Captive breeding lecture1.pdf

1 Captive Breeding Management Tania Gilbert, BSc, MSc, PhD Conservation Biologist, Marwell Wildlife 2 Learning outcomes 1. Understand how genetics & demographics affect captive breeding 2. Understand how to conduct genetic & demographic analyses to inform captive breeding 3. Apply the principle...

1 Captive Breeding Management Tania Gilbert, BSc, MSc, PhD Conservation Biologist, Marwell Wildlife 2 Learning outcomes 1. Understand how genetics & demographics affect captive breeding 2. Understand how to conduct genetic & demographic analyses to inform captive breeding 3. Apply the principles of population management Genetic terms 3 • Allele: Alternative form of a gene • Allelic diversity: Number of alleles per locus • Effective population size (Ne): The size of a randomly mating population of constant size with an equal sex ratio and a Poisson distribution of family sizes that would result in the same rate of genetic drift as that observed in the population under consideration. In its simplest form the Ne is the number of breeding adults in the population • Gene diversity (Expected Heterozygosity): The heterozygosity expected if a random mating population were in Hardy-Weinberg equilibrium • Genetic diversity: The extent of genetic variation in a population e.g. heterozygosity, allelic diversity or polymorphism • Genetic drift: Loss of alleles through random sampling of the population through Mendelian inheritance • Heterozygosity: Proportion of heterozygous individuals for a locus in a population • Inbreeding: The crossing of closely related individuals • Natural selection: The differential fitness between members of a species possessing adaptive characteristics, and those without adaptive characteristics • Founder: An individual that starts (founds) a population 4 Studbooks (SB) & Breeding Programmes (EEPs) • Introduction (SB) – What is a SB? – Who keeps SB? – Role of a SB keeper? – How are SBs used? – Tools • Introduction (EEP) – What is an EEP? – Coordinator role – Challenges with genetic management – Challenges with demographic management – How does a co-ordinator manage a captive population? Studbooks • Introduction – We need to carry out genetic & demographic analyses to maintain healthy intensively managed populations – Need current information in a standardised format – Studbooks perform this function – Studbooks also kept for wild & semi-wild populations where individuals are individually identifiable • What is a SB? o Entire (captive) history of a population or species – Major life history events: births, deaths, transfers – Individual identifiers e.g. ear tags & microchips – Parentage (sire & dam) => pedigree back to the founders 5 Studbooks • Who keeps SB? – World Association of Zoos & Aquaria (WAZA ) – International studbooks • Regional Zoo & Aquaria Associations – European (EAZA) – North American (AZA) – Australasian (ZAA) • National Zoo & Aquaria Associations – British & Irish (BIAZA) – Japanese (JAZA) • Research institutions 6 Studbooks • Who keeps SB? – – – – In Zoo associations… Member zoos & aquaria appoint keeper Keeper reports to Taxon Advisory Group (TAG) TAGs report to the EAZA EEP committee 7 8 • What is the role of a SB keeper? – Collate data from member zoos – Compile into a database – Submit data to Species360 – Publish the studbook – ZIMS module • How are SBs used? – Population management (EEP) – Identification of problems – Research • Tools of a SB keeper – ZIMS – Word – Communication tools 9 Zoological Information Management System (ZIMS): Population management module 10 Captive Breeding Co-ordination • What is an EEP? – – – – European Ex-Situ Programme Population management within a region (Europe) 400+ programmes Co-ordinator assisted by a Species Committee • What is the role of an EEP co-ordinator? – Population Management goals: 1. Maximise genetic diversity (both heterozygosity & allelic diversity) – Equalise founder representation – Minimise inbreeding, genetic drift & adaptation to captivity 2. Maintain demographic stability 3. Provide animals for reintroduction, if appropriate => Breeding recommendations – Information dissemination 11 Challenges with genetic management • Genetic changes in captivity • Three stages of captive breeding • Founding phase • Growth phase • Capacity or maintenance phase • Each stage has its own challenges • Once capacity has been reached, reintroduction may become an option Frankham et al. (2010) 12 Genetic changes in captivity fall into 2 general classes: 13 Genetic adaptation to captivity • Selection will eliminate alleles that are maladaptive in the captive environment – Antelope flight response Genetic drift • Drift will cause the cumulative loss of both adaptive & maladaptive alleles • Rare alleles lost by chance in small populations • Random process may result in an increase in deleterious alleles • Captive management must minimise genetic changes to preserve animals that may one day return to the wild Phases of Captive Propagation 14 Founder Phase • Acquire representation of wild populations when numbers are still in the thousands • But catch ups occur when wild population are very small – E.g. Mauritius kestrel - only 4 individuals but current population founded on only 1 breeding pair • Founders taken from narrow range, sub-populations • Recommendation >20 unrelated founders (yielding 97.5% of the gene diversity in the wild population) • Need more to ensure survival of 20 • Reality: Catch-ups from limited areas, few founders, not all wild-caught animals have reproduced => loss of genetic diversity Phases of captive propagation Growth Phase • Minimising the loss of founder alleles will be achieved if all founders contribute equal number of offspring • 7 - 12 offspring needed to ensure 99% chance that all founder alleles retained • Should fill all available space as soon as possible (in 1 generation) • Reality: all founders do not produce equal progeny, not enough offspring per founder, growth may be slow => loss of founder alleles & genetic diversity 15 Phases of captive propagation Capacity Phase • Imbalance in founder representation can be rectified • Priority for breeding is given to animals that are most likely to have rare alleles • Minimum Ne should be above 50 in short term & 10005000 in long term • Reality: Addressing founder imbalance require cooperation of zoos, Ne <1000 for all programmes 16 Challenges with demographic management • Growth exceeds capacity • Unequal male:female ratio • Mortality • Unstable age distribution (not enough new births) • Variable or negative growth rates 17 18 Managing a population Orange-bellied parrots 19 How to manage the captive population • Before decisions can be made studbook data must be analysed • Tools – ZIMS – PMx (Population Management x) PMx • Uses pedigree data to quantify relatedness within a population & estimate GD loss • Model the effects of various mating choices • Mean kinship & inbreeding coefficients 20 Set goals • Default is 90% GD for 100-years but each EEP should set a goal that is realistic for that population • In this instance it is not feasible with the current population parameters 21 Reproductive planning How many spaces are there in EEP institutions? or How many individuals do you need to meet goals? 22 Reproductive planning 23 For the population to grow by λ=1.0480 (4.8%) in 1-year, the population needs to increase from N=252 to N=264 Reproductive planning 24 Assuming a birth sex ratio of 50:50 An average litter size of 1 With 1 litter per year With a 50% probability that a pair would breed Reproductive planning 53.1 ± 10.1 Litters needed 106.2 ± 20.3 Pairs needed 53.1 ± 10.1 Births needed 25 26 Who to pair with whom… 27 Mean kinships • The average kinship (relatedness) of an individual with all individuals in the population, including itself = mki 28 Mean kinships • The proportion of the genome that is unique amongst the living population • Provides a measure of the genetic importance of each animal in the population + + + + + + + + = Σmki = MK N 29 Inbreeding coefficients • Measure of how inbred an animal is using an inbreeding coefficient (F) • The probability that 2 alleles at a locus in an individual are identical by descent • Co-efficients range from 0.00 to 1.00 • 2 siblings: offspring = 0.25 Studbook # 16428 20520 19908 Sex F F F Age 18 15 15 Location WHIPSNADE PARIS ZOO BRATISLAV % Known 100.0 100.0 100.0 F 0.0000 0.1094 0.4902 30 Breeding recommendations 1. Choose matings between animals of equal and low mean kinship MALES SB# MK 20024 25208 27548 27596 27572 27600 28324 28412 31152 22548 27984 30960 31860 29136 16436 0.039 0.042 0.042 0.042 0.043 0.044 0.044 0.048 0.053 0.054 0.055 0.056 0.056 0.057 0.059 Location GDANSK PELISSANE AYWAILLE LISIEUX Z LISBON LEIPZIG MARWELL WOBURNLTD AYWAILLE OPOLE PLAISANCE BUSSOLENG AYWAILLE WHIPSNADE WOBURNLTD SB# FEMALES MK Location 17852 17428 18000 17996 26700 22568 23544 16428 27612 27616 20196 22396 23512 25472 27620 0.002 0.013 0.017 0.021 0.024 0.033 0.033 0.039 0.041 0.041 0.042 0.044 0.049 0.063 0.072 LISIEUX Z PLANCKNDL MARWELL MARWELL DUBLIN AMSTERDAM AMSTERDAM WHIPSNADE WARSAW PLANCKNDL PT ST PER PLAISANCE AMSTERDAM FOTA DUBLIN Founder SB ID 5016 5020 5224 5228 5232 5236 5240 5244 5248 5252 5256 5300 5348 5392 5428 5432 5436 5532 5688 5692 5696 5704 5824 5856 5916 Founder descendants No. ofrepresentation Gives priority to those animals descended from founders with the lowest representation 300 250 200 150 100 50 0 31 32 2. Chose matings to avoid inbreeding F = 0.0161 33 F = 0.3187 34 Reality •Social considerations •Logistics •Legislation •Permits •Animal behaviour •Politics •Animal health •Co-operation •Facilities & carrying capacity •Appearance •Cost 35 36 37