Dogs are more than wet kisses and tail wags: domestic dogs as invasive species

Domestic dogs are the most abundant carnivore worldwide. The size of the global dog population has been estimated recently as almost one billion individuals, and at least 60% of them live in rural settings (Gompper, 2014). In most parts of the world, knowledge about populations of domestic dogs in urban and rural areas, as well as feral populations, is still limited. However, it is clear that domestic dogs are ubiquitous throughout large areas, and far outnumber all other native carnivore species combined (Young et al., 2011). Problems with domestic dogs are not new, but many of their impacts as invasive species have been overlooked until fairly recently (Hughes & Macdonald, 2013). As predators, dog populations have significant impacts on native species, and as a consequence have the potential to alter ecosystem structure and function in priority conservation areas. They also can compete with native predators for prey, cause losses to livestock, and transmit disease. Thus, the impacts of domestic dogs can be much more far-reaching than previously thought (Doherty et al., 2017). For the vast majority of invasive mammal species, including domestic dogs, basic information about population sizes, geographic distribution and effects on native species are lacking. In most areas, direct evidence of the ecological and economic impacts of dogs does not exist, resulting in little information for making management decisions at local and national levels. For successful control and management planning of dog populations, accurate and up-to-date species distribution data and characterization of their impacts at large spatial scales is essential. In this context, Home, Bhatnagar & Vanak (2018) took a novel approach for understanding and characterizing the impacts of domestic dogs at large spatial scales. Home et al.’s (2018) citizen science approach allowed for a robust assessment of domestic dogs’ impacts that was spatially representative in a very short time frame. A traditional approach, on the other hand, would have been logistically unfeasible, time-consuming and a financial strain. The information generated allows for the design of policies, and for making decisions that mitigate the impacts of domestic dogs. A series of policy measures are required to successfully address the problem of domestic dogs as an invasive species (Dalla Villa et al., 2010). Although the domestic dog is officially listed as an invasive species in several countries, few government agencies are directly addressing the problems associated with their impacts. In the short term, national policies for controlling and managing domestic dogs as an invasive species are unlikely to be developed. Reasons include political, economic and cultural issues such as lack of national prioritization schemes for invasive species, the relatively small economic impact dogs have on human property, lack of information about dog impacts in most areas, growth of animal rights movements, and very close relationship humans and dogs have had for several millennia. For the domestic dog, the most effective ways to prevent their introductions into wilderness areas and reduce their impacts on all native ecosystems include reduction in population sizes through sterilization programs in urban and rural areas, elimination of individuals without owners, prevention of free-ranging activity, vaccination programs to reduce the potential for disease transmission, and improved feeding and care (Young et al., 2011; Hughes & Macdonald, 2013; Knobel et al., 2014; Doherty et al., 2017). The scope of policy measures should be to control and manage free-ranging and feral dog populations. Policy should be based on three main premises: invasive domestic dogs pose serious ecological impacts and human health problems (Vanak et al., 2014); because the impacts of invasive domestic dogs are linked to human population density and human activities, control of domestic dogs has to be accompanied by changes in human behavior to be effective (Gompper, 2014); and, the promotion of responsible dog ownership can significantly reduce the number of free-ranging and feral dogs, and the extension and intensity of their negative impacts (Silva-Rodr ıguez & Sieving, 2011). Education is probably the most important element of a policy designed to reduce the impacts of invasive domestic dogs. Education should target children as well as dog owners, as children