Originally broadcast on July 19, 2006.
(check local listings for repeat airings)

Once hunted to the brink of extinction, the gray whale has made an amazing comeback in the last 80 years. But in 1999 and 2000, these unique creatures, which live along the West Coast of North America, began to mysteriously disappear by the thousands. Their population dropped by one-third.

Gray whale calves depart on their northbound journey later than the mature whales to give them ample time to accumulate as much insulating blubber as possible. (Photo credit: Matt Ferraro) Click to enlarge

Gray whales have the longest migration route of any mammal -- 8,500 to 12,000 miles -- and during their journey they pass some of the world's biggest cities, along some of the most polluted coastlines. In The Gray Whale Obstacle Course, Jean-Michel Cousteau and the Ocean Adventures team travel the length of this migration, from the warm waters of Magdalena Bay in Baja California, Mexico, where the gray whales give birth, nurse their calves, rest and play before their long journey north, to the nutrient-rich feeding grounds of the Bering Sea in Alaska. The team searches for clues about this resilient, yet threatened species to gain a better understanding of the increasing challenges, both natural and man-made, that gray whales face along the way.

The journey of Jean-Michel and his team begins with a visit to the gray whales' Arctic feeding grounds. The area is huge -- about the size of Maryland and Delaware combined. In the summer months, the region experiences nearly 24 hours of sunlight, which fuels an explosion of tiny plant and animal growth. When the whales arrive here, they feast. They haven't eaten for seven months, and they are far thinner than when they left these feeding grounds. Here, on a dive in the frigid waters, the Cousteau team collects mud from the ocean floor to find amphipods, the tiny creatures that are the staple of the gray whale's diet.

After stocking up on tiny amphipods during the summer months, gray whales lose up to one third of their total body mass over the duration of the migration. Click to enlarge

Forty-five feet long and weighing 30 to 40 tons, gray whales eat one ton of amphipods a day. In fact, over the approximately five months that the gray whales spend in the Alaskan waters, each whale eats about 396,000 pounds of amphipods. Instead of teeth, gray whales have long, thin plates of baleen that hang from their upper jaw. Baleen is made of keratin, the same material that makes up human fingernails. To feed, the whales take in large mouthfuls of water, then use their tongue to squeeze the water out through the closely layered plates of baleen, which act like filters. The amphipods get stuck in the baleen, and the whales use their tongue to lick off the tiny critters.

At this Arctic feeding ground, the Cousteau team wonders: Could the decline of the whales be linked to their food source? Or is it perhaps connected to other obstacles they face along their migration path? To explore these questions, the team meets the whales at the southern point of their journey, in Baja California, Mexico, and travels with them northward to observe, document and understand the hurdles these creatures must overcome each year.

In the 1880s and again in the early 1900s, whalers in Mexico hunted the gray whale almost to extinction. Then in the 1930s, the whales were protected, and in the 1970s, they were listed as an endangered species. Early whalers referred to the gray whale as the "devilfish" because of its reputation for fighting back and overturning boats when attacked. Ironically, today gray whales are the friendliest of all whales. In the safety of Baja's protected San Ignacio Lagoon, gray whales have been regularly approaching people since 1972.

Despite its reputation for overturning the boats of early whalers, today gray whales are the friendliest of all whales. Click to enlarge

Don Santee, the Ocean Adventures expedition leader, leans over the side of a small boat and playfully pats a friendly gray whale that has approached the vessel. The whale rolls to the side as if to take a good long look at Don with one of its large eyes.

"They were right there with us. They didn't mind us at all," says Santee later. "The baby was just playing, just laying there playing."

Once the whales begin to head north, they travel up to 80 miles a day, periodically surfacing to breathe. Females give birth every other year, and they and their calves are the last to leave the safety of the lagoons as they wait for the calves to gain strength. Nursing on milk that is 50 percent fat, the calves will double their weight by the time they reach the Arctic.

To track the whales on this journey, the Cousteau team welcomes satellite tracking expert Dr. Jeff Goodyear, of H.A.B.I.T. Research, and marine scientist Dr. Jorge Urban, of the Universidad de Baja Sur. Jeff has designed a harmless transmitter to track the whales. The transmitters are attached to whales with a harpoon-like device that penetrates only the whales' skin and upper blubber layer, without causing injury. When a whale carrying a transmitter surfaces, the transmitter sends a signal that allows satellites to determine the latitude and longitude of the whale. The tags are challenging to attach -- and how long they will stay in place is unpredictable -- but the team manages to attach a transmitter to four whales. The four tagged whales almost immediately begin moving north. Within days, however, all the tags have stopped transmitting. The team must begin tracking the whales "the hard way," by connecting with experts, waiting and watching.

Along the California coast, the team meets experts who watch for the whales on their migration. First up are volunteers from the American Cetacean Society's Gray Whale Census and Behavior Project. From December 1 to about May 15, they observe the whales from atop the cliffs of Palos Verdes. The volunteers share data with the National Marine Fisheries Service to determine the most accurate count of migrating whales each season. In addition to the number of whales, the volunteers pay attention to changes in the timing of migration, which could reflect a problem and also indicates how many calves are surviving.

