Earlier this month Kat Arney took a trip to London zoo. It wasn’t purely for fun - she was there to meet some of the team at ZSL London Zoo who are responsible for protecting and conserving species that are critically endangered in the wild. It’s a vital part of ZSL’s work, but - as she discovered when she started her visit in the tropical birdhouse - it’s not quite as simple as just sticking some animals together and letting nature take its course. There’s quite a lot of genetics to take into account too as Laura Gardner,curator of birds at ZSL London Zoo, explained.
Laura - We’re standing in the middle of the Blackburn Pavilion which is the tropical birdhouse at London.
Sitting right in front of us is one of our 5 blue-crowned laughingthrush. This is a critically endangered Chinese passerine, endemic to China. The total numbers of this bird in the wild are fewer than 320 so, really critically endangered.
The captive population in zoos across North America, Europe, and Asia are collaborating to actually secure an insurance population, should anything happen to that remnant population back in China. So we have 269 birds within the zoo population.
Kat - On a genetic level, how do you manage that population? How do you work out who’s who and who’s allowed to breed with who to make sure that that population continues?
Laura - Well, it’s a bit like online dating. It’s matchmaking with science thrown in. So we look at the genetics and the demographics of the species in order to manage that species long term.
Kat - What are the risks of this captive population not being maintained, of becoming inbred?
Laura - Well essentially, if the species becomes too inbred, it then won't be a viable breeding population and ultimately that will disappear which will, I think be really, really sad. We don’t know how secure the birds are left in the wild. We know where the birds go to to breed every year and those areas are protected by the Forestry Bureau.
But the birds disperse at the end of August every year and we just don’t know where they go. So potentially, they could all colonise over winter in the same areas. That area then becomes urbanised, developed, we lose that habitat, and potentially, all of the species upon which that habitat depends, and everything will be gone. So, this insurance population is vitally important.
Kat - You said there are 5 female birds here. From my knowledge of biology, females don’t tend to make more birds on their own. Where are the boys?
Laura - Absolutely and this is an important part. We actually had to get quite clever with how we manage our captive populations. A lot of it is the mean kinship for population. That is to say how related any one of these individual birds is to the others within the zoo population.
You can get several pairs that are very prolific and well-represented. So, their lineage is well-represented within that population. But if they produce too many chicks, and other pairs aren't breeding so successfully, you end up with a glut of birds that are actually closely related. So what this group here represents is closely related group of female birds and we just don’t have at this point in time, suitable unrelated males to pair with them.
We’ve got breeding recommendations for the birds or for the zoos that hold the pairs of birds that have underrepresented lineages. Once those birds reproduce, we will then hopefully have some males. These females will then go and join these males at other zoological collections protective breeding. And that’s what makes your population sustainable.
Kat - What is the future for these birds? What's the long term plan?
Laura - The long term plan is a combination. It’s a very collaborative response. This is a globally managed population and there's, I think, 16 species which are currently globally managed. So, the idea of the global species management plans is to bring all of the regional populations managed under one umbrella which makes sure that there's more viable long term population management.
It also includes things like husbandry, welfare, looking at veterinary issues as well, all of which would not only impact upon the captive population within our zoos, but also, have significant implications for the wild population –disease surveillance, managing parasites – all of the things that could impact upon the wild population.
Kat - You’ve described a huge amount of human effort that’s going on to understand these populations, to work out their genetics to keep them going, and make them sustainable, but what about human efforts that aren't helping with conservation?
Laura - Absolutely. I think we’re at this point with many of our threatened species because of the behaviours of people and how we impact upon the environment has a direct consequence for the species that depend upon that environment - things like land use changes, urbanisation, the building of roads, and infrastructure that supports expanding human populations quite often will have a very negative detrimental impact upon the species that normally will live within that habitat.
There are also more direct human behaviours such as the illegal wildlife trade and that’s a real focus for ZSL at the moment and many zoological collections are working collaboratively with conservation organisations and other partners out in these areas, particular across Asia where you’ve got the songbird trade and the illegal wildlife trade – both of which significantly impact on these Asian songbird populations.