Environmental Adaptations

Mammalogy (Spring 2015 Althoff - reference FDVM Chapter 9)

LEC 10B

Which is it for Mammals?

• Warm-bloodied? – can a mammal ever be alive and have “cold” blood?

• Endothermy? – body temp maintained primarily by internally produced heat

• Homeothermy? – constant body temp maintained by physiological means

• _____________ — body temp can change as a result of some amount of dormancy (hibernation, daily torpor, estivation)

Benefits of Regulated Body Temperature

• _____________________ – birds and mammals have 8X that of ectotherms

• _____________________________________ (which is what a living organism is!)

• _________________________________ enhancing neuromuscular system… thereby enhancing ability to capture prey and avoid predation

Benefits of Regulated Body Temperature…con’t

• Gain _______________ from temperature extremes common in nature, permitting extensive activity during a 24-hr period or on a seasonal basis

• __________________ can be matched better with thermoregulatory pattern for a given environment

Thermodynamic Equilibrium

• Heat production: energy ____

• Heat loss: energy _____

This is delicate balancing act…it is a matter of winning or losing the ______________________!

Heat Production achieved through

metabolism of…

• Food

• Fat

• Cellular metabolism

• Muscular contraction

FOOD

FDVMK Fig. 9.4, p159 Energy Balance Model

Energy In Energy Out

__________ energy “input” possible from…

• Solar radiation

• Thermal radiation

• Convection

• Conduction

Summary of Energy Exchange

• Fig. 9.1, p157• Note types of energy _______

RADIATION CONDUCTIONCONVECTION

• • Note types of energy ________

RADIATION CONDUCTIONCONVECTION EVAPORATION

1

1

23

2 43

Sun

FDVMK Fig. 9.1, p157

ADAPTATIONS TO COLD • _______________ zone = occurs within which

the metabolic rate is minimal AND does not change as ambient temperature increases or decreases

• _______ critical temperature = Tlc

• _______ critical temperature = Tuc

• Fig. 9.2, p158 – relationship of ambient temperature to O2 consumption

Met

abo

lism

FDVMK Fig. 9.2, p158

Adjustments to ____________

Environmental Temperatures • Change insulatory thickness

a) b)

• Behavior attributesa) b) c)

• Changing peripheral blood flow

Adjustments to

Environmental Temperatures

• Change insulatory thicknessa) subcutaneous layer (seasonal)b) ____ piloerection

• Behavior attributesa) postureb) habitat selectionc) activity

• Changing peripheral blood flow• ____________________

AVOIDANCE of ________

• Body size and metabolism• Insulation• Appendages• Coloration• _________________________• Reduction in level of activity• Dormancy

Althoff, D.P., G.L. Storm, and D.R. DeWalle. 1997. Daytime habitat selection by cottontail rabbits in central Pennsylvania. Journal of Wildlife Management 61(2): 450-459.

Surface of forms used by adult male and females cottontails by season

Debris

Debris + Soil

Soil

Winter Spring Summer Autumn

Body Size & Metabolism • Larger mammals consume more oxygen than

smaller animals…duh!

• Larger mammals, on a MASS-SPECIFICMETABOLIC RATE basis, consume less

• Fig. 9.5, p160 (handout). Can use this figure to estimate body metabolic rate for unknown species

BERGMEN’S RULE • “…races from cooler climates in species of

warm-blooded vertebrates tend to be ______ than races of the same species living in warmer climates”

• Generalize:a) energetic advantage gained through

________________________________________

b) amount of _________ depends on animal’s surface area and ambient temperature

Bergman’s Rule: Valid?

• McNabb (1971): for 47 species of mammals studied, ______ followed this prediction

• Geist (1987): “________”a) body size initially increased with

latitudeb) it reversed from 530 to 630Nc) small body size occurs at __________

and ________ latitudes

The “Poor” Weasel

• Long and thin is an advantage:

• Long and thin is a disadvantage:

Insulation

• ______________ thicknessa) fat layer (seasonal)b) fur density & hair length (seasonal)c) fluff fur

• _______ in fur (like beaver & muskrats)a) aquatic species do this to keep

skin dry

b) if air displaced by water, insulationreduced

Appendages

• ALLEN’S RULE: “appendages of endothermic animals are shorter in colder climates than those of animals of the same species found in warmer climates.”

• Generalize:a) shorter ears, legs, muzzles, tails

for more northern speciesb) _____________________________

• Allen’s Rule ____ “solid”

Appendages

Countercurrent heat exchange process in force (Fig. 9.9, p164)

a) a form of peripheral heterothermy b) warm arterial blood warms

colder blood returning in veins

_______ transferredfrom ________ to ________

______ containing cooled blood from body periphery

_______ containing very warm blood from

core of body

from core

from extremities

from extremities

Fig 9.9, p1164 FDVMK hypothetical temp changes

Tem

ps

in _

____

___

of

CC

HE

Tem

ps

in _

____

___

of

CC

HE

Fig 9.9B, p164 FDVMK Regulation of External Body Temp

Coloration

• GOLGER’S RULE –”Races in warm and humid areas are more heavily pigmented than those in cool and dry areas”

• Generalize:a) mammals closer to arctic region

are paler (less pigmented)b) may reduce predation (i.e., ability to

be detected)

Coloration

• If darker colors “absorb” more solar radiation, why are mammals in more northernly climates darker…instead of lighter?

• Does this mean predation is a stronger selective force than that imposed by homeothermy (i.e., winning the energy game?)

