1. Population Viability Analysis Lecture15

2. What sort of PVA model is appropriate? Puerto Rican parrot Black footed ferret DISCUSS What is gained from using PVAs?

3. USES OF PVA 1.Assessing the extinction risk of population Questions What type of model to use? Simple - 1 population, all individuals equal - 1 population, with st(age) structure - multisite- patch occupancy models Complex - multisite, structure+ spatially realistic Issues Data quality Parameter values may change

4. MORE USES OF PVA 1.Assessing the extinction risk of population 2.Comparing the relative risk in 2+ populations 3.Identify key life history stages to protect 4.Determining minimum reserve size 5.Determining numbers to release 6.Setting harvest guidelines

5. 2. Compare relative risks of populations Pacific salmon populations Allendorf et al. 1997 Aim: Assess threat, rank priority of acting

6. 2. Compare relative risks of populations Allendorf et al. 1997 Approach: use PVA to assess threat Used Stage-structured models Designated three levels of risk Very high: 50% within 5 yrs High: 20% within 20 yrs Moderate: 5% within 100 yrs Q. What additional factors may impinge on ranking management priorities?

7. 2. Compare relative risks of populations Allendorf et al. 1997 Combined estimated extinction risk with 1 2 3 To get overall priority for management

8. E.G. RED COCKADED WOODPECKER Endemic to southeastern US Nest in cavities in old pines Endangered Live in groups Males - breeder, helper, floater Females - breeder, floater 3. Identifying key stages for management

9. STRUCTURED MODEL

10. Modelling approach Identify stages (age/types) Data needed - transition probabilities - stage specific survival/fecundity Track numbers of each stage ASK - What parameter influences viability

11. Sensitivity analyses Sensitivity change in due to small absolute change in stage specific vital rates Elasticity change in due to small % change in stage specific vital rates

12. Parameter (M=male, F=female, Fldg =Fledgling) Q What factors had the biggest impact on lambda

13. STRUCTURED MODEL RESULTS Model most sensitive to 1.Changes in female mortality 2.Mortality of female dispersers 3.Fledglings/brood RECOVERY PLAN 1.Enhance dispersal to new sites by making nest cavities 2.Remove competing flying squirrels

14. 4. Estimating the reserve size necessary to protect grizzlies in BC Aim: establish 1 benchmark population/biogeoclimatic zone benchmark = unhunted, naturally regulated population How many bears and how big an area?

15. Approach- use PVA to get N with low risk of quasi-extinction (ie risk of falling below 100) in 20 years cubsyearlingsSub-adult F Adult F Data from 6 different grizzly bear popn’s ----> mean±SD Age-specific survival Age at first birth Fecundity (female cubs/adult female/year) Maximum age Stochasticity - environmental +demographic - no catastrophes Density dependence - none below K

16. RESULTS Initial NPextinctionTextinction (years) 100 1 1 1500.7 2 2000.0519 250 20 DensityArea needed Flathead Valley, seBC 6.4/100km 2 3900 km 2 South central BC 2.3/100km 2 10,700 km 2 But bears can/do move outside any fixed area ---> Recommendation??

17. Wielgus 2002 Biol Conservation Final recommendation for 6 reserves MVP = 250 animals = 11-15% BC pop’n Total area 51,000 km2 5% of land area of BC

18. Uses of PVA 5. How many individuals can be released Bearded vultures Disappeared from Alps in 19th century Restricted to Pyrenees, southern Balkans, Corsica and Crete

19. Uses of PVA 5. How many individuals can be released 1970’s reintroduction attempt - fails ---> captive breeding program 1986 2nd reintroduction program 1993 100 captive, 53 released into Alps Demand for captive birds was increasing How many birds can be released per year? When is the wild population viable? Bustamente 1996 Cons Biol 10 822-831

20. Approach Do PVA on captive population with varying numbers of fledglings used for reintroductions PLUG DATA INTO VORTEX Age specific mortality Fecundity - breed 7-31yrs; not density dependent No Inbreeding depression Catastrophe 1% chance Initial pop’n 50m 39f > 1 yr K = 200 set by $$$ cost

21. Kids released extinction ratetime (% in 200 yrs) 3m3f1.6 88 4m4f8.670 5m5f22.871 6m6f52.664 7m7f74.462 Q. How would you inform captive breeders what would best increase numbers to be released? actual

22. How viable is the reintroduced population? Approach PLUG MORE DATA INTO VORTEX Data available Fecundity - Pyreneean population Mortality - from released birds Inbreeding - likely Variance ??? OUTPUT - IF mortality as low as minimum estimates current population < 5% chance extinction in 200 yrs with no additional releases

23. Uses of PVA 6. Setting harvest limits for American ginseng Panax quinquefolium (COSEWIC) 1988 “threatened” 1989 export discontinued Harvest continues - but what is sustainable?

24. Approach used Nantel et al. 1996 Cons Biol 10 Stages in the life of a long lived perennial plant Seed  Seedling  1-leaf  2-leaf  3-leaf  4-leaf Assess mortality transitions and seed production 4 populations southern Ontario /Quebec Incorporate variance use between yr/between population variation

25. Seeds Seedling 1 leaf 2 leaf 3 leaf 4+ leaves Produce seeds Death Harvest Seedling 1 leaf 2 leaf 3 leaf 4+ leaves

26. Estimate growth rates of 4 populations under different harvest regimes

27. Estimate minimum viable population Ie lowest N 0 where extinction < 0.05 over 100 yrs MVP with no harvest estimated as 170 plants Quebec 3 popn’s >500 most <50 Ontario populations average 10-20 plants Canada12 known popns > 170 Implications Most pop’ns too small to harvest Annual harvest >10% will lead to extinction Rotation 5+ yrs would be prudent

28. The Major Challenges for PVA models Data requirements Developing robust variance estimators Incorporating change to the environment

29. What makes a good PVA? Understanding of the species ecology environmental disturbances/threats Species response to threats Assessment of Current state of population Future risks Evaluation of habitat as well as population Relevance to managers But NOT necessarily amount of data Why? Burgmann and Possingham 2000

30. PVAs - the bottom line Stochastic population models Tool for evaluating risk to populations Numerous uses -Accuracy - debated - - but allow assessment of the relative value of management options Major value may be that they organise information, engage stakeholders