Dr. Elke Schüttler
Researcher Universidad de Magallanes
Domestic dogs (Canis familiaris) and cats (Felis catus) are the most common carnivores worldwide. They are cosmopolitan species with estimated populations of over 9 million dogs and 6 million cats. Dogs and cats have accompanied humans to almost all places of the world, except for the Antarctic. They perform a variety of functions for humans and attitudes towards them strongly depend on culture.
When owners do not exert or lose control over their pets, they turn into free-ranging animals with different degrees of association to humans ranging from urban dogs nourishing on waste to feral dogs surviving independently of humans. Free-ranging domestic carnivores can reach much higher numbers than their wild counterparts, particularly when subsidized by humans through food or shelter. They have serious impacts for humans (e.g., transmission of diseases, attacks of people), economic activities (attacks on livestock), and on wildlife. Particularly, in settings where human settlements encroach into natural areas, cats and dogs can be considered as an invasive species with negative impacts on biodiversity: They depredate on mammals, birds and reptiles, compete with wild carnivores, transfer diseases, or disturb wildlife. Impacts of cats focus on the depredation of birds and small mammals, which can even lead to local extinctions in insular ecosystems.
The Cape Horn Biosphere Reserve, at the southernmost end of South America, is one of the last pristine regions of the globe. This wilderness area in the Magallanic Sub-Antarctic ecoregion harbors only one small settlement (Puerto Williams) of ca. 2,800 inhabitants on Navarino Island besides a handful of rural farms, and eleven posts of the Chilean Army with one family each on uninhabited islands. The distribution, abundance, ecology, and impacts of free-ranging cats and dogs in the biosphere reserve is almost unknown. There is evidence that feral dogs exist on Navarino Island (Fig. 2), but also on other islands of the Sub-Antarctic archipelago.
Their impacts on the austral wildlife include harassment and depredation of the world southernmost and isolated vulnerable guanaco (Lama guanicoe) population and the destruction of nests of ground-nesting waterfowls (ducks and geese endemic to Patagonia). A census of the local municipality's veterinarian in 2013 recorded 138 dogs and 75 cats living in 127 houses, while half of the dogs lived permanently in the streets of Puerto Williams (Fig. 3).
My study focuses on the human dimension of cats and dogs, their range and degree of independency of humans, and their impacts on biodiversity and humans in the Cape Horn Biosphere Reserve (project period March 2015-March 2018). My objectives are (1) to describe their demography, the care and functions of cats and dogs by their owners, (2) decode the immigration of pets into natural areas (Fig. 4), draw a distribution map of feral cats and dogs, describe the movement of free-ranging dogs, and (3) estimate the impact of free-ranging dogs on wildlife (e.g., native guanacos, invasive American mink Neovison vison), humans, and economic activities (e.g., livestock, tourism). The project also includes cooperation with the local authorities and veterinarian and offers outreach activities for pet owners such as a documentary (tentative title: "Depredating pets at the end of the world") and talks ("Where is my pet?) to stimulate responsible pet care among them in the long term.
I will use the following methodological approaches to reach my objectives. (1) I am using face-to-face question-naires with a representative sample of the people in town (n=216), rural farms (n=5), and families in Army posts (n=11), asking questions about demographic data on cats/dogs, care of pets, roles, sightings, experience with problematic situations, possible impacts, and acceptable solutions for diminishing the street population of dogs. (2) I am censusing the street dog population in Puerto Williams (using a capture-recapture approach during 5 days using photos for individual identification). (3) I am placing camera-traps in the surroundings of each of the 11 Army posts on uninhabited islands throughout the Cape Horn Biosphere Reserve both during the cold and warm periods. (4) I will place a total of 50 camera-traps in a grid placed in the surroundings of Puerto Williams to capture abundance and movement radius of village/feral dogs, and (5) I will use GPS collars with free-ranging village dogs (n=6) to monitor their movements, activity patterns and preferred habitats during excursions to the natural and pristine surroundings.
During the first months of this new project I have worked mainly with the questionnaires in town and Army posts, I have done my first census of street dogs identifying over hundred dogs, and set camera-traps in seven uninhabited islands. My major task during this first year of the project is to finish field work with questionnaires and the analysis of the results, so that I can provide a first set of sound information on pet's roles and care, why owners do no restrict the movement of their dogs, as well as the observed impacts on domestic animals and wildlife to the local authorities.