To attract mates and deter other males from their precious nest sites, male toadfish, Halobatrachus didactylus, make a chorus of croaks, grunts and whistles. However their symphony can be disrupted by noise pollution from shipping, so Raquel Vasconcelos, Clara Amorim and Friedrich Ladich wanted to know how shipping noise affected toadfish living in the busy Tagus River estuary in Portugal (). Measuring the sensitivity of the toadfishes' hearing in the lab, they found that when it was quiet the toadfish heard frequencies of around 50-200 Hz best, with hearing thresholds typically under 100 dB. Their hearing wasn't affected much when the team played them recordings of ambient noise from the estuary, but when they played estuary shipping noise to the toadfish, their hearing threshold increased by up to 36 dB. The boat noise was also most disruptive to their hearing between 50 and 200 Hz. Comparing recordings of the toadfishes' grunts and whistles with the hearing thresholds the team had measured under noisy conditions allowed them to check if the toadfish with higher hearing thresholds could still hear each other. They found that they couldn't hear each other as well with boat noise in the background, suggesting that toadfishes' acoustic communication is impaired when humans are around, which might impact on their survival and mean that they have to build their nests elsewhere.
