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Zoos, genetics and conservation

Zoos, genetics and conservation

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Zoos, genetics and conservation

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  1. Zoos, geneticsand conservation Peter Shaw

  2. Introduction • I know of two books about zoos which draw an analogy with Noah’s ark: • The overloaded ark (Gerald Durrell) • Lifeboats to Ararat (Sheldon Campbell) • The aim of today’s lecture is to explore the extent to which this is possible, discover Noah’s genetic limitations, and ask whether there will be a mount Ararat to land on.

  3. Zoos– a potted history • Oldest animal collection known was at Saqqarah, Egypt, 4500 BP. • Here sacred animals (ibis, crocodile, falcons) were bred – in order to be killed and their embalmed remains stored in underground tombs. These are still being excavated. • Tomb records show 5358 cattle, 1305 oryx, 1135 gazelles, 1244 antelopes, + addex, probably all from lower Egypt. Ptolemy II (283‑246 BC) introduced the chimpanzee and a 45 ft python (?).

  4. Zoo history contd.. • Alexander the Great added to zoo history Indian spp.: tigers, peafowl, parrots. • The romans used large number of animals, mainly to fight with armed humans. Their taste for lions probably contributed to the extension of the Sahara! • Charlemagne, William the conqueror and Holy Roman Emperor Frederick II had extensive animal collections.

  5. Public zoos • It was only in Victorian times that public zoos became available – previously the collections had all been private. • These Victorian zoos were pleasure gardens, with animals sometimes available for poking with sticks. They were simply a drain on wild populations – little successful breeding. • The most famous victorian collector was Carl Hagenbeck, but the capture methods were often brutal. (1 baby gorilla = 10 dead adults). 'For every good zoo in the world there are bad ones that no defense can justify. Any zoo where animals are impoverished should be changed or abolished.' Sheldon Campbell, LIFEBOATS TO ARARAT, 1978.

  6. Post-Victorian zoos • Rather little changed in the philosophy of zoo keeping from Victorian times until the 1960s, except that animals tended to be given more space, and opportunities to poke them with sticks gave way to some respect. • Zoos were for entertainment – keeping big “classic” species – tigers, elephants, camels etc. • This phase of zoos gave us at least one modern phrase: “Jumbo” was an elephant at London zoo for many years, and went into the language.

  7. Gerald Durrell • The change in attitudes can be dated to one man: Gerald Durrell, who introduced the idea that zoos should aim to conserve endangered species. His zoo on Jersey tended to avoid the big classic zoo animals, instead keeping breeding populations of endangered species. • If you haven’t read his books – you must!!! • At first his ideas were met with scepticism by the zoo-keeping community, but are now mainstream. RIP 30-1-1995

  8. Gerald Durrell Started by collecting animals for other zoos, described in books such as ‘The Bafut Beagles’ (Cameroon) and ‘The Whispering land’ (South America). Set up his own zoo at Les Augres, Jersey, where he ran programmed to conserve many endangered animals. One story among many: He had a colony of lowland gorillas, who dominant male was called Jambo. These lived in a sunken enclosure. One day a small boy fell over the edge, and ended up up the gorilla pit with concussion. Jambo strolled over, picked up the boy, and held him in a protective cuddle until keepers came to take to boy to hospital. GD was also known for exposing crooked international animal dealers. He reported how he was once offered a giant panda. On protesting that this would be impossible under import/export regulations, the dealer explained that the usual practice was to paint the animal black then call it a black bear.

  9. CITES The import/export regulations in question are called CITES. You should know about CITES. CITES - convention on international trade in Endangered species. Most major nations have signed up (excluding Taiwan), though enforcement standards vary. Appendix 1 - no trade allowed. Appendix 2 - strictly controlled trade. There is much biennial debate about which species should be classified where. Elephants remain on appendix 1, to the annoyance of some African countries with an elephant problem. Not just animals – a few timbers, and a fish (Atlantic bluefin tuna).

