- European spiny lobsters can create a sound that might, under the right conditions, be detectable up to 3 kilometers, nearly 2 miles, away.
- Researchers used underwater microphones to determine how loud lobsters are, and found that the larger the lobster, the louder the sound.
- Spiny lobsters were overharvested in the 1970s, and though populations have rebounded, there is still a need to monitor population levels.
- The study suggests that lobsters may be a candidate for acoustic monitoring.
European spiny lobsters create quite the rumble. By rubbing an antenna across its face, a spiny lobster can create a sound that might, under the right underwater conditions, be detectable up to 3 kilometers (1.9 miles) away.The sound, known as an antennal rasp, occurs when an extension of a lobster’s antennae moves across a rough patch under its eye. Lobsters likely make this sound for communication or to scare away predators.
In a recently published study in Scientific Reports, researchers asked, how far does the sound of a rasp travel? And can these sounds be used in a non-invasive way to monitor lobster populations?
Spiny lobsters (Palinurus elephas) are found in the Eastern Atlantic Ocean and in the Mediterranean Sea. Intensive fishing of lobsters for food in the 1960s and 1970s made spiny lobsters scarce in European waters and even led to local extinctions off southwest Britain. Though populations have rebounded, there remains a need to monitor and manage lobster populations from overharvesting.
Using hydrophones (underwater microphones that record sound from all directions), researchers recorded 1,560 antennal rasps from 24 individual lobsters in the Bay of Saint Anne du Portzic, France. They placed hydrophones at distances of 10, 20, 50 and 100 meters (33 to 330 feet) away from each lobster. The largest lobsters (with a carapace, or body shell, 13.5 centimeters long, or about 5 inches) made sounds detectable at 100 m distance; in general, the larger the lobster, the louder the sound.
Audio1: Antennal rasp produced by a small-sized (20 grams) spiny lobster. Credit: Youenn Jézéquel © UBO
Audio 2: Antennal rasp produced by an intermediate-sized (200 grams) spiny lobster. Credit: Youenn Jézéquel © UBO
Audio 3: Antennal rasp produced by a large-sized (2 kilograms) spiny lobster. Credit: Youenn Jézéquel © UBO
The density of seawater allows sounds to travel over greater distances compared to air. However, sound is still lost in the water, and noise pollution can get in the way of a good recording. Seismic surveys, used in oil and gas exploration, are one of the most common sources of noise pollution.
Based on the loss of sound over distances and the levels of background noise in the recordings, the researchers estimate that, in conditions of very low background noise, the large lobsters could make rasps detectable up to 3 km away. The question still remains if lobsters can hear each other across long distances, as nothing is known about lobsters’ hearing sensitivity.
Acoustic monitoring can be used as a tool to monitor biodiversity. Passive acoustic monitoring (PAM) is used in surveys of ocean mammals such as whales and dolphins. The method is relatively inexpensive and recording devices can be deployed and left in the field (or in this case, the ocean) for extended times. Recordings can tell scientists about population density, abundance, and behavioral trends for these well-studied mammals.
The authors suggest that the ability to detect the antennal rasps of lobsters in shallow water could make these chatty crustaceans a candidate for acoustic monitoring techniques.
Banner image of a juvenile spiny lobster in the hand of a scuba diver, by Erwan AMICE/CNRS.
Citation: Jézéquel, Y., Chauvaud, L., & Bonnel, J. (2020) Spiny lobster sounds can be detectable over kilometres underwater. Scientific Reports, 10(1), 7943. doi:10.1038/s41598-020-64830-7
Liz Kimbrough is a staff writer for Mongabay. Find her on Twitter @lizkimbrough_
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