Center for Animal Welfare Legal Protection    
• • , , , • , , , •
• 1990- , , •
, , -  


Autonomous non-profit organization
Center for Animal Welfare Legal Protection


Observations on Overpopulation of Dogs and Cats
Robert Schneider, DVM, MS
The Journal of the American Veterinary Medical Association (JAVMA), Vol. 167, No. 4, 1975

      Since 1970, there have been growing concerns about a critical overproduction problem among dogs and cats. A recent national conference put into perspective some of these concerns [1]. A large amount of data have been collected on the pet populations of the counties of Al-ameda and Contra Costa, California [1,7]. Some of these data are directly applicable to the current concern about overproduction of dogs and cats, and are the basis for the observations presented in this report.

Background to the Problem

      With the growth of affluence, leisure time, and the movement of human populations from the central city to the suburbs, there has been an increasing demand for pets. The demand accelerated during the 1960's, as shown by the data from Alameda and Contra Costa counties, California, a predominantly suburban area. While the human population of those counties grew by 23.5% between 1960 and 1970, the canine population increased by 85.4% (Table 1). The feline population increased approximately 66% during the same period. The accelerated demand for dogs was helped by the long period of uninterrupted prosperity in the 1960's as well as the needs for personal protection. Statistics on increasing crime rates, riots, and the general unrest of segments of the population may have been important in the decision of some to obtain dogs, particularly those of large breeds. Budgets and manpower needs of animal control facilities did not keep pace with the acclerated population growth of dogs and cats, and along with an apparent increasingly permissive attitude in contemporary society, laxness in enforcement of animal control laws also occurred.

Table 1. Growth of Human and Canine Populations, Alameda and Contra Costa Counties California, 1960-1970

YearAverage human populationAverage canine populationRatio of man to dog
Increase (%)23,585,4-

How the Immediate Problem Developed

      The sudden decreased demand for dogs late in the 1960's, which necessitated the euthanatizing of large numbers of pups and kittens, apparently caused many persons to view canine and feline population growth and related problems with alarm. The main thrust of current concern has been toward an apparent overproduction of dogs, although an even greater problem has been the continued overproduction of cats. Per intact female, queens annually produce approximately 3 to 4 times as many offspring as do bitches [7]. Apparently the kitten overproduction problem has been with us for many years, but did not bother many. Why, then, should overproduction of dogs suddenly bother so many? The reason may be that the problem developed rapidly and was dramatic. As indicated for Alameda and Contra Costa counties (Table 2), there as a peaking of demand for pups in the 1966-1968 period, with a decrease of approximately 20% in 1969, and 17% in 1970. Thus, between 1968 and 1970, the number of pups entering households in these 2 counties decreased 37.3%. Such a large decrease in demand during a 2-year period was bound to result in a large excess of pups, in asmuch as supply could not slow down as rapidly as demand.
      Reports of local animal control activities sent to the California Department of Health also indicate decreased demand after 1969 (Table 3). The placement of dogs from animal control facilities into new homes increased steadily between 1956 and 1969, except for 2 years (1964 and 1967) when numbers decreased. For the 4 years since 1969, however, numbers have consistently decreased.
      Additionally, there was a 12.4% decrease (98,973 to 86,662) in redemptions by owners of their dogs from animal control facilities between 1970 and 1971 (Table 3), about the time concern for overproduction of dogs was starting to become widespread. The only other decrease in year-to-year redemptions had occurred between 1962 and 1963, when the change was from 51,125 to 50,760, a decrease of only 0.7%.
      Another indication of supply-demand imbalance is found in the numbers of purebred dogs registered with the American Kennel Club. Registratans have decreased for at least 2 years, after having peaked at 1,129,200 in 1971 [2].

Table 2. Changes in the Number of Pups Entering the Canine Population, Alameda and Contra Costa Counties California, 1960-1970.

YearAverage canine populationEstimated pups entering households during yearPups entering canine population (%)

Table 3. Number of Dogs Licensed, Reclaimed by Owners, and Placed in New Homes from Animal Control Activities in California, 1956-1973.