The whales are counted again at Piedras Blancas, south of Big Sur, a place where the cows and calves come very close to shore and site of the official National Marine Fisheries Service census.

Killer whales carefully coordinate their attacks on gray whales. One strategy includes separating the mother gray from her calf so that she can no longer protect it. Click to enlarge

In Monterey Bay, the migrating whales reach their most formidable obstacle -- the bay itself and the Monterey Bay submarine canyon. Plunging to depths greater than 10,000 feet, over two miles, the canyon is home to a spectacular diversity of marine life -- including aggressive predators like orcas (also called killer whales), which patrol the depths, listening for the migrating gray whales. Before they reach Monterey Bay, the gray whales hug the shoreline, but when they get here, the less experienced whales opt to cross the 25-mile-wide bay, leaving the security of the shore, making them more vulnerable to attack. Gray whales are an important seasonal food source for killer whales here. One calf can feed up to 30 killer whales, serving as an important supplement to the orcas' more regular diet of sea lions and other smaller mammals.

Jean-Michel and his team are joined by killer whale expert and biologist Nancy Black. As the team cruises the bay, they spot a pod of killer whales attacking a gray mother and her calf, an event rarely witnessed even by researchers. It is a life or death fight for the calf as its mother tries to defend it. The team witnesses the struggle, and soon, the water turns red with blood. Despite her best efforts, the exhausted mother is unable to save her calf.

Continuing to follow the whales north, the team makes a short stop in Depoe Bay, Oregon, to visit Carrie Newell, a biologist who is changing what we thought we knew about gray whales. Apparently, not all gray whales travel all the way to the Bering Sea for the summer. For some, the journey ends here, in this protected bay. Jean-Michel and his daughter Celine investigate this concept of "resident" whales.

Over the last several years, Carrie has documented 56 whales that return to Depoe Bay year after year. She hypothesizes that the bay provides the whales with an ample food source -- mysid shrimp -- and protection, so they stay here instead of continuing north. Stopping here cuts their migration in half. Confirmed resident populations also exist in other places along the migration route between northern California and British Columbia. But out of the total gray whale population of between 17,000 and 26,000, the resident populations make up just a tiny fraction.

These resident whales may be on to something, though. Studies show they had a 95 percent survival rate during 1999 and 2000, far higher than the rate for most gray whales, which was about 66 percent. However, although their survival rate is higher than average, resident whales face their own obstacles. One of these could be the legal battle the Makah tribe of Native Americans in Washington State are waging to enact treaty rights from 1855 allowing them to hunt whales. The Makah want to hunt just a few whales each year as a way to keep their ancient heritage and traditions alive. But scientists feel that even this small number of kills could have a significant impact on the small resident population of only about 200. In 2002, a federal appeals court suspended whale hunting until its impact could be better understood.

Jean-Michel's team leaves Depoe Bay and heads north, where they encounter an increasingly dangerous, invisible obstacle: noise. It's only recently that scientists have begun examining the impact that noise generated by humans has on whales and other marine mammals. Activities such as underwater explosives, military sonar, commercial shipping, intrusive scientific research, and oil exploration and development make the ocean a very noisy place. High-intensity military sonar, in particular, is known to have the potential to interfere with marine mammal behaviors and cause strandings, injuries and even death. Jean-Michel talks with experts about how the noise problem is increasing.

Finally, the journey reaches its end point in the Gulf of Alaska, where the famished whales feast on the rich food supply. Jean-Michel visits Barrow, Alaska, the northernmost community in North America, where residents such as Billy Itta tell Jean-Michel about the dramatic environmental changes they have experienced. Because of global warming, the ice pack is breaking up sooner than it used to and is retreating farther than it has in the past. In fact, the rapidly retreating ice pack recently stranded more than 80 polar bears near Barrow for several months. Where there once was ice year-round, there now is ice only a few months a year.

Over the last three decades, global warming has contributed to the loss of 30 percent of the gray whale's main food source in Alaska's Bering Sea. (Photo credit: Matt Ferraro) Click to enlarge

There is great concern among marine mammal scientists about climate change because creatures such as gray whales are so vulnerable to changes in their environment. Warmer ocean temperatures mean less food for gray whales. Because one-third of the gray whale population was lost in 1999 and 2000, many due to starvation, scientists postulate that global warming could have dramatic, lasting effects on the gray whale population. Scientists have photographed and identified more than 6,000 migrating whales, observing them on their both their northbound and their southbound trips and recording their sizes. In 1999 and 2000, the years of plummeting gray whale numbers, the scientists observed that the whales were much thinner than they were in good years. That told the scientists that the population decline was likely related to nutrition.

In tracing the migration route of the gray whales up the California coast, Jean-Michel and his team encountered numerous obstacles that these gentle creatures face. From killer whale attacks to noise pollution to global warming and a reduced food source, the hazards faced by gray whales are increasing. And these magnificent creatures are still not fully understood. Scientists have many ideas, but more research and study is needed to find the best ways to protect them.

"Our goal is to get more people aware about the work being put forward and have decision makers making better decisions and to have public awareness put more pressure to support science," says Jean-Michel, who would like to see more money and effort go into studying and protecting these animals. "That way, we can ultimately pass on to the next generation something that is as good as -- if not better than -- how we found it."