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Unformatted text preview: Is augmenting the population of juvenile turtles an effective way recover the population? Lecture Four Outline Stage Structured Population Models I. Why build stage structured models? I. How to express as a matrix model I. How to gather the appropriate data I. Elasticity analyses I. Agebased models H How do we measure abundance? 1.Direct counts of the entire population 2. Directly count a random subset of the population 3. MarkRecapture methods H Direct counts of entire population Good for rare, sessile organisms What about mobile species? Mark Recapture Trap and mark and release some individuals at one time point At some later date, trap again H Mark Recapture Trap and mark and release some individuals at one time point At some later date, trap again On day 1, you marked 20 individuals What fraction of the total individuals did you capture? Example H Mark Recapture Trap and mark and release some individuals at one time point At some later date, trap again On day 1, you marked 20 individuals What fraction of the total individuals did you capture? A week later, captured 30, 10 of which were marked Thus, one third of the population is marked. H Example Mark Recapture Trap and mark and release some individuals at one time point At some later date, trap again On day 1, you marked 20 individuals What fraction of the total individuals did you capture? A week later, captured 30, 10 of which were marked Thus, one third of the population is marked. Therefore there are about 60 individuals total H Example Estimate of Population Size = # captured and marked day 1 1 Fraction marked (from 2 nd date) = 30 10 1 20 60 On day 1, you marked 20 individuals What fraction of the total individuals did you capture? A week later, captured 30, 10 of which were marked Thus, one third of the population is marked. Therefore there are about 60 individuals total H Major Assumptions: Equal probability of catching any individual at any given time Tagging the animal does not modify its behavior H Lecture Four Outline Stage Structured Population Models I. Why build stage structured models? I. How to express as a matrix model I. How to gather the appropriate data I. Elasticity analyses I. Agebased models H Model of Geometric Growth t t N N = + 1 number next year = the multiplicative number this year rate of increase t t N d b N ) 1 ( 1 + = + H N t +1 = N t deaths dN t + births bN t b is the per capita birth rate (3/4 = 0.75 births / individual / year) d is the per capita death rate (1/4 = 0.25 deaths / individual / year) Early Spring Early Spring Births and Deaths H last time Problems with the model for Big Horn sheep In reality Some are male and some are female Some are too young or too old to breed Some of the breeders will produce more young than others Some are so old that they are more likely to die t t N N = + 1 H Problems with the model for Big Horn sheep All individuals at the end of the year are treated as identical...
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 Spring '08
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