Tiger (IMAGE) University of California - Berkeley Caption Tigers are one of Earth's most critically endangered species. Extinction of the majority of such species would indicate the sixth mass extinction is in our near future. Credit Anthony Barnosky, UC Berkeley Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.