In the animal world, large carnivores like tigers, wolves and bears are among the most endangered creatures. Apart from the loss of habitats and decrease in number of prey animals available for these animals, carnivores also face threats from humans who hunt and and kill them in retaliation over livestock.

These threats pose a risk of extinction for carnivores, as entire populations can get wiped out from particular areas and reduce the ranges up to which they can be found (a species range is the geographical area where a particular species can be found during its lifetime). But due to a lack of knowledge about the extent to which former ranges have contracted due to threats, there is poor understanding of the environmental effects that a loss of these ranges have on large carnivores.

Some studies have estimated as many as 170 animals have lost over 50% of their former ranges, mainly due to an increase in human densities or other human impacts – but researchers are yet to determine a global estimate of how much carnivore ranges have contracted in the world.

Threatened with extinction

A recent study conducted by researchers from Oregon State University in the US addresses this gap by presenting the first global analysis of the extent of ranges large carnivores have lost.

To arrive at their analysis, the researchers used current range maps shared by the International Union for Conservation of Nature Red List for 24 of the 25 large carnivores of the world. Former ranges were compared to what they might have been around 1500 AD.

Range contraction maps for 25 large carnivores. Regions of persistence (i.e. inside both historic and current ranges) are shown in yellow-orange, while regions of contraction (inside historic but not current range) are shown in dark red. Species are ordered by percentage range contraction with the greatest contractions shown in the uppermost panels.

The researchers found that the carnivores that have suffered the greatest loss of habitats are the red wolf, the Ethiopian wolf, tigers, lions, African wild dogs and cheetahs. These animals have lost between 92% to 99% of their original habitat. Christopher Wolf, a doctoral student at the University and the lead author of the study said: “All six of these species are now threatened with extinction and their numbers are decreasing.”

On the other hand the Eurasian lynx, the dingo, the grey wolf and spotted, striped and brown hyenas have experienced a lower loss of habitat, between 12% to 27%.

A large number of carnivores were once found in the forests of South and Southeast Asia, with up to nine species occurring together, while in Africa as many as six large carnivore species were known to occur together. India is still considered a global biodiversity hotspot and is home to lesser known carnivores like the clouded leopard, the Asiatic wild dog, the striped hyena and black and brown bears. But this also means that Southeast Asia and Africa are where the greatest variety of large carnivores have faced a decline. Oceania (Australia and its neighbouring countries), Europe and the Americas, which had a smaller variety of carnivores, have experienced carnivore loss at a higher percentage due to the similarity in their terrain (in fact, these areas have lost all of their large carnivores).

Composite range contractions maps based on all 25 large carnivores. Variables shown are (a) historic species richness, (b) current species richness, (c) their difference (i.e. lost species richness) and (d) the percentage of species lost.

Historically, large carnivores were found on 96 per cent of the Earth’s land, except for islands like Madagascar and Papua New Guinea. Large carnivores can now be found only on 34% of the planet’s land. Species that occur in India, like the tiger, have lost nearly 95% of their former range, the snow leopard has lost 77% of its range and the clouded leopard has lost 63%.

Wolf said, “The key drivers of these range contractions include increasing human population densities and habitat loss due to agriculture and livestock.”

Being grass eating animals, livestock like cattle compete with wild herbivores for food. An increase in livestock numbers can potentially decrease number of wild prey thus reducing the naturally preferred prey of carnivores. This brings carnivores in contact with humans, as they take to killing domestic livestock. Real or imaginary threats to livestock cause humans to retaliate against carnivores. Similarly, researchers found that a conversion of suitable habitat for carnivores to agricultural farms also leads to reduction in range grounds, leaving no natural habitats for them to breed and hunt.

Remarkably, the same factors that lead to a decrease in carnivore numbers can also protect them, depending on the levels of human tolerance and government policies, as well as the animal’s ability to subsist. For instance, Ahmednagar district in Western Maharashtra, which is dominated by cropland and livestock supports leopards and hyenas. But such cases where humans are tolerant of carnivores are exceptions rather than the norm.

Regions of the world with intact or no longer intact large carnivore guilds (one or more species). Note that regions with high historic large carnivore richness (like Southeast Asia) seldom have intact guilds. Altogether, intact guilds make up 34% of the world's land area while 96% of land (excluding Antarctica) once contained one or more large carnivores.

The Oregon State University’s study has a couple of limitations due to its use of old range maps. Old maps tend to take a very broad overview of areas which do not leave out pockets where species do not occur at all. Old maps also do not consider the number of individuals of a species in an area, thus they do not truly reflect the size of their populations.

However, the research is decisive as it shows the extent to which carnivores have lost their old stomping grounds. To conserve large carnivores, the authors say: “Increasing human tolerance may be the best way to save these species from extinction along with the expansion and strengthening of protected area networks, which protect all resident large carnivores along with their prey.”

The study was published in the journal Royal Society Open Science on July 12, 2017.