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A little joey pokes a front paw and then its head out of its mother’s pouch. Dave White, a zookeeper at Chester Zoo, in England, points up to the mother perched on a branch and beams with pride. He has been watching the baby tree kangaroo develop since it was born the size of a jellybean – first tracking its growth with an endoscope camera placed inside the pouch, and now, seeing the 7-month-old emerge.
White has formed a close connection with the joey and its mother, visiting and feeding them each day. It’s the first birth of a Goodfellow’s tree kangaroo he’s witnessed, and indeed the first time in Chester Zoo’s 91-year history that it has bred the species. White says the birth is a sign of hope for the endangered species, which is threatened by hunting and habitat loss in its native Papua New Guinea.
The baby adds to an insurance population of captive animals, and it could provide crucial data on the species and its reproductive process to help inform protection efforts in the wild, he says: “This little, tiny joey can contribute significantly to conservation.”
The joey is just one of a series of rare births that Chester Zoo has welcomed in the last eight months. Sumatran tiger twins, a western chimpanzee, a Malayan tapir, a greater one-horned rhino and a triplet of fossa pups have also been born. All those species are threatened with extinction.
With the world facing a crisis of biodiversity as extinctions accelerate at an unprecedented rate, zoos could help to provide crucial protection for endangered species. Chester Zoo’s central mission is to “prevent extinction,” and those words are emblazoned on staff t-shirts and signs across the site. In 2021, it published a 10-year masterplan laying out its methods for achieving this, including scientific research and education, habitat restoration and its renowned conservation breeding program.
“(The world) is losing species at a phenomenal rate,” says Mark Brayshaw, the zoo’s curator of mammals. “It’s really important that we save species wherever we can.”
Brayshaw explains that the breeding program has a range of purposes. Some species are temporarily bred in captivity to protect them from imminent threats or to give them a head start before being reintroduced into the wild. Other times the aim is to preserve a species that is already extinct in the wild, or on the verge of extinction, while some endangered species are bred to help maintain a viable population that could be released in the wild if threats in their native habitats were eliminated.
The UK zoo in the midst of a baby boom of rare species
Other zoos also have conservation breeding programs, but Chester is regarded as a world leader due in part to its wildlife endocrinology laboratory – the only one of its kind at a zoo in Europe. This is where scientists track a species’ hormones by analyzing its feces.
“For something like the tree kangaroo, we’ll take (fecal) samples every day,” explains Katie Edwards, lead conservation scientist at Chester Zoo. “We’ll run (tests) about once a month so that we can measure reproductive hormones in our female, and that helps us understand when she’s going to be most likely ready for breeding.”
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Hormone levels indicate when a female starts developing an egg and when she’s likely to ovulate. Edwards and her team pair this evidence with visual and behavioral cues observed by zookeepers and put the male and female together at the optimal time for breeding.
Chester’s lab is attracting interest from elsewhere. Other zoos in the UK and Europe are sending in fecal samples from animals to inform breeding decisions or diagnose pregnancies, and Chester Zoo is also working with partners to replicate its endocrinology technique in Kenya to help conservation in the wild.
Edwards notes that there’s strength in numbers. “If we can collect samples from our tree kangaroos here but also from other individuals across Europe, we can learn a lot more about the species,” she says. “The more we can understand about species biology, the better conditions we can provide so that individuals and species can thrive both in human care and also on a larger conservation scale as well.”
Conservation breeding in zoos can be a thorny subject. Critics believe that breeding animals for a future in captivity is cruel, as many of these individuals will never be rewilded because their natural habits are too degraded. There has also been research that suggests that breeding programs can sometimes lead to genetic changes that can affect a species’ ability to survive in the wild.
But others argue that well-run zoos engage the public in conservation by showcasing the wonders of the planet’s wildlife. They allow scientists to study animals closely in a way that for some species would be impossible in the wild. And conservation breeding in zoos has been credited for saving some species from extinction – the first being the Arabian oryx, which was hunted to extinction in the wild by 1972 but was later reintroduced to the desert in Oman, thanks to a breeding program that began at Phoenix Zoo, Arizona.
