When Celia O'Connell's elderly mother broke her hip and needed to spend several weeks in the hospital, O'Connell's dog, Buffer, went on a hunger strike.

"My mother lives next door," explains O'Connell, who lives in San Diego. "Buffer immediately attached himself to her as her protector and companion when I was at work. We'd had him for seven months when Mother broke her hip. She was gone for over three weeks. After the second day with her gone, Buffer stopped eating. After a week of very little food and constant moping, I was worried about him."

Buffer's reaction doesn't surprise veterinarian Marie Suthers-McCabe, associate professor of human-companion animal interaction at the Virginia-Maryland Regional College of Veterinary Medicine in Blacksburg.

"I've seen this a lot," says Suthers-McCabe. When she was a practicing vet in Ohio, "I'd see people bring in a pet with symptoms such as loss of appetite, sleep disturbances, walking slowly and decreased energy. A physical exam would reveal that there was nothing wrong with the animal. At that point, the person would hesitate, and then mention that the animal was their mother's pet and that the mother had passed away recently. And then the person would ask, `Could the pet be grieving?' "

The answer, according to Suthers-McCabe and other experts, is a definite yes.

"Grief over the loss of a person is not uncommon for dogs and cats," says Nancy Peterson, human-animal bond specialist for The Humane Society of the United States, headquartered in the District. The death of a family member or departure of an elderly owner for the hospital or nursing home are obvious triggers for such grief. However, other changes in a household -- such as divorce or a younger person's going away to college -- can provoke equally strong reactions. In multi-pet households, the death or departure of one pet can prompt the remaining animals to grieve.

Even a change for the better can send an animal into an emotional tailspin, as Julie Holland of Falls Church discovered when she adopted Chesna, a mixed husky, from an animal shelter. Although the dog's fear of sudden noises and long-handled objects indicated possible abuse in her earlier home, Holland sensed that her new pet nevertheless missed her previous family. "She refused to eat much in the shelter," Holland says. "And it took about two weeks to get her eating regularly once we had her."

Not eating is one of the most common ways an animal manifests grief, according to certified animal behaviorist John C. Wright, coauthor of "The Dog Who Would Be King" (Rodale Press, 1999) and "Is Your Cat Crazy?" (IDG Books Worldwide, 1996). Mourning dogs also "may become extremely depressed -- they essentially shut down," Wright says. "They also may sit around the house and mope, and wait for the person to come back. Essentially, they give up. It's an overall failure to thrive." Lapses in house-training also are common signs of grief.

Some cats, adds Wright, may show grief or distress over a loss by meowing constantly, crying or wailing. Other felines may appear to handle the loss of their human companion with equanimity -- unless the companion returns. Then such a cat may ignore the returning individual. "They take a kind of if-you-leave-don't-come-back approach," Wright says -- at least until they have a chance to become used to the returnee's presence.

In most cases, easing a pet's grief requires just a little help from the animal's human friends. Among experts' suggestions:

Build a routine. A grieving pet may be less upset by a person's absence than by the change in routines. Dogs and cats are creatures of habit. "They really need predictable, knowable routines," Wright explains. "They need to depend on meals being at a certain time, when they'll be taken out, when the litter box will be changed." All too often, that predictability is shattered when a family member dies, a couple divorces, or a person leaves the family.

Not surprisingly, then, most experts advise owners of grieving pets to quickly return some predictability to the animal's life, either by reestablishing the old routine or building a new one. Says Wright, "Giving a dog or cat a pattern of daily activity that they can ritualize is probably the single best thing you can do" to help a pet adjust to the loss of a special person.

Plan ahead. If family members know an important person in the pet's life is leaving the household, other family members should start spending more time with the animal before the person leaves. For example, if an elderly person must give a pet to another family member before entering a nursing home, that family member should start caring for the pet on a part-time basis beforehand.

Let the pet comfort you. Even when there is no time to prepare, "someone needs to spend time with that animal," says Suthers-McCabe. "The animal will probably also help that person" by helping to lower his or her blood pressure and heart rate and just generally being a source of comfort.

Don't coddle. "Don't spend too much time consoling the animal," warns Wright. "Don't praise inactivity; get the animal moving." Instead of holding or cuddling a grieving dog, take it for a walk. For a lethargic cat, offer toys that prompt it to chase or pounce.

Monitor input and output. While loss of appetite and changes in bathroom habits are common signals of animal grief, those signals can become life-threatening if not treated promptly. For example, "a cat can actually die from weight loss or anorexia," notes Suthers-McCabe. Experts advise owners to contact their vet if an animal's appetite or normal bathroom behavior don't rebound with a couple of days.

O'Connell followed most of those suggestions when caring for her grief-stricken dog. She hand-fed him until he began eating on his own, her daughter kept him company while O'Connell was at work, and all the family members took him for extra walks. And, according to O'Connell, the effort paid off.

"I believe that having company and added activities took his doggy mind off the profound loneliness Buffer experienced without Mother," she says.

Experts agree that time and attention can go a long way toward helping a grieving pet build new bonds with new people, and rebuild bonds with returning companions. "Animals may be more resilient than we give them credit for," says Peterson. "With TLC, it's not unusual that an animal would begin to love again."