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