Harbor Porpoises' Remarkable Return
After a 65-year absence, these cetaceans are back in San Francisco Bay, providing scientists a unique view into their lives
- Anne Bolen
- Jan 27, 2014
ON A BLUSTERY CALIFORNIA AUGUST DAY, researchers are studying some of San Francisco’s least-known residents from an unlikely laboratory: the Golden Gate Bridge. Below in the bay glides a parade of boats—fishing vessels, a tall ship, a slow container barge packed with colorful boxes like giant Legos. Behind the scientists, tourists pause to snap pictures, unaware of the ongoing hunt. Through binoculars, Bill Keener suddenly spots his quarry: a harbor porpoise, its dark gray dorsal fin appearing briefly before resubmerging. Keener predicts the porpoise’s course and, just as it surfaces again, photographs the animal before it disappears. “Got it,” he declares triumphantly.
This harbor porpoise is one of more than 600 that Keener and the three other marine mammal scientists of Golden Gate Cetacean Research have recorded in the San Francisco Bay since 2008. This team, made up of Keener, Isidore Szczepaniak, Jonathan Stern (below, left to right) and Marc Webber, is compiling the world’s first photo catalog of wild harbor porpoises. “What was known about harbor porpoises until now has mainly been from dead, dying or captive animals,” says Keener. He and his colleagues have been collaborating for more than 35 years, but this is the first project on which all four have worked together, mostly on their own time and dime. “It’s an avocation rather than a vocation,” Szczepaniak says, grinning.
With financial support from the National Wildlife Federation and its donors, the researchers are taking advantage of unique circumstances that are bringing the behavior of these normally elusive animals to light. Because porpoises predictably gather in deep, turbulent waters near the Golden Gate at high tides—presumedly following small fish that school there to eat accumulated plankton—the scientists can closely observe and photograph the animals either from the bridge or a nearby shore without changing their behavior. “We are getting this wonderful, natural glimpse into their lives that no one has ever had before,” says Webber. This is remarkable given that just six years ago no porpoises were found in the bay.
Fourth-generation ferryboat Captain Maggie McDonogh never saw porpoises growing up in the Bay Area, but recalls her father describing how he heard them “snorting” in the local Tiburon harbor in the 1920s and 1930s. These puffing sounds the animals make as they surface to breathe gave them their nickname “puffing pigs.” Otherwise, they are fairly silent to us, as their high-frequency clicks that they use to echolocate prey and navigate are far above the hearing range of humans or even orcas, one of their primary predators.
Although harbor porpoises and dolphins are both cetaceans, they differ greatly. Dolphins generally have long beaks, slender bodies that can be 10 feet long and tall, curved dorsal fins. Porpoises have puglike faces, stout silhouettes about 5 feet long and short, triangle-shaped dorsal fins. Also unlike dolphins, porpoises tend to be solitary or in groups of five or fewer (below) rather than in large pods, don’t ride boat wakes and don’t leap out of the water. Therefore, their small, mostly dark, silent forms can easily go unnoticed.
About 675,000 harbor porpoises inhabit the sub-Arctic, near-shore waters of North America, Europe and Asia; the subspecies in the Black Sea and subpopulation in the Baltic Sea are endangered. The U.S. National Oceanic and Atmospheric Administration (NOAA) estimates 9,000 are in the San Francisco-Russian River coastal population. Fossilized harbor porpoise bones found in Native American shell mounds reveal they existed here at least 2,600 years before disappearing in the 1940s.
That was when the U.S. Navy stretched a 6-mile-long steel net across the mouth of the bay to thwart enemy submarines during World War II—a physical and acoustic deterrent for the cetaceans. At the war’s end in 1945, the net was removed, but by then, “The bay was a dumping ground,” says Judy Kelly, director of the San Francisco Estuary Partnership (SFEP). Its 2011 State of the Bay report says that for years the bay was so tainted by untreated residential and industrial waste that it came to be called “the Big Stench.” However, NWF, Save the Bay and other organizations fought for passage of the 1972 U.S. Clean Water Act and state legislation that led to upgrades in wastewater and solid waste treatment. About 35,000 acres of the Bay Area’s tidal wetlands, which help filter pollutants, also have been restored or enhanced.