  10. The lifeboat function Already there are several species which would be extinct were it not for zoos. • In the future this list can only expand – rhinos, tigers, great apes may all become candidates for this sad status in the next 50 years. • I want to spend a few minutes exploring the story behind some of these species.

  11. Chronologically the first such species was Pere david’s deer, mentioned in a previous lecture, but this salvation was unplanned. • The first deliberate use of zoos to prevent extinction was the Arabian oryx, always confined to the searing deserts of the Arabian empty quarter (Rub'al Khali). • It is thought to be the origin of the unicorn legend (when seen side on at distance the horns appear to merge). • It never needs to drink water, relying on juices in its plant food. • It was traditionally hunted by the Bedouin as a test of manhood. This was OK in the days of bows and spears, but when they started using fleets of landrovers with mounted machine guns, the species numbers went into serious decline.

  12. Oryx extinction in the wild • In 1960 ruling members of Qatari tribe crossed 500 miles open desert in specially equipped motorcade, to shoot 28 oryx with submachine guns. • FFPS realised that the sp. could only be saved by getting animals out of Arabia. • Capture party took nets, planes and jeeps – no tranquiliser darts then, and caught 4 animals (one died of capture shock soon after). • Last wild animals were shot in 1972. • World ppn was then 15, the other 12 being zoo stock.

  13. Oryx survival • These 15 animals were brought together in a special enclosure in Phoenix, Arizona. ($ from a US hunting club). • At this stage an outbreak of foot&mouth would have taken out the species. • 1st 6 calves born were male – useless. Corner was turned in 1966 with a female calf. • By 1977 herd was 60 strong on 2 sites. • These are now widely held in world zoos, and are being re-introduced to the wild, in Oman. • The FFPS magazine is today called Oryx, in memory of this first successful species rescue.

  14. Californian condorGymonogyps californianus • This is a pleistocene hang-over: It evolved to feed on carrion of big herds of herbivores such as bison. • Bison were nearly exterminated (to starve native americans), reducing condor populations drastically. • By the mid 1980s the species was confined to the Sierra Nevada mountains in California, and down to 5 birds in the wild (24 in zoos by then). • Survivors suffered shotgun wounds and lead poisoning – decision was made to capture the entire wild population. • The US Sierra club (similar to FoE) sued the US government over this, arguing it better to let the species go extinct rather than keep it in zoos.

  15. It worked! • These birds bred well in zoos, by 1992 population was > 60, and decision was made to re-introduce them. • Young condors never saw people – were fed with a condor-head glove. • Some have successfully returned to the wild, but others (in the Sespe corridor) hit power lines, or drink antifreeze. • Young birds who settle in the Sespe area are re-captured, but some have settled in safer wilder country – they may make it!

  16. Zoos really have helped already. • Species that would be extinct were it not for zoos: • Pere David’s deer • Arabian Oryx • Californian condor • Przewalski's wild horse • ….These might have managed, but certainly benefitted from release schemes: • Mauritius kestrel • Hawaiian goose (Ne-ne)

  17. The long-term goal: • Of zoo-based conservation is to release animals back to the wild. • This assumes suitable habitat exists! • 2 big problems to overcome: • re-training animals to survive in the wild • Genetic management

  18. Re-introduction: • Assumes suitable habitat exists. • You can’t restore cultural knowledge – apes particularly rely on cultural transmission. • Seems to work best with species whose behaviour is simple and unlearned – herbivores such as deer re-introduce well.

  19. Why capture the last wild specimens? • Both in the case of the Arabian oryx and the californian condor, wild animals were captured when there was a zoo population. Why bother? • Genetics – you should aim to preserve as much genetic variety as possible. • This is a deeply serious and complex issue, that will require me to recapitulate some basic genetics.

