1Fish and Wildlife Population Ecology:The End Game…Okaloosa Darters… How are they doing?• Choctawhatchee Bay drainage in Florida • Inhabit vegetated sand runs of clear creeks• Listed as Endangered June 4, 1973• Fish and Wildlife Service has recommended downlisting to Threatened • How would you determine their status??Time Series of Abundance EstimatesRocky Creek2Population ProjectionPopulation ProjectionNt+1= Nt*exp(µ+E)Population ProjectionNt+1= Nt*exp(µ+E)3Which Model??Model AICc DeltaAICcExponential -1.953 0Gompertz 2.21 4.19Ricker 2.24 4.16Theta-logistic 8.24 10.194Past Abundance DataFuture Projection-Based on past data and anassumed model of growthOK, Now What?• Probability of Falling Below…(thousands)Golden-Cheeked Warbler (Dendroica chrysoparia)• breeds in closed-canopy woodlands, primarily Ashe juniper and oak• declined due to habitat loss and fragmentation from clearing of juniper for urban expansion, agriculture, and commercial harvest5Fort HoodFort Hood Army Post• Largest breeding population• BIG fire in 1996• Increased training demandsRecovery Credit System• Fort Hood “buys” the conservation rights to habitat patches on private lands• Unintentional loss of habitat on Fort Hood is “offset” by these purchases• Golden-cheek metapopulation remains “unharmed”How should off-post patches be valued?The Model• Stochastic, demographic-based, metapopulation projection modelStageaS Temporal Variance (S) FbTemporal Variance (F)HY 0.40 0.058 0 0SY 0.57 0.010 1.2 0.024ASY0.57 0.010 1.3 0.0066The Model• Ceiling carrying capacity (K)• Various dispersal scenarios• Metapopulation Viability– After 20 years…– Mean final population size?Fort HoodBalcones NWRImportant Drivers of Metapopulation Viability-0.4-0.200.20.40.60.81Reproduction Survival K DispersalSensitivity (SRC)Importance of Individual Populations 00.20.40.60.811.21.41.60 2000 4000 6000 8000 10000 12000 14000ImportanceSize of Habitat PatchSmaller is more important??Fort HoodBalcones7However…• Changing dispersal assumptions• Changed conclusions, substantially!Wolf Reintroduction Wolf Reintroduction totoNorthern Northern RockiesRockies• What impact are wolves having on elk and deer populations in Idaho?• What impact in future? – decreasing elk and deer, stable numbers or oscillations?• How answer?– Ask experts and check scientific literature– Gather important data– Synthesize data and test possibilities with a modelWhy model predatorWhy model predator--prey prey interactions?interactions?• Models help us1. Define our problem2. Identify what might be important3. Understand our data4. Communicate and test that understanding5. Make predictions8Modeling Wolf EffectsModeling Wolf Effects• What is important?• What would determine their effect on elk and deer?• Is there a theory of predator-prey interactions that will help us understand, predict and manage wolf predation on deer and elk?Predicting effects of wolf reintroductions Predicting effects of wolf reintroductions on ungulate populations: Comparing on ungulate populations: Comparing model predictions to observations for elk model predictions to observations for elk and wolves in Yellowstone.and wolves in Yellowstone.– by Edward O. Garton1, Douglas W. Smith2, Bob Crabtree1, Bruce Ackerman1, and Gerry Wright1– 1. Fish and Wildlife Dept., University of Idaho, Moscow, ID83844, – 2. National Park Service, Yellowstone Center for Resources, P.O. Box 168, Yellowstone National Park, WY 821901990 Approach1990 Approach• Evaluate dynamics of Northern Yellowstone Elk Herd using available data• Predict characteristics of wolf population growth and predation from literature• Build an empirically based projection model• Validate portions of the model by comparing predictions to observed data9• 1990’s predicted success for wolves• Northern Yellowstone elk herd projected to be stable with high chance of persistence but average abundance depends on– Hunter harvest– Winter severityImplications:Implications:Hunter HarvestHunter Harvest• Population trend for Northern Yellowstone Elk herd was very sensitive to: • Human harvest rate– @ 9% harvest (‘70-’80s) - Stable with wolves– @ 11% harvest (’95-’05) - Declines with wolves– @ 7% harvest - Increases with wolves– @ 9% harvest - Increases without wolvesImplications:Implications:Winter SeverityWinter Severity• Population trend for Northern Yellowstone Elk herd at current size is very sensitive to:• Winter severity:– Average severity: population stable– Mild winters: population increases 10% / year– Severe winters: population decreases 10% /year• In 1/3 of years, population either increases or decreases at least