But in the 1980s, commercial fishermen’s gill nets were accidentally trapping and killing as many as 300 porpoises annually along the coast. By 2002, the California Department of Fish and Wildlife banned the use of such nets in the central part of the state at depths less than 360 feet, where harbor porpoises tend to swim. In the past few years, the region also has experienced a boon in some of the small, pelagic fish such as anchovies and herring that the animals prey on. The bay once again became more inviting for porpoises.
Funnel of Love, War?
Unlike harbor porpoises that migrate along the Atlantic Coast, Pacific porpoises tend to stay within nine distinct regions from California to Alaska. What else the researchers learn about the bay’s porpoises could help Pacific wildlife managers. For example, wild harbor porpoises live on average less than 12 years and take up to four years to reach sexual maturity. While Atlantic females are known to give birth to one calf every year, learning how often Pacific females have calves is important, says Keener, “because if there is a disaster like an oil spill or a disease sweeps through, conservation managers need to know how fast these animals can bounce back and what kinds of things we can do to help protect them.”
The bay itself could be a factor in how the porpoises behave. Because they must enter and leave the bay through the Golden Gate, this funneling effect gives the porpoises here 100 times more opportunity to mate than in the ocean. As Keener says, “The bay might be the best dating scene going for California’s porpoises.”
This concentration of activity also has been good for the scientists. Szczepaniak says, “I can get more photos of harbor porpoises in one day off the Golden Gate Bridge than I did in 30 years of studying them elsewhere [from boats].” The colleagues are the first to photograph wild porpoises’ “hit-and-run” approach to mating, as Stern calls it. Males, which have testes up to 4 percent of their body weight, “rush at the females again and again until they connect and try to push as much sperm into them as they can,” Keener explains. “Then it’s all over in a few seconds.” The males end with a splash, sometimes leaping fully out of the water (below).
This lively love nest, however, can also be a war zone. The researchers can catalog and follow individual porpoises through time because, in addition to natural skin patterns, many display identifying scars. These grim visual fingerprints could be evidence of encounters with fishing gear, boats or other objects.
But bottlenose dolphins also can inflict severe injuries to porpoises, and several episodes of “porpicide” have been documented. Since the early 1980s, California bottlenose dolphins have expanded their range north, reaching the bay by 2009. NOAA’s Marine Mammal Stranding Network reports that about a fifth of the 495 harbor porpoises that stranded along the central California coast between 1998 and 2010 died from trauma-related injuries, 54 from dolphin attacks and 22 from human interactions, such as net entanglement.
The Marine Mammal Center in Sausalito reports that 10 of 25 harbor porpoises its staff examined in 2013 died from dolphin-inflicted injuries but none from boats. Frances Gulland, the center’s lead scientist, says she can distinguish these injuries: “Boat props leave a characteristic clear cut,” she explains. Those animals “have really severe lacerations on their backs or heads.” Whereas, she says, “Broken ribs and hemorrhages are consequences of being beaten up from bottlenose dolphins. Others have rake marks [from the dolphin’s teeth] on their skin.”
Why some dolphins, mostly young males, attack porpoises is unclear. Keener says that in California waters, they aren’t necessarily competing for the same fish. Few of the porpoises cataloged so far have scars that can be traced to boats or dolphins, so the source of these injuries also remains a mystery. “Something is going on that is not good,” says Webber. “You don’t have to be killed for such injuries to have a negative impact on your life. You could be more susceptible to disease or predation.”
Ecosystem Under Fire
San Francisco Bay is a dynamic estuary: Freshwater streams and rivers flow into marshes that border a body of water that is also fed twice daily by saline tides. The freshwater influx helps flush pollution such as the runoff and 500 million gallons of treated wastewater from the area’s 7.5 million residents each day. This freshwater also helps create brackish wetlands that serve as spawning and nursery areas for small fish and other aquatic animals.
