How effective are captive breeding programs?

One of the most amazing attributes that humans have is our unprecedented ability to alter our surrounding environment so that it is more suitable for our daily needs; with the most obvious of such alterations being the clearing of land to make room for housing and agricultural crops. Whilst we are not the only animals to alter our habitat (many other species such as beavers and termites also build large structures), we are the only species to build and destroy at such a large scale. The fact is that we have now spread onto every continent - even having science stations of Antarctica - and wherever we go, deforestation soon follows. The result of this is that there is very little true 'wilderness' left on Earth and many animals have lost their habitats due to our destructive ways and face imminent extinction in the near future as a result.

'Slash and burn' agriculture is an ancient way of clearing land that dates back to our earliest endeavours of farming 12, 000 years ago and involves setting blaze to, sometimes, vast acres of forest. Obviously this technique is highly destructive and displaces all of the resident organisms that were previously living there, destroying their homes. The problem is made worse by the fact that land gained in such a way is very infertile so that farmers need to create new plots of land every year.

In fact, the problem is now so bad that research undertaken during the Millennium Ecosystem Assessment (MEA) has found that in the past 50 years humans have changed ecosystems more rapidly and extensively than at any other comparable time throughout our entire history! This has resulted in a huge and irreversible loss of Earth's biodiversity and the MEA found that we have already destroyed over half of the planet's forests, 20% of its coral reefs and 35% of its mangroves - all of which are essential ecosystems for providing habitats to animals, providing ecosystem services to us and in preserving the planet's future evolutionary potential. To make matters even worse, the MEA has predicted that the degradation of ecosystems is likely to get considerably worse during the first half of this century at the very least! This loss of habitat has had profound implications on the survival of many species, which are now already extinct or are endangered and this destructive human behaviour is unlikely to change any time soon. The question then, is whether or not we should try to preserve at least some of the species and ecosystems that we are threatening and of course, many people believe that we should. As the result of this, there are countless specialised conservation organisations across the globe like the WWF and the IUCN.

One of the methods that we can use to preserve endangered species then, is via captive breeding programs in which we take animals from the wild and breed them ex-situ in institutes such as zoos and aquariums. Captive breeding programs have been very successful in the past and have been sufficient to restore the natural populations of endangered species back to relatively 'safe' numbers. A good example of this is the black-footed ferret (Mustela nigripes), which has now made a remarkable recovery after its entire population was removed from the wild and bred in captivity, with reintroduction schemes running since the early 90's. In addition to breeding rare animals in an environment that is safe from illegal poaching, captive breeding programs also allow the animals to be studied by scientists; allow the public to see foreign and exotic animals in zoos, which is both interesting and may help to raise their awareness of the importance of conservation; and furthermore, helps to maintain a 'stock' population against unforeseeable events like natural disasters (which become a huge problem if all the individuals of a particular species are only found in one place!).

These elephant tusks were seized after an anti-poaching raid in Tanzania. Sadly, despite the great efforts to protect wild elephants, illegal poaching for their highly valuable ivory tusks still goes on as is very difficult to protect wild populations. Bringing endangered species, such as elephants, into captivity however makes this much easier.

However, even though captive breeding programs sound like a good idea at first glance and definitely have their good points, are they really feasible on a large scale? The IUCN has estimated that 2, 000 - 3, 000 species of terrestrial vertebrates will have to be captive bred in the near future in order to save them from extinction and sadly, the space and money that is available globally is nowhere near sufficient enough  to cope with such an epic undertaking. Thus, we may have to decide to save some species at the expense of others - decisions that would undoubtedly be both unpleasant and controversial: why is one species more important than another?

Obviously then some animals will be more suitable for captive breeding programs than others: mainly, small creatures that can be kept and maintained cheaply in small enclosures. Amphibians are a great example of such animals and furthermore, can be easily released back into the wild because they don't have any learnt behaviours that must be taught to them in order for them to survive. This is one of the main problems with reintroduction schemes, which is particularly evident in predators - without learning how to hunt and kill their prey, captive-bred animals cannot survive in the wild and thus depend on humans for their entire lives! The fact that amphibians make such good candidates for breeding in captivity is very fortunate, as over a half of all amphibians are now endangered due to the Chytid Fungus that is killing them in large numbers across the globe and due to their extreme susceptibility to anthropogenic environmental pollutants.

