The Secret Life of Lobsters

by Trevor Corson

  Whether a lobster’s eye is actually of much use to the animal underwater is another matter. It was this question that Jelle Atema and his graduate students in Woods Hole had in mind when they blindfolded two male lobsters and dropped them into a tank to fight without the benefit of sight.

  Jelle’s initial research on mating behavior, conducted with Diane Cowan and other students, had raised a host of questions about how lobsters sensed their underwater world. For instance, how did they choose mates, identify competitors, and navigate the neighborhood? Jelle’s original goal in Woods Hole had been to study chemical communication in the sea, and he’d chosen the lobster partly for its reliance on its sense of smell. That reliance had been all too clear when Diane had cut off the “noses” of her lobsters—by snipping off their antennules—and watched their mating behavior go haywire. But exactly what sort of information lobsters gleaned by smell, and just how that information was conveyed, were still open questions. So was the degree to which lobsters might be sensing the world through sight and feel.

  Experimenting with lobster combat, Jelle and his students had discovered, generated some interesting answers. Jelle had arrived at the study of lobster combat in the lab through a circuitous path that had begun in the sea. Jelle was a devotee of an Estonian zoologist named Jakob von Uexküll, who promoted the idea that animal behavior could be understood only from the animal’s perspective. Each organism had its own subjective worldview, which von Uexküll called the organism’s Umwelt—a sensory environment where the perception of objects and of other animals was defined by the organism’s specific needs. A lobster’s behavior wouldn’t be intelligible to a human observer unless the human knew how a lobster “saw” the world, and not just with its eyes. Jelle couldn’t transform himself into a lobster, but in his quest to enter the American lobster’s Umwelt, he came close to experiencing life as a nocturnal aquatic animal.

  Several nights a week over a period of nearly three years, Jelle had donned his wet suit and snorkel and motored a small boat from Woods Hole harbor to a cove on a nearby island. He was usually accompanied by two research associates in wet suits and a support team for surface logistics. As darkness fell the divers slipped into the black water like navy SEALs. Their weapons were low-power flashlights, rubber bands, pencils, and slabs of sanded Plexiglas, which would serve as underwater notepads. Floating facedown on the surface, their lights casting a dim glow over the rocks and eelgrass on the bottom, they watched the lobsters emerge from hiding.

  The scientists had drawn up rules of engagement that dictated minimal contact. When the divers saw a new lobster in the cove they would dive, capture it, record its vital statistics, and tag it with a numbered band. Then they let it go and never touched it again. Over nineteen months they tagged 334 lobsters. Three hundred of those lobsters the divers never saw a second time. But about 30 were regular residents of the cove.

  Each night the lobsters tracked down and killed prey, including small fish, crabs, snails, clams, and worms. One lobster was caught gnawing on a pork bone. But the animals spent most of their time snooping around the neighborhood interacting with other lobsters. The encounters were less violent than what Jelle and Diane had witnessed in the lab tanks, where elbow room was scarce. But the struggles for dominance were just as intense. Lobsters made frequent visits to the shelter entrances of other lobsters, and larger lobsters often evicted smaller ones. Jelle and his team also saw lobsters wandering among the rocks and through the eelgrass in what appeared to be aimless exploration. But when the scientists tried to catch these animals for tagging, it was evident that the lobsters’ investigations had been purposeful. A pursued lobster knew instantly where the closest hiding place was and made a beeline for it. If a second diver moved to intercept it, the lobster had an alternative nook already in mind and immediately changed direction. Similarly, the resident lobsters seemed to know where the occupied shelters were in the neighborhood and who was living in each. On one occasion, the scientists watched a large male emerge from his burrow, run straight to another burrow fifteen feet away, and evict the occupant, a competitor. Shortly afterward the evicted lobster left the cove.

