Durrell exists to save species from extinction. It is essential to know if we are achieving this mission, so we can constantly improve and demonstrate our impact to our supporters. This is where the Durrell Index comes in. This set of indicators, timelines and stories track the threats facing our species, the actions we take, and the difference we make to some the planet’s most threatened animals.
It provides proof that conservation works: a story of hope in the battle to save the world’s wildlife.
We are proud to be one of the first conservation organisations to have a ‘key performance indicator’ for its mission. The Durrell Red List Index of Species Survival demonstrates that, overall, we have improved the status of our species by over 100%, compared to a scenario of no conservation. It shows that at least 6 species are alive today that would have otherwise been lost forever.
Find out more about our programmes and our impacts - both globally and at the species level - by following the links below.
What is the long-term impact of Durrell’s conservation programmes on its target species’ chances of survival?
How are populations of Durrell’s target species responding to conservation? Which are recovering and which are still in trouble?
From molecules to ecosystems, how does science inform Durrell’s conservation work?
What different roles does each animal play in Durrell’s ultimate mission – conservation?
How many species has Durrell helped restore through rebuilding wild populations?
How much natural habitat has Durrell helped to place under legal protection?
How does Durrell control invasive predators in order to protect native animals and plants?
What is the global reach of Durrell’s training programmes? How many conservationists have received training?
Once thought to be extinct but rediscovered in the 1970s, the black lion tamarin (BLT) is now found only in São Paulo, Brazil. High levels of deforestation have dramatically reduced the BLT's habitat and left this species in a precarious state. Learn what steps Durrell, together with local partner and Brazilian NGO IPÊ, is taking to conserve this species.Open
The Saint Lucia Amazon parrot, known locally as the Jaquot, is the national bird of Saint Lucia and boasts an impressive conservation success story. Numbering just 100 - 200 individuals in the 1970s with a range of just 66km2, the species has undergone a population increase to an estimated 1750 - 2250 individuals, with a 70% increase in its range.Open
The Madagascar side-necked turtle, Erymnochelys madagascariensis, known locally as the rere, is the largest freshwater turtle in Madagascar and the only aquatic turtle species endemic to the island. The rere has suffered widespread population declines across its range in Western Madagascar but successful captive breeding, head-starting and habitat protection offer hope for the species.Open
Once numbering 25,000 individuals living on a single Mauritian offshore island, the orange-tailed skink would have been wiped out by the arrival of an invasive shrew if it wasn't for proactive conservation intervention by DurrellOpen
Probably the rarest snake in the world with an estimated 18 individuals in existence, the Saint Lucia racer is only found on one offshore island the size of less than 17 football pitches.Open
The only species of its kind surviving in the Caribbean, the Saint Lucia whiptail lizard sports the same colours as the flag of its home nation. The conservation of this beautiful lizard is not only important scientifically, but also has cultural value.Open
Nearly 40 years of captive breeding, intense habitat restoration and successful translocations has led to such a major recovery of the Telfair's skink that this species now supports the conservation of other Critically Endangered Mauritian reptiles.Open
Found in the tall grasslands of the southern Himalayan foothills, the smallest pig in the world is also the rarest. Loss and degradation of the pygmy hog's habitat threatens to wipe out the species, but successful reintroductions offer some hope for the future.Open
Found surviving on just one offshore island, the Round Island boa had declined to just 50 snakes by the 1970's. Following 40 years of habitat restoration and successful translocations, an estimated 1500 boas can now be found on two islands in Mauritius.Open
With a wild population of just 25 individuals, the Madagascar pochard is one of the rarest birds on the planet. Discovered surviving on a single lake, captive-breeding efforts have successfully tripled the global population.Open
With a booming call and a unique breeding strategy, the mountain chicken is one of the largest frogs in the world. Exposed to the devastating amphibian disease chytridiomycosis, an estimated 99% of the global population has been lost in the last 12 years.Open
Once thought to be extinct, the Antiguan racer was found surviving on one tiny islet. A 20 year project established by five national and international organisations, including Durrell, successfully increased this species from 50 to over 500 snakes on four islands.Open
A real success story, over 30 years of captive breeding, releases and intensive management in the wild has increased the population of the pink pigeon in Mauritius from 16 to over 400 wild birds.Open
Thank you for your interest in the science behind the Durrell Index. Throughout the Index, we have drawn upon global biodiversity indicators and databases, as well as industry standard frameworks, to ensure we are being robust and transparent in our assessments. We have aimed to provide credible evidence of our results, using published research to support our findings wherever possible.
The global and species programme indicators are themed on the Pressure-State-Response framework, used by other conservation organisations such as BirdLife International.
To assess the type and severity of threats to our species we have developed a system based the Threats Classification Scheme (Version 3.2) of the International Union for Conservation of Nature (IUCN) and Conservation Measures Partnership (CMP). Our framework for assessing the conservation actions implemented for our species is based on the IUCN/CMP Conservation Actions Classification Scheme (Version 2.0).
One of the most important global programme indicators of impact within the Durrell Index is the ‘Red List Index of Species Survival’. We use the IUCN’s Red List Index to track the conservation status of a set of our target species over time, compared to a predicted counterfactual scenario of what would have happened if conservation actions had not taken place. This is the first use of this globally recognised indicator to evaluate the impact of a conservation organisation.
The methods and results are published in the peer reviewed scientific journal Biological Conservation. Our paper Accounting for conservation: Using the IUCN Red List Index to evaluate the impact of a conservation organization can be found here Young et al. 2014. As part of this analysis, we draw on a paper by Hoffman et al (2010) on The Impact of Conservation on the Status of the World’s Vertebrates published in the journal Science to determine which of our species have improved in Red List category due to conservation.
At the species indicator level, in order to track observed changes in the extinction risk of our species, we use - where available – conservation status categories published on the IUCN Red List, which are reviewed and verified by independent experts. If a species does not feature on the Red List, Durrell’s conservation scientists who are trained in the Red List methodology conducted the assessments following the 2001 IUCN Red List Categories and Criteria version 3.1.
Counterfactual Red List categories for our target species (the Red List category that we predict a species would have in the absence of conservation actions) are determined by Durrell’s Conservation Science team. Many of these counterfactual assessments have been externally reviewed by the scientific community during the peer review process during publication of the paper Accounting for conservation: Using the IUCN Red List Index to evaluate the impact of a conservation organization. For a number of the Mauritian bird species, we follow the counterfactual assessments produced by Butchart et al (2006) in the paper published in the journal Oryx entitled How many bird extinctions have we prevented?.