Santa Cruz police officials said the blasts, which occurred three minutes apart, caused one of the scientists, his wife and two young children to flee their home through a second-story window.
"Acts of violence and intimidation such as these are unacceptable, and they continue a troubling pattern seen at UCLA and other UC campuses that should be repugnant to us all," UC President Mark G. Yudof said Monday. "These acts threaten not only our academic researchers and their families, but the safety and security of neighbors in our communities as well."
City officials joined in harshly condemning the bombings and urged members of the public who might have evidence in the case to contact authorities. They announced a $30,000 reward, including $2,500 donated by the Humane Society of the United States.
"The threats and attacks are shocking and abhorrent," Santa Cruz Mayor Ryan Coonerty said. "We as a community are unambiguous in our condemnation of these actions. Let me be clear, this is not protest. This is terrorism."
Nationwide, incidents of violence by self-described animal rights activists have been on the rise, according to the Foundation for Biomedical Research, which has tracked such attacks since 1981, when there was one.
In 2000 there were 10 such episodes against biomedical research facilities alone, and in 2006 that figure had grown to 77, according to the group's website. In addition, the type of attacks has changed in recent years.
"Prior to that, the vast majority of actions taken were against institutions -- break into the lab, steal the animals, trash the facility," said foundation President Frankie Trull. "More recently, however . . . they've become much more personal, attacking the researchers at their homes. California seems to be the focus of this activity right now, but not the only focus."
Santa Cruz Police Chief Howard Skerry said investigators had collected "an enormous amount of forensic evidence" from the two bomb sites. The FBI, the federal Bureau of Alcohol, Tobacco, Firearms and Explosives and the state Fire Marshal's office are participating in the investigation, along with the city and university police departments. Santa Cruz police said they were investigating the case as an attempted homicide.
The first bomb went off about 5:40 a.m. Saturday, destroying a car outside the home of a UC Santa Cruz researcher. Authorities have not named the researcher.
Three minutes later and less than a mile away, a second device exploded on the front porch of researcher David Feldheim's home while he and his family were asleep. As the house filled with smoke, the scientist, his wife and their children, ages 2 and 4, escaped out a window and down an emergency ladder. Feldheim injured his feet during his escape.
Both devices were incendiary, police said, but it was unclear how they were triggered. Also unknown is how many people were involved in carrying out the attacks.
UC Santa Cruz Chancellor George Blumenthal said the episodes were an attempt to stop valuable medical research.
"I think it's a form of domestic terrorism intended to intimidate people," the chancellor said. "These are incidents that could have killed someone. They are obviously intended to prevent researchers from pursuing the advancement of knowledge. They are a serious attack on academic freedom."
Police said pamphlets with the names and home addresses of some UC Santa Cruz researchers were found at a Santa Cruz coffee shop four days before the bombings.
The attacks were similar to others since 2006 on the homes and vehicles of animal researchers at UCLA, including one bomb that was mistakenly placed at a researcher's neighbor's house but did not detonate. In October, attackers flooded the home of a UCLA scientist who conducts studies using monkeys, causing more than $20,000 in damage. In June, animal rights activists claimed responsibility for setting an unoccupied UCLA carpool van on fire while it was parked at UC Irvine.
At UC Santa Cruz in February, a group of six masked protesters attempted to force their way into a researcher's home while the family was having a birthday party for a child.
At UC Berkeley, activists have mounted a "relentless" campaign of harassing animal researchers at their homes and in public places on dozens of occasions, said university spokeswoman Marie Felde. In one case, a group of activists showed up at a researcher's child's soccer game and shouted that the researcher was an "animal murderer," she said.
University officials also have reported cases of harassment at UC Davis, UC San Francisco and UC Santa Barbara. The 10-campus university system is sponsoring state legislation designed to restrict protesters' ability to harass university researchers.
Trull called the escalation "very, very worrying," particularly the firebombing of the Feldheims' home. Animal rights activists "preach this, 'We respect all living things,' and then they do that with children in the house," Trull said. "The irresponsibility was breathtaking to me."
But at least one activist applauded the attack. Jerry Vlasak, a Los Angeles physician who runs a website that highlights animal rights activism, blamed the scientists for the violence.
Vlasak, of the North American Animal Liberation Press Office website, said his organization had received no communique from any group claiming responsibility for the Santa Cruz fire bombings. Although he said he had no direct knowledge of the attacks, he also said that "the use of force" is "not unpredictable or untenable."
"The inconvenience and the suffering of any children or any family members pales in comparison to the suffering and oppression that goes on in these animal laboratories," Vlasak said in an interview Monday. Feldheim is "putting himself and his family in harm's way by continuing to abuse animals."
At the entrance to the campus Monday afternoon, about 300 faculty, staff and community members gathered at a hastily organized rally to protest the twin bombings. Among them were Blumenthal and Coonerty. Feldheim spoke briefly to the crowd and thanked them for their support.
Martin Chemers, a psychology professor who briefly served as acting chancellor at UC Santa Cruz, helped organize the demonstration to show support for animal researchers and the university. He carried a sign that said "Medical Science Saved My Life" and noted that he had suffered a brain tumor at age 18.
"For rational people, this violence is not the way you exercise your opinions in a democratic society," he said. "We support our colleagues in the sciences and the academic freedom that goes along with being a professor."