If Jonah had turned his head to look back just before being engulfed by the great fish, he might have witnessed a truly remarkable sight. A sight that would have astonished even modern-day biologist Alex Werth, who dedicates his efforts to studying the intricate feeding mechanisms of whales, despite his distant vantage point from the open sea. “Oh, to experience what Jonah did, observing the magnificent baleen in action, seated on the very tongue of a whale,” he muses.
Baleen, the remarkable filtering apparatus that toothless whales employ to sift food from the ocean, is a complex and fascinating structure. Comprising hundreds of flexible plates made from the structural protein keratin, these plates hang downward from a whale’s upper jaw, resembling the slats of Venetian blinds. Baleen whales, or mysticetes as they’re collectively known, evolved this feeding structure around 30 million years ago as a response to the competition for limited food among toothed whales. As they developed a taste and technique for capturing different kinds of prey, they eventually diverged into various species, including the majestic blue whale – the largest animal to have ever lived – along with humpbacks, grays, and right whales. Before the intensive pursuit by American commercial whalers around 200 years ago, these passive feeders, ingesting marine animals in massive quantities, flourished.
Werth’s lab at Hampden-Sydney College in Virginia, where he investigates baleen hydro-mechanics, emanates the essence of whales. Baleen is everywhere: long, dried-out plates line shelves, while a collection of tall, narrow plates wrapped in plastic leans in a corner. Fresh baleen, weighing 160 kilograms, has just arrived from collaborators in Alaska, stored in tightly sealed barrels in the hall.
Baleen reveals its structure as it ages, much like fingernails splitting. Curved plates consist of two flat keratin layers with rows of tubules, resembling miniature coils of tightly rolled luncheon meat, sandwiched between them. The constant abrasion from the whale’s massive tongue and its prey gradually releases a fringed structure along the edges. This roughness and the number, shape, and size of baleen plates vary by species, and it’s this “hairy” feature that separates food from the seawater in each mouthful.
While filter-feeding provided an evolutionary advantage millions of years ago, the oceans are rapidly changing today, particularly in regions once heavily covered in sea ice. Werth highlights that this transformation “could have dire effects on even the most adaptive marine animals.”
The bowhead whale, an inhabitant of the frigid Arctic waters, exemplifies the impact of these environmental changes. With its distinctive black exterior and white “soul patch,” this whale is currently navigating a changing habitat. Melting ice is causing shifts in ship traffic, seismic exploration, oil and gas development, and fishing in the Arctic. For marine mammals like the bowhead, these changes translate into increased risks of ship strikes, net entanglements, and elevated noise levels. “Are they stressed out? Is human activity affecting their reproduction?” Hunt questions, as these issues remain unknown.
Kathleen Hunt, like Werth, capitalizes on baleen as a valuable source of data. Her primary goal is to comprehend how bowhead whales are coping with the mounting human impact on their environment. As traditional methods of sampling whales are challenging, Hunt turned to baleen for answers. Unlike tranquilizing or capturing whales, which prove nearly impossible, hair, hooves, horns, and nails – all keratin-based vertebrate structures – store vital information, including endocrine data.
Surprisingly, baleen holds similar information, extractable from drilled-out and pulverized samples. As the plates grow throughout a whale’s life, they chronicle hormonal signals from adrenal glands, gonads, and the thyroid. “We can get data not just from the new part [of the baleen], but from the bit that’s been underwater for a dozen or more years,” Hunt explains. Eroding at one end while growing at the other, each plate represents a slice of a lifetime, encompassing up to 15 years’ worth of information.
Hunt’s insights into whale reproduction stem from studying baleen extracted from two female North Atlantic right whales – Stumpy and Staccato – that have been observed off New England since the 1970s. Their life histories, including calving successes, were well-documented, enabling Hunt to establish a timeline for each whale up until its demise (both were victims of ship strikes, one of them pregnant at the time). By matching extracted hormone data with the whales’ life experiences, considering their approximate growth rate, Hunt discovered significant correlations.
“Reproductive phenomena such as estrus cycles and age of sexual maturity, pregnancy rates – these are really a black box for researchers,” Hunt explains. With baleen, there’s potential to unravel these mysteries. Patterns in hormones like progesterone, notably elevated during pregnancy, coupled with fluctuations in stress hormone cortisol, became evident. Additionally, thyroid hormones could reveal signs of starvation or stress. Such information, combined with environmental data like sea temperatures, opens new doors for understanding complex questions, like why females breed in one area but not another.
Further, identifying connections between changes in stress hormones and reproductive success could significantly impact policymaking. Moreover, in the broader context of climate change, a burning question looms – the effects on whales. As prey patterns shift due to rising ocean temperatures, researchers may discern nutritional stress in whales through thyroid and other data. The untapped potential of baleen data offers a unique opportunity to decode whales’ responses to a changing world, guiding conservation efforts and potentially unlocking the mysteries of their lives in unprecedented ways.
