A Springtime Story: Love Among Leviathans
Ankle-deep in a sea of blue-eyed grass and poppies, from atop the promontory the watchers peered through binoculars downward, at the dark blue Pacific. Below, just beyond the breakers, a group of gray whales churned up a boil as they milled and rolled, splashing and lurching in a confused tangle, sinking, surfacing and regrouping. Migrating, or mating? But, this isn’t Baja – right?
Greater Farallones National Marine Sanctuary is notable for its over 30 species of whale, dolphin and porpoise – known collectively as cetaceans. It’s key to the recovery and stability of these populations. Most of our “great whale” species – blue whales, fins, some humpbacks and others - are still endangered. With the cessation of whaling and other legal protections they have begun to rebound. Some feed here; others breed here as well. These rich waters are critical to the future of many magnificent animals, but food alone will only ensure the survival of one generation. It’s sex that propels all of us forward into the future.
THE BIRDS AND THE BEES: Successful conservation requires that we learn everything possible about cetacean life history: population structure, behaviors, geographic distribution, foraging, and reproduction -- even their most intimate habits. By learning how they procreate we can understand why some have been more successful than others at escaping near-extinction. We can assess how tightly sustainability is linked to reproductive patterns and behaviors. And we can help identify and measure current and emerging threats such as ocean noise and pollution.
THE DATING/MATING GAME. The prize: The winner passes on her or his DNA. Males often get the first move. There are rules; there is competition, though some males work as a team. They need a strategy, and a female, maybe several. But before boy meets girl, he must find her.
LOVE SONGS: Some whales, like grays, are promiscuous, and congregate in lagoons where they can find each other easily. Fern bar, Party City. But not all lagoon liaisons are successful, and some breeding occurs at sea during migration, where the whales must vocalize to solicit potential mates. The ocean is naturally noisy, with sounds of wind and waves, dolphin clicks and whistles, fish grunts, sea lion barks, even landslides. Whales have evolved with those noises, and they adapt. But anthropogenic noises from ships, seafloor mining, seismic surveys or drilling, may frustrate whale couplings by masking their calls. Pollution can obscure or overwhelm the alluring scent of a receptive female.
Gray whale mating groups range from three, up to 20, but triads are common. Males evaluate a female’s status by rubbing and stroking her. Males may support each other, or nudge her into position, belly to belly. She may demur for days, while she tests her suitors’ worthiness. It’s to her and her offspring’s advantage that she be selective, and mate with the strongest, boldest, most dominant. And she couples with more than one. Gray whales are not known to be combative, unlike other species like blue or sperm whale bulls, known to battle fiercely over mating rights.
NURSERY TALES: Cetacean love is about maternity, too. While whale paternity is limited to donating DNA, whale motherhood is a time and energy-intensive undertaking. Grays are pregnant just over a year, and nurse for a further year or so, producing 55% fat-rich milk. Whale moms also call to their young, to reinforce their bond, and to find them when they stray. If noises drown her out and they are not reunited, the calf may not survive.
Happily, gray and most other whales are recovering here. Greater Farallones and Cordell Bank national marine sanctuaries are working to conserve whales and other marine life. Through vessel impact studies, creation of a soundscape of natural and human-generated noises in our region, and other efforts, we are learning what whales need to survive here. We can determine how to mitigate human impacts by understanding how threats affect reproduction, and direct and prioritize our efforts accordingly.