A University of California, Davis, graduate student who has spent more than two years studying titi monkeys in the remote Peruvian Amazon is missing and presumed dead, after swimming in a jungle lake Thursday evening, UC Davis officials said today. His body has not yet been found. Francis J. Bossuyt, 30, a doctoral candidate in animal behavior, had been living near Boca Manu, Peru, and based at the Cocha Cashu Biological Station operated by Duke University researchers under the auspices of the Peruvian government. Bossuyt's research associates in Peru reported that he'd gone for a swim in Cocha Cashu (Lake Cocha) before supper Thursday, and when he didn't return, they went to look for him, finding only his shoes and towel on the dock, according to UC Davis anthropology professor Peter Rodman, one of Bossuyt's major professors. A search is being conducted by rangers at the Manu National Park and local police, Rodman said. Rodman traveled from Davis to Peru on Sunday to assist in finding Bossuyt. Bossuyt was a site manager at the research station, where he was responsible for managing the yearly budget, buying supplies and equipment, supervising the site caretaker and coordinating the entrance and exit of researchers and student groups to and from the site. He worked under the supervision of John Terborgh, James B. Duke Professor of Environmental Sciences at Duke University, who has operated the station for more than 20 years. Bill Mason, a UC Davis psychology professor emeritus affiliated with the campus's Primate Research Center, was also a major professor for Bossuyt. Mason said that Bossuyt had been doing a critically important long-term field study of "a species of monkey I'd studied for a long time. He's been there for several years, and was actively engaged in research. He gave a talk on campus earlier this year to the animal behavior graduate group." Bossuyt's Jan. 10 talk was sponsored by the departments of anthropology and psychology. Bossuyt's death has saddened those on the UC Davis campus who knew him. "Francis was an admirable person, who showed great professional promise," Mason said. "He was just an absolutely amazing field worker, yet he was a mild, gentle sort of person. I've never been more excited about news from the field as I was about the reports I got from him. His work was rich," Rodman said. Supported by grants from the National Science Foundation and the Leakey Foundation, Bossuyt was doing highly promising work, Rodman said. While in Davis, Bossuyt was close to Rodman's family, he said. "I am deeply saddened by Francis Bossuyt's death. He was a very promising scholar and a fine human being," said Cristina Gonzalez, dean of UC Davis Graduate Studies. "This is a terrible loss for all of us." Bossuyt's death is the second tragic death in his family during the past five years. His father, Luc Bossuyt, a chemical engineer who frequently traveled internationally for business, died in the July 1996 TWA Flight 800 crash off Long Island. Following his death, his company and family created the Luc Bossuyt/Bristol-Myers Squibb Endowment to underwrite international travel for UC Davis graduate students to attend scientific meetings in the field of structural biology. In a 1997 UC Davis Division of Biological Sciences newsletter, it was noted that "Francis Bossuyt inherited his father's adventurous spirit. He has already traveled to Kenya and the Alaska Peninsula to conduct wildlife studies. This summer he ventures off to Peru to evaluate sites for census studies of the titi monkey, the subject of his thesis research." "Education and the spirit of adventure have been very important to Bossuyt's family. Many UC Davis students have already benefited from the family's support of international travel by young scholars," said Mark McNamee, dean of the UC Davis Division of Biological Sciences. "I am just stunned by this terrible tragedy." Bossuyt earned his undergraduate degree biology and chemistry in 1990 from Earlham College in Richmond, Indiana. Prior to attending graduate school at UC Davis, he spent more than four years working as a residential administrator, supervisor and child counselor at the Burt Children's Center for Severely Emotionally Disturbed Children in San Francisco. His family was originally from Belgium, with Bossuyt actually living in South Africa until he was 5, when his family moved to the United States, Rodman said. Bossuyt is survived by his mother, Myriam, of Trumbull, Conn., and his brother, Stephen, of Los Angeles.