In southern Mexico and northern Guatemala are a series of globally important dry broadleaf and pine forests home to an exceptional level of small mammal diversity. In terms of threatened small mammal conservation, the Mexican dry forests is the number one priority region in the world. This region has by far the highest overall small mammal species richness (166 species) and the highest number of globally threatened species (24 species) of any of the SMSG’s Key Regions. Furthermore, the most notable feature of this diversity is the high number of globally threatened small mammals with severely restricted ranges that live here. Mexico is the country with the world’s highest number of Alliance for Zero Extinction sites triggered by small mammals, with a total of 31 AZE trigger small mammal species. Particular concentrations of these AZE species can be found on the Baja California peninsula as well as in the southern Mexican dry forests. Comparing this to Indonesia, the country with the second most AZE trigger small mammals with only 13 species, clearly demonstrates the global importance of Mexico. Southern Mexican forests are also home to 5 of the 20 SMSG’s Key Species (top 100 EDGE small mammals): Nelson’s small eared shrew, San Cristobal shrew, Sclater’s shrew, Chiapan climbing-rat and Tumbalá climbing rat. This small mammal fauna of this Key Region is dominated by 88 species of new world mice and rats from the Cricitedae family. Among these is the large number of globally threatened deer mice from the genera Habromys and Peromyscus as well as the giant deer mice Megadontomys, totalling 16 species which occur in the southern Mexican dry forests and Baja California. Other notable features include 20 species of pocket mice and kangaroo rat from the Heteromyidae family and 26 shrew (Soricidea) species.

Urban development, tourism, agricultural plantations and ranching are all high-impact threats to the dry forests of southern Mexico. These pressures in turn impact on small mammal populations, many of which are extremely restricted in geographic range and therefore highly vulnerable to habitat loss.

In terms of small mammal conservation, the main response needed is increased protection of habitats both within and outside of the existing protected area network. For some of the AZE trigger small mammals, captive breeding responses may be necessary due to extremely high levels of extinction risk.

Surveys are desperately needed to map at fine scale the distributions of the globally threatened small mammals and how this relates to the protected area network and its management effectiveness. There are 7 Data Deficient species in this Key Region.