Behavior

Question 1

• Natural selection favors behaviors that help

individuals survive and reproduce

Answer 1

• Proximate causes of behavior
– How stimuli initiate behaviors
• Ultimate causes of behavior
– Why a behavior has evolved

Question 2

Activity Rhythms

Answer 2

• Rhythmic, cyclic, or predictable activity patterns
– Nocturnal, diurnal, or crepuscular
– Migratory or seasonal movements
– Timing of reproduction
– Torpor and hibernation
• Circannual—cycles that occur year to year
• Circadian—cycles based on a 24-hour cycle

Question 3

Circadian Rhythms

Answer 3

• Based	on	a	24-hour	light-dark	cycle
• Universal	in	mammals
• Endogenous	control
– Internal	mechanism	or	“clock”
• Cluster	of	neurons	in	the	superchiasmatic nucleus	(SCN)	
in	the	brain	in	mammals
• Exogenous	control	(external	stimuli)
– Changes	in	day	length	or	temperature

Question 4

Circannual Rhythms

Answer 4

• Cycles	lasting	approximately	one	year
– Typically	in	seasonal	environments
• Breeding
• Migration
• Hibernation
– Controlled	by	environmental	cues
• Temperature	and	precipitation	changes
• Day	length	changes
• Changes	in	food	abundance

Question 5

Foraging Behavior

Answer 5

• Optimal foraging – Natural selection should favor foraging behaviors that deliver the
highest payoff
• Each food has a unique: – Nutritional value
– Abundance in environment
– Pattern of availability in the habitat
– Set of risks related to capture and processing

Question 6

Caching Behavior

Answer 6

• Used	by	some	shrews,	moles,	rodents,	
carnivores,	lagomorphs
• Seeds	are	most	commonly	cached	food
– Concentrated	energy	source
– Can	remain	dormant	for	long	periods
– Chipmunks	bite	off	embryo
• Kangaroo	rats transport	seeds	for	
caching
– “Manage” the	cached	seeds	for	degree	
of	fungal	growth,	diet	diversification,	
and	to	prevent	germination

Question 7

Caching Behavior

Hoarding

Answer 7

• Scatter hoarding
– Few food items stored at many locations throughout the territory
– Adaptive only if the cache remains intact and is not lost to conspecifics
or other thieves
• Larder hoarding
– Many food items stored at a central site

Question 8

Fossorial Foraging

Answer 8

• Burrowing is energetically expensive
• Burrowing patterns cover maximum area
– Burrow forks and burrow lengths are uniform
• Burrowing behavior is constrained by
physiological, morphologic, and climatic
factors

Question 9

Shelter-Building Behavior

Answer 9

• Shelter-building	behaviors	provide:
– Protection	from	predators
– More	stable	temperatures
– Places	to	store	food
• Shelters	can	be:	
– Underground
– In	tree	holes	or	under	leaf	“tents”
– In	ponds	(beaver	lodges)

Question 10

• Communication signals are “behavioral,
physiological, or morphological characteristics
fashioned or maintained by natural selection
because they convey information to other
organisms” (Otte 1974)

Answer 10

• Can be visual, olfactory, auditory, tactile, or

any combination

Question 11

Visual Signals

Answer 11

• Intraspecific communication
– Submissive	vs.	aggressive	postures
• Interspecific communication
– Alarm	displays	in	lemurs
• Types	of	visual	signals:
– Facial	expressions
– Body	postures
– Anatomical	structures
• Anatomical	structures
– Antlers	and	horns
– Weapon	automimicry
– Aposematic coloring

Question 12

Olfactory Signals

chemical

Answer 12

• Pheromone
– Chemical signal that elicits a response in a
conspecific receiver
• Allomone
– Chemical signal that elicits a response in an
allospecific receiver
• Specific chemicals may convey unique
messages
• Scents dispersed in air travel long distances

Question 13

Olfactory Signals

scent and glands

Answer 13

• Scent marking
– The maturation and use of scent glands are
controlled by gonadal hormones produced at
sexual maturity
– Most scent marking is done by dominant males
– Scent marking is often associated with the
possession of a territory
• Urine and fecal signals
– Convey information about individual’s physical
condition
– Establish and maintain territorial boundaries
– Males recognize females in estrus
– May help establish reproductive synchrony among
herd/pack
• Scent Glands
– Source of
pheromones and
allomones

Question 14

Olfactory Signals

organ

Answer 14

• Vomeronasal Organ
– Important	in	receiving	
sexual	pheromones
– Flehmen behavior
(ungulates	and	Carnivora)

Question 15

Olfactory Signals

individual

Answer 15

• Self-anointing
– Smearing scent on the body
– Used for mother-young recognition
– Defensive behavior
• Hedgehogs use toxins from toads to self-anoint
• Rats may self-anoint with weasel scent to mask their
own scent
• Individual recognition
– Discriminate between individuals by scent

Question 16

Acoustical Signals

Answer 16

• Sense of hearing in mammals is acute
• Auditory communication is of great importance
– E.g. Virtually continuous noises made by members of a
herd
• Vocal communication varies among species from short,
simple calls to a large and varied vocal repertoire
• Singing mouse

