In a forest, animals like voles and wood lice feed on plant roots and barks respectively. Among the other carnivores, foxes, shrews and owls are present in that forest. Following predictions are made by a group of observers who have visited the forest : 1. If the roots of the tree develop a disease, then voles and foxes will starve and not the owls. 2. Population of voles is dependent on wood lice population through food web. 3. If owl population declines, it will indirectly affect wood lice population. 4. If barks of tree are affected due to a disease, then reduction of wood lice will affect the shrew population forcing owls to eat more voles. Which of the above predictions is/are correct?

In this forest food web, voles (root-feeders) and wood lice (bark-feeders) are primary consumers [2]. Foxes, shrews, and owls act as carnivores. Prediction 1 is incorrect because owls, as generalist predators, often consume voles; thus, a decline in voles due to root disease would affect owls [3]. Prediction 2 is incorrect as voles and wood lice occupy different niches (roots vs. bark) and are not directly dependent on each other [3]. Prediction 4 is flawed because shrews are primarily insectivorous and would not necessarily force owls to switch to voles in a simple linear fashion without considering other prey. Prediction 3 is correct: a decline in the owl population (top predator) leads to a trophic cascade where their prey (like shrews or voles) increases, subsequently increasing predation pressure on invertebrates like wood lice [3].

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Decomposers or Saprophytes > p. 31
2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 1: Ecology > Herbivores are primary consumers which feed > p. 7
3. [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > Sl{ANl<Ari ffi IASACADEMY ,:: ' > p. 13