Mantis Shrimp #1: “Bbbbrrrnanndndndggghhhh” (MARCO!)
Mantis Shrimp #2: “Grrryyyyybbbbbghhhhhhhh” (POLO!)
Communication can be difficult even for us humans – otherwise how on earth would fashion magazines make their money off of columns like “Male Body Language Decoded – how to tell if he’s the one.” But, that’s perhaps why we spend a lot of time and effort analyzing how animals say “Heyyyy how you doin’?” This can be especially difficult in environments – like the bottom of the ocean – where it’s so dark that organisms can’t even see, let alone pick up the intricacies of body language.
In this pitch-black world, California mantis shrimp (Hemisquilla californiensis, a vibrantly colored benthic dwelling crustacean that lives in muddy holes along the ocean floor of the west coast) use sound. Or more specifically, they ‘rumble’. A study by six scientists from the University of Miami, UMass Amherst, Cornell, and Berkeley looks at how deep sea dwelling mantis shrimp flirt, scare off rivals, escape predators, and say hey get off my porch.
The research graces the August cover of Aquatic Biology and shows that not only do mantis shrimp communicate through low frequency muscle vibrations or rumbles, they each have a unique “voice”, too. It’s hard to study this in a lab because the shrimp vary their rumbles acoustically and temporally to a much higher degree in the wild. So, in addition to recording shrimp in lab tanks, the researchers strapped on their scuba gear and placed high tech audio-visual equipment – an autonomous recording unit (audio) and a hydrophone array (visual/location calculator) – near mantis shrimp burrows on the ocean floor near Catalina Island in California.
“These sounds recorded in the field were different than what we recorded in tanks, so to hear these creatures communicating in the wild was very special. Our research team noted the ‘rumbles’ were so synchronized that it sounded like a chorus, similar to that of groups of birds or frogs” – Erica Staaterman (co-author on the study and creator of the lovely artwork above included in the research paper)
The team found that groups of three or more males make rhythmic rumbles to attract females and deter rivals. Mantis shrimp are also most active during dawn and dusk, when they spend a lot of time foraging and defending their territories.
Scientists have always thought that the primary means of communication for deep-sea organisms was sound, but this is the first study that looks at not only whether or not crustaceans do this, but also how they do it. One other aspect that I found interesting is that the researchers found that from an ecological perspective the huge amout of boat traffic along the California coast is causing a lot of mixed signals. The sounds of the ocean floor are a “cacophony of snaps, squeaks, hums, grunts, and rasps,” and the low rumble of powerboats could be messing with the chorus of mantis shrimp, as well as other crustaceans.
A google image search on these colorful crustaceans has inspired me to contemplate a mantis shrimp Halloween costume for this October….