Captive breeding programs

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Captive breeding programs
(Conservation vs. preservation revisited.)
2
Purposes of captive breeding programs

• protection of threatened species (captive
  maintenance)
• habitat is completely lost
• threats to extinction cannot be overcome
• duration of captivity has irrevocably altered
  species

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Purposes of captive breeding programs

• conservation of threatened species
• objective to restore wild populations (no wild
  individuals
• left)
• objective to supplement wild populations that
  have
• declined or are threatened

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maintain in permanent captivity
re-establish wild population
supplement wild population
minor major
consequences of genetic mismanagement
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Stages in a captive breeding program

• decline of wild population, genetic consequences
• choice of founder population
• growing captive population
• maintaining captive population
• reintroducing individuals
• managing reintroduced population

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Issues for captive propagation

• source of founder population(s)
• space requirements in captivity/space
  availability in zoos
• courtship/mating behaviors
• intrinsic rate of increase
• isolation of sub-populations
• availability of wild populations as sources of
  new variation

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Rules for captive propagation

• Founding the population - minimize genetic and
  phenotypic change
• collect random sample of founders
• collect data on locality, habitat of origin
• collect genetic data from founders

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Rules for captive propagation

• Maintenance of the population
• maximize N and Ne (maximize sex ratio)
• maximize generation time (minimize generations in
  captivity)
• maintain equal family sizes

Lion average family size 1.65 variance in family
size 32.7 reduces effective popn. size to 8
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Rules for captive propagation

• Maintenance of the population
• golden lion tamarin - founder population 242
  individuals
• 48 contributed to subsequent gene pool
• most of offspring (2/3) from single pair

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Rules for captive propagation

• minimize loss of genetic variation
• maximize N and Ne (maximize sex ratio)
• maximize generation time
• maintain equal family sizes
• minimize behavioral changes
• minimize duration of captivity
• minimize inbreeding
• conduct pedigree analysis/management
• outcross population with new individuals

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Rules for captive propagation

• manage demographics
• determine reasonable carrying capacity (note
  effect on other taxa)
• achieve carrying capacity rapidly
• stabilize population at carrying capacity
• maintain representation of age classes
• what to do with excess animals?

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Rules for captive propagation

• Species Survival Plans (SSPs) for zoo species
• goal preserve genetic variation 90 of H over
  100 years
• list each individual in a studbook sex, sire
  and dam, likely alternatives if uncertain
  parentage
• acquire data age-specific fecundity, mortality,
  lifetime reproductive success, inbreeding
• equalize reproductive contributions of each
  individual
• pair individuals of lowest mean kinship
• work with other zoos to share genetic material
• Limits to zoo taxa.

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Rules for captive propagation

• Use 50/500 rule
• 50 parents for single generation
• Ne of 500 for long-term maintenance
• Conduct periodic genetic checking
• compare present population variability with that
  of founder/wild population(s)

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Problems with captive propagation

• Deliberate (artificial) selection
• for increased productivity fecundity, growth,
  or both
• for better type or traits (color, size)
• for tractability (handling, breeding season)
• problems with linkage of undesirable traits

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Problems with captive propagation

• Deliberate (artificial) selection
• to remove genetic diseases
• Chondrodystrophy in California condor
• - lethal recessive trait hatchlings die
• - gene could be removed in one generation by
  removing 77 of 146 condors
• - careful breeding program was implemented
  instead

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Problems with captive propagation

• Accidental selection
• for increased productivity fecundity, growth,
  or both
• domestication select for fitness under captive
  conditions
• tends to homogenize differences among
  sub-populations

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Problems with captive propagation

• Absence of selection

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General post-release problems

• lower fitness in wild
• domestication genetic and/or behavioral
• loss of variation
• increased fitness in wild
• loss of wild populations through competition for
  mates, habitat captive-bred may be healthier
• different development stages

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General post-release problems

• lower fitness in wild
• increased fitness in wild
• Lake trout (Foster 1984)
• rapid early growth in hatchery
• young age at sexual maturity
• premature reproductive senescence

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General post-release problems

• captive individuals may hybridize with wild
  indivs.
• pollution of wild genome
• loss of variation if lowered variance in captive
  stock