All living tigers trace back to a late Pleistocene bottleneck about 110,000 years ago. A 2018 study in Current Biology sequenced whole genomes from 32 tiger specimens and found six clades that match the living subspecies. In one whole-genome study of tiger specimens, gene flow between subspecies was very low, which supports the recognized geographic groups. Another genome study described nine genetically validated tiger subspecies, four extinct in the wild last century, leaving five.
Debates persist over whether tigers form six, five or two subspecies. The Smithsonian's National Zoo says recent analysis suggests little reason to divide living tigers into subspecies, since all are nearly identical genetically and physically. Some scientists suggest a simpler split into island tigers and mainland tigers. A 2018 Current Biology paper said the lack of agreement on how many tiger subspecies exist has partly hindered recovery efforts, because captive breeding and landscape work increasingly need clear conservation management units.
The body-size-related gene ADH7 appears to have been strongly selected in the Sumatran tiger, perhaps linked to adapting to the tropical Sunda Islands. Indochinese male tigers are smaller than Siberian tigers in body size, but have the longest skull of any tiger subspecies, 319 to 365 mm. The Amur tiger is the largest kind of tiger, and the Sumatran tiger is the smallest kind of tiger.
The Smithsonian's National Zoo says the tiger's closest relative is the lion. A genome study published in 2013 found that the tiger's genome is 95.6% similar to the domestic cat's, and that the tiger and the domestic cat diverged about 10.8 million years ago. A 2013 study compared the genomes of an Amur tiger, a white Bengal tiger, an African lion, a white African lion and a snow leopard, and found genetic signatures that may reflect adaptations to the big cats' hypercarnivorous (mostly meat) diet and muscle strength.
White tigers cared for in some zoos are not albino: they are white and tan with blue eyes. The white coat seen in some tigers comes from a double recessive gene, like red hair in people. In white tigers, which have white fur and dark stripes, the genetic basis is one amino-acid change (A477V) in the transporter protein SLC45A2. The white coat could in theory be present in any tiger subspecies but has only been found in the Bengal subspecies. In 2011 the Association of Zoos and Aquariums banned its accredited institutions from breeding white tigers.
Dark stripes on a pale background break up a tiger's outline as it waits for prey to come near, and deer cannot see red, so a tiger's orange coat looks green to them. How well a colour hides an animal is hard to test, because it depends on size, viewing distance, height above the ground, lighting, occlusion, the habitat and the visual system of the observer. Researchers at the University of Bristol used machine learning and image processing to embed targets in two different environments, and found the colour that would either minimise or maximise how visible a target is. Animal Diversity Web says the spots on the backs of a tiger's ears and its stripe pattern may also be used to communicate with other tigers.
Because tigers live in dense forests, they are hard to find, and counting them from the air or from vehicles does not work well. Scientists can tell individual wild tigers apart by their stripe patterns, and they use motion-sensitive cameras in forests that let tigers take their own photographs. Matching thousands of tiger photographs by eye is hard, so a pattern-matching program called ExtractCompare, developed by statistician Lex Hiby, extracts stripe patterns and shortlists the closest matches. Trained technicians then pick the tiger from the shortlist. By 2015 one team's two decades of camera-trap photographs had identified almost 800 individual tigers by their stripes.
Earlier, India estimated its tigers with track counts that identified individual tigers by their pug marks (footprints). This failed to give reliable estimates because of erroneous assumptions. Most early methods of counting tigers failed because they did not take three things about tigers into account: tigers are scarce, their range is huge, and they are secretive. As recently as 15 years before 2022, scientists made educated guesses about tiger numbers; camera traps, genetic testing and data modeling have since improved counting.
A 2022 IUCN assessment estimated between 3,726 and 5,578 wild tigers in Asia, with an average of 4,500, and 3,140 of the 4,500 estimated wild tigers were adults. The assessment suggested a rise from 3,200 tigers in 2015 to 4,500 in 2022, but scientists say better counting explains part of it, so comparing years is unreliable. Panthera says inconsistent monitoring methods in tiger range states have produced false increases in population counts, and that earlier IUCN assessments used highly conservative estimates, nearly guaranteeing increases in later estimates. The 2022 assessment is described as the first reasonable baseline against which scientists can measure future changes in the global tiger population.
Tigers lost 93% of their historic range, and their numbers went from 100,000 in the last century to potentially 4,500 in 2022. As of November 2026, wild tiger numbers dropped by around 95% from the beginning of the 20th century, and WWF-UK says tigers occupy around 8% of their original range. The 2022 IUCN assessment said South Asia held 76% of the global tiger population and that its tigers were gaining numbers, particularly in India and Nepal. It said that in Northeast Asia tiger numbers were relatively stable in Russia and likely increasing along the border with China, and that Southeast Asia's tigers had fared worst, having been lost from Cambodia, Lao PDR and Vietnam since the turn of the century.
In 2010 in St. Petersburg, leaders of 13 tiger-range countries met with scientists to create a comprehensive strategy to save tigers. In 2010 the world set a goal of doubling tiger numbers, or reaching at least 6,000 by 2022. In July 2022 Panthera said the goal had been missed and that range states would set a new 12-year recovery plan at a second Global Tiger Summit. Smithsonian efforts to save tigers began in 1972 with the Smithsonian-Nepal Tiger Ecology Project, and in 2008 the Smithsonian joined the World Bank Group and the Global Environmental Facility to launch the Global Tiger Initiative. Rangers in tiger-range countries are trained in SMART patrolling, a Spatial Monitoring and Report Tool.
As of November 2026, Panthera says that with partners it helped more than triple the number of tigers detected in Manas National Park, India, a former conflict area where the tiger population was nearly poached to local extinction. In Western Thailand's Huai Kha Khaeng Wildlife Sanctuary, where WCS has worked since 2004, the population of wild tigers has increased by 50%, as of November 2026. Nearly 1 million square kilometers of potential tiger habitat remain vacant and could host recoveries, according to the 2022 assessment. WWF-UK says tiger recovery areas have been identified, and that many of them serve as critical carbon sinks, as of November 2026.
Female Indian tigers have home ranges of 200 to 1000 square kilometers, and a male's home range averages 2 to 15 times larger. Young female tigers often settle near their mother's territory, while young males disperse farther from home. Tigers can share home ranges peacefully or wander with no home range at all. Tigers keep several dens within their home range, often in dense plants, a cave or a hollow tree, and they mark their range with a musky scent sprayed on grass, trees and rocks, and with scrapes and claw marks.
Words to know
- bottleneck: a population crash
- Pleistocene: ice age epoch
- baseline: a starting measure
- subspecies: a kind
