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The world's most extraordinary species are also some of the most threatened



he Thylacine or Tasmanian Tiger (Thylacinus cynocephalus) is one of the saddest examples of how a species can become extinct due to irresponsible human behaviour.

The thylacine was the largest marsupial carnivore and the last remaining representative of an entire mammal family. Thylacines were once widespread across the Australian mainland, but became extinct there and survived only on Tasmania. The reasons for its disappearance in mainland Australia and its continued survival in Tasmania remain a mystery, although climate change (Journal of Biogeography, 27.09.2017), an increase in human activity and the presence of dingoes are high on the list of culprits. Only when driven to the brink of extinction by human persecution in Tasmania as well, the species was finally awarded legal protection in 1936. Sadly, this action came too late for the thylacine. Hunted out of existence by Australian farmers who feared that the striped, canine-like marsupials would kill their sheep, the last thylacine died in captivity in Hobart Zoo 75 years ago next week, on September 7, 1936 (although the species was not officially declared extinct by international standards in 1986). Even more sadly a recent study revealed that the predator was probably not a threat to sheep after all. Its notably long jaw, one of the animal's most distinctive features, could open to an amazing 120 degrees but was too weak to kill sheep (Journal of Zoology, 31.08.2011)

Footage of the last known thylacine, and its striking jaw, shot before its death in captivity:



EDGE of Existence programme

The EDGE of Existence programme is a conservation programme of the Zoological Society of London (launched in January 2007), and is the only global conservation initiative to focus specifically on threatened species that represent a significant amount of unique evolutionary history. Using a scientific framework to identify the world's most Evolutionarily Distinct and Globally Endangered (EDGE) species, the EDGE of Existence programme highlights and protects some of the weirdest and most wonderful species on the planet. EDGE species have few close relatives on the tree of life and are often extremely unusual in the way they look, live and behave, as well as in their genetic make-up. They represent a unique and irreplaceable part of the world's natural heritage, yet an alarming proportion are currently sliding silently towards extinction unnoticed.

Whether or not this particular loss of unique evolutionarily historical genes, will decrease Planet Earth's resilience to human overexploitation, we will never know if we do not stop this loss of diversity


The EDGE of Existence programme seeks to:
  • Raise awareness of the world's most Evolutionarily Distinct and Globally Endangered (EDGE) species
  • Identify the current status of poorly known and possibly extinct EDGE species
  • Develop and implement conservation strategies for all EDGE species not currently being protected
  • Increase conservation capacity in the countries in which EDGE species occur, through supporting and training local scientists and conservation professionals to undertake research into the focal EDGE species
  • Support all ongoing conservation activities for EDGE species

Each year a number of the most poorly known and neglected EDGE species are selected for conservation attention. The top one hundred EDGE animals are presented on a comprehensive interactive website which highlights the actions necessary to save them from extinction. EDGE mammals button EDGE amphibians button EDGE coral reefs button EDGE birds button

So, the aim of the EDGE programme is to put these species on the map and catalyse conservation action to secure their future.

The methodology of identifying and ranking the EDGE animals

Every species in a particular taxonomic group (e.g. mammals or amphibians) has been given a score based on the amount of unique evolutionary history it represents, and its conservation status according to the IUCN Red List of Threatened Species, the world's most comprehensive assessment of the conservation status of plant and animal species. These scores are used to identify and rank EDGE species.

EDGE phylogeny
Each species is given an 'Evolutionary Distinctiveness' (ED) score, which is calculated from a family tree or phylogeny. In this phylogeny (see figure A), species A would have a higher ED score than either species B or C - it represents a branch rather than a twig on the tree of life. If species A were to go extinct, there would be no similar species left on the planet and a disproportionate amount of unique evolutionary history would be lost forever.

A 'Globally Endangered' (GE) score is then calculated for each species based on the 2006 IUCN Red List. Species which are Critically Endangered receive a higher score than less threatened species, which in turn receive a higher score than those not currently in danger of extinction. The two scores are then combined to produce an EDGE score for each species. EDGE species are species which have an above-average ED score and are threatened with extinction (Critically Endangered, Endangered or Vulnerable).

EDGE photos buttonEDGE map button



An introduction to the EDGE of existence conservation programme

An introduction to the EDGE of Existence conservation programme by Professor Jonathan Baillie, who is a global authority on the status and trends of threatened species. When EDGE was set up he was Conservation Programmes Director at the Zoological Society of London and worked on a large number of projects which focus on monitoring the status of rare and threatened species. In 2021 he was appointed CEO of On The Edge Conservation – the foundation that uses media combined with the cutting edge technology to reconnect humanity with the natural world.

A selection of videos featuring Evolutionarily Distinct & Globally Endangered species

EDGE fellow Arun Kanagavel recorded what he believes to be the first video footage of two EDGE...
Dramatic video footage of two critically endangered Javan rhinos and their calves. (The second...
The solenodon, an EDGE mammal that is currently receiving conservation attention from the 'Last...
Selection of male pregnant Darwin's frogs (R. darwinii) showing tadpole movements within the...
The Escudo sloth is the world's smallest sloth and according to sloth-expert Bryson Voirin, the...
Fantastic nocturnal wild footage of the rare giant spiny anteater who oddly prefers worms to...
A former hunter allows David Attenborough to get close to the once elusive indri.
Camera trap proves existence of Sumatran rhino on Kalimantan, Borneo


Please go to the EDGE pages for further information and donation.


Most of the above text is reprinted from materials available at EDGE. Original text may be edited for content and length.

Goal: 7000 tigers in the wild

Tiger range countries map


"Tiger map" (CC BY 2.5) by Sanderson et al., 2006.


about zoos and their mission regarding breeding endangered species, nature conservation, biodiversity and education, while at the same time relates to the evolution of species.