info:eu-repo/semantics/doctoralThesis
GRADUAL AND ERUPTIVE DYNAMICS OF RODENT PESTS: Outbreaks in house mice in Australia and common voles in Spain
Autor
Correa Cuadros, Jennifer Paola
Institución
Resumen
Rodent plagues are usual on crops around the world causing severe economic damage and health problems by zoonoses. The thesis project worked on two rodent plagues: Australian house mouse and Spanish voles which generate economic loss on crops. They have complex population dynamics with endogenous and exogenous influence factors, and an absence of a causal explanatory mechanism to predict their outbreaks. House mice in Australia are a plague with irregular population dynamics and cause considerable damage on cereal crop systems. We used a 20-year mouse mark-recapture dataset from Walpeup (Victoria), Roseworthy (South Australia) and Darling Downs (Queensland), and climatic and predator variables. We employed seasonal and annual models to understand the increase and decrease of the population through different drivers. In south-eastern Australia, the rate of increase was best explained by low evaporation in summer, high cumulative winter rainfall, and an index of abundance of the Nankeen kestrel (Walpeup), and the Brown falcon (Roseworthy) during summer to autumn. The Queensland mouse outbreaks were explained by spring to summer rainfall from two years before the plague, and previous mouse abundances. On the other hand, the South-eastern decline rate was explained by outbreak abundance and predators like the Barn owl to Walpeup and Swamp harrier to Roseworthy. The Queensland collapse was related to outbreak abundance (density-dependence) and Barn owl density. We conclude that South-eastern mouse dynamics can be defined as an eruptive dynamic caused by weather triggers that allow the population to obtain more and better resources avoiding being consumed by predators. Queensland outbreaks can be defined as gradual because they are generated by changes in rainfall and a strong density-dependence. These results are useful to explain and predict the outbreaks, understanding the mechanisms that cause the mice explosion on wheat production sites.
The common voles in Spain are an example of an irruptive species that every three or four years reaches plague numbers and causes considerable damage in cropping systems. We used an 11-year mark-recapture dataset from Castilla y León region (Zamora, Valladolid, and Palencia) and various climatic, competitors and predator variables, employing seasonal and annual models to understand the drivers of the population increase and decrease. We examine the climatic effects, interspecific competition (Wood mouse, Algerian mouse, and Shrew), and weasel’s abundance to examine the predators’ role. The rate of increase of vole populations was best explained by high cumulative rainfall (autumn to spring) in the two years prior to the outbreak, spring and summer humidity, and spring weasel’s abundance. The rate of population decline over winter was best explained by abundance in the peak season (density-dependence) and autumn precipitation. We conclude that the outbreaks of Spanish voles are classified as eruptive because depended on precipitation and humidity, an index of food supply and burrows, and weasel’s density. The results are useful to predict future outbreaks to reduce their economic impact on alfalfa and cereal crops.