Monitoring changes in feral swine abundance and spatial distribution

Abstract

Swine (Sus scrofa) have been introduced in many places throughout the world, and in many places they adversely affect the environment, economically impact agriculture, and/or harbour diseases transmittable to domestic livestock or humans. An easily applied method to assess their abundance is an important need for their management. To monitor efficacy of a swine control programme in Florida, data from passive tracking plots provide an index of feral swine abundance. The same track data coupled with plot locations to numerically describe the spatial pattern of swine activity gave an index of pervasiveness, and a simple rate of interception of damage sites to index damage was used. The assessments were conducted in January, May, and August 2000 in Jonathan Dickinson State Park, Florida, USA. Between the first two assessments a swine control programme removed 25 feral swine from the 8.3 km² study area, after which the value of the passive tracking index was reduced by 81% and the fresh damage index by 89%, while the index of spatial pattern (pervasiveness index) showed only a small localized concentration after control. In the three months following the second assessment, Park personnel removed three additional swine from the study area, and a follow-up assessment indicated slightly less swine activity than immediately after the post-control assessment, however the index of pervasiveness showed a similar spatial pattern of activity as the initial assessment, possibly indicating re-invasive pressure. The passive tracking plots proved to be an uncomplicated, easily applied means to gather data for assessing and comparing swine abundance and distribution.