Fire Effects on Animal Populations

Most research regarding fire effects on fauna focuses on the population level, reporting changes in abundance and reproductive success of particular species following fire. Population changes are the net result of the behavioral and short-term responses such as injury, mortality, emigration, and immigration plus longer term responses that occur over years to decades. Studies of animal populations and communities are helpful in providing insights about the vigor or sustainability of a species in an area.

Numerous population studies report abundance and density of animals in relation to fire, but information on productivity and other demographic factors may be essential for understanding population responses. Research on the threatened Florida scrub-jay provides an example. The scrub-jay requires scrub oak associations (myrtle, Chapman, and sand live oak, ericaceous shrubs, and saw palmetto), often in areas with open pine cover (less than 15%), where pine densities are kept low by frequent understory fires. The best vegetation for the jays consists of mosaic of different age classes of scrub, most of which have burned within the last 20 years. Optimum scrub height is about 4.5 feet (1.5 m), interspersed with shorter scrub (Breininger and others, in press; Woolfenden 1973). Without fire, the oaks become too tall and the habitat too dense for the Florida scrub-jay because predators are not easily seen (Breininger and others 1995). Florida scrub-jay densities in areas with tall shrubs are sometimes greater than in areas with optimum-height shrubs. However, jay mortality in tall scrub exceeds reproductive success; the jay is unable to sustain a population in tall scrub, as it can in shorter scrub (Breininger and others, in press).

For information on how fire affects a specific group at the population level, see the following sections:

• Fire effects on bird populations
• Fire effects on mammal populations
• Fire effects on reptile and amphibians
• Fire effects on invertebrates

For information on how fire exclusion has effected animal populations in understory, stand-replacement, and mixed-severity fire regime types, see:

• Effects of altered fire regimes on animal populations