1800s, the Eurasian lynx has returned to several countries, including Switzerland, France, Italy, Austria and Germany, thanks to a series of reintroduction programs that began in the 1970s. However, the fragmentation of these populations is still a barrier and conservationists are now exploring ways to connect animals scattered in isolated groups across the continent.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”968″ width=”1600″/>
Tasmanian devil hasn’t always been restricted to Tasmania. Around 3,000 years ago, the cute marsupials once roamed across Australia but were forced out when dingoes arrived. Their numbers were further decimated by Devil Facial Tumor Disease (DFTD), a contagious form of cancer that killed 90% of the remaining population. In 2020, the creatures were reintroduced to a wildlife sanctuary in New South Wales in Australia, helping to expand the animal’s population beyond its namesake island and control feral cat and fox numbers.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1920″ width=”2560″/>
1999, a survey found around 100 animals in the wild at just 10 locations, but in 2001, captive breeding and reintroduction programs started returning small numbers of the reptiles to protected areas. In 2019, a further release of 120 alligators more than doubled the wild population.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1997″ width=”3000″/>
10,000 years ago. Now, Kent Wildlife Trust is leading a project to bring back its close relative, the European bison. The UK is one of the world’s most nature-depleted countries, and the project hopes that as “ecosystem engineers” the bison will help to revive Kent’s ancient woodland. The first herd is due to be released into woods near Canterbury in 2022. ” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”2000″ width=”3000″/>
1970s. Since then, it has been reintroduced in Israel, Oman, Saudi Arabia, Jordan and the United Arab Emirates. The IUCN estimates more than 1,200 Arabian oryx live in the wild, with over 6,000 in captivity, and changed its status from “endangered” to “vulnerable” in 2011, reflecting the success of the reintroduction programs.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”918″ width=”1600″/>
2,400 left in the wild by the 1990s. In recent years, conservation efforts have more than doubled their numbers, and reintroduction programs are returning the rhino to countries and communities where it was entirely extinct. Translocating 3,000-pound animals like rhinos is no easy task: in the past decade, conservationists have started moving some animals from areas that can’t be accessed by road, by helicopter — hanging them upside down in the air. Robin Radcliffe (pictured), a researcher at Cornell University, studied how being hung upside down affects rhinos, and found that it’s better for their health than lying them on their sides.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1468″ width=”2207″/>
41 gray wolves were reintroduced to Yellowstone National Park. Their 70-year absence had a huge knock-on effect across the park’s ecosystem: the elk population expanded unchecked, overgrazing on willow and aspen trees, and in turn, beavers had no food or shelter, and almost disappeared from the park too. As of January 2020, there were at least 94 wolves in the park, and more than 500 in the greater area, but the program has struggled to manage the population beyond the park’s borders. There continues to be opposition from ranchers over concerns for livestock, despite the fact that only 2% of adult cattle deaths in 2015 were caused by predators, and of those only 4.9% involved wolves — less than half the number of cattle killed by dogs. Wolves beyond the boundary of the park are offered little to no protection: in Wyoming, wolves can be hunted freely across 85% of the state.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”2000″ width=”3000″/>
Mongolia in 1992, and as of 2018, it is estimated over 500 horses are roaming free in the country. China launched its own program in 2001, releasing the horses into semi-wild nature reserves for part of the year. Przewalski’s horse also returned to Russia’s Ural region in 2016, and there are plans for future reintroductions in Kazakhstan. The combined wild and captive population numbers around 1,900 today. ” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1067″ width=”1600″/>
large blue butterfly was successfully reintroduced last year. Conservationists spent five years preparing the area in Rodborough Common in Gloucestershire, southwest England, for the butterfly’s return, with around 750 of the distinctive insects appearing last summer. ” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”2250″ width=”3000″/>
red wolf on the brink of extinction in the 1970s, conservationists rounded up the remaining animals for a captive breeding program. Just 17 were found, and in 1980, the species was declared extinct in the wild. The captive breeding program was a success, though — four pairs were released in North Carolina in 1987, and the population peaked at 130 wolves in 2006. However, mismanagement of the program means the red wolf is facing extinction in the wild for the second time: in February 2021, there were just 10 known free-living animals.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1999″ width=”3000″/>
