Group Territoriality, Dispersal and Population Persistence in an Endangered Species

Endangerment

• Loss of Required/Preferred Habitat• Habitat Fragmentation• Habitat Degradation

Number of TerritoriesDispersal Distance Between Territories

Red-Cockaded Woodpecker

Picoides borealis

Endangered 1985- USFWS

Group TerritorialityCooperative Breeding

Male Helpers

Red-Cockaded Woodpecker

Excavate Nesting Cavity80+ Year-Old Pine, Heartwood

Endemic

Mature Pine Forests, Southeast

Extinction: Causes

1. Demographic StochasticityAmong-Individual Variation

2. Environmental StochasticityAmong-Generation Variation

3. Catastrophe4. Inadequate Genetic Variation

Avoid Extinction: Viable Population

Commonly Large Enough to Withstand Demographic and Environmental Stochasticity

Catastrophe Difficult to Plan

Red-cockaded WoodpeckerUSFWS: Large Enough to Avoid Loss Alleles Thru Genetic Drift

Red-Cockaded Woodpecker

Recovery Plan• Preserve Breeding Habitat and Establish

New Populations• Maintain Viable Local Populations

Challenges• Habitat Loss (Fewer Territories)• Fragmentation (Greater Dispersal Distance)

Red-Cockaded Woodpecker

Letcher, Priddy, Walters & Crowder (1998)Biol. Conservation 86:1 – 14.

• Between-Sex Behavioral Differences in Dispersal

• Territory Availability

• Spatial Aggregation of Territories“Clumped” Reduced Dispersal Distance

Letcher, Priddy, Walters & Crowder (1998)Biol. Conservation 86:1 – 14.

Territories “fixed” by availability of old trees

Breeding pair and non-breeding helpers Competition for breeding status/territory

Female fledglings disperse, long distanceMale fledglings remain as helpers

Breed on natal territoryDisperse, short distance

Female Life History: Disperse to Breed

Male Life History: Most help before breeding

Letcher, Priddy, Walters & Crowder (1998)Biol. Conservation 86:1 – 14.

J. Walters: 25 yrs.; behavior and life histories

> 200 groups in North Carolina> 2000 individuals

Data to parameterize demography/conservation model

Territory number (habitat loss)Spatial pattern (dispersal distances)

Letcher, Priddy, Walters & Crowder (1998)Biol. Conservation 86:1 – 14.

Letcher, Priddy, Walters & Crowder (1998)Biol. Conservation 86:1 – 14.

Letcher, Priddy, Walters & Crowder (1998)Biol. Conservation 86:1 – 14.

Letcher, Priddy, Walters & Crowder (1998)Biol. Conservation 86:1 – 14.

Population Persistence

Clutch size (obvious)

Female Dispersal (Long Distance)

Avoid Mortality, Find Breeding OpportunityNumber of Territories

Male Dispersal (Short Distance)Find/Compete Breeding OpportunitySpatial Aggregation of Territories