Small Population management Flashcards
What are 3 important factors in small population management?
- genetics
- demography - population structure
- Reproduction - breeding (promoting) and Contraception (Preventing)
Why is demography important?
- Zoos need to consider demography at different levels - Individual, Regional and Global
- Studying demography helps to understand-
Future growth or decline of zoo-based
populations and The potential to experience a loss of genetic diversity - Populations have parameters
o Birth and Death Rates
o Immigration and Emigration Rates
o Density and Distribution - Determining population parameters allows comparison in
o Time
o Geographical location
o Between different Zoos
What 3 important factors in demography?
- age structure
- shape - growth, stable or decline - Sex ratio - influences the effective population size (animals avaliable that can breed)
- depends on species - reproductive strategy
- affected by inbreeding depression - life tables
- records mortality of each age class
- static LT - snapshot, one point of time
- dynamic LT - follow cohort over time
What is a survivorship curve?
Plot of survivors vs age class
provides mortality data analysis
allows comparison of;
different zoo populations of same species
wild v captive mortality
Male v female mortality
What is demographic stochasticity?
results from chance independent
events of individual mortality and reproduction, causing random
fluctuations in population growth rate, primarily in small populations. Demographic stochasticity is particularly important
in short-lived species (e.g., small dasyurid populations, semelparous species)
What is environmental stochasticity?
results from temporal fluctuations
in mortality and reproductive rates of all individuals in a population in the same or similar fashion, causing population
growth rate to fluctuate randomly in populations of all sizes – small populations are more susceptible to catastrophes .
What is demographic extinction? and what animals is an example?
o Definition - a zoo population that is not self sustaining
o A population that contains too few individuals
o Example - Asian elephant population predicted drop to
10 animals by 2050 = demographically extinct!
o Solution – take from the wild to support captive breeding but this is highly controversial
Why is Genetic management important
maintain genetic diversity
managed by studbooks
Essential to long-term viability of captive populations
How many animals are required to maintain genetic diversity?
500 - but limited space
What is an alternative to having 500 animals?
Attempt to conserve 90% of genetic
variation in a population for 200 years.
o This can be estimated by considering
- Proportions of male and females available
- Generation time of the species
- When GT is short – need large numbers
- When GT is long – smaller numbers will do
What is the effective population size?
The effective population size is number of individuals that are effectively contributing genes to next generation
Effective population size is a measure of how well the population maintains genetic diversity from one generation to the next
Small populations lose genes as a result of chance or stochastic events – genetic drift, so it is important to know the effective population size not just the actual numbers of
animals.
What influences the effective population?
- Sex ratio
- Reproductive success of individuals
- Mating system (Monogamy reduces Ne, whereas promiscuity increases Ne)
- The degree of mate selection – non-random selection of mates
What is minimum viable population (MVP) size?
Population Viability Analysis (PVA) provides a means of predicting the probability that a population will become extinct
What deterministic factors does MVP account for?
- habitat loss
- over exploitation
What stochastic factors does MVP account for?
- demographic
- environmental
- Genetic
What is a evolutionary significant units?
the minimum unit of conservation management - could be at different levels, species, sub-species, geographical race or a
population
Relies upon information from molecular genetics - mtDNA
- mtDNA is passed downed from the mother and remains largely unchanged from generation to generation – allows
tracking of evolutionary history
What is inbreeding, and how is it managed?
Occurs when closely related animals breed
Occurs when dam and sire of an individual share common
ancestors
Inbreeding increases homozygosity and reduces heterozygosity (We want heterozygosity!)
If recessive alleles cause disease, then expression of the disease increases with inbreeding
