Can predators regulate small mammal populations? Evidence from house mouse outbreaks in Australia

Abstract

During a 2-yr study Mus domesticus increased from rarity to abundance in 2 phases: in phase A mice reached medium densities and declined, in phase B they reached very high densities before declining to near extinction. Mice were apparently regulated by predators in phase A, but escaped from regulation to form plagues in phase B. The impact of predators at lower prey densities (phase A) was density-dependent. At higher densities (phase B) total predator response was inversely density-dependent and predators were unable to regulate the mouse population. The functional response curve increased linearly at lower densities and indicated a constant predation rate without satiation. At higher densities predators ate a similar amount regardless of density and appeared to be satiated. The main density-dependent effect was derived from the numerical response; at lower mouse densities raptor numbers increased proportionally with density, but remained constant and at lower numbers when mice were at higher densities. Predation of female mice was density dependent in phase A, but that of males was density-independent. At low mouse densities, predation and disease seemed to act on the mouse population, each independently of the other. Their additive effect may have regulated the mouse population in phase A, but failed to do so in phase B. -from Authors Show more