temperature regulation and metabolism heterothermy daily seasonal myotis tenrec bradypus macaca...

Temperature regulation and metabolism

HeterothermyDaily Seasonal

Myotis

Tenrec

Bradypus

Macaca

Homeothermy

Costs of Endothermy

metabolic response to temperature extremes

Ambient temperature

low high

Metabolic rate and body size

SMALL MAMMALSLarger relative surface area

Higher rates of heat exchange

Coping with seasonal environments -- Migration

Lasiurus cinerea

Lasionycteris noctivagans

Lasiurus cinerea

COPING WITH COLD

Subnivean zone

-30° -20° -10° 0°

Snowsurface

Temperature profile

Mouse runways gopher “eskers”

Heterothermy

Heterothermy

Homeothermy

Eptesicus fuscus

Thermal neutral zone

Heterothermy -- Daily torpor

Chaetodipus californicus

10 h torpor bout

Heterothermy -- Daily torpor

85% energy savings

Seasonal heterothermy

Hibernation (winter dormancy)

Spermophilus parryii

arousal bout

Seasonal heterothermy

Hibernation + Aestivation(winter + summer dormancy)

Spermophilus mollis

Active 4 months(spring growing season)

Dormant 8 months(hottest AND coldest months)

Temperature (°C)-5 10 15

Soil temperature profile -- Great Basin

Ammospermophilus leucurus

Year-round daytime activityBUT

Seasonal shift in behavior

Behavioral & Physiological tolerance

August

January

COPING WITH HEAT

Summer heat avoidance

Surface activity bouts (and resting in shade)

underground

Daily activity profile (mid-summer)

Desert Animals Potential evaporative water loss

SMALL MAMMALSLarger relative surface area1) Higher heat loads2) Higher evaporative loss

Burrow microclimate

Sundevall’s Jird(Meriones crassus)

Negev Desert, Israel

Daytime (underground)

Temperature

Burrow

Surface

Relative Humidity

Burrow

Surface

Mid-summer profiles

Water conservation in desert rodents

Merriam’sKangaroo rat(Dipodomys

merriami)

SouthwesternUS

Water conservation in desert rodents

Ord’s kangaroo rat (Dipodomys ordii) Western US

Kidney structure and water conservation

Dilute Concentrated

1200

med

ull

a

Dromedary(Camelus

Dromidarius)

Bactrian Camel(Camelus bactrianus)

Guanaco(Lama guanaco)

Desert adaptations in large mammals (Camelidae)

Keeping the brain cool

Countercurrent heat exchange

Keeping extremities warm

Marine mammals

Temperature regulation

depth (m) duration (min)Humans skin diver 100 2 scuba 300

Deep Diving

Human technology attack submarine test depth 400 “crush” depth 600 research submarine Alvin 4,500 bathyscaphe Trieste 10,912Otariidae fur seal 200 8 sea lion 250 10

Phocidae Harbor seal 200 10 Weddell seal 600 73 Elephant seal 1,600 90

Whales Fin whale 500 20 Pilot wale 610 Beluga 650 20 Killer whale 1,000+ Sperm whale (feeding) 500-1000

(record) 3,200 80 (maximum) ?

DEEP DIVING feeding dives of sperm whale (Physeter macrocephalus)

Elephant Seal Diving

Animals Dives Duration (min)

Surface Interval (min)

    Mean   Max Mean

21 Females

116,555   24         89     2

15 Males 100,662   23         80     3

Depth (m)

Mean 

Max

493 1567

365 1581 

DEEP DIVING -- feeding dives of elephant seal (Mirounga angustirostris)

DIVING PROBLEMS

Problem 1 -- Oxygen supply

Physiological adaptations: Increased blood volume & hematocrit more hemoglobin and myoglobin selective shunting of blood, lower heart rate lower metabolic expenditure higher tolerance of CO2 & lactic acid

Phoca vitulina (common harbor seal)

DEEP DIVING Diving Bradycardia - lower heart rate, blood diverted to essential organs

From: Elsner (1988)

DEEP DIVINGReduced energy expenditure during dive

Passive gliding descentActive stroking

(Mirounga angustirostris)

Problem 3 -- Nitrogen Decompression sickness the “bends”

Nitrogen narcosis

DIVING PROBLEMS

Problem 2 – Water pressure

Sperm whale (Physeter macrocephalus)

Spermaceti organ

Possible functions:

Hydrostatic

Echolocation

Weapon (ram)

DIVING PROBLEMS

Problem 4 -- Navigation

Foraging at depths where there is little or no ambient light

Toothed whales sophisticated underwater sonar

Seals -- Don’t have echolocation

Acute “passive” hearingHigh visual acuitySensitive tactile vibrissae