Short Takes: 03/06

Why Feral Cats Come Back

Even the best TNR (trap-neuter-return) programs for reducing feral cat populations ultimately falter because of human and feline nature, according to a study in the Journal of the American Veterinary Medical Association (Vol. 227, No. 11).

Veterinary researchers studied TNR programs in Californias San Diego County and Floridas Alachua County, where thousands of feral cats have been humanely trapped, surgically neutered and returned to roam.

At first, results of the TNR programs seemed encouraging. The populations of pregnant female cats did drop. But a 10-year review of the California and Florida programs showed feral cat populations returning to what wildlife biologists call the environments carrying capacity.

To figure out why TNR fails to reduce population in the long run, the researchers thought about what affects population density of wild animals – things like starvation, predation, disease and reproductive success – and now they think they have a couple of clues. First of all, neither predation nor disease helps much. Feral cats have few predators and hunting by humans is not allowed. Deliberate introduction of disease (feline panleukopenia virus) on the Indian Oceans Marion Island failed to control feral cats there.

Of course the reproductive success of the TNR-treated cats was not a factor, but trapping programs cant keep thousands more reproduction-ready cats from joining the population. And its all but impossible to neuter every free-roaming cat in places like San Diego County, where the feral cat population is estimated at 240,700.

Starvation? Not likely with all the kind-hearted humans around. Nationally up to 20 percent of households set out food for feral cats. In Alachua County, about 12 percent of households were feeding three or four feral cats per household. In San Diego, about nine percent were feeding two or three feral cats per household.  

Consider the fact that San Diego County has more than 1,040,000 households. Then do the math and youll see why feral cats are not an endangered species.


Weight Control in Pet Cats

From adequately nourished feral cats to way-too-well-fed domestic cats, a study in the Journal of Feline Medicine and Surgery (Impact of time-limited feeding and dietary carbohydrate content on weight loss) reveals what doesnt help tubby cats lose pounds.

In place of ad libitum feeding (food in the dish all the time), cats in the study were restricted to four hours of dinnertime a day. At first cats lost a little weight – until they figured out how to gobble a days worth of food in four hours. 

What did help overweight cats lose weight was switching to a therapeutic low-carbohydrate diet. 


Treating High Blood Pressure

An article in the journal Waltham Focus (Vol. 15, No. 1) titled Diagnosis and management of feline hypertension calls for more blood pressure screening for at-risk cats, while recommending a particular treatment if hypertension is found. 

Chronic renal failure or hyperthyroidism puts cats at risk of hypertension, according to Harriet M. Syme of the Royal Veterinary College in London. To forestall further harm, such as blindness from hemorrhaging in the eye or detached retinas, Dr. Syme recommends more routine blood pressure screening.  

As for hypertension treatment, the calcium-channel blocker amlodipine is best, Dr. Syme says. In her opinion, beta-blockers and ACE inhibitors may not reduce blood pressure enough to prevent eye damage.