Mammalogy Lecture Exam 3

As the velocity of an animal ____, so does the cost of locomotion

increases

How has the evolution of specialized forms of locomotion affected costs?

Specialized forms of locomotion often reduce the costs

Basal metabolic rate

The rate of energy utilization for life sustaining functions.The animal must be at rest, post-absorptive, and not growing or reproducing

Hopping, flying, and swimming are ___ energetically demanding than running

less

What are the most efficient forms of locomotion?

Swimming/diving and flight

What fitness benefits were likely gained with the evolution of diving and flight?

- Less costly

-Abundance of food

- Reduced predation

What physiological barriers had to be overcome for diving to evolve?

- Low oxygen

- High pressure

- Nitrogen accumulation in tissues

What environmental barriers was the same for both diving and flying?

Navigation in the dark

What environmental barriers had to be overcome for diving to evolve?

High heat dissipation

What is a TDR?

Time depth recorder

How have time depth recorders (TDR) revolutionized our understanding of diving in marine mammals?

They allow us to track marine mammals and their movements, allowing us a better understanding of their dive patterns, eating habits, etc.

Barotrauma

Trauma associated with rapid changes in pressure

How did marine mammals adapt to high pressure?

- Breathing out before a dive

- Allowing their lungs to collapse

How do marine mammals collapse their lungs?

- A unique surfactant in their lungs facilitates reinflation

- Robust cartilaginous rings around the trachea and branches within lungs prevent airway collapse

Nitrogen narcosis

a physiological condition caused by an increased partial pressure of nitrogen, resulting in symptoms similar to those of intoxication

Oxygen toxicity

Ultimately causes cell death, most common impacts on central nervous system (convulsions, lose consciousness), lungs(difficulty breathing), eyes (visual impairment)

What adaptations allow marine mammals to support energy demands without oxygen intake during dives?

- They rely on stored oxygen and reduce energy demands

- They use anaerobic metabolism as needed

What allows marine mammals more oxygen storage?

- Higher blood volume

- Higher hematocrit

- 3x more myoglobin than humans

Hematocrit

percentage of blood volume occupied by red blood cells

Myoglobin

Holds oxygen like hemoglobin but more tightly

What adaptations allow marine mammals to reduce their oxygen consumption

- Bradycardia

- Hypometabolism

- Vasoconstriction of extremities in extreme cases

Bradycardia

slow heart rate

Hypometabolism

slower than normal metabolism

Vasoconstriction

Constriction of blood vessels

What is the aerobic dive limit?

- The time at which oxygen is no longer used as fuel

- The animal will begin using anaerobic metabolism

What are the consequences of exceeding the aerobic dive limit in marine mammals?

- Glycolysis

- Lactic acid accumulates exponentially

- Animal must dissipate lactic acid before the next dive

What is echolocation?

A method of evaluating the environment where an animal evaluates the echoes of its own emitted sounds.

What taxa does echolocation occur in?

- Cetecea

- Chiroptera

- Soricidae

- Tenrecs

- Some rodents

Cochlea in bats and cetaceans

more turns in bats and cetaceans than in terrestrial species, making them more sensitive to a wide range of sounds

In bats:

- Pinnae receive sound

- Sound is projected from pinnae to the tragus that produces a second echo and gives directionality

What types of calls are associated with echolocation in bats?

- Frequency modulated (FM) calls

- Constant frequency (CF) calls

What types of calls are associated with echolocation in dolphins?

Frequency modulated (FM) calls

Constant frequency calls

- The frequency of a call's echo increases as the bat approaches an object

- The bats compensate for this change in frequency, and reducing the frequency of their call, so that all echoes return at approximately the same frequency.

- Cochlea of the bat is particularly sensitive at this focal frequency

- Provides strong resolution on the velocity of target and fluttering of prey wings

- Best in open spaces

Frequency modulated calls

- Provides precise information about the distance to and shape of an object

- Higher frequency attenuates faster

- Delay between echo used to determine distance

- Shape of echo (sound quality) provides information about shape

- Can distinguish 2 objects 1 mm apart

- Lower range discrimination than CF

- Best on edges or in clutter

Doppler effect

an increase (or decrease) in the frequency of sound as the source and observer move toward (or away from) each other

How are echolocation calls generated in bats?

Produced by larynx and vocal cords, projected through the mouth and nose

How are echolocation calls generated in odontocetes?

- Produced by nasal system

- Whistles

- Clicks

Whistles

Narrow-band of continuous tones, for intraspecific communication (not echolocation)

Clicks

Broad-band pulses used for echolocation

How do the echolocation sound characteristics differ between odontocetes and bats?

In Odontocetes: High frequency signals ~100 kHz and Lowest frequency used 30-60 kHz

In bats: Range between 10-150 kHz

Adaptations for sound detection in Cetacea

- Tympanic bullae detached from skull

- Bullae and inner ear insulated with air sinuses and fat pads - slows sound, allows for localization

Passive heat exchange

- Radiation

- Conduction

- Convection

- Evaporative water loss

Radiation

Transfer of heat from a warm body to a cooler one, without contact

Conduction

Transfer of heat between objects in contact

Convection

Heat is transferred by movement of a heated fluid, such as air or water

Evaporative water loss

Water/heat lost via evaporation of water from respiratory surfaces or skin

Active heat exchange

- Endogenous sources

- Requires ATP

Endothermy

Organisms with bodies that are warmed by heat generated by metabolism. This heat is usually used to maintain a relatively stable body temperature higher than that of the external environment

Homeothermy

Regulating, maintenance of constant body temp via physiological means

Ectothermy

Body temperature determined by outside sources

Poikilothermy

- Type of ectothermy

- Body temperature varies with temperature over a wide range with environmental conditions, active over a wide range of temperatures

Heterothermy

Body temperature varies with region of the body (regional heterothermy) or at different times (temporal heterothermy)

Thermoneutral zone

The range of environmental temperatures over which a constant basal metabolic rate can be maintained

Upper critical limit

Temperature increases, metabolic rate increases

Lower critical limit

Temperature decreases, metabolic rate increases

Where does body heat come from?

