Source:  Marcot, B. G., and M. Vander Heyden. 2001. Key ecological functions of wildlife species. Pp. 168-186 in:  D. H. Johnson and T. A. O'Neil, editors. Wildlife-habitat relationships in Oregon and Washington. Oregon State University Press, Corvallis OR.
 

1  Trophic relationships
    1.1  heterotrophic consumer
         1.1.1  primary consumer (herbivore) (& see below under Herbivory)
              1.1.1.1  foliovore (leaf eater)
              1.1.1.2  spermivore (seed eater)
              1.1.1.3  browser (leaf, stem eater)
              1.1.1.4  grazer (grass, forb eater)
              1.1.1.5  frugivore (fruit eater)
              1.1.1.6  sap feeder
              1.1.1.7  root feeders
              1.1.1.8  nectivore (nectar feeder)
              1.1.1.9  fungivore (fungus feeder)
              1.1.1.10  flower/bud/catkin feeder
              1.1.1.11  aquatic herbivore
              1.1.1.12  feeds in water on decomposing benthic substrate
              1.1.1.13  bark/cambium/bole feeder
         1.1.2   secondary consumer (primary predator or primary carnivore)
              1.1.2.1  invertebrate eater
                   1.1.2.1.1  terrestrial invertebrates
                   1.1.2.1.2  aquatic macroinvertebrates
                   1.1.2.1.3  freshwater or marine zooplankton
              1.1.2.2  vertebrate eater (consumer or predator of
                       herbivorous vertebrates)
                   1.1.2.2.1  piscivorous (fish eater)
              1.1.2.3  ovivorous (egg eater)
         1.1.3  tertiary consumer (secondary predator or secondary carnivore)
         1.1.4  carrion feeder
         1.1.5  cannibalistic
         1.1.6  coprophagous (feeds on fecal material)
         1.1.7  feeds on human garbage/refuse
              1.1.7.1  aquatic (e.g., offal and bycatch of fishing boats)
              1.1.7.2  terrestrial (e.g., landfills)
    1.2  prey relationships
         1.2.1  prey for secondary or tertiary consumer (primary or
                               secondary predator)

2  Aids in physical transfer of substances for nutrient cycling
  (C,N,P, etc.)

3  Organismal relationships
    3.1  controls or depresses insect population peaks
    3.2  controls terrestrial vertebrate populations (through predation or
         displacement)
    3.3  pollination vector
    3.4  transportation of viable seeds, spores, plants, or animals
         3.4.1  disperses fungi
         3.4.2  disperses lichens
         3.4.3  disperses bryophytes, including mosses
         3.4.4  disperses insects and other invertebrates
         3.4.5  disperses seeds/fruits (through ingestion or caching)
         3.4.6  disperses vascular plants
    3.5  creates feeding, roosting, denning, or nesting opportunities for
         other organisms
         3.5.1  creates feeding opportunities (other than direct prey
                relations)
              3.5.1.1  creates sapwells in trees
         3.5.2  creates roosting, denning, or nesting opportunities
    3.6  primary creation of structures (possibly used by other organisms)
         3.6.1  aerial structures
         3.6.2  ground structures
         3.6.3  aquatic structures
    3.7  user of structures created by other species
         3.7.1  aerial structures
         3.7.2  ground structures
         3.7.3  aquatic structures
    3.8  nest parasite
         3.8.1  interspecies parasite
         3.8.2  common interspecific host
    3.9  primary cavity excavator in snags or live trees
    3.10  secondary cavity user
    3.11  primary burrow excavator (fossorial or underground burrows)
         3.11.1  creates large burrows (rabbit-sized or larger)
         3.11.2  creates small burrows (less than rabbit-sized)
    3.12  uses burrows dug by other species (secondary burrow user)
    3.13  creates runways (possibly used by other species)
    3.14  uses runways created by other species
    3.15  pirates food from other species
    3.16  interspecific hybridization

4  Carrier, transmitter, or reservoir of vertebrate diseases
    4.1  diseases that affect humans
    4.2  diseases that affect domestic animals
    4.3  diseases that affect other wildlife species

5  Soil relationships
    5.1  physically affects (improves) soil structure, aeration (typically by
         digging)
    5.2  physically affects (degrades) soil structure, aeration (typically by
         trampling)

6  Wood structure relationships (either living or dead wood)
    6.1  physically fragments down wood
    6.2  physically fragments standing wood

7  Water relationships
    7.1  impounds water by creating diversions or dams
    7.2  creates ponds or wetlands through wallowing

8  Vegetation structure and composition relationships
    8.1  creates standing dead trees (snags)
    8.2  herbivory on trees or shrubs that may alter vegetation structure and
         composition (browsers)
    8.3  herbivory on grasses or forbs that may alter vegetation structure and
         composition (grazers)

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