Helping zoos make sure captive species survive

Yang Guang at Edinburgh Zoo. Picture: Neil Hanna
Yang Guang at Edinburgh Zoo. Picture: Neil Hanna
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Genetic research can lead to better breeding, says Dr Rob Ogden

We often get asked how we ensure there is sufficient diversity within the captive zoo population of endangered species so that we’re not creating a time-bomb of inbreeding in the future.

Edinburgh Zoo's giant panda Tian Tian. Picture: Ian Rutherford

Edinburgh Zoo's giant panda Tian Tian. Picture: Ian Rutherford

Traditionally we have used the all-important studbook: a computerised record for each animal species held in zoos. It lists their name, date of birth, transfers between zoos and details of breeding activity. Its purpose is to keep healthy, genetically diverse captive populations by breeding individuals which are as well suited as possible in terms of their relatedness and genetic importance. We also aim for natural behaviours and compatibility between mates. Studbook records are also used to identify issues such as declining birth rates, increasing mortality or potential disease.

The ideal end point is that should the worst happen in the wild and species become extinct, we have a broad-based, genetically diverse population within our zoos which we can consider re-introducing.

Edinburgh Zoo and the Highland Wildlife Park, both owned by the conservation charity the Royal Zoological Society of Scotland (RZSS), manage 13 studbooks – testimony to our expertise in management of particular species such as gentoo and king penguins, the L’Hoest monkeys and Pallas cats.

Molecular genetic methods

However, it is increasingly recognised that reliance on the available studbook data alone is not always the most accurate method of making decisions on breeding suitability. A studbook generally assumes that all wild founders in the pedigree are unrelated. However, that is not necessarily true. Gaps in the existing studbook data and mistakes in the recorded pedigree also mean that, for some species, calculations of relatedness and subsequent breeding recommendations may be subject to error.

As a result, the use of molecular genetic methods to carry out DNA profiling of animals is becoming an increasingly important tool in the planning of breeding programmes. Within the Society, we are fortunate to have the WildGenes Laboratory, one of the world’s pioneering applied conservation genetics teams, and they are currently carrying out work on validating certain studbooks using DNA analysis. Through such profiling, the additional information the team provides can either substantiate or correct existing pedigree data.

The question arises of whether DNA analysis will ever replace the traditional studbook approach. In the short term, probably not – current methods limit our ability to reconstruct historic family relationships with complete confidence and we’re largely restricted to assessing first or second order relatives. However, since the turn of the century, the genomic revolution has cascaded from human genetics, through agricultural research, into wildlife conservation and may soon provide the potential to address some of these limitations.

But while the technology is on our doorstep, the resources are not and may arguably be better spent elsewhere. So, for now, the challenge faced by zoo population managers is how to combine studbook-based computer dating with genetic profiling, which is proving to be as complicated as it sounds!

Beavers, wildcats and birds of prey

Genetic analysis has much more to offer conservation, though, and the same DNA profiling techniques are used by RZSS to inform wildlife managers regarding population structure, genetic variability, individual dispersal, census size and breeding behaviour.

In Scotland, the WildGenes Laboratory has worked with beavers, wildcats and birds of prey to establish the genetic diversity and size of natural populations and to inform future management decisions.

Further afield, studying DNA recovered from faecal material is particularly useful for understanding species such as the pygmy hippo, or dama gazelle, where actual animal sightings are uncommon and DNA samples are one of the few ways we have to gain important new information necessary for species conservation.

Both ex situ (zoo) and in situ (wild) conservation rely on conservationists having a very clear picture of what it is they are trying to conserve. It may seem surprising, but questions as fundamental as “What is a species?” still perplex zoologists, leaving the taxonomy of many animal groups fairly confused. This has practical implications when it comes to population management of endangered species: do we mix different populations and risk hybridisation of separately evolving forms, or do we keep populations apart and increase the risks of inbreeding within each one? Once again, DNA analysis has a role to play in addressing these questions, enabling zoos to make sensible breeding decisions.

How the world will look in the future and the species that inhabit it will depend on many of the decisions taken now. We don’t underestimate how important it is to use every tool available to us to get this as right as we can.

• Dr Rob Ogden is head of conservation science at the Royal Zoological Society of Scotland

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