A general introduction
On Implications, effects, Problem Definition

Of all domestic animals, dogs are the ones who have been living with human for the longest time, for approximately 10.000 years. The importance of companion animals to humankind is inestimable because of emotional benefits, as well as the improvement of physical and mental health. A lot of people (51% in United States) consider their dog a family member. Worldwide, the dog population increased by 12% between 1998 and 2003, to an all-time high of 283 million dogs (Datamonitor, 2004).

Published data on aspects of domestic pet demographics are available from several countries, including Australia, the USA, Canada (Leslie et al., 1994), Italy (Slater et al., 2008, Di Nardo et al., 2008), Brazil (Serafini et al., 2008), Zimbabwe (Butler and Bingham, 2000) and Chile (Acosta-Jamett et al., 2010).

In some countries information is limited to market research to be used by the pet food industry. Data are available from animal welfare groups as well. In Europe, the presence of dogs was estimated at 41 million in 2003, more than 13,000 of these are guide dogs for blind, deaf or other disabled persons. At present the number of households with pets is estimated by the European Pet Food Industry Federation (FEDIAF, 2010) to have reached 62 millions with an estimate 56 millions of dogs. Despite this global attachment of our society towards companion animals, thousands of dogs are relinquished to shelters each year and several million of those are euthanised (HSUS, 2002).

In fact, euthanasia is the number one killer of all companion animals (Sturla, 1993). Professionals in the veterinary, animal control and animal welfare fields are now seeing companion animal overpopulation as a "people problem" rather than an animal problem (e.g., Arkow, 1991; Arluke, 1991; Miller, Staats, Partlo & Rada, 1996; Moulton, Wright & Rindy, 1991) with the individual and collective behaviour of people as a causal agent, while variables in the environment (animal welfare agencies, pet industry, media) are also believed to be contributing factors.

Other than being placed in overcrowded shelters and/or euthanised, many dogs are strays and roam free, becoming a nuisance and causing illness and harm to the community (Allen & Westbrook, 1979). These animals are either owned and allowed to roam unsupervised, or without an owner. Between these two extremes are animals which have some interaction with humans but do not officially belong to one particular person or family (neighbourhood or community owned dogs/cats) (Wandeler, 1985; Slater, 2002).

A subgroup of free roaming dogs are strays: recently owned but lost, escaped or abandoned animals and their offspring (Rubin and Beck, 1982; Slater, 2002).

Further complicating the classification of these subpopulations is the fact that dogs may move between these subpopulations during their lives, becoming more or less socialized or going from a pet to a stray to a pet again. Free roaming dogs are commonly socialized to some degree and they have contact with human beings who provide the food and shelter needed for survival. While feral dogs do exist, they are rather rare and elusive (Boitani et al., 1995). The situation of free roaming dog is comparable in central and southern America, Africa, Asia and southern Europe (Beran, 1982; Beran and Frith, 1988; Daniels and Bekoff, 1989; Matter et al., 2000; Butler et al., 2004; Ibarra et al., 2006; Ortega-Pacheco et al., 2007; Slater et al., 2008), although there are differences.

In Zimbabwe all dogs are owned but ranging free and breeding freely. The majority of dogs in India are strays, but though not owned and unprotected they often thrive in communities and may be fed by a group of people. In Bangkok, in 1999, it was estimated that of 630,000 dogs living there, approximately 110,000 (17%) were considered to be ownerless.

A questionnaire on the status of animal welfare legislation and its implementation was distributed by the World Organisation for Animal Health (OIE) to 172 Member Countries in 2006, in order to collect data on the different national approaches to dog population control. Free roaming dogs were invariably considered to be a problem in most of the respondent countries (Dalla Villa et al., 2010).

Among all the problems considered, the stray dog management issue was ranked as "major" or "severe" more often than any of the other ones, confirming dog overpopulation as a complex web of multifaceted problems.