What defines an indicator species?

An indicator species is specifically defined by its ability to reflect the environmental conditions and health of its ecosystem. These species can be sensitive to changes in their habitat, such as pollution levels, climate changes, or other ecological pressures. When the population of an indicator species declines or fluctuates, it can signal potential problems in the ecosystem that may need closer examination.

For example, the presence of certain amphibians can indicate good water quality, whereas a decline in their population may suggest pollution or habitat degradation. This characteristic makes indicator species extremely valuable for environmental monitoring and conservation efforts, as they help scientists and ecologists assess the overall health and integrity of ecosystems.

The other options provided do not accurately define the role of an indicator species in ecological studies. The size of a species, the mobility, or whether it is a predator does not inherently relate to its capability to indicate ecosystem health.