Question

The predator-prey relationship between gray wolves and moose on Isle Royal in Lake Michigan has been studied for decades. Although both populations fluctuate, the moose have never been driven to extinction. In this case, as well as many others, wildlife ecologists and managers often refer to the victims of predation as a “doomed surplus.” Use the concepts of reproductive value and survivorship to discuss what this means.

Answer 1

The moose population never seems to go extinct because the victims of predation are doomed surplus. Doomed suprlus refers to that proportion of a population which will die and eventually won't be able to achieve the mean reproductive value of the population even in the absence of predation. Such individuals are doomed to die anyway and may die due to several natural ecological factors such as starvation due to limited resources and increased population density, sickness, etc.

This concept presumes that predation does not affect overall survivorship in moose population since predators take down the individuals which have low fitness (health and reproductive) such as the weak and sick who would die even in absence of any predation. Due to this, predation will not affect either the reproductive value or survivorship of any age class. This type of predation is called compenstory predation since it compenstaes for other existing sources of mortality.

Compensatory predation suggests that predators do not control any prey populations and rather take down the already doomed to die individuals (doomed surplus). Thus predators will not have any additive effect to prey mortality.