The sperm whales of the Gulf of Mexico may be making a comeback, but studying these deep-sea divers isn't easy.
By Elaine Robbins
"There is one knows not what sweet mystery about this sea, whose gently awful stirrings seem to speak of some hidden soul beneath." — Herman Melville, from Moby-Dick
The sea still harbors its mysteries, and perhaps the gulf's best-kept secret is the existence of its biggest resident: the sperm whale. Once hunted to near extinction, this deep-water denizen has started to make a remarkable recovery. Some 360,000 sperm whales are found in the world's oceans, from tropical seas to the edge of the polar ice caps. Although still listed as an endangered species, an estimated 1,300 — most of them females and juveniles — are year-round residents of the northern gulf. Yet most Texans are surprised to learn that they're there.
How do you hide a 20-ton sperm whale? It helps that they spend much of their time in places that humans can barely enter. To find one of their secret spots, you'd have to head 50 miles out from the Brownsville coast, where the continental shelf drops off to the deeper waters of the continental slope. From there, leave the sunlit sea behind and descend 3,000 feet to a place where no light penetrates. In this watery world of eternal night, where the desert emptiness is broken only by occasional upwellings of nutrients that attract phytoplankton and other forms of life, the majestic leviathan made famous by Herman Melville's Moby-Dick dives day and night, far from prying human eyes.
"Almost everything about whales is a tantalizing mystery," writes Diane Ackerman in The Moon by Whale Light. "We ache to know about other forms of equally intelligent life in the universe, and yet here are creatures as unknown as extraterrestrials right among us, moving in a slow-motion ballet under the oceans, hidden from our view."
The sperm whales that inhabit the gulf's subtropical waters can be found anywhere along the continental slope or deep waters, with particular concentrations off the Brownsville/Matamoros coast, at the mouth of the Mississippi, and west of the Florida Keys. Swimming in pods of about 10 female relatives, friends and juveniles, some dive for food while one or two stay behind to watch the calves, whose young bodies presumably can't withstand the pressure of such depths. Although sperm whales spend most of their time diving, for a few hours each day — usually in the afternoon — they return to the surface to socialize and loll about, communicating with a distinct series of Morse code-like clicks called codas.
"I watched a group for 1 1/2 hours one day and they were rolling up against each other and mouthing each other," says Keith Mullin, a research fishery biologist for the Southeast Fisheries Science Center who conducted the first ship and aerial sperm whale counts in the gulf. "That is about as animated as I've seen them."
In contrast to the stay-at-home females, males leave the warm-water breeding grounds at around age 6 to spend their lives traveling the world's seas.
"Medium-sized males are part of loose-knit 'bachelor schools' found in generally cooler waters than the family units," writes sperm whale expert Hal Whitehead in Whales, Dolphins, and Porpoises. "As males grow, they may venture nearer the poles in smaller schools, until the largest males, nearly 60 feet long and approaching 60 tons, may be seen along the edges of the pack ice in both hemispheres."
British zoologist Jonathan Gordon once observed a male being greeted warmly upon his return to the breeding grounds. Females "crowded in on him, rolling themselves along his huge body. They just seemed delighted that he was there. For his part the male was all calm serenity and gentleness. Even the calves were interested, and on one occasion we saw a male gently carrying a calf in his mouth."
Over millions of years, the sperm whale has evolved to exploit a unique ecological niche: that of deepwater squid specialist. Diving to the sea's 24-hour sushi bar, sperm whales consume as much as a ton of squid a day. Impressively, that puts their collective annual seafood catch on the same level as that of humans.
How do they achieve this remarkable feat? With a uniquely designed body that an Olympic diver would kill for. Although sperm whales typically dive half a mile deep and stay down for 40 or 50 minutes before surfacing to breathe, they are able to reach depths of nearly 2 miles and can hold their breath for as long as two hours. Human recreational divers, by contrast — even with the help of scuba gear — are limited to a wimpy 130 feet with 10 minutes maximum bottom time. Exceed those limits, and we're susceptible to "the bends" and nitrogen narcosis — a condition that impairs judgment and has induced many a diver to swim off in giddy ecstasy to his or her death.
