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The Hunter's Breath: On Expedition with the Weddell Seals of the Antartic

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_The Hunter's Breath_ by Terrie M. Williams is an engaging account of six field seasons the author and seven colleague spent studying the Weddell seal of the Antarctic, where they spent 10 weeks at a time in a camp on the sea ice of McMurdo Sound, off the western coast of Ross Island, situated near openings in the ice where seals could haul out and sun themselves (and in particular pregnant seals could give birth, and raise their pups).

For years scientists had been frustrated in studying the Weddell seal, in particular observing how they feed and behave beneath the ice. The seals operated under many meters of ice, in very deep and very cold waters that were inaccessible to human divers and even submersible robotic probes. In 1997 miniaturized video technology finally caught up with the dreams of Dr. Williams and other researchers. Williams and her colleagues invented a device called a VDAP or Video Data Acquisition Platform, a waterproof device able to withstand tremendous pressure that could house a Sony 8mm video camera connected to a microcomputer. Also connected to the computer were an array of sensors, including devices to measure dive depth, swimming speed, compass bearings, heart rate, water temperature, a hydrophone to record sounds heard and emitted by the seal (seals are very vocal underwater), and a tiny acceleratometer mounted near the seal's tail to record the swing of every flipper stroke. Attached to the seal on a neoprene pad, the devices performed brilliantly.

The device invented, the team selected with great care a suitable study area and camp site. They wanted to find an area containing cracks large enough to allow the seals to breathe and haul out but not so thin or fractured as to be unable to support the weight of the camp.

The team went to great efforts to counter the various dangers posed by Antarctic research, notably frostbite, hypothermia, dehydration, and the sometimes fierce weather. They contended with temperatures as low as -70 degrees Fahrenheit and hurricane-force blizzards called herbies, monstrous storms with driving grit-like ice blown in from the continent in winds between 60 and 75 miles per hour. After three back-to-back herbies and then an actual snowfall the camp site had so much snow that the ice started to bend and the camp started to sink; quick work was required to save the facility.

Their efforts were well worth it, as they accumulated many dozens of hours of footage of seals beneath the ice, mountains of data, and enough results for a slew of scientific papers. You can see some video stills (along with many of the test subject seals, such Ally McSeal, their first test subject seal, Godzilla, the only male they used, and Ms. Zodiac, a lazy seal that spent so much time on the ice sunning herself that they eventually removed her equipment) in beautiful photographs in the book.

Although the trials and tribulations of the researchers were interesting the seals were the stars of the book. A mild-mannered species of phocid seal, Weddell seals are the only year-around mammalian resident on the permanent ice shelf in Antarctica. They survive colder temperatures, dive deeper, and live further south than Antarctica's three other seal species (Ross, Leopard, and crabeater). They are usually nine feet or more in length and average about three and a half feet in width in the middle. Colors range from bluish-black to soft gray and they have whitish spots that are particularly prominent on their upturned bellies when they sun themselves (originally they were called sea leopards). They were first mentioned by Captain James Weddell in a book recounting his Antarctic explorations from 1822-1824 and formally scientifically described a few years later. Though apparently not seriously hunted by sealers, some were killed by Antarctic explorers to provide blubber to burn for heat and to melt snow and ice for drinking water (explorers as a result often appeared dirty in photographs thanks to the oily soot of Weddell blubber) and to feed sled dogs.

Weddell seals are champion divers; only sperm whales and elephant seals can perform as well or better. She compared the dives of these seals to a person running a 10K race on a single breath of air. They can travel up to four miles under solid ice on one breath, can stay submerged up to 82 minutes (a typical dive is 20 minutes), and dive to depths of 1,312 feet.

The seals have huge eyes to enable them to see in the depths, eyes two and a half times the size of a human's, almost the size of a tennis ball. This, along with their keen hearing and whiskers enable to them be excellent hunters of giant Antarctic cod, schools of flittering Antarctic silverfish, and fish dubbed "borks" (_Pagothenia borchgrevinki_), which live just beneath the ice in 27 degree Fahrenheit water.

Every year the seals make an annual trek under miles of solid sea ice to ice cracks in McMurdo Sound to find mates and raise pups, as cracks always open in the ice in certain areas thanks to tidal stresses and ocean currents. Simply getting there is a tremendous feat, requiring unerring navigation and careful calculations of how far they can get on a breath of air; to make a mistake would mean drowning. They make use of every single hole, weak spot, or air pocket they can find to get a breath along the way, covering a distance of 80 miles from the open sea to their final destination (30 miles more than normal thanks to the giant iceberg B-15, 170 mile long and 1000 feet thick iceberg that completely disrupted the annual cycle of sea ice formation, breakup, and dispersal). In addition, their anatomy is adapted to enlarging even the smallest hole in the ice; their large, reinforced canine teeth stick out from their skulls, giving them a bucktooth-appearance but enabling the seals to scrape ice from the sides of holes in a behavior termed reaming.

Dr. Terrie Williams has written an enchanting book about her research and her enthusiasm for the natural world---a world few of us have the chance to experience. The book blends the rigor of her scientific approach with a fine-tuned talent for story telling. If this book were an eye into the harsh world of the Antarctic it would have a twinkle in it.