Cat population

Two interesting science articles about regulation of the domestic cat population size, tip Saving Pets.

"Each cat-owning household kept 1.3 cats on average, with the majority keeping one (75.8% households) or two (18.7%). For the 260 cats, the mean age was 7.1 years, the median 6 years, with a range of 3 months to 22 years. There were significantly more female (143; 55%) than male cats (117; 45%). Only seven cats (2.7%) were sexually entire, and these were all ≤6 years. Crossbred cats outnumbered pedigree cats by a ratio of 3.3:1." (Demographics and husbandry of pet cats living in Sydney, Australia: results of cross-sectional survey of pet ownership doi:10.1016/j.jfms.2008.06.010 )

"Recently, neutering of domestic cats has been encouraged by veterinary surgeons and rescue organisations as a means of population control for both the pet and feral populations. This is likely to have profound effects on cat population dynamics (and population genetics). In an attempt to quantify this, we have carried out population studies, by means of door-to-door surveys in Southampton and the surrounding area. The aims were to quantify levels of neutering, and investigate the recent reproductive status of the cat population.

The most comprehensive of these surveys was carried out in a 50 ha area in the Shirley area of Southampton (UK). Householders were interviewed from 949 (80.8%) of the 1175 residences in the area. This revealed a population of 315 cats, of which 21 were pedigrees (and were excluded from further analysis) and 294 were mongrels. Overall neutering rates were very high: 96.8% of adult males and 98.7% of adult females were neutered. The oldest cats in the survey had been born 18 years previously, so it was possible to examine trends in neutering over this time period. However, many females were allowed to reproduce before being neutered, so a more informative analysis came from relating lifetime fecundity (mediated by neutering) to year of birth. Mean lifetime fecundity could be calculated for each cohort where all the females had ultimately been neutered. The regression (Fig. 1) shows a dramatic decline in the mean number of litters born per female, from over 0.6 in 1978 to 0.12 in 1991–1992. With a measured median litter size of 4, 0.5 litters/female are needed to keep the population size constant; increasing neutering has meant that the cats in the Shirley survey area fell below this level of fecundity in the early 1980s. In 1994, owned cats in the area could only produce sufficient kittens to maintain the population at approximately 25% of its present level."

(Feral cats: their role in the population dynamics of Felis catus doi:10.1016/S0168-1591(99)00086-6)

So, a combination of education and help with costs where needed can prevent pet over-population and the need to put down healthy animals.