The Indigenous Range of the Tiger (Panthera tigris)

Abstract

Aim

Indigenous range maps are fundamental documents in biogeography, phylogeny and conservation. We define the indigenous range of a species as ecoregions (or parts of ecoregions) where the species was likely found before humans became a major factor shaping the species' distribution, beginning at a time when the geographical alignment of the continents and the prevailing climate are (or at least were) roughly consistent with current conditions. We developed a structured, generally applicable method to map a species' indigenous range and applied this process to the tiger (Panthera tigris).

Location

Terrestrial Asia.

Methods

To guide our mapping, we synthesised a database of over 70,000 tiger observations with dates and locations. We developed a structured Delphi process to assign categories of indigenous range to ecoregions aided by a climate niche model. We analysed tiger habitat change at the ecoregional scale using the anthropogenically modified biomes (‘Anthrome 12K’) dataset to suggest dates of first significant human impact. Finally, we estimated extirpation dates for ecoregions where tigers have been extirpated.

Results

We found the tiger once occupied a likely indigenous resident range of approximately 11.5 million km², crossing 116 ecoregions. We also mapped an additional c. 11.7 million km² of exploratory range and 1.2 million km² of possible resident range. Collectively these areas overlap with 36 modern countries. Significant human disruption of the species' habitat seems to have begun over 6000 years ago in some areas, but in other regions has yet to materialise. In few arid ecoregions, human activities appear to have modestly increased habitat availability in the past, yet overall tigers have lost between 90% and 95% of their indigenous range over the last 8500 years.

Main Conclusions

We define the ‘indigenous range’ of a species, develop a replicable biogeographical procedure, apply the procedure to the tiger and discuss transferability to other species.