Disease risks and overabundance of game species

Abstract

Different studies have evidenced the relationship between host abundance and health status of wildlife populations. Diseases that benefit from wildlife overabundance can affect not only the fitness and trophy quality of game species, but also public health, livestock health, and the conservation of endangered species. This paper reviews a number of European examples to highlight the relationship between overabundance and disease in game species, and discusses the possibilities of limiting the associated risks. Management tools to estimate overabundance are needed for legislative purposes and for the monitoring of wildlife populations, but artificial feeding interferes in the objective measurement of overabundance. Therefore, we propose a multidisciplinary approach to diagnose if a given wildlife population is overabundant. This includes not only signs such as adverse effects on the soil, vegetation or fauna (first group), poor body condition scores, low trophy scores or low reproductive performance (second group), or increased parasite burdens (third group), but also the measurement of infectious disease prevalences (the fourth group of overabundance signs). This combined assessment of overabundance ideally requires the cooperation of wildlife managers, botanists, and veterinarians. Once a given wildlife population is defined as overabundant, it is difficult to establish palliative management actions. These can consist in banning certain management tools (e.g. feeding) or increasing the hunting harvest, but both of them are difficult to implement in practice. A close monitoring of both wildlife densities and wildlife diseases, the establishment of reference values for all signs of overabundance, and the mapping of the disease and density hotspots will be needed to design adequate risk-control measures for each particular situation.

Sarcoptic mange in red deer from Spain: Improved surveillance or disease emergence?

“…Gortázar et al, 2006). However, density-reactive indicators of fitness such as KFI, parasitation levels, trophy and body measurements, or fertility rates estimated by 138 complete red deer necropsies carried out by the authors in the affected and unaffected areas in Asturias show no significant difference, suggesting no relation of these factors with deer mange (data not shown).…”

Risk factors associated with the prevalence of tuberculosis-like lesions in fenced wild boar and red deer in south central Spain

“…Host populations enclosed by a fence (more or less permeable) are similar in many ways to extensively managed livestock, and therefore could be referred to as captive or semidomesticated animals. However, a precise definition for large game mammals in fenced estates is problematic since management systems vary widely [12,16]. This is even more complex for the ubiquitous wild boar, which is easily able to "undercross" fences.…”

“…A variety of hunting estates may be found across SCS, which can be classified as containing captive fenced cervid populations (large enclosures, generally at relatively high densities [12]) or having free-ranging native cervid populations (not enclosed). In addition, a small number of deer farms are present in Spain, although no data were available to include them in the present study.…”

When hunting benefits raptors: a case study of game species and vultures

“…In this context, due to the high consumption of hunting remains by vultures observed in our study area, it is necessary to monitor the effect of lead and other potential hazards on the scavenger population. At the ecosystem level, overabundance of game species could have negative impacts such as overgrazing or sanitary problems (Gortázar et al 2006). In fact, in the study area, a possible negative impact of red deer overpopulation on capercaillie conservation has been highlighted (Pollo et al 2003).…”