SAK Does Not Work in Earn-A-Buck Units Key Assumption of SAK: –Buck Harvest can Index Population Trends –Buck Harvest Rates are Relatively Stable Buck Harvest Rates Affected by: –Earn-a-buck Permit Structure

1996 Earn-A-Buck Units 16 farmland management units Developed a accounting-style model Patterned after POP-II –commercially available big game population model Similar to bear and furbearer population model we have used for many years

Accounting Population Models Deterministic: checkbook accounting style models Simulates changes over time in number of deer in each sex- and age-class. Model does not directly estimate population size: –Requires input of population size in initial year –Simulate seasonal changes in population size over several years –Simulated trends sensitive to initial population size –Can estimate likely population size if independent population trend data exists Assess effects of future harvest strategies

Population Model Inputs Initial population size, sex & age composition Harvest mortality by sex and age Age- & year-specific pregnancy rates, litter size Age-specific rates of summer and winter non- harvest mortality Registration compliance

Population Model Logic 1. Create pre-birth population for initial year A. Initial number of deer B. Sex ratio of adults in initial year C. Age composition in initial year 2. Determine fawn production A. Age-specific pregnancy rates B. Mean litter size C. Age composition of females in pre-birth population D. Sex ratio of fawns 3. Add fawn production to pre-birth population for post-birth population and increase ages by 1 (eg. fawns become yearlings, etc.)

Population Model Logic 2 4. Subtract summer non-harvest mortality from post-birth population to determine pre-hunt population 5. Determine harvest by age and sex using: A. Total registered harvest by antlered/antlerless (mandatory registration) B. Age structure of harvest (aging data) C. Estimate of registration compliance 6. Subtract harvest from pre-hunt population to determine post-hunt population 7. Subtract overwinter non-harvest mortality from post-hunt population to determine pre-birth population in year 2 8. Repeat steps 2-7 for year 2, year 3, etc.

Example of calculations used to create pre-birth population in year 1

Example of calculations used to determine kit production

Kit production is added to pre-birth population for post-birth population

Summer losses = post-birth population * summer non-harvest mortality rates

Subtract summer losses from post-birth population to determine pre-hunt population

Harvest by sex and age

Subtract harvest related mortality from pre-hunt population to determine post-hunt population

Winter Losses = Post-Hunt Population * Winter Non-Harvest Mortality Rates

Subtract Winter Losses From Post-Hunt Population to Determine Pre-Birth Population in Year 2

Simulated Population Trend for Wisconsin Fishers

Simulated trend sensitive to initial population size

Fisher Tracks/Transect, Statewide,

Calibrate simulated population to independent information on population trend

Population Model Assumptions Does Not Assume: –Harvest age structure reflect population age structure –Buck harvest rates are stable Does Assume: –Initial population size and composition can be accurately estimated –Nonharvest mortality rates and reproduction can be accurately estimated

Accounting Models Most Useful When long histories (10+ years) of independent estimates of population size or trend are available