11/30/09 SI A Ecl 365

Behavioral adaptations to environments

  1. What is torpor?
  2. Physiological state in which energy expenditure is greatly reduced by decreasing body temperature and rate of metabolism
  1. When does Torpor occur?
  2. Occurs when environmental conditions exceed an individual’s capacity for homeostasis
  3. (e.g., harsh climate or food/water shortage)
  1. What is another term for torpor?
  2. Dormancy
  1. What vertebrates become torpid (or dormant)?
  2. Regular cycles of dormancy are major features of herp lifestyles, especially in extreme environments.
  3. Among endotherms, many small to medium-sized mammals and some birds abandon homeothermy daily or seasonally
  1. How are ectotherm and endotherm torpor different?
  2. Ectotherms do not regulate body temperature during torpor and cannot awake (arouse)
  3. Endotherms regulate body temperature during torpor (albeit at low levels) and can awake (arouse)
  1. The types of torpor are ______torpor and ______torpor.
  2. Daily and seasonal.
  1. How often can daily torpor occur?
  2. Daily…. Everyday
  1. What are two types of seasonal torpor?
  2. Hibernation (winter)
  3. Estivation (summer)
  1. How is daily torpor beneficial?
  2. Saves energy during the inactive period of the day
  3. Lasts only a few hours
  1. What types (size, class) animals experience daily torpor?
  2. Small mammals and small birds
  1. Why do small mammals / birds utilize daily torpor?
  2. Fast use of energy/poor reserves
  3. Variable food (insects, nectar) resources
  1. In daily torpor, the body temperature falls _____ - ______C below the animal’s ______normal temperature. Also, oxygen consumption is less than ______to ______of the normal consumption rate.
  2. 5-15C below normal temp., 1/3 to 1/40
  1. Describe what happens during winter torpor or hibernation.
  2. Body temperature (Tb) can be reduced to within 1 degree or less of ambient temperature (Ta)
  3. O2 consumption markedly reduced
  4. Heart rate markedly reduced
  5. Prolonged periods of breathing apnea
  6. Body slows down much more than in sleep
  1. What is the only known avian hibernator?
  2. Common Poorwill
  1. What types of mammals hibernate?
  2. Carnivores (bears, badgers)
  3. Rodents (many --e.g., woodchucks, chipmunks, ground squirrels, dormouse, hamsters)
  4. Insectivores (e.g., African shrews, golden moles)
  5. NA bats: some species (7+) migrate; others (9+) hibernate
  6. Smaller marsupials
  1. What factors induce hibernation?
  2. Cold weather
  3. Low food supply
  4. Increased fat
  5. Increased serum magnesium levels
  6. Change in respiratory control center sensitivity to CO2
  1. Describe the three steps to entering hibernation.
  2. 1. decrease in heart rate & breathing rate
  3. 2. drop in oxygen consumption
  4. 3. drop of body temp
  1. True / False A sudden drop in temperature results in deeper torpor in hibernating species.
  2. False – they wake up
  1. At what temperature are arctic ground squirrels either frozen or awake?
  2. -15C
  1. True / False Hibernation is a continuous torpid state for months.
  2. False – there are periodic arousal periods
  1. True / FalseIn all mammals that hibernate, arousal takes about the same time.
  2. False – time needed differs among species – larger take longer, etc.
  1. Hibernation arousal is an ______process involving a high rate of ______production. ______fat tissue generates heat during the early stages of arousal.
  2. Active, heat, brown
  1. What are the stages of hibernation arousal (3)?
  2. Increase in heart rate
  3. Increase metabolism
  4. Reset temperature regulating mechanism
  1. Since arousal from hibernation takes a lot of energy (it is equivalent to the energy used in ~10 days of hibernation), why do animals “wake-up?”
  2. Eliminate build-up of N wastes
  3. Restore water lost by evaporation
  4. Fat storage depletion
  1. Where do herps usually spend winter?
  2. A place where Ta will not dip below freezing
  3. Bottom of lakes usually 4 C (mud & water)
  4. Terrestrial hibernators usually find sites below frost line
  5. Snakes ball up in communal dens; this does not keep them warm, but may reduce water loss
  6. Many herps rest on bottom of water body, not in mud, increasing cutaneous respiration
  7. In mud, must switch to anaerobic respiration; have high lactic acid tolerance
  8. Common to find turtles swimming under ice
  1. Freezing is not lethal to herps.
  2. False – it is, they can withstand brief periods of supercooling
  1. How do ice crystals physically damage cells and tissues (when the animal freezes)?
  2. Intracellularly - dehydrates cells, raising osmolality
  3. Extracellularly - blocks O2 and nutrient flow
  1. What happens when freeze tolerant herps are frozen?
  2. Heart stops, metabolism stops, no brain activity detected for up to 2 weeks in frozen wood frogs…
  3. Vital functions return within 1-2 hours of thawing!
  1. What is cryoprotectant?
  2. Antifreeze inside cells = cryoprotectant (glycerol and/or glucose)
  1. What happens to extracellular body water when herps are frozen?
  2. Extracellular body water becomes ice (this can be up to 40-60% of total water in body!)
  1. What is estivation?
  2. Seasonal torpor  summer torpor
  3. Less severe depression of core temperature and metabolic rate
  4. Generally in response to drought or extreme heat
  5. (dehydration would occur quickly)
  1. What animals estivate?
  2. Amphibians in desert face long periods of low humidity and no rain
  3. Lungfish in S. America & Africa also estivate
  4. Some desert rodents estivate
  5. (e.g. cactus mouse, mohave ground squirrel)
  1. What is a benefit or torpor?
  2. balance the energy budget in extreme environmental conditions
  1. What are costs of torpor?
  2. animal is helpless, little or no growth, reduced reproductive period
  1. True / False Torpor is a last resource when animals cannot deal with environment in a better way (such as insulation, or migration).
  2. True