The aftermath of a fire looks very devastating with the blackened ash and the landscape apparently void of vegetation. However, within a few days the green sprouts of plants begin to appear. The question is what has happened to the animals? Have they been destroyed by the fire? Is the fire as good for them as it is for plants such as the warm season grasses?

Answers to these questions have been sought over the past ten years on the Konza Prairie Research Natural Area, which is in the northern Flint Hills of Kansas within the tallgrass prairie ecosystem. The fires, which occurred in April, were controlled burns on areas not grazed by cattle (Bos taurus). The animals investigated from the population biology perspective include below ground macroinvertebrates, grasshoppers, earthworms, birds and mammals.

There are three categories of response to fire by a species: 1) fire neutral, 2) fire positive, and 3) fire negative. Whether a species is in one of these three categories depends on the time of the fire within the season, the frequency of fires over time, the extent of the fire, and the intensity of the fire relative to the life history of the animal under study.

Fire neutral species are species that do not show a change in population after the fire relative to population size before the fire, or they show no differences on burned areas relative to unburned areas. Fire positive species show an increase in population size after a fire relative to population size before the fire or higher populations on burned areas than on unburned areas. Fire negative species show a decrease in population size after a fire relative to population size before the fire and have lower populations on burned areas than on unburned areas.

In general those small mammal species that eat leafy materials (folivores) and typically have nests made of leafy material at the soil surface, such as prairie voles (Microtus ochrogaster) and hispid cotton rats (Sigmodon hispidus) are fire negative. Species, such as the western harvest mouse (Reithrodontomys megalotis), that have leafy nests at the surface and are more omnivorous (i.e., eating both seeds and invertebrates) are also fire negative. Fire positive species, such as the deer mouse (Peromyscus maniculatus), hispid pocket mouse (Chaetodipus hispidus), meadow jumping mouse (Zapus hudsonius), and the thirteen lined ground squirrel (Spermophilus tridecemlineatus), eat primarily seeds and insects in habitats that have little cover and nest in burrows under the ground. The diversity of small mammals is highest with an intermediate frequency of fire because both fire positive and fire negative species are present.

Among grasshoppers, fire positive species forage on grasses, while fire negative species are species that forage on forbs. Both of these patterns are modified by the way the grasshoppers overwinter (i.e., as eggs or larvae and where these eggs or larvae are located during the fire). Those species that have eggs or larvae in litter or on vegetation are typically fire negative, while those species with eggs or larvae at or below the soil surface are fire positive. Fire frequency seems to set broad limits to the assemblage of grasshopper species within a local community. The diversity of grasshoppers is highest with an intermediate frequency of fire.

Among grassland nesting birds the only species found to be strongly fire negative is the Henslow's sparrow (Ammodramus henslowii). Some species such as the greater prairie chicken (Tympanuchus cupido) and upland sandpiper (Bartramia longicauda) are fire negative early in the nesting cycle and fire positive later in the nesting cycle (i.e., they rarely nest in burned areas) but take their precocial young to the recently burned areas. Greater prairie chickens will move their lekking ground a few meters to be on recently burned areas. Dickcissels (Spiza americana) are fire neutral because some of the forbs in which they nest are negatively affected by fire and some of the forbs are positively affected by fire. Birds that are nesting during the time of the fire have their nest destroyed, but all renest including greater prairie chicken, ring-necked pheasant (Phasianus colchicus), mourning doves (Zenaida macroura), and northern bobwhite quail (Colinus virginianus). Mourning doves show a negative response to fire early in the breeding season by not nesting on burned areas, but show a positive response later in the breeding season.

Three species of large mammals - the white tailed deer (Odocoileus virginianus), bison (Bos bison), and pronghorn (Antilocapra americana) - can all run from the fire. None of them typically have their young during the spring burning season. All have been shown to prefer foraging in recently burned areas in late spring and early summer and thus are fire positive.

In general, the biomass of below ground invertebrates increases with fire for those groups studied. Below ground macroinvertebrates are more numerous in annually burned areas than unburned areas. Biomass of the native earthworms Diplocardia smithii and D. verrucosa increases with burning, while the biomass of an introduced European species Aporrectodea turgida decreases with fire. This difference in responses may reflect the evolution of the native species and its interactions with fire as compared to the European species.

Fire obviously kills those individuals that are caught in the fire and cannot escape, and slow moving animals are more susceptible to being burned (e.g., turtles and snakes). There are some reports of many individuals killed by fire, but remember that most prairie animals have evolved with these periodic events we call fire and have adapted to the presence of fire. How a species is affected depends on the life history of the animal, the time and intensity of the fire, and the frequency of the fires.