Endangered pilot whales in the Strait of Gibraltar are struggling to communicate due to intense underwater noise from heavy shipping traffic [1].
This acoustic interference threatens the survival of the species because these whales rely on vocalizations for pod cohesion, and navigation after deep dives [1, 2]. When communication is severed, the social structure and safety of the pod may be compromised.
According to a study published in the Journal of Experimental Biology in 2024 [4, 5], the whales are exposed to medium to high levels of shipping noise [2, 3]. Researchers said maximum ship-engine noise levels reached 144 dB in the narrow passage between Spain and Morocco [1].
The Strait of Gibraltar is one of the world's busiest shipping lanes, with more than 60,000 ships passing through annually [1]. This constant traffic creates a wall of sound that drowns out the natural calls of the pilot whales (Globicephala macrorhynchus) [1, 2].
To be heard over the din, the whales have been forced to "shout," vocalizing at the upper limit of their acoustic range [2, 3]. While some reports suggest the whales can slightly increase the volume of certain calls [3], other findings indicate they are already calling as loud as possible [2]. This suggests the animals have reached a physiological limit and can no longer compensate for the increasing background noise [2].
Because the noise levels are so pervasive, the whales' ability to coordinate their movements is limited [1, 2]. The loss of clear communication channels makes it difficult for the pods to maintain the tight-knit bonds necessary for their survival in a high-traffic environment [2].
“Pilot whales are shouting to hear themselves over ship noise.”
The findings highlight a critical conflict between global commerce and marine conservation in narrow maritime chokepoints. Because the whales have reached their maximum vocal capacity, further increases in shipping traffic or noise levels could lead to a complete breakdown in pod communication, potentially increasing calf separation and reducing foraging efficiency for the endangered population.
