Question

A population of wolves predates a population of moose on Isle Royale, Michigan, where there are fewer wolves than moose to start. The wolves prey on the moose and eat well, allowing them to have abundant offspring. However, as the wolf population rises, the moose population drops, and over time, the wolf population begins to drop also because of the reduced availability of resources. As the wolf population drops, moose are able to better survive and reproduce, causing the moose population to rise. With this abundance of moose, the wolf population is able to rebound until their population exceeds the moose population’s ability to support the number of wolves. Which population dynamic does this series of oscillations represent?

Answer 1

Complete question:

A population of wolves predates a population of moose on Isle Royale, Michigan, where there are fewer wolves than moose to start. The wolves prey on the moose and eat well, allowing them to have abundant offspring. However, as the wolf population rises, the moose population drops, and over time, the wolf population begins to drop also because of the reduced availability of resources. As the wolf population drops, moose are able to better survive and reproduce, causing the moose population to rise. With this abundance of moose, the wolf population is able to rebound until their population exceeds the moose population’s ability to support the number of wolves. Which population dynamic does this series of oscillations represent?

1. Delayed density dependence
2. Delayed density independence
3. Extinction vortex
4. Carrying capacity

Answer:

1. Delayed density dependence

Explanation:

The Delayed density dependence occurs when two species are in interaction (prey-predator or parasite-host), and the dynamic of each population follows the dynamic of the other population. The natality and mortality rates of one species follow the rates of the other species.

Delayed density dependence dynamics regulate populations and allow the occurrence of equilibrium or balance in nature.

Predator-prey scenarios

Assuming that the prey lives in the ideal environment with no predators, it shows an exponential growth rate. Prey can grow, develop, and reproduce, increasing its population size. The more available items, the more predator there will be. The predator population increase in size, and its presence affects the prey populations, leading it to decrease. So there are fewer available items to prey on.    

The prey population also affects the predator population. After the increase in the predator population size, the number of available prey decreases. The predator lives in an ideal environment but depends on the prey density. The more predators there are, the fewer prey there will be left. The predator population decreases exponentially due to the item's lack. The predation rate depends on density as well as natality and mortality rates.

So, to sum up,

1. prey population increases in size
2. predator population increases in size
3. prey population decreases in size
4. predator population decreases in size

In this particular example, the wolves population follows the moose population and vice-versa. It is not simultaneous. It happens with a delay.

Moose influences the wolf population because they are their source of food. The more moose, the more wolves there are. The fewer moose, the fewer wolves there are.

This is a density-dependent dynamic because both populations are affected when they reach a high value.