Story | 27 May, 2016

The Top 20 Threatened Small Mammals

When most people think of endangered mammals they jump to the iconic giant pandas, tigers or elephants, but not to be overlooked are the equally charismatic and curious small mammals of the world.


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Photo: Carolos H Salvador

Small mammals are the most numerous, globally diverse and least known mammalian group. They have adapted magnificently to almost every habitat in the world and are often crucial to the healthy functioning of ecosystems, however, there are currently 437 of them facing extinction. In some cases populations have collapsed to less than 50 individuals and for others the entire global range is a few kilometres on a tiny island or mountaintop.

The Small Mammal Specialist Group (SMSG) is working to achieve a greater knowledge and understanding of the world’s 2,800+ small mammals and promote effective conservation action. The list of ‘Top 20 Threatened Small Mammals’ includes species that require urgent surveys in order to inform appropriate conservation measures and prevent extinction.

All of the top 20 species are critically endangered and in population decline; in just 10 years the populations of Cozumel Harvest Mouse (Reithrodontomys spectabilis), Poncelet’s Giant Rat (Solomys ponceleti) and Biak Giant Rat (Uromys boeadii) have declined by more than 80%. Number 15 on the list; the Vancouver Island Marmot (Marmota vancouverensis) is considered one of the rarest mammals in the world. In 2004 the population was estimated at just 35 individuals. Its critically endangered status has earned it fame as a conservation symbol in British Columbia. A captive breeding program is in place but huge areas of potential habitat still need to be surveyed in order to save wild populations from extinction.

All 20 species occupy extremely limited ranges. Half are endemic to small islands, others to a single sandy beach or patch of cloud forest and in the case of the Kondana Soft-furred Rat (Millardia kondana); a small plateau of less than 1km2. Number 4 on the list; The Santa Catarina’s Guinea Pig (Cavia intermedia), has the smallest geographical range of any mammal, found in only 0.04km2. A stable population was first discovered in 1999 on a small island of the coast of Brazil, but hunting for meat has driven it to the brink of extinction and it is now estimated at only 42 individuals. The island it inhabits is protected and entry prohibited, but it is not enforced and people still enter to hunt.

Habitat loss is a major threat facing the overwhelming majority of the 20 species, followed closely by predation from feral cats. Both threaten the Okinawa Spiny Rat (Tokudaia muenninki), aptly named due to the spiny protrusions from its thick fur. Found only on Okinawa Island, Japan, it is thought to occur in an area of less than 3km2. Although protected, there are no specific conservation measures in place and its habitat is being destroyed through government forestry programs.

With the rate of mammal extinction accelerating the need to save those most at risk is more urgent than ever. To learn more about the SMSG Top 20 Threatened Small Mammals click here.

Author: Rachael Gerrie

For more informatoin please contact: Rosalind.Kennerley,  Programme Officer, IUCN SSC Small Mammal Specialist Group