1. Energetics Metabolic scaling relationships Behavioral thermoregulation Torpor and hibernation Fat storage Migration Biological clocks

2. Discussion Readings Kortner, G. and F. Geiser 2000 The temporal organization of daily torpor and hibernation: circadian and circannual rhythms. Chronobiology International 17:103- 128. Geiser, F. and R.M. Brigham 2000 Torpor, thermal biology and energetics in Australian long-eared bats (Nyctophilus) J. Comp. Phyiol. B 170:153-162. Park, K. J., G. Jones, and R. D. Ransome. 2000. Torpor, arousal and activity of hibernating Greater Horseshoe Bats (Rhinolophus ferrumequinum). Functional Ecology 14:580-588.

3. Aerobic respiration Occurs in mitochondria of all aerobic organisms Glucose + oxygen + water => carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2 + 6H 2 O => 6CO 2 + 12H 2 O + energy Energy is stored by converting ADP -> ATP 1 mole of glucose contains 670 kcal Consequently, oxygen consumption can be used to measure energy production

4. Energetics of homeothermy Energy expenditure in the western pipistrelle (Pipistrellus hesperus) Homeothermy: maintain constant warm body temperature. Most mammals are at 35-39 o C Heterothermic: allow body temp to fall with ambient temperature Animals must spend energy to keep warm or cool off when the ambient temperature is out of their thermal neutral zone

5. Thermal conductance Log-log plot Heat conduction occurs when there is a temperature difference between body and air. Depends on surface area of animal. Measured as the amount of energy needed to maintain that difference. Note that small mammals have high conductance due to high surface area to volume ratios. Bats have higher conductance than other mammals due to large lungs and large wing membranes

6. Metabolic rate scales with body mass.75 Note: if y = aM b then log y = log a + b*logM If b < 1, then y increases slower than M If b > 1, then y increases faster than M

7. Therefore, mass specific metabolic rate declines with body size in birds and mammals Nonflying eutherian mammals

8. Diet influences metabolic rate

9. Reasons for energy budget fluctuations Availability - e.g. seasonality Demand - e.g. pregnancy Both - e.g. winter, night

11. Lactation is costly

12. Roost selection

13. Behavioral thermoregulation Nycticeius humeralis Evening bats Phyllostomus hastatus Greater spear-nosed bats

14. Torpor is a reduction in body temperature

15. Torpor saves energy Energy use increases linearly as ambient temperature decreases for an active animal that maintains a constant body temperature

16. Arousal from torpor can be expensive

17. Hibernation = long torpor Ground squirrel maintained at 4 o C

18. Hibernation has evolved twice in bats and has allowed some species to occupy cold climates Vespertilionidae Rhinolophidae

19. Hibernacula temperature preferences During hibernation bats maintain body temperature about 1 o C above ambient, but rarely below 6 o C

20. Some bats move north to hibernate Gray bat (Myotis sodalis) Bats rarely roost deep in caves because the temperature is too warm. Consequently, they have to move when it gets cold or warm outside. This makes them vulnerable to disturbance during hibernation.

21. Body weight during hibernation

22. Bats can arouse faster than other hibernators a =ventral temperature, b = rectal temperature

23. Due to nonshivering thermogenesis Brown adipose tissue (BAT) contains fat cells with many blood vessels and mitochondria which gives the tissue a brown color. When BAT is oxidized, the blood is heated quickly. Myotis myotis

24. BAT seasonal accumulation Myotis californicus

25. Migration permits other species to occupy temperate regions Molossidae Phyllostomatidae

26. Temperate migration patterns Nyctalus noctula Noctule Lasiurus cinereus Hoary bat

27. Migration routes of lesser long- nosed bats (Leptonycteris curasoae) Feed on cactus going north, agave going south

28. Biological clocks Clock periods –Circannual –Circalunidian –Circadian Clock Entrainment

29. Hibernation follows annual rhythm in golden-mantled ground squirrels Five animals were isolated at birth and kept in darkness at 3 o C

30. Circannual clocks in bats

31. Testes growth and feather molt in stonechats follows annual cycles Nestlings were removed from Kenya and reared in Germany with constant temperature and photoperiod and yet retain annual molt and testes cycles. Notice that the clock period drifted.

32. Kangaroo rat feeding shows lunar cycles K-rat activity at a feeder is confined to dark periods occurred during period of seed shortages

33. Vampire bats also avoid moonlight

34. Entrainment by environmental cycles Environmental cues set cycle period –Species specific Types of cues –Photoperiod –Light pulse –Food availability

35. Mouse activity entrains to light 10 mins of light per day are sufficient to reset the clock 12h light:12h dark 24 h dark 10 min light

36. Frequency of flights within a cave by Myotis Note that bats show strong circadian rhythm before and after winter

37. Distribution of circadian clocks in tissues and taxa

38. Mammalian clock pathways

39. Clock summary per/tim/tau(dbt) genes control pacemaker Pacemaker occurs in SCN (suprachiasmatic nucleus) in vertebrates, but is distributed in brain cells in some insects SCN signals pineal gland to release melatonin Short pulses of light entrain SCN and pineal cells Drosophila, honey bees, hamsters and humans share same genes - likely common ancestor was a flatworm that lived about 600 MYA