Ecological Physiology of Daily Torpor and Hibernation (Fascinating Life Sciences)

This book provides an in-depth overview on the functional ecology of daily torpor and hibernation in endothermic mammals and birds. The reader is well introduced to the physiology and thermal energetics of endothermy and underlying different types of torpor. Furthermore, evolution of endothermy as well as reproduction and survival strategies of heterothermic animals in a changing environment are discussed. Endothermic mammals and birds can use internal heat production fueled by ingested food to maintain a high body temperature. As food in the wild is not always available, many birds and mammals periodically abandon energetically costly homeothermic thermoregulation and enter an energy-conserving state of torpor, which is the topic of this book. Daily torpor and hibernation (multiday torpor) in these heterothermic endotherms are the most effective means for energy conservation available to endotherms and are characterized by pronounced temporal and controlled reductions in body temperature, energy expenditure, water loss, and other physiological functions. Hibernators express multiday torpor predominately throughout winter, which substantially enhances winter survival. In contrast, daily heterotherms use daily torpor lasting for several hours usually during the rest phase, some throughout the year. Although torpor is still widely considered to be a specific adaptation of a few cold-climate species, it is used by many animals from all climate zones, including the tropics, and is highly diverse with about 25-50% of all mammals, but fewer birds, estimated to use it. While energy conservation during adverse conditions is an important function of torpor, it is also employed to permit or facilitate energy-demanding processes such as reproduction and growth, especially when food supply is limited. Even migrating birds enter torpor to conserve energy for the next stage of migration, whereas bats may use it to deal with heat. Even though many heterothermic species will be challenged by anthropogenic influences such as habitat destruction, introduced species, novel pathogens and specifically global warming, not all are likely to be affected in the same way. In fact it appears that opportunistic heterotherms because of their highly flexible energy requirements, ability to limit foraging and reduce the risk of predation, and often pronounced longevity, may be better equipped to deal with anthropogenic challenges than homeotherms. In contrast strongly seasonal hibernators, especially those restricted to mountain tops, and those that have to deal with new diseases that are difficult to combat at low body temperatures, are likely to be adversely affected. This book addresses researchers and advanced students in Zoology, Ecology and Veterinary Sciences. Preface Contents About the Author Chapter 1: Introduction, Background and Definitions Definitions Chapter 2: Quantifying Torpor Trap and Recapture Torpor Use Sawdust Method and Activity Sensors Infrared Thermometers Thermocouples and Thermistors Respirometry Torpor Induction and the Time to Steady-State Torpor External Thermal Sensors Temperature-Sensitive Radio Transmitters, Data Loggers and Heart Rate Transmitters/Loggers Transmitter and Logger Size Transponders Thermal Cameras Chapter 3: Diversity and Geography of Torpor and Heterothermy Ectotherms Torpor in Endotherms Birds Landfowl, Galliformes Nightjars and Relatives, Caprimulgiformes Swifts, Apodiformes Hummingbirds, Trochiliformes Cuckoos, Cuculiformes Pigeons, Columbiformes Raptors, Ciconiiformes Penguins, Sphenisciformes Petrels, Procellariformes Owls, Strigiformes Mouse Birds, Coliiformes Kingfishers, Coraciiformes Songbirds, Passeriformes Mammals Egg-laying mammals, Monotremata Pouched Mammals, Marsupialia Opossums, Didelphimorphia Shrew Opossums, Paucituberculata Monito del Monte, Microbiotheria Insectivorous/Carnivorous Marsupials, Dasyuromorphia Marsupial Moles, Notoryctemorphia Possums, Diprotodontia Placental Mammals, Placentalia Afrotheria Tenrecs and Golden Moles, Afrosoricida Elephant Shrews, Macroscelidea Aardvark, Tubulidentata Xenarthra Armadillos, Cingulata Sloths and Anteaters, Pilosa