Captive breeding is nothing new, but it’s become a bigger, hotter topic now that the amphibian crisis has emerged. You’ll be introduced below to Richard Frankham, a top researcher from Australia. He wrote last year: “For terrestrial vertebrates alone, it has been estimated that approximately 2000–3000 species may have to be captive-bred. The recent amphibian crisis has approximately doubled this number.”
A rush of articles, including one a few hours ago on the BBC News site, is exploring the question: can captive-bred wildlife survive when reintroduced into the wild? This is a fundamental question for a program like Amphibian Ark. Before I review the scholarly discussion, let’s review the four hops to the Amphibian Ark plan:
- Amphibian Ark arranges for about 50 of a near-extinct species to be placed into “protective custody.”
- After the species is plucked from the rainforest, or the mountain, the amphibians are placed in biosecure facilities in different parts of the globe (so that an outbreak of disease in one facility can’t deliver a species coup de grace).
- The frogs are bred, and multiply. At the same time, now that they’re in protective custody, scientists can methodically search for an answer to amphibian chytrid fungus.
- Once the external threats are neutralized — i.e., the scourge of chytrid has been neutralized somehow, and habitat has been protected from, well, “us” — the species is returned to the wild.
But what if it takes two, five, ten generations before the outside world is fit again for the amphibians? Will the species have lost its survival gene?
The first article on this I came across is from David T Suzuki, PhD, chair of the David Suzuki Foundation, and Dr. Faisal Moola, the foundation’s director of science. First of all, you need to know the article is about captive breeding in general, not amphibians specifically. But the article states, “Saving a species from extinction may well require captive breeding. But it’s really a Hail Mary pass to the future. Without habitat, a species is a mere caricature of what it is in the wild. The longer creatures are in captivity, the less likely they will be to ever survive on their own, even if we manage to stop destroying their homes. And that makes saving their homes all that more important in the first place.”
Dr. Suzuki referenced in his paper an article in Molecular Biology by the aforementioned Richard Frankham, emeritus professor in the Department of Biological Sciences at Macquarie University in Australia. Here is the full text of Frankham’s paper. The upshot is that he was studying the impact of captive breeding for all sorts of animals — fish, wild rats, amphibians, turkeys, plants, etc.
Just learning a little about this topic makes a novice, like me, wonder if placing frogs in captivity is just a posptonement of inevitable extinction — after all, wildlife make genetic adjustments to living under house arrest that seem to render them too wimpy to go back to the old neighborhood.
EMAILS FROM THE EXPERTS
So I was fortunate to have been put in touch with Professor Frankham, who happens to be at the National Zoo in Washington, DC, this week. I asked him to provide some perspective on captive breeding as it applies to amphibians, and the Amphibian Ark project. What he emailed to me was heartening:
“Here are a few observations [from memory, as I am travelling and away from primary sources]:
- My populations were in captivity for 50 generations. The decline in wild fitness was relatively linear — e.g., (from an original pool of 500 animals, the wild fitness) declined at an average of 1.7% per generation. They have 14% relative fitness cf wild after 50 generations.
- …(but) the populations rapidly readapted to the ‘wild’ — in 14 generations their fitness rose to 70% of that of the wild population, a 5x increase.
- I am strongly in favour of captive breeding as it is the only option to save many species.
- What I am trying to do is to provoke an improvement in captive breeding methods so they minimise genetic adaptation to captivity, while retaining as much genetic diversity as possible.”
- “(Let’s not forget) that Frankham’s studies covered something like 80 generations in captivity. Breed something that long in captivity and it will indeed be genetically unsuitable for release back into the wild. My own work (on Peromyscus mice) shows noticeable adaptation to captivity after just 9 generations. This is faster than I would have expected, but still does not preclude saving something for a handful of generations in protective care.
- Natural selection (to captive conditions) can indeed be a problem. But it is also the solution. Frankham’s own work suggests that although the captive stocks of his flies had low fitness under wild conditions, within just a few generations back in wild conditions they significantly readapted to the wild conditions. This means that we will need to expect a lot of losses on initial reintroductions. It also means that preserving genetic variation during captive generations is absolutely critical (as that variation is essential for future adaptation).
- The considerable number of populations and species that have been successfully reestablished from captive stocks (peregrine falcons, Arabian oryx, red wolves, Puerto Rican toads, lion tamarins, etc.) indicates that if captive breeding to prevent extinction is a “hail Mary pass” (and that characterization does have some validity to it), then it is a pass that is often caught for a touchdown. Of course, Suzuki is quite right that the strategy is a last chance (like a Hail Mary pass — but that is what amphibians are facing), and that protection of the wild habitat and reversal or amelioration of the original threats is absolutely essential if there will be any long-term conservation benefit of the short-term captive rescue.
- Indeed, one point that Frankham emphasized recently was that one reason that we need to do more to learn about and manage the effects of selection in captivity is because captive breeding has become the last chance for so many amphibian species (and some other species).
- Moreover, it is possible to design breeding protocols that will minimize (but not stop altogether) the rate of adaptation to captivity. Dick Frankham has made some good suggestions for breeding protocols that would help us do this, and he has noted that the protocols are ones (such as maintaining each species subdivided among a number of sites) that should be possible to implement in zoos. I think that we do need to make sure that our captive breeding programs are well designed and scientifically rigorous, so that we don’t end up producing a bunch of animals that have no future.”