Both cats and dogs are likely hosts for “cat fleas.” • According to the Presidential Pet Museum, only two U.S. presidents were completely pet-free while in office: Chester A. Arthur and Franklin Pierce. All other presidents and their families have shared their lives with many different companion animals, starting with George Washington, who was wellknown for his fine eye for a good foxhound. The presidential pets have had a lot of interesting names, but perhaps the one that says most about the power of the presidency is the name James Garfield gave to his dog: Veto.

• “Only the strong survive” has been suspected for generations. But now, scientists are finding ways to further prove the idea. A study on Colorado mountain lions found that sick mule deer were more likely to become a meal for big cats by establishing that the deer were sick before the lions grabbed them. The carcasses of deer killed by lions were tested for chronic wasting disease, with the rate of infection compared to that in deer killed by area hunters. The study, published in Biology Letters, found the deer killed by mountain lions had a higher rate of infection than deer killed by the hunters, suggesting that mountain lions were more likely to kill sick deer. The lions do not seem to be affected by the illness and may be aiding the overall deer population by decreasing the number of infected animals.

• Dogs have cat fleas, sort of. The flea that drives both cats and dogs — and their owners — crazy is Ctenocephalides felis, the “cat flea.” But it could have just as easily been named after dogs. In 1934, a French scientist pulled the flea off a cat and named it after the host. He could have just as easily found one on a dog and named the pest accordingly. There is a flea called Ctenocephalides canis, but cat fleas are much more common on both dogs and cats.

— Dr. Marty Becker and Mikkel Becker Shannon