As if extreme diving wasn't enough, sperm whales later evolved sophisticated built-in sonar to locate large squid in the night-black depths, much like bats evolved sonar to catch insects at night. "They change the pitch and frequency of clicks and change to a buzz when they home in on prey," says Texas A&M University oceanography professor Doug Biggs, who co-led an international team of researchers who observed gulf sperm whales' foraging behavior as part of the recently completed five-year Sperm Whale Seismic Study. "When they put microphone tags on the whales, they found that whales do these buzzes from a dozen to three dozen times during the course of a 50-minute dive. That means that every three to five minutes, they're detecting prey and changing turning radius. We propose that they're eating a dozen to three dozen prey items a dive."
Some scientists think that the sperm whale uses sonar not just to echolocate but to stun prey. When hunting, the sperm whale produces one of the loudest sounds in the animal kingdom. Forget your ideas about the humpback whale's entrancing songs or the dolphin's winning whistles: the sperm whale's ultrasonic clicks are "about as loud as a rifle shot three feet from your ear," according to Danish biologist Magnus Wahlberg. It's no wonder that Yankee whalers, listening from the surface to the sperm whale's hammering-nails-into-boards rhapsody, dubbed the species the "carpenter fish."
A Sea Change
But with its incredible ecological success, is the species out of hot water? Although sperm whale numbers have rebounded, its recovery is not yet ensured.
That's a concern for all of us, since these marine mammals play a key role in the gulf ecosystem. "Sperm whales are apex predators," says Biggs. "They help regulate species diversity and richness. In terrestrial environments, predators like wolves are important in keeping levels of carnivores in the middle of the system stabilized. That's as true in the ocean as it is on land. If there were no sperm whales, the system could be thrown off balance."
The latest research has implications for managing the species' recovery. The Sperm Whale Seismic Study provides the first definitive proof that sperm whales in the gulf — at least the females and juveniles that make up the resident population — are a genetically distinct stock. Researchers gathered three types of evidence — photographs of gulf whales' tail flukes (which are as distinctive as fingerprints), mitochondrial DNA from skin samples and recordings of vocalizations — and compared them with those of their brethren in other oceans. "None of the gulf whales match any sperm whales in the Mediterranean, the western North Atlantic, or the North Sea," says Biggs. When the researchers studied recordings of the whales' vocalizations using pattern recognition software, they also found that gulf whales have a distinct dialect ("Hi, y'all" is no doubt part of their vocal repertoire). "We recommended to the National Marine Fisheries, the agency that is tasked with managing endangered species, that it regard the gulf stock as a separate population for conservation purposes," says Biggs.
In the struggle against manmade odds, the sperm whale enjoys several factors in its favor. A worldwide whaling ban protects it from direct mortality by humans, its biggest enemy. It doesn't compete with humans for territory, so habitat encroachment is not an imminent threat, as it is for many other endangered species. It doesn't even compete seriously for food, since its favorite seafood — deepwater squid — is one of the few types of seafood that humans don't have much of a taste for. And because the sperm whale spends so much time in deep water, it may be less vulnerable to ship strikes and entanglement in fishing gear than other species of whales and dolphins.
But the sperm whale's reliance on sound to navigate, find food and communicate makes it particularly vulnerable to a more insidious threat: underwater noise. Its ocean home has become 10 times noisier in the past 40 years, according to a recent study by researchers at the Scripps Institution of Oceanography. Some 30,000 loud large ships ply the world's oceans, creating an unprecedented level of background noise. The U.S. Navy's mid- and low-frequency active sonar blasts sound underwater as it listens for enemy submarines in coastal waters. Since 2000, several incidents of whale strandings have occurred after Navy sonar operations around the world. In one case, several stranded whales showed evidence of the bends, which may have been caused by precipitous diving to avoid noise.
In the gulf, ironically the biggest threat may come from the same industry that once helped save the species from the brink of extinction: oil and gas production. Decades before the whaling ban, the introduction of kerosene oil in the 1850s had the immediate effect of reducing pressure on whale stocks by reducing demand for whale oil. But today oil and gas production is moving farther into the deeper waters of the gulf, where the sperm whale lives. "Over 70 percent of the oil and natural gas deposits extracted from U.S. waters come from the northern Gulf of Mexico, where there are nearly 4,000 oil and gas related platforms with about 500 in waters deeper than 200 meters," wrote Mullin and Gregory L. Fulling in a 2004 article in Marine Mammal Science.