  Normally all this would be occurring without even the dim glow cast by the scientists’ flashlights. Moonlight and even starlight provided some natural illumination, so the ingenious light collectors of the lobster’s eye surely conferred occasional advantage. But could they provide the animals with enough information to identify other lobsters, and the local terrain, over long distances? Probably not. On many a cloudy night in the murky Atlantic, Jelle thought the lobsters he was watching could just as well have been blindfolded without impairing their ability to see.

  Each of the Fernald lobstermen on Little Cranberry Island possessed an uncanny nose for sniffing out lobsters, but Dan Fernald had the eye of an artist as well. He stepped back from the easel and studied the pastels on his canvas. His painting was a typical island scene—a lobsterman and his two boys hand-lining mackerel off the co-op wharf, the hills of Mount Desert in the background. Nine years had passed since Katy had talked Dan into attending a painting class in 1985, and he’d since developed a style of his own. Dan saw the boreal coast of Maine in colors and shapes that evoked the vibrancy of the tropics. His pictures of the lobster boats in the harbor or the island’s clapboard houses by the sea blazed with sunny yellows, flowery pinks, and kelly greens. On his easel now, the wharf and mackerel fishers were bathed in rich red, ocher, and lime. Behind them a sea of turquoise and purple swirls sucked lavender mountains down the sides of the picture.

  Little Cranberry’s summer scenery had long attracted artists to its shores. One day an artist who’d made the acquaintance of Dan and Katy had asked if he could store a finished painting in the attic of their little barn, which had once housed the fishermen’s lobster-trap factory. Katy had mentioned the painting to another visitor and, without really trying, arranged a sale. Before long, Dan and Katy had cleared out the attic and transformed it into a gallery. Some of the Little Cranberry lobstermen thought this was frivolous, even a betrayal of the Fernald family’s fishing legacy. But the artists who frequented the island encouraged Dan. He began to display his own paintings alongside theirs, and soon his work was selling for thousands of dollars. When the attic was no longer sufficient, Dan and Katy refinished the first floor of the barn as well. Where equipment for shaping and cutting wire had once served the goal of trapping lobsters, framing tables and glass cutters now served to encase the creations of island artists for display.

  Beginning in 1994, Dan could afford to spend more time painting and less time fishing because suddenly he was catching more lobsters. Dan and his fellow lobstermen on Little Cranberry had been hearing about the rise in catches along the western half of the Maine coast for a few years, but now catches had risen in some regions Down East as well. No one knew why.

  To celebrate their good fortune the lobstermen converged on the restaurant wharf for a party. Electric guitars, amplifiers, and a drum set were boated out to Little Cranberry Island and hefted onto the dock by a group of musicians. The restaurant proprietor printed up tie-dyed T-shirts with the words “Rock the Dock” and handed them out to the band and the lobstermen. Before the party got under way, Bruce Fernald felt flush enough to host a lobster-eating contest for the musicians. The electric bass player ate thirteen.

  After dinner the band began to play. Late into the night, the lobstermen danced with their wives to Rolling Stones songs while teenage boys and girls from summer families eyed each other across the dance floor—a few disappeared to neck on the beach. One woman wore a shirt painted with a pair of lobster claws cupping her breasts. After a few beers, Jack Merrill jumped behind a microphone with his harmonica.

  Getting up to go lobstering at five o’clock was going to be murder. In the summertime it wasn’t unusual for lobstermen in Maine to wake to a coast enshrouded in fog. If a fog bank blew in before morning, Jack would have an excuse to stay home and sleep. Gathering the dancers
into in a ring while the band dropped down to a rhythmic backbeat, Jack gave birth to something like a lobsterman’s rain dance.

  “Fog!” Jack chanted, encouraging the others as they circled in a kind of drunken Macarena. “Fog! Fog! Fog!”

  In Woods Hole, the boxing ring in Jelle Atema’s lab was a sixty-gallon glass aquarium with an opaque divider down the middle. The combatants, all of them male and equally matched for size, had been purchased from local lobstermen, and prior to fighting they were isolated in separate tanks for forty-eight hours. At fight time the researchers lowered one lobster into each side of the boxing tank and then raised the divider. Without blindfolds or other encumbrances, the two lobsters went at each other with the usual show of strength—aggressive posturing, antenna whipping, body shoving, and even the locking of claws.