The endangered black-eyed tree frog, Agalychnis moreletti, is currently being bred in captivity in Chester Zoo. The zoo is participating in an international effort called the Amphibian Ark (AArk) program that aims to preserve amphibian life and safe-guard them against their global decline.

The lack of space that is available in zoos however, sadly makes the captive breeding of large animals much less feasible than programs that incorporate smaller species. This is particularly true for large predatory mammals such as lions and tigers, which need very large territories to thrive and do not respond well to being kept in captivity. In addition, they require so much space and cost so much to keep that zoos can only afford to keep relatively small numbers of them in captivity. This means that only a small number of individuals can be bred from so that the captive populations would become vulnerable to inbreeding depression and would suffer from low genetic diversity and have reduced fitness as a consequence. To explain this further, a small breeding population rapidly becomes inbred because simply put, there are no animals available for a individual to breed with that they are not related to. Over time the population becomes more and more inbred and deleterious alleles build up in individuals. Usually such maladaptive alleles are recessive and are masked in outbred individuals who have a 'normal' and healthy allele for the gene so that they don't suffer from its effects, even if they are carrying it. However inbreeding increases the chances of an individual having two copies of the deleterious allele (which are then are said to be homozygous for the allele) so that they suffer from its ill effects - a phenomenon known as inbreeding depression.

The lion, Panthera leo, is one of the most majestic predators in the world. Sadly however, captive lions usually have extremely low sperm counts and a very high percentage of what little sperm they do produce is abnormal. This problem, due to inbreeding depression, is very common in species of big cat and is exacerbated even further by the fact they they rarely even try to mate when in captivity! Problems that makes them very unsuitable for captive breeding programs.

As well as inbreeding depression, captive breeding programs have two other serious problems. The first is that keeping many animals of the same species in a small confined space that often has poorer than desirable hygiene means that the spread of infectious diseases becomes very likely (unless a vaccination against the disease is available). This can be disastrous for the recovery efforts of a species, which is highlighted in the case study of the before-mentioned black-footed ferrets where canine distemper killed all of the first ferrets that were taken into captivity! Sadly this could easily have led to the extinction of the species as more individuals had to be removed from the wild - an example that highlights the final disadvantage of captive breeding programs: removing individuals from an already dwindling population could actually push the species into extinction in the wild, as there may be too few left to breed successfully! Unfortunately, there is no way around this problem and all conservationist biologists can do is make a decision on what they think would be best for a species in its own specific case of circumstances and hope that it's the right one!

So in conclusion, captive breeding programs are undoubtedly very effective measures for preventing species from becoming extinct. However, due to the lack of space that is available and the unsuitability of some species for such schemes, they cannot be used to save every endangered species of animal so we must also take measures to preserve them in-situ in the wild. Often, this is accomplished by protecting animals from hunting under law and by setting up designated animal reserves or parks that specifically aim to protect them and conserve nature (click here for a recent example of a national park).

Death of the giant eagle

700 years ago the largest bird of prey and one of the largest aerial predators that has ever lived hunted in the skies over New Zealand's South Island - Harpagornis moorei, more commonly known as Haast's Eagle. The bird, weighing up to 15kg (which is very heavy for a bird as they have hollow bones), had a wingspan of 3m and was the top predator in its ecosystem - hunting the moa (Dinornis novaezealandiae), a 12 foot high flightless bird that weighed in at almost 230kg!

Haast's Eagle was a specialist predator and almost exclusively hunted moa, soaring at high altitude before dropping out of the sky at speeds that are estimated to be as fast as 50mph, striking the flightless bird with enormous force! Wounds on the bones of moa suggest that once the eagle was within striking distance of the hapless bird, it grabbed its prey's pelvis with one talon and the crushed the back of its neck with the other. It is believed that the eagle then landed on top of the moa and, if it was still alive, quickly finished it off using its very large and razor sharp beak. Unlike many modern-day predators that have to compete with scavengers for their kill, the isolated island habitat of New Zealand did not have such animals, which enabled H. moorei to have consumed all of its kill by itself, returning to the carcass for up to a week after it was killed! The fact that the eagle could utilise the vast majority of its kill is believed to be one of the reasons that the species evolved to be so large.

