Fire’s Effects on Wildlife

Direct Effects• Few studies, marked re-capture approach ideal

– Body size and mobility, i.e. burrowing, influence direct mortality

• Life cycle stages are impacted differently• Depends on fire regime

– Frequency, intensity, extent, and season– Extent-small area, greater ability to repopulate

• Must look at populations rather than the individual

Indirect Effects

• Fire severity and resulting successional patterns dictate wildlife habitats and the effect on wildlife

• Importance of fire regime

• (+/-) Consumer response is species dependent

Mechanisms of post-fire population change

• Population response to fire regulated by:– Availability of food resources– Changes in cover– Movement of populations in/out of

burned/unburned areas (migration, immigration)

Understanding the Consumer Response to Food Resources

• Fire alters production, species availability, and food quality

• Migration and immigration • Short term effects

– Deer mice in prairies or grasslands• Some mortality during fire may decrease populations • Adapted to postfire environment: insects, wind-

dispersed seeds, soil seed bank• Populations may increase several-fold in burned areas

Understanding the Consumer Response to Food Resources

• Alternatively, shift in food sources– Ex. Australian eucalypt forest

• Bettongs exploit fire adapted fungus

-- Ex. Primates in Borneo shifting food sources

• Flowers and fruits unavailable• Shift to foliar/herbaceous vegetation and caterpillars/larvae of wood boring insects

Consumer Response and Food Quality

• Pulse of higher quality new growth– Increase in protein (nitrogen content) in new

growth– New tender shoots with greater digestibility– Increase in population growth rates

• Ex. Domestic grazers

Changes in Cover• Burned vegetation results in drastic change in both physical and

thermal cover– Grasshoppers – decline after fire, require a well-developed litter layer

for habitat– Earthworms – found 10-20 cm below soil surface, direct affects only

with severe fires; may increase postfire due to increased plant productivity

• Physical protection from predation– Structure provides protective habitat– Affects visibility

Red-cockaded woodpecker in loblolly pine forests

• Forage behavior of woodpeckers: – Foraged at greater heights in areas of tall and dense

midstory vegetation– Concentrate foraging activities in forest stands or

openings with reduced midstory vegetation• Fire regime in Loblolly pine

– Fire-maintained, frequent surface fires – Changes in fire regime: fire suppression

TTYP• Why do red-cockaded

woodpeckers require fire in order for long-term survival of their populations in loblolly pine forests?

• What are the specific mechanisms?

Mortality of Cavity Trees

• Disturbance by prescribed burning, thinning, winds, and southern pine beetle increases cavity tree mortality.

Balancing Protective Cover and Food Availability

• Tallgrass prairie example• Bird response

• Increase in seed/insect availability• Decrease in cover, nesting habitat, and predator

protection

• Small mammal response • Some small rodents, i.e. prairie vole, are small

navigate litter layer and find seed• Other larger rodents, prefer burned area with

easier seed access

Structural Diversity• Interspersion of food resources and

cover

• Positive or negative effects depending on the severity and extent and the wildlife considered

• Reduced habitat heterogeneity by large extent, severe fires

Example: Structural Diversity• Habitat diversity

and complexity, each supports a specific faunal community– Ex. Snags

important for birds, mammals, reptiles, amphibians, and invertebrates

Plant Succession and Animal Response: moose & caribou in boreal forests

• Discuss the following questions:– How are moose/caribou affected by fire?– How would you design a management plan to

manage for moose OR caribou?– How would you design a management plan to

manage for moose AND caribou?

Plant Succession and Animal Response

• Browsers in North American boreal forest– Caribou eat lichen, slow

growth, easily burned• Caribou in late

successional – Moose eat woody

resprouts (birch, aspen)• Moose in early

successional

Structural Diversity and Patchiness• Mature cover provides

refuge for migration• Adjacent high quality

growth in burned areas

• Mosaics of food resources and cover create structural diversity– Ecotones - boundaries