Researchers from Curtin University and the Taronga Conservation Society Australia carried out the first auditory tests on Australian sea lions and fur seals of the species Arctocephalus forsteri, establishing a reference for the sounds that these species can hear and which could help assess the effects of noise produced by human activities.
The tests were conducted at Taronga Zoo Sydney with two Australian sea lions and two fur seals of the species Arctocephalus forsteri. The animals were trained to respond to sounds by pressing a small platform when they heard a particular tone. When they answered correctly, they received fish as a reward.
Both species showed greater sensitivity to sounds near 3.2 kilohertz, enabling the first detailed reference to their auditory sensitivity.
“Before we can understand whether a noise is affecting an animal, we need to know whether it can hear that noise,” explains Christine Erbe, the lead researcher of the study and a professor at the Centre for Marine Science and Technology at Curtin University.
This information is particularly relevant for the Australian sea lion, an endangered species whose population is estimated at about 12,000 individuals. Hearing plays an important role in communication, foraging, navigation, and threat detection.
Noise from vessels and coastal construction
The researchers also compared the hearing capabilities of fur seals of the species Arctocephalus forsteri with the noise levels produced by boats, ships, aircraft, trains, and construction activities. The results indicate that many of these sounds would be audible to the animals when they are on land.
The research could contribute to future environmental impact assessments and to noise management measures, at a time when activities such as maritime transport, coastal development, and offshore operations are increasing.
For Benjamin Pitcher, a behavioral biologist with the Taronga Conservation Society Australia, the fact that the animals voluntarily participated in the tests, through positive reinforcement, allowed assessing their ability to perceive sounds while keeping them engaged in the process.
Researchers emphasise, however, that knowing the sounds these animals can hear on land is only the first step. The next step will be to understand how the noise affects them underwater and at what levels it may begin to interfere with behavior or with hearing itself.
The study was conducted by researchers from Curtin University and the Taronga Conservation Society Australia and was published in a peer-reviewed scientific journal.