An artists impression of Haast's Eagle hunting moa. Despite the eagle's very large size, which is pushing the boundaries of body mass for powered flight, it had a very short wing span. This is believed to be an adaptation for hunting over the scrubland and forests of New Zealand because it allowed them to hunt in dense vegetation.

The other reason that the eagle grew to such an impressive size is believed to be due to a phenomenon called 'island gigantism', which is likely the main driving force behind the evolution of its growth. Island gigantism is a relatively common biological trait where species that live on isolated islands with no contact to the mainlands grow to be unusually large. This may seem strange, but makes sense biologically as these isolated islands often develop their own unique ecosystems due to the fact that the more abundant species that live on mainlands cannot get across to them. As a consequence of this, there are relatively few species inhabiting the island so that such animals are under little competition for resources. Thus, animals on isolated islands are able to fuel large body growth and often evolve to be unusually large. The isolated nature of such islands also means that many of the species that live there have evolved independently from those on the continent so that many of the organisms found on cut-off islands are unique, being found nowhere else. A good example of such novel species are the strange species of marsupials that are found in Australia, which broke away from Africa 184 million years ago. These marsupials have therefore, evolved independently from continental species for a very long period of time.

Growing to lengths of 3 metres the Komodo dragon, Varanus komodensis, is the world's largest species of lizard and the world's biggest poisonous animal. The lizard is found spread across certain islands in Indonesia and is an excellent example of island gigantism, with its large size being attributed to a lack of competition over prey as there are no other species that fill its niche on the islands.

Bizarrely, phylogenetic analysis of the DNA of H. moorei has found that the eagle is not related to other large species of predatory eagle as you might expect, but is instead most closely related to the Little Eagle, Hieraaetus morphnoides. This rather small bird of prey is about the same size as a Peregrine Falcon, weighing a mere 815g! Although it is slightly odd that the ancestor of the Little Eagle remained at such a diminutive size while one of its cousins became one of the most massive aerial predators ever, it in fact supports the idea that island gigantism fuelled the evolution of the colossal size of H. moorei: a small number of the ancestors of the two eagles were trapped in New Zealand after it separated from Antarctica between 130 and 85 million years ago, whilst others remained over the larger continent. Those over the continent had greater competition for resources so could not fuel the growth needed to reach such huge sizes and consequently, evolved into the Little Eagle. Those trapped in New Zealand however, had an abundance of food and evolved into the giant Haast's Eagle.

This shows the foot of H. moorei (left) compared with that of a Little Eagle (right). It has been calculated that the massive eagle's talons could have pierced and crushed bone up to 6mm thick under 50mm of skin and flesh!

Although the large size of the eagle is very impressive it also, rather unfortunately, led to its downfall. Unsurprisingly its extinction was due to the arrival of man to New Zealand, as one of the main characteristics of human invasion into a new environment is the extinction of its endemic megafauna - such large animals provide excellent sources of food and are typically very vulnerable to the alterations that humans make to their habitat. In this case however, humans did not hunt and kill Haast's Eagle directly; instead killing it by wiping out the moa, leaving the eagle with nothing to eat. Obviously, a 12 foot flightless bird was easy pickings for the early Maori settlers (who came from Hawaii) and they exploited the bird, hunting it mercilessly. This over-hunting would have wiped the moa out eventually, but the problem was made even worse because moa eggs were also considered as a delicacy and were raided from the birds nests. This was a huge factor in the moa's rapid extinction because they only laid a few eggs every year; meaning that there were nowhere near enough young moa to replace the adults that were being killed by humans for meat!

Once the moa became extinct it was only a matter of time before Haast's Eagle followed it into the abyss,  mainly because it had evolved to a specialist predator that hunted moa almost exclusively. However even if H. moorei knew how to have hunted the other animals resident to New Zealand, none of them were large enough to have fed it for long so the birds would have eventually starved to death anyway. Although such an end to a species is not uncommon and has happened many times in the past, it is still a sad and rather undignified end for such a majestic species and Haast's Eagles have not soared above the far-flung islands of New Zealand for over 600 years...

Help save the bees!