POLAR BEARSHollow hairs to

“trap” air

But….skin is _______

Modification of Microclimate

• Construction and use of nest• Communal nesting• Huddling--____________________ surfaces

(either curling and/or contact with nest mates)• Differences can be dramatic – (see Fig. 9.14,

p168 handout)

• Insulation: rabbit bedsite (earlier data)

___________________

• Defined-- “period of inactivity characterized by a reduced metabolic rate and lowering of body temperature”

• ___________--a form of dormancy with lower body temp, metabolic rate, respiration rate, and heart rate

• ___________--”profound” dormancy: 2-50C for periods of weeks during the winter

TORPOR

• ______________________: can be for a day…portion of a day

• Effort to achieve energy savings• Body temperature declines…but usually not

below 150C• Known examples: many rodents

(including Peromyscus), many marsupials, insectivores, bats, and some primates

HIBERNATION

• _________ period of time: can be for many weeks to several months

• Effort to achieve energy savings• No mammal remains constantly in a dormant state

during the entire period of hibernation• Known examples: many rodents (including

many ground squirrel species like chipmunks) marmots, woodchucks, and hedgehogs

What BEARS do…is not, technically

hibernation

They exhibit

_____________________

Winter Lethargy

• Body temps decrease only 5 - 60C, lowering it to about 330C

• Adaptation found only in _________ mammals…the only ones capable of _______ _________ required for arousal in light of only “modest” drop in body temperature

Dormancy, torpor, hibernation, winter lethargy…all could be considered forms

of:

ADAPTIVE _______THERMIA

Bats…the best of both worlds?

• Some _________• Some _________• Some do _______!• Most _________ species (Vespertilonid bats)

hibernate in caves

Bats…patterns of hibernation

• Typically, bat’s temp about 1 C more than ambient (typically 5 C) temperature

• Arousals:a) 1 -3 weeks apart for few hoursb) animal urinates, drinks water,

possibly changes location

Resistance to COLD: Brown vs. White Adipose Tissue

• BROWN ADIPOSE TISSUE--the site of “________________________… no muscle contractions involved. It is found in ALL hibernating mammals. Multiple, small droplets with _____________________

• WHITE ADIPOSE TISSUE--single droplet of __________________________

_________ Adipose Tissue (vs. White)

• Highly ___________, well ____________

• Cells have _________ mitochrondria

• Higher rate of O2 consumption, therefore higher _______ production

• Heat produced “_______” directly to bloodstream

• ______ important form of adipose tissue for insulation

Adaptations to _______

• Mammalian body composition: 70% water

• _________________: primarily a function of the kidneys (internal salt-water concentration)

• ________________--an important device for cooling, is a major process resulting in loss of water

Water Economy

• Mammalian kidney (Fig. 9.19, p177)a) 1.5 nephrons per kidney b) glomerular filtration

tubular reabsorptiontubular secretion

_______ c) papilla of the medulla (Fig. 9.20, p178)…further extension of renal capsule of into ureter pronounced for small desert

rodents

NEPHRON

“the workhorse”of the kidney

_____ “H20” limited ____ “H20” limited

Kidneys…con’t

• Loop of the nephron (loop of the Henle)…longer it is, more concentrated the urine

• Desert heteromyids, pallid bats, canyon and house mice, and golden hamsters among those species with the most highly concentrated urine …_____________

Other adaptations

• Feces with low water content• Desert heteromyids, pallid bats, canyon and

house mice, and golden hamsters -- most highly concentrated urine

• Highly concentrated milk producedex. Merriam’s kangaroo rat…____% water

• Desert rodents, some canids, kangaroos reclaim water by consuming dilute urine & feces of young

Diet

• Critical for desert mammals• Many subsist on _____________-created by

oxidation of food (particularly carbohydrates) …kangaroo rat gets all H20 needs from seeds consumed

• Some (desert woodrats and cactus mice) consume cactus--high in H20 content

• Xeric-adapted canids, badgers, etc. can subsist on H20 content obtained from ____________ of prey

TEMP REGULATION

• Transpirational water loss:a) through skinb) from surfaces of the respiratory tract

• Sweating (a) - ______ controllablevs.

• Panting (b) - _____ controllable

Panting

• Air flow over moist surfaces, thus controlling degree of evaporative cooling

• Unlike sweating, no loss of salt…no loss of electrolytes, therefore ___________ stress

• Requires ______________, thus generates more heat …a down side

Cool Brains

• Form of panting• Important for keeping brain temp below elevated

body temp• Noted for carnivores and artiodactyls• Accomplished through _________________ heat

exchange process• ________________ SINUS

Fig. 9.21, p181• Lower brain temp 2-3 C from body temp

ARTERIAL BLOOD

_____ VENOUS BLOOD

______ VENOUS BLOODTO BRAIN

Saliva Spreading

• Known for some rodents & marsupials

• Saliva spread on limbs, tail, chest, etc.

• ______________ heat loss

• _____ as efficient as sweating because fur must be ______ wet before heat is lost from underlying skin

What is Estivation?

• Is it a form of dormancy?

• Is it a phenomenon associated with a) cold conditions …or…b) hot and dry conditions?

• Name a species known to exhibit estivation

Explain this…dealing with _____ temperatures

• Fig. 9.29, p186• Activity patterns of antelope ground squirrels, Fig.

9.30, p187• Dromedary, Fig. 9.32, p187• The camel’s hump p188• Desert antelope: oryx, gazelles, and elands, p188

including Fig. 9.33 on p189