Pilot Whales Increase Call Volume to Overcome Shipping Noise in Strait of Gibraltar

Long-finned pilot whales in the Strait of Gibraltar increase the volume of certain calls to compensate for underwater noise produced by shipping traffic, researchers reported on May 7 2026. Milou Hegeman and Frants Jensen of Aarhus University in Denmark, along with an international team, attached suction-cup recorders to 23 pilot whales between 2012 and 2015.

The devices, mounted on a 6-meter pole, recorded the animals' movements, depth and acoustic environment for up to 24 hours before detaching and floating to the surface. The recorders captured 1,432 calls that the team classified into four types: short pulsed calls, high-frequency calls, low-frequency calls and two-component calls used for long-distance communication.

Background noise levels ranged from 79 to 144 decibels, comparable to the sound of a vacuum cleaner in a busy restaurant.

The whales raised the volume of their quieter high-frequency and short pulsed calls in response to increased vessel noise. However, the low-frequency and two-component calls, which are used after deep dives to locate group members, were already produced at maximum volume and could not be amplified further.

Jensen stated that the rising background noise reduces the effective communication range, making it harder for separated animals to find each other. The long-finned pilot whale is a highly social, matrilineal species that typically remains with the same group for life.

Many of their dives are synchronized to reduce separation risk, though individuals can still become separated at the surface or during dives.