How to estimate population size N

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How to estimate population size (N)

• Mark a subset of individuals (M)
• Release M back into initial area
• Recapture another subset after a delay (n)
• Count marked individuals (m) in subset n
• Compare ratios m/n M/N
• N M(n/m)
• Problems with this method?

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How do you mark a tree frog?
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Australian gecko
Nice amphibian toes . . .
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Population dynamics
and dispersal
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R0 Net reproductive rate the average number
of offspring produced by an individual in a
population during its lifetime or per
generation
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Per capita rate of increase r

• r birth rate minus death rate
• r (ln R0)/T
• R0 net reproductive rate
• T average generation time

Use for overlapping generations (continuous
breeders e.g., humans, bacteria)
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• ? Geometric rate of increase
• Nt1/Nt
• Nt initial population
• Nt1 pop. one round later

Use for populations with non-overlapping
generations (e.g., annual plants, yearly breeders
like deer, loons)
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Population increase for phlox, an annual plant

• Non-overlapping generations, so R0 equals Nt1/Nt
• Nt1 2408
• Nt 996
• 2408/996 2.418
• r (per capita rate of increase) lnR0/T
• r 0.88

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Size of organism versus generation time
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Survivorship Curves
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Dall Sheep Type I survivorship
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American robin (Turdus migratorius) Type II
survivorship
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Maple trees Type III survivorship
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Population age structure
Rio Grande Cottonwoods
White oaks
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Large cactus finches (Galapagos islands)
Age distribution
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Age structure human populations
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Range expansion March of the Killer Bees
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Range expansion of collared doves
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Rates of range expansion