The noisiest part of oil and gas operations is the seismic surveys conducted to search the ocean floor for mineral deposits. Survey ships drag arrays of airguns, which emit pulsing blasts that are louder than a jackhammer. According to the Acoustic Ecology Institute, "Each survey (there have often been a hundred a year in the Gulf of Mexico) lasts anywhere between a few days and a few weeks … [T]he survey ship travels in a grid of parallel tracks, firing the guns every 10 – 60 seconds."
For years the oil and gas industry has partnered with federal agencies to support scientific studies on the effects of manmade noise on whales, in compliance with the Endangered Species Act and marine mammal protection legislation. The Minerals Management Service, in cooperation with five oil and gas companies, funded the fieldwork for the Sperm Whale Seismic Study. During the cooperative study — which brought together scientists from Texas A&M University, the Woods Hole Oceanographic Institution, Oregon State University and other sperm whale experts — researchers used an oceanographic research vessel working in tandem with a commercial seismic vessel to gather information about gulf sperm whale behavior and noise avoidance. They tagged 41 sperm whales with depth-profiling and acoustic recording digital tags and 57 other whales with location-reporting satellite-monitored radio tags to gauge short- and long-term behavioral response to seismic exploration. According to researchers, none of the tagged sperm whales avoided the approach of the seismic vessel, although some slowed their feeding activities.
But the cacophony of human sounds invading the sperm whale's world is still a grave cause for concern. According to the National Marine Fisheries' draft recovery plan, "Sound transmissions in the marine environment may impact sperm whales by causing damage to body tissue or gross damage to the ears, causing a permanent threshold shift or a temporary threshold shift. … If the noise is chronic, individuals may have an increased vulnerability to disease or increased potential for negative cumulative effects, such as chemical pollution combined with noise-induced stress … It is important to recognize the difficulty of measuring behavioral or stress responses in free-ranging whales. The cumulative effects of habitat degradation are difficult to define and almost impossible to evaluate."
As the searing summer heat attracts humans to the surf, a juvenile male sperm whale will lift his huge tail fluke, plunge to the depths and leave the Gulf of Mexico for the first time. If all goes well, he will spend his life swimming the world's seas. By the end of his long life of 60 to 80 years, he will have circled the globe many times and produced as many as 60 offspring. Will that be enough to help his species fully recover from the brink of extinction? That, like so much else about the sperm whale, remains a mystery.
The Biggest, Loudest Texan
If everything's bigger in Texas, then perhaps the uncelebrated sperm whale deserves recognition as the biggest Texan. But it's not just size in which the sperm whale excels. The biggest creature in the Gulf of Mexico also:
- Has the biggest brain of any creature on earth.
- Is one of the deepest divers (only beaked whales and elephant seals dive deeper).
- Makes one of the loudest sounds of any animal.
Prized by Yankee whalers for their abundant oil, particularly the high-quality spermaceti oil they carry in their huge heads, sperm whales were pursued to the ends of the earth in the 19th century. "By the 1860s the open-boat whaling industry had probably reduced most sperm whale populations to less than 25 percent of their pre-exploitation size," slaughtering an estimated 700,000 sperm whales, according to Whales, Dolphins, and Porpoises. Although Yankee whalers from places like Nantucket and New Bedford were better known for their exploits in the northern seas, they also operated more than 50 kill sites in the Gulf of Mexico. Later, in the 20th century, modern factory ship whaling operations killed another 600,000 sperm whales. Finally, after more than a century of hand wringing about the fate of the great whales, whaling was banned worldwide in the 1980s — although the Japanese still kill a few sperm whales each year "for scientific purposes." — Elaine Robbins
More Unusual and Elusive Gulf Visitors
By Wendee Holtcamp
The world's largest living fish, whale sharks roam the world's temperate and tropical oceans, including some parts of the Gulf of Mexico. The distinctively spotted sharks grow up to 60 feet long with a gaping mouth that opens up to 5 feet wide. They open it wide and suck up algae, plankton and krill, more technically known as filter feeding. "Whale sharks are fairly regular visitors at the Flower Garden Banks National Marine Sanctuary each year," says the sanctuary's Education Specialist Kelly Drinnen, "most often during the months of July, August and September." Sanctuary biologists are engaged in a study to identify individuals by their spot patterns and are using acoustic receivers to determine how often they visit each of the three banks of the Flower Garden Sanctuary. Divers can safely swim with giant and awe-inspiring whale sharks.