  If one lobster didn’t win within twenty minutes, the pair was disqualified. One lobster usually capitulated before the time limit, signaling its surrender with a display of groveling. But it turned out that the loser’s subservience lasted longer than the end of the fight. Jelle and his students staged rematches between the same lobsters twenty-four hours later. As soon as the divider went up, the lobster that had previously lost folded back its antenna, lowered its claws, and cowered. The winning lobster, its superiority already established, left the subordinate alone.

  Somehow a lobster was capable of recognizing a former opponent who’d bested him in battle. Attaching blindfolds made little difference. The lobsters’ eyes may have been sensitive light detectors, but as Jelle had suspected, they weren’t necessary for the animals to identify one another. Jelle and Diane Cowan had shown that lobster behavior in the boudoir was governed by scent. Perhaps in the boxing ring as well, lobsters detected social cues by smell.

  On each of four consecutive nights the scientists staged fights between fourteen pairs of lobsters. The fight on the first night established a clear winner in each pair. On the following nights the scientists desensitized the antennules of seven of the pairs by exposing them to distilled water just before the rematch. Sure enough, without their sense of smell the losers failed to recognize their former opponents and unwisely chose to fight a second, third, and even a fourth round, with the same humiliating results.

  By contrast, the seven losers who retained their sense of smell recognized the previous winners within seconds and retreated to the corner of the ring, forfeiting every follow-up match. Subsequent experiments revealed that losing lobsters remembered the opponent that had beaten them for as long as a week. It wasn’t simply that the losers had become cowards. Nor was it simply that the winners were broadcasting aggressive intent. When a loser was paired with an unfamiliar opponent, even if the new opponent was a dominant male, the loser would still fight ferociously until it lost the first fight—only then would the loser submit. Clearly, the lobsters were identifying and remembering each other as individuals.

  Three forms of water current are controlled by the lobster around its body, and these currents are crucial to how a lobster senses the world. At the base of the lobster’s walking legs, hidden under the bottom edge of the carapace, are twenty pairs of feathery gills and a series of leaflike fans that draw water into the gill chambers. This powerful current is expelled straight forward from either side of the lobster’s head, creating an expanding plume of water that reaches seven body lengths in front of the animal. But the lobster can also hold a pair of its mouthparts just in front of the outflow ducts, deflecting the current backward. With another set of mouthparts the lobster can then fan its own face, generating a current that sucks water from in front of the animal toward its antennules. Finally, the lobster can pulse the swimmerets along the underside of its tail, creating a rearward thrust that can help propel it up a rock face or eject water out the back door of its shelter, drawing fresh water in.

  Given the lobster’s ability to project a plume of water forward, or to suck another lobster’s plume toward its own nose, Jelle suspected that a peculiar quirk he’d noticed in the lobster’s anatomy was more than an evolutionary mishap. The American lobster urinates not from some posterior region of its body, but directly out the front of its face. Two bladders inside the head hold copious amounts of urine, which the lobster squirts through a pair of muscular nozzles below its antennae. These powerful streams mix with the gill outflow and are carried some five feet ahead of the lobster in its plume. Quite possibly, lobsters were sensing each other and sending signals—“I beat you up last night, remember?” or “Would you like to mate with me, I’m about to get undressed?”—by pissing in each other’s faces.

  Finding out, of course, would require a lobster catheter. One of Jelle’s students cemented latex tubes to the urine nozzles on a lobster’s face with superglue. The two tubes curved over the lobster’s shoulders to a Y-connector fastened to the lobster’s back. From there a tube ran up to a vial that floated on the surface. Returned to his aquarium and readied for a social encounter with another male, the catheterized lobster wandered the tank, pursued by the floating jar overhead that would collect his urine. The experiment would be akin to sending an angry man into a street-corner altercation with a soundproof hose strapped to his mouth, delivering all his words into a balloon floating above his head.

