Rehabilitation can aid species conservation through releasing healthy individuals into wild populations and educating the public about threats to their survival. But how well does it work and can it save every species?
Plant species are often not the focus of rehabilitation conservation stories. Plants are perfect for minimum use of resources for storage and conservation of seeds. So much so that the famous Svalbard Seed Bank in the Arctic Circle currently holds 862,309 seeds and has the capacity to contain 2.5 billion seeds. The permafrost and thick rock ensures a natural freezer all year round. Countries that usually do not cooperate have come together to provide numerous species of plants to the bank. See the video below
So has the introduction of plants been successful?
A review, published in Biological Conservation, investigated the success of plant reintroductions and found a number of key attributes that ensure increased success. Introducing seeds into protected areas and increasing the number of reintroduced seedlings is one attribute that works, however, reintroduced plants were also identified to have low fruiting and flowering rates.
The review highlights insufficient monitoring following reintroduction and lack of documentation showcasing the failed trials. The authors suggest there is an overly optimistic evaluation of success based on short term results, providing false hope of successful reintroduction. A plant must be able to sustain and maintain a healthy population without aid in order to be classed as successful.
The challenge by conservation biologists is ensuring management is consistent with new data about a species and how it corresponds with its habitat. Strategies must consistently adapt and introduce new protocols in order for reintroduction to the wild to be successful. Especially in the light of changing habitats due to habitat fragmentation, climate change and the introduction of invasive species.
Keystone species are particularly important for releasing into the wild as they provide key ecosystem services, ensuring a healthy ecosystem. The Orangutan is a natural seed dispersal system for the ecosystem. They are persecuted by hunters and have lost most of their habitat to deforestation.
The release of rehabilitated orangutans displays the need for post-release analysis and monitoring. The history of rehabilitating orangutans extends over 40 years, but only in the 1980s was release back into the wild an overall goal. Since then 70 rehabilitants have been released and monitored closely. Females are of high priority as they produce babies and released females have been seen to reproduce earlier, probably due to their better feeding and diet in captivity. Although, infant mortality is higher within released females, this is probably due to lack of knowledge that is usually passed down from their wild mothers. The hardest thing to change about released orangutans is their lack of foraging for less narrow diets (e.g. insects underground) and the human behaviours they pick up.
But how effective is releasing captive individuals? In the Orangutan’s case, it has aided in their conservation but has done little to prevent the causes of their declines (habitat loss and hunting for trade).
What about large carnivore reintroductions? It may seem like a risky strategy but apex predators are essential for ensuring an ecosystems health. The most famous example of trophic cascades is from wolf reintroductions into Yellowstone. The number of grazers decreased, allowing the overgrown grasslands to die back and other plant species to establish.
Apex predators are usually solitary creatures that require large and interconnected habitats in order to hunt and mate successfully. The problem with finding food in a fragmented habitat means the predators often come into contact with humans and their livestock. The Critically Endangered Sumatran Tiger has had a significant amount of their jungle territory replaced with farmland, so they often come into conflict with man in the hunt for food. So far, 265 Sumatran tigers have been killed and 97 have been captured after being prosecuted for being man killers. After a while, the zoos started to become too full with tigers so a millionaire named Tomy Winata stepped in.
Tomy owns 170 square miles of Indonesian jungle that is surrounded by a National Park. Tomy takes pride in his tiger conservation project he has started as the area is more protected from poachers and logging than the neighbouring National Park. Tomy collects the aggressive and stressed tigers to be released onto his private island. The tigers go through a rehab process and are then released. They are radio-collared and their movements are consistently monitored. There is one problem though; there are many villagers still living on the island and most tigers are released only metres from the villages.
It may seem crazy releasing man eating tigers on an island with humans in such close proximity, but since the first release in 2008, there have been no incidents or deaths. Before Tomy’s program, there were already 50 tigers in the area so the villagers are used to their presence.
Dr Alan Rabinowitz, the head of Panthera, travelled to see Tomy and the tigers. He stated that most tigers in zoos do not have an aggressive nature left; they have lost hope and are unable to survive in the wild. Does this mean the most aggressive individuals are actually the most suited for release after rehabilitation? The first tiger Tomy released has now had a litter of cubs, proving that previously caught tigers involved in conflict can be released into the wild without problems and are then able to breed.
The millionaire’s technique is controversial but with critically endangered Sumatran tigers it may be the boost they need. Only time will tell if this method is a sound one for aggressive species as the number of tigers in the area increase, they may start heading towards the villages as a food source.
Release of whales and dolphins is more complicated due to their advanced social interactions in the wild being key to survival, as well as the size of their captive tanks being far smaller than the vast expanse of the ocean. Often, captive dolphins and whale can be seen in costal areas trying to interact with humans as they were their source of food in captivity.
The ideal candidates are whales from wild family groups where their close family members are still alive and thriving in the wild.
For whales that have been in captivity for too long they are often mentally or physically scarred. WDC and Merlin Entertainments are creating an exiting project that creates a sanctuary for captive whales and dolphins through letting them live the remainder of their lives in a natural cover or bay enclosure. There they will perform no shows and only be observed by the public from afar.
There are pros and cons of any method but in order to establish them there needs to be thorough reviews. A 2013 survey identified many rehabilitation centres have studies on post-release but not so many on rehabilitation methods. In order for release to work it should allow long-term additions to the wild population gene pool, so this must be addressed.
Effective post release monitoring has influenced decision making in numerous species. The African penguin is one of the greatest rehabilitation success stories and monitoring still shows the vulnerable, endemic populations are recovering. Monitoring of released and tagged leopards and cheetah has shown all were killed by humans after leaving the protected release site. Clearly, successful rehabilitation is not solely dependent on the rehabilitation process.
I am in no doubt sure that the release of species will become more successful with increased data as it can now be paired with advances in veterinary medicine and the social sciences.
So rehabilitation of species can be successful for certain species and individuals that are suitable for release, as displayed by plants and African penguins. For those who have spent too long in captivity, there are some exciting movements where cetaceans may live in larger natural enclosures. Where rehabilitation and release is unsuccessful, it seems more economically effective to prevent the cause of decline in the first place.
See Frontier's Sumatran Tiger Conservation Volunteer Project here
See Frontier's Orangutan Conservation Volunteer Project in Sumatra here
See Frontier's Whale and Dolphin Monitoring Conservation Volunteer Project here
By Meike Simms - Online Media Intern