians, who had warned that the animal did not seem to respond to sound signals.
This type of test, which consists of the detection of brain waves in response to the emission of a sound, is routinely used to determine the hearing of dolphins and small cetaceans. However, its application to the acoustic study of orcas is pioneering in the world, given there is only one precedent with two individuals from fourteen years ago.
With the confirmation of this hearing incapacity, the trainers continue to make visual adaptations to the communication system for managing Morgan. At the same time, and in conjunction with the advice of specialists in animal behaviour from the Free University of Berlin, new lines of work will be developed that will allow us to understand in more detail the limitations of Morgan.
Cetacean Acoustic Deficiencies
In recent decades, there has been growing concern about the detrimental effect that noise could have on the survival of some species of cetaceans. In this regard, in a study carried out with stranded cetaceans, and published in the journal PLoS ONE in 2010, scientists found that more than half of the bottlenose dolphins tested in that study suffered severe or profound loss of hearing ability. One conclusion from this research is that because the Odontocetes (toothed whales, like dolphins and killer whales) depend on echolocation for foraging and orientation, acoustic disability could lead to beaching. In this sense, the study recommends to assess the acoustic ability of any cetaceans in rehabilitation because it can affect their ability to survive.
Interview with Dr. Dorian Houser
Interview with Klaus Lucke
Edited 11-04-2013: Acoustic report realiced by IMARES.