To date, little scientific data is available to assess the impact of cat predation on prey populations outside of agricultural situations. Even well-fed domestic cats may hunt and kill, mainly catching small mammals, but also birds, amphibians, reptiles, fish, and invertebrates. Hunting by domestic cats may be contributing to the decline in the numbers of birds in urban areas, although the importance of this effect remains controversial. In the wild, the introduction of feral cats during human settlement can threaten native species with extinction. In many cases, controlling or eliminating the populations of non-native cats can produce a rapid recovery in native animals. However, the ecological role of introduced cats can be more complicated. For example, cats can control the numbers of rats, which also prey on birds' eggs and young, so a cat population can protect an endangered bird species by suppressing mesopredators.
^ Zorro, the last cat of a colony at the Merrimack River in Newburyport, Massachusetts, died in 2009 at age 16. "Trap-Neuter-Return Effectively Stabilizes and Reduces Feral Cat Populations: Trap-Neuter-Return Humanely Stabilized and Reduced in Size the Merrimack River Colony" Archived 5 March 2016 at the Wayback Machine, Alley Cat Allies, accessed 18 August 2014; an earlier article in the LA Times was written when Zorro was the last remaining living cat: "Advocates report success with trap, neuter, return approach to stray cats" Archived 6 March 2016 at the Wayback Machine, Los Angeles Times, 29 September 2009.
Kittens require a high-calorie diet that contains more protein than the diet of adult cats. Young orphaned kittens require cat milk every two to four hours, and they need physical stimulation to defecate and urinate. Cat milk replacement is manufactured to feed to young kittens, because cow's milk does not provide all the necessary nutrients. Human-reared kittens tend to be very affectionate with humans as adults and sometimes more dependent on them than kittens reared by their mothers, but they can also show volatile mood swings and aggression. Depending on the age at which they were orphaned and how long they were without their mothers, these kittens may be severely underweight and can have health problems later in life, such as heart conditions. The compromised immune system of orphaned kittens (from lack of antibodies found naturally in the mother's milk) can make them especially susceptible to infections, making antibiotics a necessity.
The cat (Felis catus) is a small carnivorous mammal. It is the only domesticated species in the family Felidae and often referred to as the domestic cat to distinguish it from wild members of the family. The cat is either a house cat or a farm cat, which are pets, or a feral cat, which ranges freely and avoids human contact. A house cat is valued by humans for companionship and for its ability to hunt rodents. About 60 cat breeds are recognized by various cat registries.