  What the researchers discovered during the ensuing fights was that dueling lobsters accompanied their most punishing blows during combat by intense squirts of piss at the opponent’s face. What was more, in scenes akin to a showdown at the OK Corral, the winner of the physical combat almost always turned out to be the lobster that had urinated first. And well after the fight was over, the winner kept pissing. By contrast, the loser shut off his urine valves immediately. In an underwater world navigated by scent instead of sight, the tactic was clearly an attempt to hide.

  But what, exactly, were lobsters doing when they peed at each other during fights? One possibility was that the lobsters weren’t communicating at all but instead using urine as a kind of chemical weapon—some insects inject caustic chemicals into their urine and pee at predators as a form of defense. But that seemed unlikely. There were two other possibilities.

  Dissections in Jelle’s lab had revealed an unexplained gland inside the lobster’s head that emptied directly into the urinary tract. Conceivably, the gland was used to produce proteins that registered a unique odor signature for each individual. Indeed, a urine analysis of several different lobsters revealed a unique pattern of molecular weights in the protein content of each animal’s pee. Mice are known to employ proteins in urine to convey individual identity, but a similar system has never been shown to exist in invertebrates. Perhaps what lobsters were doing when they squirted urine during fights was simply the equivalent of the angry man on the street corner shouting his own name every time he punched his opponent. “This pain goes with this name,” the lobsters seemed to be saying, “so remember it well.”

  The second possibility, even less certain, was that victorious lobsters might be reinforcing their own aggression through increased reception or production of a chemical motivator such as serotonin. The result might be to instill a sense of confidence, so to speak. Chemically, this condition wouldn’t be unlike the enhancement a human gets from a cup of coffee—caffeine delays the reuptake of serotonin, which makes more of the motivating chemical available in the brain. A dominant lobster with enhanced chemical motivation might exude some sort of chemical clue to the heightened level of aggression in his urine, which in turn could be detected by the animal’s peers and paramours.

  Jelle and one of his students designed an experiment to test whether other lobsters could detect something like a sense of confidence exuding from a winning male. First they forced a pair of males of equal size to compete for a single shelter in a tank. As expected, one of them emerged as the dominant animal and the shelter’s sole occupant. Meanwhile, at the head of another tank called a flume, the scientists installed two shelters behind a sheet of wire mesh. Jelle’s flume was nine feet long, and it had a water current
flowing straight through it from one end to the other. The scientists then separated the two shelters with a wall that ran halfway down the flume, creating a pair of parallel waterways that emptied into a single space downstream. One male was then ensconced behind bars in each waterway upstream, at the top of the flume. From a pool of twenty female lobsters, none of whom had encountered either of the males before, the scientists placed one female at a time in the tank downstream, where the waterways converged. The female thus had two streams of scent to choose from, one originating from each of the unfamiliar males.

  Initial trials, with the males catheterized, revealed that when a female drew near one of the shelters, the male inside it pissed with vigor out the door at her. When the catheters were removed and the urine could flow freely down the flume, the females spent most of their time trying to push through the bars of the shelter containing the male that had proved himself dominant in the other tank. Since the females hadn’t met him before, the only way they could have known of his superior status was by detecting some indication of the sense of confidence he exuded. Presumably, his piss smelled better.

  On subsequent trials the scientists compared the attractiveness of two males that were both dominants in their own right in separate tanks. One of them, however, had won a greater number of fights than the other. The females in the flume had no way of knowing that, and yet they consistently preferred the male that had won the greater number of fights.

  Jelle remembered the first time he had imagined how lobster mating worked, the female poised to receive suitors in her shelter, emitting a sexy scent and attracting males from downstream. For nearly twenty years Jelle had followed the trail of chemical communication in the sea. He still didn’t know exactly what combination of individual identity and general confidence gave a particular lobster its social status. But it was clear that in a natural setting, the basic pattern of lobster mating was just the opposite of what he had first envisioned.