Heat is generated when chemical bonds are broken during metabolism

Specific dynamic action

Thermic effect of food (TEF)or dietary induced thermogenesis (DIT)

Why do animals have white fur in the cold?

- Skin often black

- Dark layer absorbs all E

- E passes through white layer and absorbs into the skin

Blubber in marine mammals

- White adipose tissue

- Effective barrier against high heat capacity of water

Dormancy

Period of inactivity characterized by reduced metabolic rate and lower body temperature

Torpor

Dormancy with reduced body temperature, lower metabolic rate, lower respirations, and lower heart rate

Hibernation

- Typically obligate

- Profound dormancy in which animal's body temperature remains at 2-5C higher than freezing for weeks during winter

- True hibernators are small, likely too costly to rewarm

What is the largest hibernator?

Marmot

Bears in the winter

- Winter lethargy

- 5-7 months

- Body temp. reduced 5-7C from ~38C

- Heart rate drops from 55 to 9beats/min

- Parturition and early lactation occur during lethargy

- Similar winter lethargy in badgers, skunks, and raccoon dogs

True hibernation

- Typically occurs in a den, nest, cave, or building that does not drop below freezing

- Bouts of torpor interspersed with periodic arousals

Preparation for hibernation

- Hyperphagia and fat deposition before hibernation

- ~80% increase in body mass in ground squirrels

- Cues (low food, low body temp, day length)

- Entrance into hibernation

Hypotheses for why animals arouse from hibernation

- To evaluate the environment

- To expel metabolic byproducts

- To repair cellular functions

___ is associated with 83% of the costs of hibernation

Arousals

Brown fat

Tissue in neck and between shoulders of some mammals that is specialized for rapid heat production.

Uncoupling protein 1 (UCP1)

- Prevents ATP production

- Protons flow out of intermembrane space and generate heat

Winter lethargy

- Use of shallow torpor during winter

Facultative torpor

- Typically, occurring optionally in response to circumstances

- Response to low energy availability

How do desert species reduce water loss?

- Concentrate urine

- Lower fecal water loss

- Produce a low water, high fat milk

- Re-ingest feces of suckling pups

- Unique nasal passages

Unique nasal passages in desert species

increase water retention across nasal turbinates (higher surface area, narrow walls)

Increasing body water

- Targeting high water food items i.e. succulent plants and animal prey

- Target high fat food items to increase metabolic water production

- Metabolize stored body fat

Evaporative cooling

- Sweating

- Panting

- Saliva spreading

Sweating

- Loss of water via eccrine glands

- Found in species with limited fur

- Primates and several ungulates

Panting

- Rapid, shallow breathing that increases evaporation from respiratory tract

- Many carnivores and small ungulates

Saliva spreading

- Active licking and spreading saliva across fur to facilitate greater heat loss by radiation or convection

- Many rodents

Behavioral regulation of body temperature

- Fossorial locomotion

- Seeking shade

- Nocturnal lifestyle or limiting activity to morning and evening

Insulation

- Fur holds heat away from skin

- Fur may vary in length and density

Guanacos and insulation

- Long hair on dorsum - captures heat away from skin

- Short hair axilla, groin, scrotum, mammary glands

- Creates thermal windows for heat loss

Estivation

Summer torpor. Enables animals to survive long periods of high temperatures and scarce water supplies.

Counter-current exchange

- Brain cooling in Cetartiodactyla

- Blood in vessels of nasal passage cooled by evaporative water loss

- Warm blood from heart carried to cavernous sinus in nasal passages

- Arteries cross network of cool veins where heat exchange occurs

- Blood temperature reduced by 2-3 degrees C before entering brain

Somatic cells

Any cells in the body other than reproductive cells

Gametic cells

reproductive cells (sperm and egg)

Oviparity

- Egg laying

- Monotremes

Viviparity

- Development of the embryo inside the parent

- Live birth

- Therian animals

Major components of the female reproductive system

- Ovary

- Oviducts

- Uterus

- Cervix

- Vagina/Cloaca

Follicle

Ovum plus surrounding granulosa and theca cells

Gametes

Ovum

Remnants of the follicle become

Corpus luteum

Hormone

a regulatory compound produced by an endocrine gland and transported in blood to stimulate specific cells or tissues into action

Ovary and testis both function as ___

Endocrine glands

The ____ and _____ of the brain function as endocrine glands and play a role in gamete development and ovulation

hypothalamus, anterior pituitary

GnRH (gonadotropin releasing hormone)

produced by hypothalamus, regulates FSH and LH, sensitive to environmental stimuli

FSH (Follicle-stimulating hormone)

produced by the anterior pituitary, stimulates the maturation of the follicle by stimulating the production of estrogen by the granulosa cells

LH (Lutenizing hormone)

produced by the anterior pituitary, induces progesterone production in the theca cell, ovulation, and the transition of the follicle to a corpus luteum

Hormones involved in oogenesis

- Estrogen

- Progesterone

Estrogen

produced by developing follicle (granulosa cells), promotes proliferation of the endometrium, induces estrus behaviors