Since small mammals have a large surface to mass ratio, one would expect them to quickly dehydrate and perish at high environmental temperatures. Nonetheless, a large number of small mammal species inhabit deserts. This fascinating phenomenon is investigated by Prof. A. Allan Degen in his book. The majority of small desert mammals are rodents, but shrews of several grams and small foxes of 1 kg are also present. Their survival is due mainly to behavioural adaptations and habitat selection, however, physiological adaptations also contribute to the success. Interestingly, many small mammals that live in different deserts of the world show similarities in their adaptive traits although they have different taxonomic affinities.Since small mammals have a large surface to mass ratio, one would expect them to quickly dehydrate and perish at high environmental temperatures. Nonetheless, a large number of small mammal species inhabit deserts. This fascinating phenomenon is investigated by Prof. A. Allan Degen in his book. The majority of small desert mammals are rodents, but shrews of several grams and small foxes of 1 kg are also present. Their survival is due mainly to behavioural adaptations and habitat selection, however, physiological adaptations also contribute to the success. Interestingly, many small mammals that live in different deserts of the world show similarities in their adaptive traits although they have different taxonomic affinities.1 Introduction.- 1.1 Ecophysiology.- 1.2 Small.- 1.3 Desert.- 1.4 Mammal.- 1.5 Small Desert Mammals.- 2 Deserts.- 2.1 Definition of Deserts.- 2.2 Formation of Deserts.- 2.3 World Deserts.- 2.4 Desert Soils.- 3 Body Size and Allometry.- 3.1 Allometric Scaling.- 3.1.1 Correlation Coefficient and Standard Error of Estimate in Allometric Relationships.- 3.1.2 Interspecific and Intraspecific Allometric Relationships.- 3.2 Body Size and Environment.- 3.2.1 Bergmanns Rule and Body Size of Animals.- 3.2.2 Allens Rulelsť