Question 17

Alarm or Contact Calls

Answer 17

• Alarm	calls	may	be	predator-specific
• Contact	calls	may	serve:
– As	territorial	advertisements
– To	maintain	group	cohesion
– To	identify	individuals

Question 18

Individual Recognition

Answer 18

• Individuals may have unique vocal signatures
• Mother-infant recognition in nursery colonies
• The calls of many social animals (in Chiroptera, Primates,
Carnivora, Proboscidea, Sirenia, and Rodentia) signal
individual identity

Question 19

Infrasonic Signals

Answer 19

• Sounds	below	human	hearing	range
– Elephants	use	14–24	Hertz	infrasound
• Low	frequencies	attenuate	slowly
• Elephants	use	infrasound	to:
– Locate	individuals	or	groups
– Signal	aggressiveness
– Convey	reproductive	cues

Question 20

Aquatic Sounds

Answer 20

• Determining direction of sounds produced
underwater is difficult
• Cranial adaptations to hearing underwater
– Thin, dish-shaped area on the dentary bone
– Middle ear suspended from ligaments
– Fatty connection from middle ear to dentary

Question 21

Underground Communication

Answer 21

• Only	a	narrow	range	of	frequencies	work	
efficiently
• Low	frequency	sounds	are	optimal
• Seismic	signals	also	effective
– Vibrations	transmitted	through	soil
– Head	tapping
– Foot	drumming

Question 22

Tactile Signals

Answer 22

• Allogrooming
– Grooming	of	one	animal	by	another
– Important	social	function	in	primates
– Conveys	information	on	social	status
– Reinforces	social	bonds
– Dissipates	aggression
– Ritualized	greetings
• Non-grooming	tactile	signals
– Precopulatory	behaviors
– Reciprocal	flipper	rubbing	in	dolphins
– Bonobo	societies
• Female-female	genital	rubbing
• Male-male	genital	rubbing
• Oral-genital	contact
• Tongue-kissing

Question 23

Kin Selection
• William Hamilton proposed that kin selection is a
type of natural selection in which “the frequency
of a gene in a population will be influenced by
survival and fertility of all individuals carrying that
gene, including relatives”

Answer 23

• Fitness refers to an individual’s success in passing on
genes to future generations
– Offspring share 50% of genes with each parent
– Siblings share 50% of genes with each other
– Cousins share 12.5% of genes in common
– Fitness benefit is same for helping 4 cousins or 1 brother
• Coalitions of male lions
• Alarm calling ground squirrels

Question 24

Reciprocal Altruism

What it is

Answer 24

• Short-term cost of providing another with a
resource is offset when recipient returns the
favor later
• Evolves only when:
– Donor and recipient recognize one another
– Repayment is likely
– Benefit to recipient > cost to donor

Question 25

Reciprocal Altruism in Vampire Bats

Answer 25

• May	starve	to	death	if	
no	meal	for	two	
consecutive	nights
• Begging	for	blood	
meal	can	save	a	life
• Recipient	gains	5%	in	
blood	meal	or	16	
hours	until	
starvation 
• Share	blood	meals	
with	roostmates
• Donor	gives	blood	to	
roostmate
• Donor	loses	5%	of	
body	mass	or	six	
hours	of	time	to	
starvation
• Recipient	gains	5%	in	
blood	meal	or	16	
hours	until	
starvation

Question 26

Mating Systems
• The costs of producing offspring (individual) are very
different for males and females

Answer 26

• Males
– Produce large numbers of tiny, energetically inexpensive
gametes
– Never certain of paternity
– Maximize fitness by fathering as many offspring as possible
• Female
– Produce few, larger gametes
– Expend energy on pregnancy and lactation
– Invest greatly in each offspring
– Should choose mates carefully

Question 27

Mating Systems

• Sexual conflict between males and females

Answer 27

– Females invest much more in each offspring
– Females are a limiting resource for males
– Males must compete with each other for females
(male-male competition)
– Females seek best possible mate(s) from many
courting males (female mate choice)

Question 28

Mating Systems

• Variation in mating systems probably due to:

Answer 28

– Need for males to assist in rearing young
– Ability of males to guard females or their ranges
– Predictability of locating females

Question 29

Monogamy
• Exclusive mating between one male and one
female during one or more breeding seasons

Answer 29

• <	3%	of	mammals	are	monogamous
• Even	“
monogamous
” species	may	have	extra-pair	
paternity

Question 30

• Obligate monogamy

Answer 30

– Little	sexual	dimorphism
– Members	of	pair	interact	frequently
– Environment	has	low	carrying	capacity
– Male	help necessary	to	rear	offspring
– Occurs	in some	canids,	rodents,	and	sengis

Question 31

• Polygyny

Answer 31

– Males mate with multiple females, but females
mate with a single male
– Male territory overlaps many females
– Males can defend resources females need

Question 32

• Promiscuity

Answer 32

– Both males and females mate with multiple

partners

Question 33

• Female defense polygyny
– Males monopolize several females, forming
defended harems

Answer 33

• Resource defense polygyny
– Males control access to resources required by
females
– Few dominant males secure most matings
– Satellite males may challenge the primary male or
copulate on the sly