Porpoises 'buzz' less when boats are nearby
Jakob Højer Kristensen, BionautHarbour porpoises produce fewer "buzzes" - short sounds they use to feed and socialise - when boats are nearby, new research shows.
Scientists from the University of Exeter's Penryn campus used underwater microphones to record and map the sounds of porpoises against those of vessel traffic in the Little Belt - a narrow strait that connects the Baltic with the North Sea.
The research showed a 45% decrease in porpoise buzzes during the busiest vessel traffic periods, project leaders said.
Harbour porpoises eat almost constantly, and concerns have been raised that this drop in activity could have "major impacts" on populations, they added.
The study showed that porpoise activity dropped most significantly during summer daytime hours, when the Little Belt was busiest; and increased when vessels were not present.
Rachel Lennon said "chronic boat traffic may be limiting porpoises' ability to feed and socialise effectively".
Lennon, who co-led the study, said "We know from other studies that disruption to foraging can affect porpoises' health, body condition and ultimately reproduction and survival."
While the object of the study was not to directly assess the impact of boat traffic on porpoises, co-lead author Sharon Merkle said the disruption found was "likely to affect their ability to cope with other environmental stressors".
Jonas Teilmann, professor at Aarhus University, which collaborated on the research, said: "This study adds to the growing understanding of how underwater noise and the increasing vessel traffic affects our environment.
"Our hope is that the results of this study will be used in future managing of the number of vessels, how fast they may move and their distribution in protected areas."
