Does the interface with plantation forests provide suitable habitat for axis deer (Axis axis) to avoid systematic hunting pressure in a protected area of north-eastern Argentina?

Abstract

Axis deer (Axis axis), an introduced invasive species of growing concern around the globe, have rapidly expanded through the southern cone countries in South America. Despite increasing culling efforts over 14 years, axis deer remained abundant at El Palmar National Park in north-eastern Argentina. We tested whether this continued abundance possibly reflected control failures as a result of adjacent plantation forests providing a safe-haven refuge for deer. We carried out a cross-sectional survey of deer faecal pellet groups and tracks in 77 matched pairs of 25 m2 plots deployed at random over the park–plantation interface and assessed the presence of deer trails along the 14.2-km wire fence between both land-use types. The relative odds of having at least one pellet group (occupancy) were 4.5 (95% CI 1.5 to 18.3) times higher among park plots than plantation plots. Using generalized linear mixed models, the relative odds of occupancy decreased significantly with increasing distance to the main permanent water course, but it was 83% lower in plantation plots than in the park plots. Principal component analysis of shrub cover, plant structure and plant height revealed greater shelter within the park. Deer trails were spatially aggregated up to 2300 m and were directly associated with deer occupancy. These results indicate that, in El Palmar National Park interface, plantation forests do not provide a refuge or selected habitat, and suggest instead that the environmental characteristics and diversity of habitats within the protected area are relevant for the effectiveness of the exotic ungulate management program.