BACKGROUND:   Sterilization is one of the most commonly used and effective strategies for the control of dog populations world-wide. In developed countries this has been very successful: responsible dog ownership is taken seriously, and seeing a dog in the street with no owner is a rare and alarming occurrence. In developing countries however, the uncontrollable population growth of free-roaming dogs, and all its direct and indirect effects, is a serious and overwhelming problem that is growing in magnitude, and rapidly becoming a major platform issue in many governments and world-wide non-governmental organizations. Yet it is incredible that there is no concrete information about how successful sterilization campaigns are in controlling the growth rate of free-roaming dog populations, because in-situ scientific studies on humane control of free-roaming dogs have NEVER BEEN DONE! How is it possible therefore, to design programs with sensible objectives?

In Latin America, the sterilization of male dogs is often not accepted culturally, therefore male dogs are rarely neutered, and there are many misconceptions about sterilization of males. In a “machismo” culture, even women regard the removal of dogs’ testicles as offensive. To tackle the issue, we need more tools that are acceptable in a variety of cultures, thus the growing interest in chemical neutering1 which also results in permanent sterilization; the procedure is very rapid, economical, and the testicles are not removed.  

Although safety data for some of these chemical products are abundant, there is no information regarding the possible changes in reproductive, aggressive and roaming behaviours in free-roaming dogs following sterilization. In Latin America, male dogs fulfil important roles in the community, some of which include the protection of people and property in areas where crime is rampant. The fears expressed by owners that sterilized males will no longer perform their duties are a major reason for declining to sterilize dogs.


1 Esterilsol™ is one chemical sterilant that has recently been approved bv the United States’ Food and Drug Administration.


OUR PROJECT:   For this reason, Veterinarians Without Borders – Canada, together with international collaborators, have decided that understanding the behavioural changes that may or may not be seen in male FREE-ROAMING DOGS following surgical and chemical sterilization is prerequisite information needed in the quest to identify global solutions to this problem.

Group of international and local collaborators visiting the site of Puerto Natales, Chile.


With the international collaboration of the Chilean Agriculture Agency (SAG), the Chilean Ministry of Health, the Istituto G´Caporale from Italy, and the University of Pennsylvania: Animal Welfare Department from United States, our study is comparing male dog behaviours before and after they are chemically and surgically sterilized, as well as obtaining information of overall acceptance and understanding towards male dog sterilization.

VWB/VSF veterinarians spend time with children teaching them about responsible dog ownership and community health.

This project commenced in May 2011, and to date we have 157 owned, free-roaming dogs enrolled in the study. Dogs are divided into three groups (control, surgical, and chemical sterilization groups). Every dog has been physically examined by a licensed VWB/VSF veterinarian, and treated for ecto- and endo-parasites. We also surveyed owners to find out about their dog’s behaviour. Additionally, owners and their children attended education seminars on the benefits and techniques of sterilization in male dogs.

On October1st 2011, the first phase of pre-sterilization data collection commences. Each dog will be fitted with GPS data logger collars to

monitor their daily movements, and video-monitored for a total of 3 days. This will be followed by sterilizations, then repeat data collection of all dogs with methods identical to the pre-sterilization phase.

The reality for dogs and people here in Puerto Natales is unlike the reality that many of us are used to in North America and Europe. Here, and in many developing countries of the world, owned dogs are left to forage for their own food. Many resort to hunting as a means of supplementing their diets. They are often in very poor condition, with multiple health concerns such as distemper and parasitic skin infections. These large populations of roaming dogs living in marginal conditions have profound effects on people’s health and livelihoods. Veterinarians Without Borders-Canada together with other partners and funders are committed to finding long term solutions to this global problem.

Many dogs resort to hunting wildlife to feed themselves.