Dear Dr. Fox:

Our hamsters always seem to die after a year and a half. We understand that this is about the average lifespan, but the timing also seems to coincide with their teeth growing very long. The last hamster would not use a chew toy and it got to a point where he seemed unable to open his mouth wide enough to take food or water. It was almost like he starved to death. Do you think they would live longer if a vet cut their teeth?

S.J., Chevy Chase, Md.

Yes! All rodents (and rabbits, too) need to have their teeth checked to see if they are too long, growing abnormally, ulcerating the mouth and/or preventing the animals from being able to close their mouths and even eat.

Chew toys won't do it -- these animals prefer to gnaw on a piece of hard wood, bone (like a beef soup bone) or even a cow horn, which also provides a source of minerals and other nutrients that they may crave.

In the wild, rodents gnaw on and recycle bones, antlers and horns, and, in the process of supplementing their diet with trace nutrients, also keep their constantly growing front teeth trimmed.

Overgrown teeth need to be snipped regularly by a veterinarian or an experienced animal caretaker (with the right tools and appropriate restraint) who will avoid splitting a tooth, breaking the jaw or accidentally cutting off the tip of the animal's tongue.

Dear Dr. Fox:

I read with interest your recent column in which you caution dog owners never to give them Lyme vaccine. I have also read many articles on the dangers of over-vaccination and I had pretty much decided not to give my dogs LymeVax this year. That was before I spoke at length with my vet.

He told me that renal borreliosis is the second most common canine syndrome and is generally fatal! Given the risk of this fatal disease (caused by the tick nymph and completely incurable), wouldn't we be better off vaccinating our dogs? I would rather my beloved German shepherd dogs be safe from severe protein-losing nephropathy, which cannot be cured or treated with antibiotics.

J.E., Cooperstown, N.Y.

Giving a dog the Lyme disease vaccination is a judgment call based on the dog's risk of exposure and the prevalence of this disease in the area where you live. Because the vaccine is not 100 percent reliable, dogs in high-risk areas who are often outdoors should be groom-checked daily for tick removal with a fine flea comb. Blood tests (when dogs develop suspect signs of this disease) are not reliable and are confounded by vaccination, so immediate antibiotic therapy is called for. Dogs at risk should be given two vaccinations at three-week intervals, beginning as early as 9 weeks of age, followed by an annual booster vaccination.

Dear Dr. Fox:

Our domestic shorthaired 13-year-old male cat, Baxter, has been diagnosed with lymphosarcoma. He is now being treated with long-term steroid shots, starting 30 days apart, after a few short-term shots lasting a few days. He was a big cat, but he is now gradually losing weight. He has an unusual and perplexing habit of licking concrete. If he is not taken outdoors, he will lick the bricks on the fireplace hearth. Yes, he had one bout of toxic illness.

Baxter has been a patient of the best allergy and dermatology clinic for animals in the area since birth. His veterinarian cannot explain this behavior and neither can I. He runs to the door when he observes me leaving, and dashes outside to lick the concrete.

I was raised on a farm and remember the salt licks in the pasture for the outdoor farm animals. I put a dish of salt on the floor beside his food for a few days, but he did not partake of it. His veterinarian told us that salt would not hurt him, but she did not believe a lack of salt in his system was the answer. She did believe that it might be a sign of a lack of some mineral. Is Baxter trying to tell me something?

C.W., Livonia, Mich.

Animals who are experiencing chronic pain, discomfort or irritation, as from cancer (like your cat) or tonsillitis, gingivitis or intestinal inflammation, will engage in what is called pica. They obsessively lick solid surfaces like wood or concrete floors, brick walls and iron pipes, and sometimes chew and swallow all kinds of materials from soil and leaves to pieces of carpet and upholstery. They will also do this to their own bodies when extremely disturbed.

Pica caused by a nutritional deficiency in calcium, phosphorus and other dietary essentials is rare. But to be on the safe side, have your veterinarian prescribe a multi-mineral and multivitamin tablet or liquid drops for your cat.

Pica caused by boredom, anxiety and frustration is seen in dogs who are left home alone all day, in factory-farmed sows in narrow stalls, and in many caged wild animals in zoos, circuses and laboratories all over the world. Pica indicates that the animal is suffering (and your cat clearly is), and the steroids may be contributing to the problem.

Michael Fox, author of many books on animal care, welfare and rights, is a veterinarian with doctoral degrees in medicine and animal behavior. Write to him in care of United Feature Syndicate, 200 Madison Ave., New York, N.Y. 10016. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

(c) 2004, United Feature Syndicate Inc.