weasel) began to disappear from British woodlands in the 20th century — which allowed populations of grey squirrels, the pine marten’s main prey, to boom. This was bad news for the native red squirrel, which subsequently fought a losing battle for habitat and food. Between 2015 and 2017, more than 50 animals were successfully relocated from their stronghold in Scotland to Wales, to strengthen the pine marten population there. In 2019, the project was replicated in England with 18 pine martens released in the Forest of Dean in Gloucestershire. A further release is planned later this year. ” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”2000″ width=”3000″/>
thousands of years ago, and before their recent revival, are thought to have been last seen in the 1200s. In 1952, a Sami reindeer herder, Mikel Utsi, brought a small herd from the chilly north of Sweden to the cool climate of the Cairngorm Mountains in Scotland in an unofficial reintroduction of the species. The herd has grown to 150 in recent years, but researchers are still exploring their impact on the environment.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1065″ width=”1600″/>
used extensively in hat-making, beavers all but disappeared from rivers across Europe and North America. In the UK, they haven’t been seen in the wild for 400 years. But the amphibious rodents play a vital role in the ecosystem, by building dams that reduce flooding by regulating water flow. The changes in water level can also help to increase fish stocks, with one study finding 37% more fish in pools made by beaver dams, compared to stretches of river with no dams. In Devon, in the west of England, a decade-long beaver reintroduction trial concluded last year, with a single pair spawning 15 family groups.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”2289″ width=”3434″/>
93% due to hunting and habitat loss. The big cat became extinct in many of its historic territories, including India, and 90% of its former range in Africa. A reintroduction program in Malawi’s Liwonde National Park (pictured) in 2017 saw the predatory mammal return to the country for the first time in 20 years, but the population still struggles with low numbers and a lack of genetic diversity which makes them vulnerable to disease.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1688″ width=”3000″/>
Guam rail was given a second lease of life when conservationists rescued the last 21 birds on the western Pacific island in 1981. After an eight-year captive breeding program, they began releasing them into the wild on Rota, a small, snake-free island 30 miles northeast of Guam. Conservationists hope they can return the bird to Guam in the next few years.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”2592″ width=”4608″/>
50-year absence, the harmless snake was reintroduced to Devon, in the west of the country, in 2009 as part of rewilding efforts in the area. In 2019, the Amphibian and Reptile Conservation Trust received over £400,000 for a four-year project, Snakes in the Heather, to better understand the snake’s habitat and enhance community awareness for its continued conservation.” class=”image_gallery-image__dam-img image_gallery-image__dam-img–loading” onload=’this.classList.remove(‘image_gallery-image__dam-img–loading’)’ height=”1063″ width=”1600″/>
These animals went extinct in the wild. Scientists brought them back
Plus, zoos like Chester bring in big money for conservation, says Brayshaw. As one of the largest zoos in the UK – boasting more than 27,000 animals from 500 different species of plants and animals – it welcomes around 2 million visitors a year. Ticket sales, visitor spend on site and membership fees make up 97% of the zoo’s annual income, he says.
As a non-profit, all of this goes back towards funding the zoo, its staff and conservation efforts. According to the 2021 annual report, around £21 million ($25 million) was spent on conservation that year, 46% of the its income, and in 2022 (the report for which has not yet been published) this rose to £25 million ($30 million).
“We put our money where our mouth is,” says Brayshaw. “We are lucky. We’re a large zoo with a good income that can devote resources to (conservation), and we are effective in doing so.”
For Jon Paul Rodriguez, chair of the IUCN Species Survival Commission, the hallmark of a good zoo is one that makes a difference to the survival of species in the wild; that is not simply breeding animals to attract more visitors, but it is motivated to protect them in their native habitat. He believes Chester Zoo fulfils these criteria.
“Ultimately, what we all seek is a species that lives in the wild (and is) playing their ecological role,” he says. There will be some cases when habitat is restored enough for species to return; there will be others where species will be reintroduced to new habitats; and there will also be cases when species will be stuck in captivity for perpetuity, he says. “But if we don’t have those insurance populations, there is no hope at all.”