YearNo. licensedNo. reclaimedNo. to new homes

Source State of California Department of Health, Quarterly Reports of Local Rabies Control Activities from counties declared as areas enzootic for rabies, 1956-1973.

Table 4. Annual Productivity of Fertile Dogs and Cats, Alameda and Contra Costa Counties California, 1970.

Total offspring born alive69,85095,306
Total adopted when < 1 year old42,66143,256
Total born alive, less adoptions27,18952,050
Neonatal deaths *13,97019,061
Excess above adoptions and normal deaths13,21932,989

* Based on various groupings of the survey data [7], indicating probable neonatal death rate of approximately 20%.

The Current Problem

      Three major aspects of the current dog and cat overproduction problem are: (1) supply-demand imbalance; (2) unwanted pets; and (3) pet owner irresponsibility.
      Supply-Demand ImbalanceNormal, the supply of pups does not greatly exceed demand. For Alameda and Contra Costa counties in 1970, however, there was an estimated excess of 13,219 pups over the 42,661adopted (Table 4). The sum of these 2 figures, 55,880, approximated the 56,604 pups entering households in 1969 (Table 2). Apparently, 1970 production was closely related to 1969 demand. Had the demand in 1970 been as great as or greater than that of 1969, there would not have been any overproduction of pups. For kittens, however, production continued in excess in 1970 (Table 4), as in previous years. An excess of kittens can be expected in this populations (at 1970 demand levels) until 75 to 80% of all queens are neutered, an objective that would be difficult to achieve because of the ages of maximal reproductivity in queens and the turnover rates of queens in these ages, as discussed later.
      Unwanted PetsUnwanted pets appear to be the major group of animals found in pounds and shelters [1]. Reasons for disposal of healthy pet dogs and cats are unclear. In Alameda and Contra Costa counties, a follow-up survey was done 1 year after. The 1970 survey [7] to find out what happened to the animals enumerated in the initial survey. Approximately 12,000 households were contacted in the follow-up survey. Adopted pets leaving households for any reason in 1971 constituted approximately 15% of the canine population and 25% of the feline population. On these losses, approximately 40% of dogs and 30% of ats were given away by their owners. The most marked loss of dogs, after becoming household pets, was among those less than 1 year old. Approximately 35% were no longer in the household at 1 year of age. More than 50% of this loss was because the pups were no longer wanted. Those given to pounds and shelters were approximately 33% of the total loss, The median period in a household for an adopted pup that left during its 1st year of life was 4.4 months. Assuming the average pup entered the household at 6 weeks to 2 months of age, the median age at which such pups were disposed of would be approximately 7 months of age, which agrees with the age pattern of dogs found in pounds and shelters. Many dogs turned into pounds and shelters as unwanted appear to be half-grown. Clearly, additional studies are needed to uncover the reasons behind giving up a dog or cat after it is taken into a household as a pet.
      Pet Owner IrresponsibilityPet owner irresponsibility, which includes infringement on the rights of others by their pet, is an area of grave concern [1]. Some basic concepts of pet psychology and health are involved. For example, the question is often raised, "How much, if any, freedom or running at large does a dog or cat need?" Freedom of pets to wander has probably entered a new era, however. As both human and pet populations have increased in the same geographic area, more and more human-animal contacts have occurred! A proportion of these contacts have resulted in increasing numbers of bites and damage to property. With the additional financial needs of animal control activities failing to parallel pet population growth and the increased growth in pet-related problems, the point at which other measures are necessary appears to have been reached. In general, these measures currently are aimed at controlling growth of dog and cat populations. The real problem centers around the irresponsible owner, however.

Will Attempts To Control Growth of Canine and Feline Populations Work?

