How Do Species Interact?

Grizzly Bear Feeds on a Jumping Salmon, Alaska
Ron Crabtree / Getty Images

Wildlife species interact with each other in numerous, complex ways. Fortunately, we can make some general statements about these interactions. This enables us to better understand the role species play within their communities and how individual species can positively or negatively affect the species around them.

Of the various types of interactions between species, most involve resources and consumers.

A resource, in ecological terms, is something (such as food, water, habitat, sunlight, prey) that is required by an organism to perform a vital function such as grow or reproduce. A consumer is an organism that consumes a resource (such as predators, herbivores, or detritivores). Thus, most interactions between animals involve one or more competitor species vying for a resource.

Species interactions can be categorized into one of four basic groups based on how the participating species are affected by the interaction. These include:

  • competitive interactions
  • consumer-resource interactions
  • detritivore-detritus interactions
  • mutualistic interactions

Competitive interactions are interactions involving two or more species that are competing for the same resources and all species involved in the competitive interaction are negatively impacted. Competitive interactions are in many cases indirect, two species consume the same resource but they do not directly interact with each other, instead they impact each other by the effect they have on the resource.

Consumer-resource interactions are interactions in which individuals of one species consumes individuals of another species. Examples of consumer-resource interactions include predator-prey interactions and herbivore-plant interactions. These consumer-resource interactions affect the species involved in different ways, the resource species is negatively impacted while the consumer species is positively impacted.

Detritivore-detritus interactions involve a species that consumes the detritus (dead or decomposing organic matter) of another species. The detritivore-detritus interaction is a positive interaction for the consumer and has no impact on the resource.

Finally, mutualistic interactions are interactions in which both species, resource, and consumer, benefit from the interaction.