Dan Crocker and his students track the life of the elephant seal
On any given day of the year, Dan Crocker, biology professor, is out at the beach—or wants to be. His trips, though, are not for the faint of heart. They generally begin in the early hours of the morning as Crocker and his undergraduate, graduate and post-doc students load up one or two vans with cases of tracking and recording devices, bottles of a powerful large-animal tranquilizer and tubes of epoxy.
The drive south is along the coast through the wintry-white fog, brisk winds, pouring rain or heat-wave temperatures to Año Nuevo State Park, a point jutting staunchly out into the Pacific Ocean just north of Santa Cruz. There, with a population of 3,000 and climbing, resides one of the smaller colonies of the northern elephant seal (Mirounga angustirostris). Even a mile away, the bellowing grunts and trumpeting of the bulls can be heard. A bit closer, the short barks of the young pups and the snort and gurgle of females fill the air. Down on the beach, the noise can sometimes be stupendous; the booms from the bulls can be felt as sub-sonic waves through the sand.
Elephant seals earn their name from their immense size and the long trunk-like proboscis of the male. Hunted extensively for their blubber in the mid-1800s, they were declared extinct by the Smithsonian Institute by the end of the century—no individuals were then known to exist. Early in the1900s, however, a small herd of about 20 to 30 seals were discovered off the coast of Mexico on the Guadalupe Islands. Mexico promptly protected the species and the population rebounded quickly. Today several colonies exist, some of them with up to 30,000 animals; worldwide their population is well over 100,000.
The team arrives at the seals’ rookery ready to get to work. Their main goals are to attach a data recorder and a satellite transmitter to likely elephant seal candidates or retrieve these devices from previously tagged seals. On a good day, depending on the circumstances, Crocker and his students can tag anywhere from one to five seals; over the past several years, they have managed to tag about 100 seals per year.
The tagging itself is a rather challenging procedure that requires engaging the attention of a specified male or female (preferably a beast at the edge of the crowd), and enticing them to move further out from the herd, where a fellow researcher tranquilizes them as quickly as possible.
This is the dangerous part of the job; these animals might look awkward in their immensity, but they can move faster than humans can over the dunes and loose sand. They really are immense: an average cow weighs from 750 to 1,000 pounds, an average bull weighs 4,000 pounds; there are reports of bulls weighing three and four tons. As Crocker is discovering, they are huge animals providing large, though inadvertent, assistance to the planet and even fellow marine mammals.
Once the elephant seal is properly and thoroughly tranquilized, the students and Crocker move in to attach the two devices, the data-logger mid-back and the satellite locator squarely on the top of the head, like a jaunty sailor cap. “The tags allow us to find out how these creatures make their living” says Crocker, “how and where they forage, what they do in the ocean.” Because they dive deep and disperse across large expanses of the Pacific, little has been known about the open ocean, or pelagic, life of these creatures. Information collected from the tags is beginning to change that.
The team paints a name on the beast near the tail to aid in identification, and takes morphometric measurements to determine the volume and age of the individual. Then, depending on which particular project they are working on, they collect samples of blood or milk. They also weigh the juveniles and females, a process generally involving tarps, ropes and a very large, very sturdy tripod.
For the males, Crocker (and many, many helpers) once dragged a truck scale down the bluffs to the beach and employed a papier-mâché decoy to lure the bulls onto the scale. When they are finished with the process, the team watches the animal carefully until it has recovered enough to be safe, particularly should it venture near the water.
Early in the fall, the males arrive at the home beaches; soon they are quite violently and bloodily fighting for domination and mating rights. A month or so later, the females arrive and give birth. Within a month of weaning the pups they are pregnant again. During this three-month breeding season, the team is on the beach seven days a week, at least eight hours a day (not counting the two hour drive each way from SSU), conducting fasting research. Despite this high activity, the seals neither eat nor drink during this time and they will lose up to a third of their body mass.
“Elephant seals are extreme animals,” says Crocker, “they fast for three months, yet are not hibernating. They are hyperglycemic, with high blood sugar levels and really low insulin levels, like a diabetic, and yet they suffer none of the damaging effects that we do.” He sees these studies of elephant seals’ glucose metabolism benefiting mankind in several ways, diabetes research for instance.
At the end of the breeding season, the male and female seals go their separate ways on long foraging journeys, four months for the males, three months for the females. This is when Crocker’s devices earn their keep. The data logger records dive depths, swim speeds, ocean temperature, salinity and chlorophyll content in water. The information in the data logger is collected when the animals return to their home beaches before the “catastrophic molt” that they undergo each year, in which all the fur and the top layer of skin slough off, including the glue used to secure the tags. However, the team goes out whenever a tagged seal returns to land; the transmitter on their head, operating by satellite, lets them know when one is heading homeward and where it lands.
The studies so far have been quite enlightening. Elephant seals dive much further than previously thought, close to a mile under the surface and can stay submerged, not breathing, for up to two hours. The seals also act as “animal oceanographers,” collecting data in places humans rarely get to, for much longer times, and over sweeping distances. “Currently we are able to share the oceanographic information we collect with other scientists through the National World Ocean Database,” says Crocker. These far-ranging creatures are providing an immense boon to researchers working to put together an accurate picture of the ocean in all its stresses.
Many of Crocker’s projects have been funded by the National Science Foundation and the Tracking of Pacific Pelagics (TOPP) foundation, an international effort to gather as much data as possible using various animal species as information gatherers in their habitat.
Elephant seals are one of the 21 designated species because of their wide range of territory and their reliability in returning to their home beaches. The satellite transmitter beams the elephant seals’ location back to TOPP where it can be seen as live data on their website, allowing anyone to follow the travels of these intrepid oceanographers.
Likeable, friendly and intense, Crocker is known for his speedy motoring through the hallways of Darwin Hall on campus. He is a very busy professor. In addition to conducting cutting edge research with the seals, he teaches a full load of classes in the Biology Department and is the coordinator of the Biology graduate program. Crocker, who earned his PhD in Biology from UCSC in 1995, is particularly proud of the graduate students who work with him — their dedication, scholarship and enthusiasm.
Students apply to SSU’s graduate program to work specifically on the elephant seal projects; several post-doctoral students a year continue their elephant seal research under the program’s auspices as well. To date, Crocker has mentored ten students through the program; many have gone on to earn or are in the process of earning their doctorates.
His students have had lead roles in top-tier nationally funded programs, conducted internationally recognized research and been published in top physiology journals. Two have won prestigious National Science Foundation predoctoral fellowships, and another, Gitte McDonald, won an Environmental Protection Agency Star Fellowship, some of the highest awards for students in the field. This fall, Cory Champagne was one of five finalists for the Young Sholander Award, a prestigious award and “a big honor,” says Crocker.
Champagne has worked with Crocker for close to ten years, having started at SSU as an undergraduate around the same time Crocker began teaching here, and continuing through SSU’s graduate program for his Masters. Currently in the doctorate program at UCSC in biology, Champagne continues his elephant seal work with Crocker at SSU.
Crocker generally has several projects going on at any given time. In addition to those for TOPP, he is currently developing a device that can reliably and accurately determine the elephant seal’s sound-sensitivity in order to analyze the impact of noise pollution from sonar-devices and huge mega-ships on ocean animals. The ultimate goal is to apply this knowledge to beached whales.