      The most obvious method to control growth of canine and feline populations is by preventing reproduction. Mass neutering (ovariohysterectomy and castration) is the means being advocated at the present time. But will such an approach work? From the data collected in Alameda and Contra Costa counties [7], it would appear that such programs will not have the expected effects. Before the concern for overproduction was publicized, pet owners were voluntarily having their bitches and queens neutered at record proportions, and still the overproduction occurred. For the period 1965-1970, in Alameda County, the total population of bitches increaHod 37.4%; however, the number of neutered bitches increased 70.5%. The net effect of this voluntary neutering was to increase the proportion of neutered bitches in the Alameda County population from 36.8% in 1965 [4] to 45.7% in 1970yet, with almost 50% of the bitches neutered in both counties [7] production of pups still was 33% more than needed in 197Q (Table 4). In the same period, the proportion of neutered queens increased from 48.4% [4] to 64.3%, Even when almost 66% of queens in both counties were neutered [7] production of kittens was still almost twice the number that could be placed in homes (Table 4).
      It will likely become more and more difficult to increase the proportions of neutered dogs and cats in many geographic areas. Taking the proportions neutered in Alameda and Contra Coata counties as an example, at the end of 1970 there already were 47.8% of female dogs, 64.6% of female cats, 7.4% of male dogs, and 51.8% of male cats neutered [7]. These appear to be high proportions (with the exception of male dogs), considering the large numbers of replacement pups and kittens entering the population each year (Table 2). In addition, the 1970 survey indicated that productivity was concentrated in the 1- to 3-year-old category for both dogs and cats, with 62.9% of litters produced by bitches and 74.4% of litters produced by queens in that age group [7]. These are the ages at which owners appear less inclined to neuter an animal, possibly because of the large numbers of animals that leave households during those ages. Survival data indicated that only approximately 50% of bitches and 33% of queens were still in households by 3 years of age.

Table 5. Distribution of Total Dog and Intact Bitch Ownership and Pup Production, by Income of Owner, Alameda and Contra Costa Counties, California, 1970.

1969 total income ($1,000)* Canine population owned (%)Intact bitches owned (%) Pups produced
< 8 8,27,48,1
8 - 914,716,016,7
10 - 1126,028,826,1
12 - 1327,929,031,7
>= 14 23,218,817,4
Total animals224,81557,03669,850

* Median income of census tract of residence.

Table 6. Distribution of the Proportion of All Queens Neutered and Those 1 to 3 Years Old, by Income of Owner, Alameda and Contra Costa Counties, California, 1970.

1969 total* income ($1,000)Neutered, as (%) of all queensNeutered, as (%) of queens 1-3 years old
< 859,157,3
8 - 959,456,9
10 - 1161,857,5
12 - 1364,360,7
>= 14 70,662,3

* Median income of census tract of residence.

       Another reason that a major emphasis on neutering may not help with dogs is because estimated demand appears to be a major factor affecting production of pups. That owners can regulate productivity of bitches is suggested by the annual litter production found in the Alameda and Contra Costa survey (0.2 litters/intact bitch) [7]. This rate was low, considering the feline reproductive rate of 0.9 litters annually per queen [7]. Though canine and feline breeding activities may not be directly comparable because of differences in type and frequency of estrus, females of both species still are expected to produce only 2 litters per year at maximal breeding efficiency. Hence, the difference between 0.2 and 0.9 litters is quite large. This difference, in part, represents dog owners' control of the breeding of their bitches, inasmuch as queens in the population, being more difficult to keep from sexual activity, are probably breeding at or close to their maximal breeding efficiency. Economic factors and ease of placement of pups, both constituting a demand measurement for owners of intact bitches, are thus strong motivating factors in canine breeding considerations. This potential for monetary profit would further defeat any attempt to control the canine population through a neutering approach. An increase of only 0.1 litter per intact bitch (from 0.2 to 0.3 litters) per year, which is still only 33% of the reproductive rate of cats, would result in 50% more pups in the Alameda and Contra Costa area.
      Among the reasons for advocating organized neutering clinics at reduced fees is that many pet owners cannot afford the usual surgical fee. As found (Table 5), however, the ownership and productivity of dogs in Alameda and Contra Costa counties are principally in the hands of persons whose incomes are relatively high. In 1970, only 8.2% of dogs were owned by persons residing in census tracts where the median income was less than $8,000 in 1969. Intact bitches owned in such census tracts produced only 8.1% of the pups in 1970. Thus, not only are fewer dogs owned by persons living in low-income areas, relatively speaking, but those owned are not reproducing at rates in excess of their overall ownership of dogs. In effect, organized neutering programs would likely be concerned mostly with replacement pets of the middle class owner, and, thus, probably would not have a major effect on the proportions neutered in the total canine and feline populations.

