1. Sustainable harvest of Finnish moose population? Esa Ranta, Anne Luoma, Veijo Kaitala &FGFRI

2. Contents Basic information on Finnish moose population and harvest

3. Contents Basic information on Finnish moose population and harvest Stochastic IBM model

4. Contents Basic information on Finnish moose population and harvest Stochastic IBM model Four questions

5. Contents Basic information on Finnish moose population and harvest Stochastic IBM model Four questions Four answers

6. Moose (Alces alces)

7. Economical damages (forest damages, traffic accidents) -> pressure to decrease the population size (expecially the winter population size) Economically important game animal -> pressure to keep the size of the harvestable population high

8. Population size estimates: Hunter observations (during the hunting season) +their estimate of post-harvest pop.size Wildlife triangle (snow track census) Aerial surveys 20-50% of population is killed annually. Age structure of population is controlled. Reproduction rate is high (mostly due to high harvest rate of young animals) Moose population in Finland

9. The moose population and the annual harvest in Finland 1930 - 2000. 0 20 000 40 000 60 000 80 000 100 000 Winter population Harvest 1930195019701990 Number of moose 2000

10. Killed animals (ind/100km 2 )

11. with individual based, stochastic model Modelling moose population dynamics Annual reproduction rate = 0.9 calves/ a female Non-hunting mortality = 5% of winter population Hunting mortality (hunting rate) 15 - 25% of the harvestable population

12. Hunting mortality Mortality Cows Bulls 2-Years -old Cows 2-Years -old Calves (Male) Calves (Female) Population renewal Maturation

13. Question #1 Given the current population status What is the risk of moose population decline? (10 year time-window)

14. Probability of population decline Hunting rate of females

15. Answer #1 The risk of moose population decline increases substantially when annual harvest fraction inceseses from 15% of the harvestable population size (10 year time-window)

16. Hunting mortality Mortality Cows Bulls 2-Years -old Cows 2-Years -old Calves (Male) Calves (Female) Population renewal Maturation

17. Question #2 Given the current population status, with errors in population estimates The wish is to reduce current population to a much lower lewel What will happen? (10 year time-window)

18. There are reasons to limit the population size. But if we want to get the pop. size really low, It is important to know: What if.. - the population size is overestimated or underestimated? - estimations tend to be biased? How crucial effects do inaccurate estimates have on moose population?

19. RealEstimated Population size in winter: 10 0008 000 - 12 000 Targeted population size 5 000 Population size in autumn: According to model 1.5 * winter pop. (realistic and productive populations); 10 000 - winter= 12 000 - 18 000 mortality + birth Hunting (h): h = Estimated pop. size - 5 000 animals Left: pop. in autumn - h = ?estim.pop. - h = 5 000

20. Different types of estimation errors: 8500 11500 10000 No peakPeak: Real population size = 10 000 Real 800012000

21. ”Realistic” population structure Population sizes after hunting

22. ”Realistic” population structure 0 500 1000 0 300050007000 9000 Population size after hunting Cumulative sum

23. Answer #2 With uncertain population estimates reduction of curent population size to a lower targeted size will yield to population sizes that are much lower than the target (10 year time-window)

24. Hunting mortality Mortality Cows Bulls 2-Years -old Cows 2-Years -old Calves (Male) Calves (Female) Population renewal Maturation

25. ”Mooses come walking over the hill Mooses come walking, they rarely stand still When mooses come walking they go where they will When mooses come walking over the hill” - Arlo Guthrie

26. Question #3 How does landscape structure influence risk of moose population decline due to harvesting?

27. Moose populatin in landscape

28. Moose population in landscape Risk of population decline Dispersal success

29. Answer #3 Under many different dispersal scenarios risk of population decline is the highest in the corner units, then come the border units The risk is the lowest in the central units

30. Hunting mortality Mortality Cows Bulls 2-Years -old Cows 2-Years -old Calves (Male) Calves (Female) Population renewal Maturation

31. Question #4 What is the hunting strategy yielding the highest harvest with a given targeted population size?

32. Moose harvest in Finland Winter herd, ind. 10 km -2 Harvest, ind. 10 km -2

33. Harvest scenarios Harvest Winter herd size

34. Maximum harvest, target = 4 ind. km -2 Total harvest, ind. km -2 Intercept Slope

35. Answer #4 Winter herd size Harvest

36. Conclusions The simple IBM model on moose population renewal has served us well in answering a few basic questions on the future of moose and moose harvesting in Finland

37. Conclusions The model does not rely upon very complex assumptions (births, deaths, sex, harvesting), yet we believe it captures the essence of moose life

38. Conclusions The model prompts where more information is needed –dispersal, population estimates, harvest management Some of the answers would not necessarily have called for an IBM model