Predator-Prey Dynamics: The Role of Predators in the Control of Problem Species

A study was conducted to look at the relationship betweenpresence and numbers of wild dog (Cuon alpinus) andpresence and abundance of wild boar (Sus scrofa). This wascorroborated with scat analysis to get percentage of the preyconsumed by wild dogs and other predators. A preliminarynationwide presence-absence survey of C. alpinus populationshowed that with the exception of Trashigang, SamdrupJongkhar and Pemagatshel, all the other dzongkhags reportedpresence of wild dogs. Wild dog density was then comparedwith relative wild boar density using a simple linearregression analysis.A negative relationship between increasing wild dog numbersand decreasing wild boar density was detected. The R2 valuefor the regression was 0.60 — meaning that about 60% of therelative amount of variance in wild boar density is explainedby the number of wild dogs present in an area. Theunexplained 40% could be due to other factors such ashabitat conditions, food availability, control measures, otherlarge predators, diseases, and so on.An analysis of variance (ANOVA) carried out on therelationship gave a significant value (F= 12.30 >> Fs = 0.007),meaning that the average number of boars in the differentstudy areas are significantly different from each other, or thatdifferent pack sizes of wild dogs have significantly differenteffects. The slope of the regression line was negative 0.1. Thusfor every unit increase in wild dogs presence there is a 0.1unit decrease in relative wild boar density.About 37% of wild dog diet consists of domestic animals suchas cattle and horses. The other 63% is wildlife. Of this 63%,65 numbers of scat found contained wild boar remains. Thisindicates that from the wild herbivores preyed, about 58% ofwild prey consumed are wild boar. Overall, includingdomestic animals, wild boars make about 36% of the wilddog’s diet.In terms of resource partitioning based on sign densities, thethree predators (tiger, leopard, and wild dog) avoid conflictwith wild boars by using different habitats and throughengaging in vastly different hunting behaviour. For instance,leopards have more fixed and stable home ranges, closer tohuman habitation while tigers have larger home ranges butwell away from any human settlement. Wild dogs are moretransient and travel frequently over a large distance; theirhome ranges overlap with that of tigers and leopards. Sincetheir presence is fleeting, they rarely come in conflict with theother predators.