Proposed Solutions to the Overproduction Problem

      The critical factor in maintaining canine population balance is the law of supply and demand. As demand increases, prices increase and additional pups become available through more breeding activity, both planned and unplanned. This increased productivity becomes an excess when demand recedes. The major way to control periodic overproduction is to regulate demand more closely. A way to regulate demand is to educate potential owners as to their responsibilities if they obtain a pet, not by offering them low-cost neutering services. Such services only will make them complacent.
      Cats, on the other hand, are probably reproducing close to their maximal productivity, for reasons given earlier. Hence, any decrease in productivity will occur only from increasing the proportion of queens neutered or changing the age distribution of the intact queen population. An older population will produce fewer litters, on the average. It would appear that many owners may be unwilling to neuter their queen for reasons other than ability to pay the fees. As shown (Table 6), for various income levels there appears to be little difference between proportions of neutered queens, especially in the high reproductive ages of 1 to 3 years old, when 74.4% of feline litters are produced [7]. A major reason owners, regardless of income, may be reluctant to neuter their queens is the high probability of that animal not staying long in the household. More than 50% of queens entering a household as a pet are no longer in that household by 2 years of age66% by 3 years of age. Neutering clinics data reflects the reluctance of cat owners to have their queens neutered. In the Los Angeles low-cost neutering clinics for the 1973 to 1974 fiscal year, only 28% of the neuterings were cats [6], even though of kittens is a more acute problem than is overproduction of pups. Thus it appears that low-cost feline neutering programs also may be of limited value.
      The most rewarding means of controlling periodic dog and cat overproduction, therefore, would be through activities aimed at current and potential pet owners. Such activities, suggested by many [1,3,5], would include enforcement of leash laws, differential licensing fees for neutered and intact pets, registration of cats, charges for euthanatizing an unwanted pet or litter, and educational programs as to the pet owner's responsibilities to the pet and to others. These activities would have the effect of consistently reminding owners of their responsibilities and of their potential contribution to needless animal production. Educational campaigns by all interested groups should supplement direct local governmental actions. It should be kept in mind that, if affluence continues in the United States, numbers of owned dogs and cats will continue to increase, and problems associated with human-pet interactions will probably also increase, but at anfaster rate.


      1. American Veterinary Medical Association: Proceedings of the National Conference on the Ecology of the Surplus Dog and Cat Problem, Chicago, II, May 21-23, 1974, 65, (July 15, 1974): 140-143.
      2. Anon: Dog and Litter Registration. Purebbed Dogs/Am Kennel Gazette, 90, (March, 1973): 17; and 91, April, 1974): 25.
      3. Beck, A. M.: The Ecology of Stray Dogs: A Study of Free-Ranging Urban Animals. York Press, Baltimore, Md, 1973.
      4. Dorn, C. R., Terbrasch, F. G., and Hibbard, H. H.: Zoographic and Demographic Analysis of Dog and at Ownership in Alameda County. California State Department of Public Health, Berkeley, Ca, 1967.
      5. Feldman, B. M., and Carding, T. H.: FreeRoaming Urban Pets. Health Serv Rep, 88, (Dec, 1973): 956-962.
      6. McNamara, J., Department of Animal Regulation, Los Angeles, Ca: Personal Communication, Nov 15, 1974.
      7. Schneider, R., and Vaida, M. L.: Survey f Canine and Feline Populations: Alameda and Contra Costa Counties, California, 1970. JAVMA, 166, (March 1, 1975): 480-486.

      Authers of article are from the Animal Neoplasm Registry, Department of Epidemiology and Preventive Medicine, School of Veterinary Medicine, University of California, Davis, Ca, 95016.
      Supported in part by NIH grant A-14916 from the National Cancer Institute.

Return to table of contents

Return to main page