Ecophysiology of Small Desert Mammals

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 Bergmann’s Rule and Body Size of Animals.- 3.2.2 Allen’s Rule and Thermoregulatory Effective Surfaces.- 3.2.3 Dehnel Phenomenon and Seasonal Body Mass Changes.- 3.2.4 Body Mass Changes in Free-Living Small Mammals.- 3.2.5 Fasting Endurance and Body Size.- 4 Heat Transfer and Body Temperature.- 4.1 Heat Exchange Between Animal and Environment.- 4.1.1 Radiation.- 4.1.2 Convection.- 4.1.3 Conduction.- 4.2 Operative and Standard Operative Environmental Temperatures.- 4.3 Body Temperature of Mammals.- 4.3.1 Torpor.- 4.4 Overall Thermal Conductance.- 4.4.1 Pelage and Seasonal Changes in Thermal Conductance.- 4.4.2 Thermal Exchange and Effective Surface Area.- 4.5 Shivering and Non-Shivering Thermogenesis.- 5 Behavioural Adaptations.- 5.1 Temporal Patterns.- 5.1.1 Small Nocturnal Mammals.- 5.1.2 Small Diurnal Mammals.- 5.1.3 Shuttling.- 5.1.4 Nocturnal vs Diurnal Activity for Small Desert Mammals.- 5.2 Refuge Microhabitat.- 5.2.1 Burrows.- 5.2.2 Rock Crevices.- 5.2.3 Nests.- 5.2.4 Geothermally Heated Mines.- 5.3 Dietary Habits.- 5.3.1 Granivory.- 5.3.2 Herbivory.- 5.3.3 Insectivory and Carnivory.- 5.3.4 Omnivory.- 5.3.5 Dietary Preference and Selection Indices.- 5.4 Locomotion.- 6 Water Requirements and Water Balance.- 6.1 Water Input.- 6.1.1 Water for Granivores.- 6.1.2 Water for Non-Granivores.- 6.2 Water Output.- 6.2.1 Evaporative Water Loss.- 6.2.2 Salivary Water Loss.- 6.2.3 Kidney Function and Electrolyte Excretion.- 6.2.4 Nitrogen Excretion.- 6.2.5 Unorthodox Method of Eliminating Electrolytes.- 6.2.6 Hormonal Control of Urine Concentration.- 6.2.7 Faecal Water Loss.- 6.3 Total Body Water Volume and Its Distribution..- 6.4 Body Fluid Regulation.- 6.4.1 Colloid Osmotic Pressure.- 6.5 Cardiac Output and Its Distribution During Dehydration.- 6.6 Water Flux.- 6.6.1 Water Flux of Free-Living Mammals.- 7 Energy Requirements and Energy Flux.- 7.1 Digestibility and Energy Value of Food.- 7.1.1 Digestibility of Seeds.- 7.1.2 Digestibility of Vegetation.- 7.2 Anti-Nutritional Compounds.- 7.2.1 Bezoars and the Ibex.- 7.3 Digestive Tract and Absorption of Nutrients.- 7.4 Basal Metabolic Rate.- 7.4.1 Comparison of BMR Among Mammals.- 7.4.2 Seasonal Changes in BMR.- 7.4.3 Maximum Metabolic Rate.- 7.5 Average Daily Metabolic Rate.- 7.5.1 Linear Regression to Estimate ADMR.- 7.5.2 Total Daily Heat Production to Estimate ADMR.- 7.5.3 Energy Balance and Body Mass Change to Estimate ADMR.- 7.5.4 Comparison in ADMR Among Small Mammals.- 7.6 Field Metabolic Rate.- 7.6.1 BMR, ADMR and FMR.- 7.6.2 Doubly Labelled Water Method.- 7.6.3 Calculation of Daily Energy Expenditure, Metabolizable Energy Intake and Energy Retention in Animals Not in Energy Balance.- 7.6.4 Comparison of Field Metabolic Rates Among Mammals.- 7.6.5 Seasonal Field Metabolic Rates.- 7.6.6 Water Influx to FMR Ratio.- 8 Reproduction.- 8.1 Timing of Reproduction.- 8.2 Water Intake, Milk Production and Pup Growth.- 8.3 Water Budget During Pregnancy and Lactation.- 8.3.1 Recycling of Water During Lactation.- 8.4 Energy Requirements for Pregnancy and Lactation.- 8.4.1 Energy Partition in Lactating Female.- 8.5 Reproduction, Metabolic Rate and Body Size.- References.