Insectivores, Lipotyphla Bats, Chiroptera Pangolins, Pholidota Carnivora Primates Rodents, Rodentia Squirrels, Sciuridae Dormice, Gliridae Pocket Mice and Kangaroo Mice, Heteromyidae Jerboas, Jumping Mice, Birch Mice, Dipodidae Hamsters, Cricetidae Fat and Pouched Mice, Nesomyidae Mice, Muridae Mole Rat, Heterocephalidae Heterothermy in Large Mammals and Birds Hibernating Humans? How many heterothermic Species are there and why do Patterns of Torpor differ among Taxa? Chapter 4: Patterns and Expression of Torpor Patterns of Torpor Hibernation Daily Torpor Two Patterns of Torpor or a Continuum of Variables? Are Short Torpor Bouts in Hibernators Daily Torpor? Aestivation Torpor Expression in Response to Food and Water Availability Spontaneous torpor (Food ad libitum) Overabundant Food Induced Daily Torpor (Food Restricted) Unpredictable Food Availability Water Conservation and Restriction and Torpor Use Chapter 5: Physiology and Thermal Biology Cooling and Rewarming Thermoregulation During Torpor The Range of Body Temperatures During Torpor and the Effect of Body Mass Metabolic Rate and its Reduction during Torpor Evidence for Inactivation of Normothermic Thermoregulation at Torpor Entry Evidence for the Temperature Effect on MR during Torpor Evidence for physiological inhibition Evidence for the Effect of the Tb-Ta Differential on TMR Evidence for the Influence of Thermal Conductance on TMR Effects of Body Mass on Metabolism Torpor Entry Steady-State Torpor Torpor Versus Hypothermia Heart Function Breathing Patterns The Duration of Torpor Bouts Effects of Temperature on Torpor Bout Duration Why Do Animals Arouse from Torpor? Chapter 6: Seasonality of Daily Torpor and Hibernation Preparation for the Torpor Season Hibernacula and Torpor Sites Body Mass, Fattening and Food Storage Hibernators Daily Heterotherms Fat Tails Ghrelin and Leptin Seasonal Control of Torpor Seasonal Occurrence of Torpor Hibernators Yearlong Hibernation Hibernation from Summer to Spring Hibernation from Autumn to Summer Hibernation from Autumn to Spring Hibernation from Autumn to Winter Hibernation from Winter to Spring Hibernation in Winter Hibernation in Spring Hibernation in the Cold Season and Short Bouts of Torpor in the Warm Season Daily Heterotherms Yearlong Daily Torpor Seasonal Daily Torpor More Pronounced Torpor in Summer than in Winter Seasonal Change in Torpor Expression and Torpor Patterns Chapter 7: Ecological and Behavioural Aspects of Torpor Torpor and Geographic Distribution of Heterothermic Endotherms Intraspecific Comparisons of Geographic Differences in Torpor Patterns Torpor Use and Migration Torpor and Locomotion Passive Rewarming from Torpor Interactions Between Torpor Use and Huddling Behaviour Temperature Selection and Torpor Use Torpor Use in Relation to Fires Torpor Use and Survival of Droughts Torpor Use and Survival of Floods Torpor Use in Response to Storms Torpor Use and Inter-Specific Competition Torpor Use and Fasting Endurance Life Span Torpor and Mammalian Extinctions The Advantages and Disadvantages of Torpor Use 8: Torpor During Reproduction and Development Reproduction Birds Mammals Monotremes Marsupials Placentals Afrosoricida Xenarthra (Sloths) Lipotyphla, Insectivores Bats Carnivora (Bears and Badgers) Primates (Lemurs) Rodents Why is Torpor used during Reproduction? Development Birds Mammals Monotremes Marsupials Placentals The Limited Data on Torpor During Reproduction and Development Chapter 9: Dietary Lipids, Thermoregulation and Torpor Expression Ectotherms Endotherms Dietary Lipids and Hibernation in Captive Mammals Field Studies Effects of Dietary Lipids on the Physiology of Daily Heterotherms Dietary Lipids, Thermal Physiology and their Implications Chapter 10: Evolution of Endothermy and Torpor The Link Between the Evolution of Endothermy and Heterothermy The Role of Heterothermy at the K-Pg Boundary Chapter 11: Concluding Remarks Diversity Function Ecology Appendix 1 Glossary Acclimation Acclimatisation Aestivation Daily Heterotherms Daily Torpor Ectotherm Endotherm Eutherm or Normotherm Heterothermic Endotherm Hibernation or Multiday Torpor Homeotherm Hypometabolism Hypothermia Metabolic Rate Poikilotherm Torpor Appendix 2. International Hibernation Symposia References Index