Dive Dry with Dr. Bill

#226: Mating Mantis Shrimp May Get Munched

Divers and non-divers occasionally ask me "Why do you continue to submerge in Catalina waters, day after day, week after week, year after year? Don't you get bored? Haven't you seen it all?" I guess you could ask the same thing of someone who commutes to work every day along the same route. Of course in their case, the motivating factor is probably a paycheck. I haven't seen one of those in close to seven years. I also haven't seen the stress that goes along with earning one! Even the daily commuter at some point "discovers" something "new" that he or she has been driving past for years. The same goes for me... if I do enough dives, the odds are I'm going to see things I've never seen... or filmed... before. In fact, it happens almost every day I dive... even with my eyes!

A few weeks ago I had one such experience at a site I've visited so many times before over the past five decades on the island. Hen Rock between White's Landing and Camp Fox is a frequent dive site for us on the King Neptune. It is a good, shallow dive with lots of reef structure to investigate. I've poured over the inner and outer reefs, and the sandy bottom there more times than a Xanadusian could count on his 118 pea green fingers (the females only have 98)! This time Captain Tony brought us in close to the real Hen Rock and the sandy bottom outside the yacht club moorings there. I dropped down hoping to locate a few critters worth filming... but this turned out to be one of those very special dives.

More than a year ago I wrote about the mantis shrimp that frequents sandy bottom habitats in our waters. They usually come out at night when I'm listening to karaoke at El Galleon or editing the day's video footage. In my 38 years of off-again, on-again diving in Catalina waters, I have never seen one out in the open long enough to film it when I had a camera. Due to my awkward, flailing diving style, everything within a mile knows I'm in the vicinity... including the great white sharks which flee as soon as I hit the water! By the time I see a mantis shrimp, it has quickly scurried into its burrow and is peering out with its stalked eyes, undoubtedly asking the question "What is THAT?"

This time I started my slow descent to the bottom, a mere 35 feet beneath me. No sooner had the bubbles cleared away from my mask than I saw it. Yes, a mantis shrimp out in the open staring up at me. I had turned my camera on before dropping down, so I started filming as I slowly drifted toward the sand. It looked, then turned around... but it didn't run away. It didn't duck into a nearby burrow. I knew I had to work fast since it would soon regain its senses. I inched toward it with the camera rolling. Closer and closer I got until... it started to run across the bottom. Hmmm, how long before it finds its hole and ducks inside? Well, 46 minutes later I had my answer... it didn't. I spent the entire dive following and filming this apparently crazed mantis shrimp out in the open where predators like giant sea bass could easily take them.

I couldn't believe my luck. I knew I'd have some good footage of this beautiful critter once I returned home and downloaded the video to my computer. I did a four minute safety stop, even though one wasn't necessary (safety first), and swam back to the boat. Even before I climbed up on the swimstep, I was hooting and hollering about the dive... and the mantis shrimp. Once I was on board, Captain Tony told the other divers "Only Dr. Bill could get so excited about spending 46 minutes with a worm!" Now Tony is a great captain, but he's a lousy invertebrate biologist. Mantis shrimp aren't worms, they're crustaceans related to the crabs and lobster.

As I edited the video footage that night, the colors on the mantis shrimp really struck me. It had a bright, golden yellow tail with two dark blue spots on it. Its dorsal (upper) surface had a pink cast to it that was especially pronounced near the head. Missy, one of my dive buddies is very fond of pink... pink BCD, pink weight belt, pink fins, pink drysuit (I haven't checked her undergarments... that is the drysuit ones). She'd love this critter. Via e-mail I heard from former Catalina Conservancy Diver Steve Benavides that the pink coloration indicates a male in mating "plumage." Now I understood. This critter spent all that time out in the open because it was mind altered by "drugs" known as sex hormones. Nothing was going to stop it from searching for its mate, not even at the risk of becoming a meal. Now I may spend a lot of time looking for mates myself, but I don't do it blindly and place my life in jeopardy. Of course I don't succeed either!

I ended up with 29 minutes of edited footage of the mantis shrimp. Of course a lot of it was filmed from behind... most underwater photographers have a large collection of images of fish's tails (and I'm not referring to fishing tales, even though things look bigger underwater). Every so often the shrimp would stop and indulge in a behavior I could capture on tape... cleaning its antennae, using its lightning fast weapons to capture prey, rotating its stalked eyes to scan the terrain for the lovely lady mantis shrimp he sought. I was quite pleased with the results from that dive.

Some time back, Mari, a diving friend of mine from the Philippines, had sent me a picture of two tropical mantis shrimp she had purchased there for $1 each to eat. Hers were very brightly colored as is often the case with tropical species. Mari said they tasted quite good. Another dive friend, Akiko from Singapore, sent me several pictures she had taken of other tropical mantis shrimps in Malaysia. While I find our species to be quite colorful, it does pale in comparison. Some day I'll have to go dive with them to film the incredible colors I saw in their pictures... and enjoy the much warmer waters!

But, dear reader, if this is giving you ideas of going out to harvest mantis shrimp now that lobster season has ended (yesterday), I've got a few words of advice for you. Lobster have certain fairly effective defense strategies. However, they pale in comparison with those of the mantis shrimp. They don't have spines on their tails like their distant relatives, but they do have some of the most powerful weapons of any marine invertebrate. The modified claws that they use for catching food can strike with the force of a 22 caliber bullet. In other words, this is one food source that can really fight back. I'd suggest a nice tofu or vege-turkey salad instead.

© 2007 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles," "Gentle Giants: Giant Sea Bass" or "Common Fish and Invertebrates of the Sea of Cortez" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Head region showing modified feeding appendages and blue legs, bright pink male mating coloration;
yellow and blue tail, full body shot. .

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia