The Global Mammal Assessment , coordinated by the IUCN and completed in 2008, assessed all 5,487 mammal species known to date. The results are included in Schipper et al. (2008) Science 322, 225-230. The list has been updated with twelve additional species since.
Mammals are warm-blooded vertebrates which have fur or hair, sweat glands and produce milk to nurse their young. This allows them to dwell on all continents and in marine, terrestrial and freshwater systems. Mammals play a key role in ecosystems (e.g. grazing and predation) and also offer important benefits to humans such as food and income. Mammals are also of cultural importance in many societies and numerous mammal species have been domesticated.
22% of all mammal species are thought to be threatened with extinction. Habitat loss/degradation and harvesting are by far the major threats affecting mammal populations. Accidental mortality and pollution are the dominant threats for marine mammals. Populations of more than half of mammalian species are falling, with Asian primates particularly at risk, and recent extinctions including the Yangtze River Dolphin.