Leave endangered bustards wild – why captive breeding isn’t always the answer

When a species faces imminent extinction captive breeding is often the go-to method to ensure the preservation and bolstering of wild populations. Not only does this aid the recovery of the population, producing more individuals for release whilst other in-situ conservation efforts are underway , but it also acts as a potential safety net should the wild population be wiped out. This seems like a sensible precaution, but is captive breeding always the best option? For the critically endangered great Indian bustard - perhaps not.

The value of captive breeding programmes depends on the ability to re-establish a population in the wild. While there are many success stories, it can be a challenging and unpredictable process - the difficulty of getting giant pandas to breed is a prime example (it took eight years before a single cub was born).

Standing a metre high and weighing nearly 15kg the great Indian bustard is one of the largest bird species in the world, making it a prime hunting target in the past for both food and sport³. While this initiated its decline, current threats stem mostly from habitat loss and degradation due to agricultural expansion, infrastructural development such as road networks and electricity pylons, as well as mining and industrialisation¹. As a result the species has undergone severe population declines, from over 1,000 in 1970¹ to around 250 or fewer individuals today³.

In a recent study a team of scientists from the University of East Anglia, in partnership with Birdlife International, used population models to evaluate the potential effectiveness of a range of captive breeding and release programmes for the great Indian bustard, compared with wild (in-situ) conservation.

Given the already depleted wild population, any collection of bustard eggs for captive breeding would need to have a strong chance of survival and reintroduction to make an ex-situ conservation programme worthwhile. So the key question is whether the benefits from releases of captive bred animals outweigh the loss of wild individuals captured to begin captive breeding. First and foremost then, you need to be able to breed plenty of birds and be confident that they will reproduce as well as their wild counterparts.

With the potential effectiveness of a captive breeding programme for bustards already looking pretty bleak, it is essential that any such plans for ex-situ conservation undergo rigorous evaluation, something the study authors say is often lacking. As well as the usual methods of assessment (showing that captive breeding would not jeopardise the wild population and would have a high probability of success), the authors argue it should also be standard procedure to evaluate and compare alternative (i.e in-situ) conservation practices.

To do so, the team explored four different scenarios of breeding programme quality, from ‘below average' to ‘best possible' (based on existing exemplary breeding programmes), and evaluated the probability of captive population extirpation within 50 years, and the number of adult females likely to be established in the wild following release. Their results showed that investing in habitat preservation and allowing the birds to breed in the wild could offer the species a better chance of survival.

Even with ‘best possible' standards across all aspects of a captive breeding programme, as well as working under the assumption that released birds will breed as well as wild ones (which is not always the case), the study found that implementing in-situ conservation over the next decade would recruit more adult females to the wild within 30 years.

This isn't to say that captive breeding is completely infeasible - their modelling showed that egg collection and rearing could establish a captive population capable of surviving for at least 50 years, but only in the most favourable conditions. Such a programme would also require a large number of wild eggs to be removed, around ten a year for eight years according to the study, putting the wild population under greater stress. This means anyone undertaking a captive breeding programme would need to assess the considerable expertise, materials, labour and money it would require to sustain an ‘above average' performance for over half a century - no mean feat in an already under-funded sector. And even then they would need effective wild conservation and habitat restoration alongside to ensure released birds have sufficient habitat to return to.

Even such a bet-hedging approach - collecting eggs as back-up while carrying out in-situ conservation to preserve the wild population - has not been effective for other large bustard species, such as the great bustard, due to low source numbers, high post-release mortality and unclear evidence of breeding success in released birds. According to the authors there is no evidence of a release programme for large bustard species that has resulted in a self-sustaining population, making this a precarious prospect.

Instead, if in-situ actions such as habitat restoration were undertaken early enough it could remove the need for captive breeding programmes altogether. In the case of the great Indian bustard attention and resources are better focused on serious, immediate investment in in-situ conservation efforts than an arduous and unpredictable captive breeding programme. While it may still seem a dicey decision, putting all your bustard eggs in one basket, the authors argue that by saving their habitat the wild population can bounce back unaided.

References:

1. BirdLife International. Species factsheet: Ardeotis nigriceps (2015).
2. Dolman, P. et al. "Ark or park: the need to predict relative effectiveness of ex situ and in situ conservation before attempting captive breeding". Journal of Applied Ecology 52 pp.841-850 (2015).
3. IUCN "Big birds lose out in a crowded world" June 7, 2011.

Photo credits:

1. Great Indian Bustard by Prajwalkm on Wikipedia.
2. The Great Indian Bustard by Henrik Grönvold in The game-birds of India, Burma and Ceylon. Volume 2 on Flickr.