  20. Genetics • Big topic – I need to recapitulate a little basic genetics with you. • All vertebrates contain 2 sets of genes, one from their father and one from their mother. • Thus for any given gene function (hair colour, a given enzyme) animals have two different genes to do the job. • Normally both versions contribute. • If one version is faulty and does not work, the second copy is relied on. Only when both copies are faulty does the problem become manifest – such genes are said to be recessive. 2 functional copies: all is well No functional copies: a genetic problem appears 1 functional copy: all is well A a a a A A

  21. The way to get problems with recessive genes: • Is to encourage matings with close relatives. It is very likely that this is why most societies (human and animal) avoid consanguineus pairings. • Trouble is – in very small populations it is unavoidable. This applies especially to zoos, where a few “compliant” individuals who mate well tend to dominate the gene pool. • Example – a zoo population of an antelope of a normally nervous, timid species proved to be genetically deaf. Fine for staying sane in zoos – useless for the wild. • Even in the wild, small populations are vulnerable to genetic problems. Rule of thumb: popns < 100 animals are liable to stochastic extinction.

  22. Genetic bad luck • Stochastic extinction refers to the effect by which a small population goes extinct by an accumulation of random bad luck. • A surplus of males will reduce future population size – big deviations from 50:50 are much more likely in small populations. • There is a genetic ratchet: the gene pool can get smaller, but can’t enlarge. By chance, genes become eliminated. • (Gene pools become gene puddles ) • The more inbred a population, the less likely it is to survive disease, habitat change etc.

  23. Population bottlenecks • There are several examples known of populations that have come through a bottleneck, and emerged with some odd features. • Florida puma – 30 left, all with bent tip of tail, 90% faulty sperm, undescended testicles… • Californian sea lion and sea otter both show very reduced genetic diversity and morphological changes Pre-human stage Near-extinction stage Recovery – but highly inbred. Population Time

  24. A textbook example: The Cheetah • Acinonyx jubatus: This is the fastest land animal alive, peaking at 70mph. • It lacks retractile claws. Keepers find it to be less intelligent than other big cats. Zoos have always found it a hard species to breed. Akbarthe great of India had 1000 cheetahs captured for use as hunting animals, and was desperate to get them to breed. they were even given the run of the palace gardens, but even so only 1 litter of cubs ever appeared. • They are now bred in zoos, sporadically. Their fertility is low – 70% sperm are faulty (vs 30% in most cats), and infant mortality high.

  25. Because of a bottleneck: • Genetic tests on cheetahs looked for variation in 52 enzymes – and found NO VARIATION AT ALL in these 52 loci. This was unheard-of in any sexual population – these animals were virtually clones. • It proved possible to transplant skin from one cheetah to another, randomly chosen adult! • This species went through a desperate bottleneck. DNA analyses suggest that the population was down to 1 female + her cub, about 10,000 BP. (At the same time another species of Acinonyx went extinct). • Just by luck, this family had no lethal recessives, + a superb body design for extreme speed – they hung on. • (An interesting thought: another species showing evidence of a genetic bottleneck, and which has lots of odd features – Homo sapiens! There is more genetic variation in 1 troop of chimpanzees that the entire human population.)

  26. Stud books • Zoos must aim to minimise loss of genetic diversity. • Oddly, the best way to do this for the long term is to freeze gametes – no loss at all. Any small sexual population will lose genes. • Next best is to use computers to keep track of the heritage of all known individuals, and use this to dictate who mates with whom to minimise inbreeding. • These databases are known as stud books, and are now maintained for many of the critically endangered species in zoos. • This is why we capture wild individuals – their DNA is needed to maximise diversity in the long-term gene pool.

  27. The ark image • Conservationists worry about the planetary “demographic winter”, in which steadily growing human populations squeeze out all large pristine natural habitats. In this case zoos must act as arks to carry species through time, until suitable habitat is re-created. • We will lose species under this model – some life forms just can’t be conserved. Human Population / use of planetary productivity Habitat restoration Demographic winter Time

  28. Things we can’t save in zoos: • >99.9% of invertebrates, or indeed anything that people won’t pay to see! • species unable to survive without a host extinct in the wild: ie the passenger pigeon feather louse. (Note that zoos control parasites). • Most rainforest plants (for practical reasons). • Species that won’t breed in captivity: • mountain gorilla • sumatran rhinoceros • +/-giant panda Sumatran (hairy) rhinoceros Dicerorhinus sumatrensis