Harbor porpoises can eat up to a tenth of their body weight in fish and squid each day, so the researchers are determining how many porpoises the bay can support, or the “flukeprint of these animals,” says Stern. “It is important to look at how these predators fare in a fluctuating ecosystem.”
California already has dammed, dredged and filled many of its rivers and wetlands and diverted a significant amount of the region’s fresh water south to thirsty cities and farmlands, reducing freshwater flow into the estuary by half. “The bay is in a state of chronic drought,” says Kelly. This increases the water’s salinity, which not only kills fish eggs and larvae but can allow some exotic species such as invasive shrimp and snails that can survive in these altered environments to overtake native life. Yet California’s governor has proposed another project to divert water to the south that some residents fear could sap more fresh water from this ecosystem.
In addition, while the bay is cleaner than it was four decades ago, trash and toxic chemicals such as flame-retardants and mercury still pollute its waters. NOAA has been able to distinguish four harbor porpoise populations along California not just from their genetics but also from pollutants in their systems: Those north of Monterey Bay contain higher levels of industrial chemicals, whereas more agricultural pesticides and fertilizer are found in those to the south. While the full impact of such pollution on harbor porpoises is not known, agricultural runoff can feed toxic algal blooms that produce domoic acid, which poisons porpoises and sea lions.
A Wave of Hope
The harbor porpoises’ return has inspired conservationists, scientists, fishermen and residents alike. “To have these charismatic megafauna coming back into the bay is really hopeful,” says Kelly. “At least something is healed,” agrees Zeke Grader, president of the Pacific Coast Federation of Fishermen’s Associations, “which is ultimately good for fishermen.” However, he stresses, “We really need to redouble our efforts to support the science so we have a better understanding of what is causing this and we are better prepared to protect these animals and the ecosystem.”
What the research team discovers also could help harbor porpoise populations elsewhere. “I can’t tell you how exciting this is to those of us who study porpoises,” says Duke University marine biologist Andy Read. “We can really gain a much richer understanding of the population biology and social behavior of these animals.”
Other behaviors the researchers are documenting include how the porpoises spin quickly to corral fish and that cormorants pursue porpoises to snag leftovers. They also have photographed one of only two known all-white Pacific harbor porpoises (right), dubbed “Mini-Moby.” Next, the team hopes to be able to buy underwater listening devices so they can map exactly where and when the porpoises swim in and out of the bay, day or night. The scientists may find that the animals have decided to once again make the estuary their permanent home.
This could be good for porpoises and people. In 2012, the state established new policies to promote science-based forage-fishing quotas, which help protect small, schooling fish. And like the sea lions on San Francisco’s Pier 39, porpoises could become one of the city’s hottest tourist attractions.
Riding on “Captain Maggie’s” sunset cruise through the bay, Keener spies a porpoise’s fin just above the waves, and he records it in his ever-present notebook. Maggie proudly announces the sighting over a loudspeaker to her passengers. “I love seeing things come back around,” she says. “I have three children that are growing up. I want them to be able to get out on the water and see the seals, the harbor porpoises and the birds—and enjoy all of it. If people don’t know about them, what has happened to them, they can’t be inspired to care.”
Watch the video of this harbor porpoise mother and calf.
NWF Partnerships: Helping Porpoises
The Federation is supporting the work of Golden Gate Cetacean Research. “This research is going to tell us so much about harbor porpoises,” NWF California Director Beth Pratt says, “including why they came back and how we can continue to make the bay a home for the many animals that live here.”
You can be a citizen scientist and contribute your sightings of San Francisco Bay porpoises to this project. To learn more and download NWF’s free harbor porpoise curriculum, go to www.sfporpoises.org.
Managing Editor Anne Bolen wrote about monk seals in the December/January 2013 issue of National Wildlife magazine.
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