Hi all,

This isn't a proper post as I won't be writing any new articles now until early June (after my exams have finished), but I wanted to draw your attention to a petition by AVAAZ that is trying to get Bayer shareholders to vote to stop the company from producing very harmful neonicotinoid pesticides that are killing large numbers of bees globally and are significantly contributing to their catastrophic decline.

As you may or may not know, bees are crucial organisms for pollinating many species of plants and flowers and without their services very few of the planet's ecosystems will be able to survive. Bees are known to help in the production of around a third of all human food and represent an estimated US$40 billion in terms of the services that they provide to the agricultural industry. Simply put, they are irreplaceable. 

Although these pesticides aren't the only factor contributing to the decline of bees, they are a major 'player' and stopping their use is under our direct control. Please spend a few seconds to sign this petition, which is in the best interests of everyone worldwide and can have a direct result as Bayer are one of the major manufacturers of these harmful chemicals.

Thanks, 

David

Is evolution in danger of extinction?

Everyone is familiar with the concept of extinction. Sometimes species are lost forever, whether it is due to natural and unavoidable catastrophes like a large asteroid hitting our planet, which many scientists believe wiped out the dinosaurs, or due the activities of humans. The extinction of a species is sad, but the brutal fact is that it is not all bad and the death of one species allows the evolution of another to occur and fill the now empty niche. A good example is that the mass extinction of the dinosaurs allowed the previously oppressed group of mammals to evolve and become one of the most dominant forms of life on the planet, which has worked out pretty well for us... These events are called extinction spasms and follow all mass extinction events, with the 'bounce-back' time of species taking millions of years. For example, it took 20 million years after the Cretaceous Tertiary Extinction Event for the surviving marine invertebrates to establish as many new families of organisms as they'd lost.

The Barringer Crater in Arizona is 1 mile wide and 570 feet deep. It is believed to be the crash site of the city-sized KT asteroid that hit the Earth 65 million years ago with the force of million nuclear bombs, wiping out half the life-forms on the planet, including the dinosaurs.

Therefore, life has always recovered after mass extinction events and many new species have appeared after them. This is mainly because the past five mass extinction events have left many of the key environments for evolution intact, such as rainforests and underwater environments. Such environments are sometimes called 'evolutionary powerhouses' and are critical for the development of new species, having produced substantially more new species of organism than any other environment, including almost every major group of vertebrate.

The planet is currently undergoing its sixth and largest mass extinction event, which is due to the destructive activities of humans. The most damaging of our activities are mainly mass hunting and deforestation, which have resulted in many species already falling extinct. The problem with this mass extinction however, which sets it apart from the others, is that we are destroying the powerhouse environments and are killing every other category of animal at the same time, rather than just certain ones. This is resulting in a rapid loss of the planet's overall genetic diversity - diversity that is essential for life to recover after we wake up, stop destroying the planet and take steps to halt the extinction event.

An aerial view of the border between Haiti (left) and the Dominican Republic (right). The heavy logging in Haiti for the charcoal and firewood industries has resulted in mass deforestation and as a result, only 3% of Haiti's forests now remain.

As according to Charles Darwin, evolution works when a gene randomly mutates and that this mutation gives the individual an advantage over others of its species, helping it to survive for longer. Thus, the individual can breed more because it is around for a greater length of time and gradually, the mutated allele (which is naturally selected for), increases in frequency throughout the population of the species. Once a species has gone however, its genes are lost and cannot change or be passed on so their potential for evolving into a new species is also gone. New species usually evolve when separate populations of a particular species live in different environmental conditions and cannot breed with each other. Therefore, the different populations will be under different selection pressures for new genes and will undergo speciation, slowly becoming different subspecies and eventually, different species altogether.

Thus, the recovery of life after a mass extinction event depends upon the species that survive it and the genes that remain - genes cannot just appear from nowhere! Therefore the rapid loss of forested habitats, which have survived remarkably well in past mass extinctions, is greatly reducing the planet's genetic 'resource base' and is pushing even more species extinct. Worryingly, it is looking more and more likely that the process of evolution will become severely limited in its capacity to create new species of life and ultimately, may fail and become extinct itself. If this should happen life on Earth will die (eventually humans will die out as well as we'll have no food) and will not be replaced, leaving the planet as just another barren and lifeless rock drifting through space...