Monitoring wild pig populations: a review of methods

Abstract

Wild pigs (Sus scrofa) are widespread across many landscapes throughout the world and are considered to be an invasive pest to agriculture and the environment, or conversely a native or desired game species and resource for hunting. Wild pig population monitoring is often required for a variety of management or research objectives, and many methods and analyses for monitoring abundance are available. Here, we describe monitoring methods that have proven or potential applications to wild pig management. We describe the advantages and disadvantages of methods so that potential users can efficiently consider and identify the option(s) best suited to their combination of objectives, circumstances, and resources. This paper offers guidance to wildlife managers, researchers, and stakeholders considering population monitoring of wild pigs and will help ensure that they can fulfill their monitoring objectives while optimizing their use of resources.

Sympatric prey responses to lethal top-predator control: predator manipulation experiments

“…[37,38,88,[103][104][105]. We monitored populations of native and exotic amphibians, reptiles, ground-foraging birds and mammals of various sizes from small rodents (~15 g) to large herbivores such as kangaroos (Macropus spp.)…”

Evaluating and validating abundance monitoring methods in the absence of populations of known size: review and application to a passive tracking index

“…These peculiarities do not render the PTI method invalid because the precision of the estimates and the annual long-term abundance trends (measured at consistent times of year) reveal valuable information about these species. Examining trends across years using surveys from the same time(s) of year each year is an essential component for valid study design, regardless of the monitoring method (Engeman 2005;Engeman et al 2013). Besides, independent studies like that of Thomson (1992) on wild dogs show that these peak activity times are associated with increased vocalisation and territory maintenance during mating.…”

“…Some are also in relatively low numbers in the landscape and/or they occupy terrain and vegetation that makes them difficult to observe (Engeman and Witmer 2000;Witmer 2005;Engeman 2005). Various methods of surveying presence/absence, abundance or density are used to assess free-ranging species (see review in Lancia et al 1994) with the method chosen being a function of the objectives of the study, the resources available and the size, abundance and behaviour of the target species (Pollock 1995;Engeman 2005;Engeman et al 2013). Where direct observations or density estimates are not required or possible, indirect counts or indices of relative abundance are employed from which population trends may be monitored (Caughley 1977;Lancia et al 1994;Pollock 1995;Evangelista et al 2009).…”

Quantifying site-level usage and certainty of absence for an invasive species through occupancy analysis of camera-trap data

“…(Engeman et al 2013;O'Connell et al 2010). However, some analytical methods for estimating population metrics (e.g., density, abundance) and quantifying associated detection rates are not well suited for low density populations, for example, removal modeling (Davis et al 2016) and capture/recapture methods (Seber 1982).…”