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Owls as natural rodent control in Argentina: an approach to mitigating hantavirus infections

By Carlos Ale

Barn Owl carrying prey. Photo by Nico Perez.


Raptors, and owls in particular, are among the best sources of natural rodent control in the world. In northern Patagonia, South America, four owl species regularly live in association with forests, including the Barn Owl (Tyto alba), which is recognized as a highly efficient consumer of rodents. A Barn Owl can eat more than a thousand mice in a year, providing a very important service in terms of pest control and mitigating the spread of diseases rodents carry. In Chile and Argentina, such diseases include hantavirus, a zoonotic disease caused by ANDV South, an endemic virus of Patagonia, which may be transmitted to people.

Estimated hantavirus risk in southern Argentina. Map by Andreo et al. 2014.


Once a person is infected with hantavirus, it develops very quickly, affecting the lungs and causing deaths in 30-50% of cases. There is no vaccine against this virus, so prevention by reducing human-rodent contact is the best strategy to avoid it. Transmission to humans occurs by inhalation of the virus in aerosols with particles of saliva, feces or urine of vector rodents in contaminated environments. Rodents that act as hantavirus reservoirs live in natural environments, such as woodland and bushy habitats, but tend to increase in numbers in human-modified environments. These include areas that have been transformed by farming and other rural and domestic activities, which in turn feature elevated disease risks for people who live or work in such environments.

Carlos Ale searching for owls in Lago Puelo National Park, Chubut, Argentina. Photo by Ernesto Juan.


Paradoxically, in the areas where human expansion increases hantaviral disease risk, owls face habitat loss and also fall victim to poisons used to combat rodents. Anticoagulant rodenticides affect owls by sickening and killing owls that consume poisoned rodents. Moreover, owls are frequently persecuted due to negative perceptions of them by misinformed citizens, further exacerbating the threats they face from habitat loss and poisoning.

Map of the study area at Lago Puelo National Park, Chubut, Argentina. Map courtesy of Lago Puelo National Park.


Supported by a Partnership Grant from IBCP, I am working to increase the visibility of owls and their roles in rodent control in and around Lago Puelo National Park, Chubut, Argentina. Through my research and outreach, I aim to increase public appreciation and esteem for owls and to generate awareness of the environmental and health risks of anticoagulant rodenticides among citizens in the northern Andes of Patagonia. Gaining a greater appreciation of owls and their benefits will in turn allow people greater understanding of the ecosystem services provided by all birds of prey, along with greater incentives to avoid practices that threaten them.

Lago Puelo National Park, Argentina. Photo by Carlos Ale.


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