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Life Table Applications

Life Table Applications. Population Sampling. Problems Where is the population? Does it have borders? How much do you sample for population estimate? Some estimates indicate that as much as 50% of the population needs to be captured at some time. Live Census.

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Life Table Applications

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  1. Life Table Applications

  2. Population Sampling • Problems • Where is the population? Does it have borders? • How much do you sample for population estimate? • Some estimates indicate that as much as 50% of the population needs to be captured at some time.

  3. Live Census • Capture-Recapture (Peterson method)

  4. Assumptions • Assumptions of the Petersen Method • Population is closed, so N is constant (no immigration or emigration) • All animals have equal chance of getting caught in first sample • Marking individuals doesn’t affect catchability (not trap shy or trap happy) • Marks are not lost between sampling periods • Marks are reported on discovery in second sample

  5. Schnabel Method • Series of samples, marking each time • Ct = Rt + Ut • Ct = Total # of individuals caught in sample t • Rt = # of individuals already marked when caught in sample t • Ut = # individuals marked for 1st time & released in sample t

  6. Application of Method

  7. Omnivores

  8. Yellowstone Grizzlies

  9. Life span Adults can live approximately 25 years.

  10. Average age composition: Cubs 19% Yearlings 13% 2 yr. olds 11% 3-4 yr. olds 13% Adults 14%

  11. Grizzly claws

  12. Den Excavated - don’t use natural shelters About 5 X 4 X 8 feet Entrance normally faces north Entered in snowstorm - usually late November

  13. Dump Congregations

  14. Trapping

  15. Data • Information is taken for heart and other physiological data

  16. Weight is taken • Sex recorded

  17. Aging • Teeth impressions • Molar extraction

  18. Tag Application • Ear tag • Lanyards

  19. Radio Collar

  20. Bear taken to more remote area • Often returned

  21. Triangulation

  22. Triangulation

  23. Den • Tracking to Den • Data taken including temperature

  24. Satellite Data Recording • Data for den temperature and bear body temperature are recorded daily

  25. Sensor Placement • Temperature and light sensors • In den • On bear • Outside den

  26. Life Tables • Survivorship Data • Follow population over time • Census population • Death Data

  27. General Form

  28. Cohort (Horizontal, Dynamic)

  29. Time Specific (Vertical or Static)

  30. Combination • Average of many years’ census • (Combines static tables)

  31. Life Table & Reproduction

  32. Values Over Time

  33. Reproductive value The average contribution to the next generation that members of a given age group in a population give between their current age and death.

  34. Reproductive value • Reproductive value at an individual age OR

  35. Reproductive value Sum of current output and future possibilities taking survival into account Female gray squirrels Phlox drummondii

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