These clear roundish Australian natives recently were introduced into the Gulf of Mexico, probably by traveling in a ship's ballast. Their sting is not dangerous to humans, but the non-natives may wreak havoc on the delicate Gulf of Mexico marine ecosystem. Not only do they muck up commercial trawl nets, the jellyfish also have voracious appetites for eggs and larvae of fish and shrimp and other commercially important species. When a species gets introduced into a non-native habitat, they often lack predators and competitors, and their populations can grow unchecked. In Australia, these jellyfish grow only to the size of a baseball, but in the Gulf of Mexico they grow to the size of a dinner plate! And in the Gulf of Mexico, their population is rapidly expanding.
Right whales do not normally visit the Gulf of Mexico, but in December 2005, a tanker pilot spotted a North Atlantic right whale and her calf in Corpus Christi Bay — the westernmost sighting in history. Fewer than 400 of these critically endangered marine mammals remain, with their primary habitat off North America's eastern shore. Scientists have a photographic catalog of right whales, from which they use skin patterns on each whale's head and scars to fingerprint individuals. Scientists identified this 11-year-old first-time mother as "Boomerang," and scientists spotted it the following summer in feeding grounds in the Bay of Fundy, off Nova Scotia. Turns out, in 2004 another right whale with a calf had been spotted in the Gulf of Mexico, the first two sightings here since a 1972 stranding in Freeport.
Scientists recently discovered a colorful new species of fish at the Flower Garden Banks National Marine Sanctuary. The 2- to 4-inch fish flit about coral reefs, and typical of wrasses, they have two distinct color phases. Males and females alike start life with a reddish color and a white stripe down their side. When they grow large enough, they undergo a change as remarkable as Clark Kent changing into Superman. If they're male they transmogrify into a brilliant purple, yellow and blue-green. And females transform into males and take on the same brilliant colors. First seen in 1997, it took a decade before biologists catalogued and published the new species account in 2007.
Regularly found in the warmer nearshore areas around the Florida panhandle, endangered Florida manatees rarely stray into Texas waters. But in 2007, the Texas Marine Mammal Stranding Network responded to calls of a manatee in the Corpus Christi Ship Channel, where he'd been attracted to the warm water outflow from a refinery. The network transported "Tex" to Lowry Park in Florida, where biologists are rehabilitating the vegetation-munching marine mammal, with hopes to release him back into the wild.
One of the world's smallest whales, this dolphin-sized species ranges in warm marine waters throughout the world. The Japanese call them "floating whales" because they rise slowly and stay at the surface for long periods of time, rather than rising quickly and blowing air like most whales. Their large, melon-shaped heads contain a spermaceti organ that whalers once harvested from their cousins, giant sperm whales. The spermaceti contains oil that was sold for use in candles and cosmetics. Scientists don't know the purpose of the organ, although recent studies suggest the spermaceti gives sperm whale males extra padding in head-butting contests to win females. Scientists know virtually nothing about the species in the wild or their population status in the Gulf of Mexico or worldwide, other than a few strandings that have occurred. In 2005, a pygmy sperm whale and her calf stranded alive on the Bolivar peninsula. Rescuers pushed both back into the water; the mother disappeared, but the calf stranded again.
False Killer Whale
One of the largest members of the dolphin family, false killer whales grow about four times the size of a bottlenose dolphin. Like their killer whale (orca) relatives, they also attack and kill other cetaceans, but unlike the striking black-and-white coloration of orcas, false killer whales are all gray. They range throughout the world's warm temperate and tropical oceans in pods of 10 to 50 animals. Much of their natural history remains unknown. One false killer whale stranded in Texas in 1996 and another in Alabama in 1999. Around 1,000 live in the Gulf of Mexico, according to the National Oceanic and Atmospheric Administration. They are not considered endangered, but are protected under the Marine Mammal Protection Act.