So, before we can tell whether less snapping hints at damage to habitats, we have to understand what’s normal for each of them.ĭuring the SanctSound project we have been listening to underwater habitats within national marine sanctuaries all over the country for a few years. The same is true of snapping: we expect some differences in the amount of snapping that we hear among different healthy shallow water habitats. To know when an elevated temperature means that you are sick and when it doesn’t, you have to know your own normal body temperature. Some peoples’ bodies run warmer than others. So we know that our temperatures aren’t 98.6 degrees all the time, even when we are healthy. We’ve all been taking our temperatures a lot this year. In order to understand whether changes in snapping relate to how healthy a habitat is, we need to first understand why snapping varies to begin with. Sounds pretty snappy! But there are big caveats. Because their sound plays an important role in navigation, directing marine larvae and fishes to suitable habitats, their early return to the soundscape can potentially alert other organisms to the suitability of the habitat. These studies are showing that the amount of snapping can help us understand how our restoration efforts are doing, or even help us rebuild ecological communities. Anecdotal recognition that we are hearing less snapping in these places than we used to is transitioning to analysis of underwater recordings before, during, and after efforts to restore habitats that are damaged. Since many avid divers are so tuned into the sounds they hear underwater, people have started to take notice of changes in what they are hearing after a habitat is damaged by an oil spill, hurricane, coral disease, or bleaching. This 10 second recording in Gray’s Reef National Marine Sanctuary portrays what we hear when we are diving near snapping shrimp: their collective snapping generates the loudest sounds (lighter blue to yellow colors) across most of the tones or frequencies that we recorded (vertical axis). Spectrograms are ways of looking at sound. For those who have not experienced this, it sounds a bit like the popping sound Rice Krispie cereal makes when you pour milk over it. The crackling sound that you can hear when you are snorkeling or diving is often the most distinctive and memorable sound in places where snapping shrimp are prevalent. Snaps are most commonly recorded during fights between shrimp who are defending territories, while they are digging burrows or in response to changes in their environment, but scientists think they also use the sound to stun prey and deter predators. Photo: Anker A., Grave, via Wikimedia Commons.ĭespite being loud, their small size and love of crevices means that we don’t know much about why they make this sound. Snapping shrimp are actually a group of many different species of shrimp, all with asymmetrical claws. At 183-210 decibels, this makes them some of the loudest sound producers in the ocean. When closed, the claw’s hinge produces a bubble which bursts and makes a loud snap sound. They measure in at a couple of centimeters, yet their snapping claw can grow to be half the size of their body. Snapping shrimp, or pistol shrimp, live in a variety of different shallow water ocean places, from coral reefs to temperate kelp forests to sponge dominated and rocky bottom habitats. But in many underwater environments, the smallest animals are among the loudest. When asked to think of loud animals, we gravitate towards the big ones: the roar of a lion, the trumpet of an elephant, and, underwater, the song of the mighty blue whale. Oh Snap! What Tiny Shrimp Can Tell Us About Habitat Health.
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