Although long fascinated by sharks, particularly their predatory habits, marine scientists have known little about how these ancient ocean roamers of fearsome reputation have perpetuated themselves.
Until now, that is. For the first time, sharks' most intimate behavior has been captured on film, by Baltimore's Nick Caloyianis.
"Before this, nothing has existed of this whole event," says the prominent underwater photographer, beaming like a proud papa he displays his unprecedented photographs of nurse sharks mating in the wild.
Some of the pictures appeared in the May issue of National Geographic magazine, and a film of the scientific accomplishment can be seen on cable television tonight, in "National Geographic Explorer" (9 p.m., TBS).
In "A Savage Kind of Love," the Catonsville-based Mr. Caloyianis and his partner, Clarita Berger, take viewers into "the bedroom of the sharks," as the documentary narration phrases it.
The footage was captured last summer and the year before at an undisclosed location -- somewhere "in the far-flung reaches of the Florida Keys" -- where two scientists, Harold "Wes" Pratt and Dr. Jeffrey C. Carrier, have been observing shark mating behavior for several years.
The show conveys a sense of astonishing intimacy, not only because of the subject but also because of the obvious proximity of the scientists and the photography team to the lusty action.
The mating takes place in shallow water, no more than 3 or 4 feet deep, and the observers wear nothing more protective than wet suits and snorkel gear as they hover within a few feet of the roiling 8- to 10-foot sharks.
As the show documents, in a successful mating, a male shark firmly clamps one of the female's pectoral fins between his teeth, then struggles to turn her over to permit coupling to take place. They roll and writhe, stirring the bottom and splashing the surface.
"These females, they'll sometimes roll the males over like sumo wrestlers [and] . . . in this maelstrom of water movement, it's hard to see what's going on," says Ms. Berger, who swam at Mr. Caloyianis' shoulder to hand him cameras and other necessary gear. She co-wrote the script for tonight's program with co-producer John Bredar of the National Geographic Society.
The film notes that sharks are "perhaps the envy of males in any species" because they possess dual sexual organs, called "claspers," which are used according to the side from which the males approach.
Surprisingly, Mr. Caloyianis says, the human swimmers worried more about being bounced into razor-sharp coral than about being attacked by the sharks. Their wet suits were torn after a few days of shooting, and Mr. Caloyianis was bumped several times by the sharks.
A photo in the National Geographic spread shows his camera housing -- he designs his own underwater photo gear -- with two hands steadying it within inches of a flailing tail. Ms. Berger explains, "The left hand is his, and the right one's mine."
"Nurse sharks are not normally violent, but they can be provoked, and they have a tenacious, suction style of bite," says Mr. Caloyianis, who knows something about shark bites. His most recent film work for "National Geographic Explorer," a "Mysteries of the Deep" segment telecast in August 1993, included footage of himself being attacked by a bull shark off the coast of Mexico.
He suffered serious bleeding from leg and hand injuries, since healed, but says he felt no reluctance to get back into the water with the animals he has swum with for almost two decades.
"I could be crazy, but I'll let someone else decide that," he says with a laugh.
"I think he respects them," adds Ms. Berger. "Nick is a very careful person. Whenever we gear up for a project, a lot of thought is given to as many things as we can think of that might happen."
Pictures of fish
She adds, however, that when she embarks on a shark expedition -- the pair are back in the Florida Keys this month shooting more shark footage -- "I just tell my family I'm going with Nick to take pictures of fish."
Mr. Caloyianis, a 1973 marine biology graduate of the University of Maryland, says he is proud to have produced a shark film that does not dwell on vicious behavior. He hopes it produces public support for efforts to ensure the survival of the more than 300 shark species found around the world.
"Personally, I'm not interested in just doing shows on shark predation. I'm interested in behavior that hasn't been seen before," he says.
Indeed, Mr. Caloyianis and Ms. Berger fear that publicizing the mating behavior, even through the environmentally sensitive National Geographic Society productions, could threaten the sanctity of the mating area.
"If it got opened to eco-tourism, for example, this place would be wiped out in two years," says Mr. Caloyianis, adding gloomily, "I'm afraid it's probably going to happen."
His environmental interests include whales, too. "Saving Inky," a documentary produced by Mr. Caloyianis and the National Aquarium in Baltimore, recently won a Golden Camera award in the environmental program category of the 28th International Film and Video Festival in Chicago, and a Bronze Award from the Houston International Film Festival. It documents the rescue of a pygmy sperm whale, found critically ill from the effects of ocean pollution on a New Jersey beach on Thanksgiving Day, 1993. The whale was released to the wild after six months of care at the aquarium.
During the shark-filming expeditions, which involved long hours and days of waiting for the sharks to arrive and begin mating, the scientists and photographers were sometimes approached by curious fishermen or cruising yachtsmen.
"We'd just say, 'We're studying fish behavior,' " says Ms. Berger.
In addition to the mating behavior, "A Savage Kind of Love" also offers rare footage of a newborn nurse shark, a miniature, spotted swimmer perhaps 20 inches long. Mr. Pratt cradles it in ** his hand, crowing, "This means this is a nursery ground and has to be protected."
For Mr. Caloyianis, the photographic achievement was the culmination of an intermittent quest to capture shark mating habits that dates back to 1980. At that time, he took a National Geographic Society-sponsored expedition to the Red Sea with Eugenie Clark, a professor at the University of Maryland College Park who is one of the world's foremost shark authorities. The project involved photographing the "Moses sole," a flatfish that produces a natural shark repellent. But for days, the divers checked out reports of gray reef sharks mating in a deep underwater trench off the Sinai Peninsula.
Although they saw female sharks with deeply scarred fins, they saw no romantic encounters. "I began to wonder if it were ever possible to get this," Mr. Caloyianis says, noting that sharks are believed to mate only two to three weeks in a year.
Sharks also take eight to 10 years to reach sexual maturity, and the photographers fear many young animals are caught by fishermen before having a chance to reproduce.
"Our goal is for the world to understand these animals," says Ms. Berger.