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Lecture 3.1_Mammalian Social Behavior and Communication

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hey gang welcome to the first lecture in

module three entitled mammalian social

behavior and communication in this

lecture initially I'll Define the

spectrum of social behaviors that we

observe in mammals then I'll explore

both the costs and benefits of living in

groups well think about why behavioral

sociality even evolved in the first

place and then lastly we'll survey a

suite of different means by which

animals communicate with one another

this is going to be a fun intellectual

ride so kick back and let's think about

why these howling wolves live in packs

social systems Encompass an array of

interactions between members of the same

species including interactions like

mating systems and parent Offspring

interactions both of which we'll cover

next week competition and cooperation

between related or unrelated individuals

which will Explore More fully in module

6. so big idea right off the bat

sociality is not binary meaning species

are either social or asocial but it's more

um appropriate to think about sociality

on a spectrum where at one end we have

species that are solitary as adults like

this leopard hanging out in the tree

other solitary species as adults include

Bears skunks opossums armadillos pocket

gophers and the irascible rhinos

at the opposite end of the spectrum of

potential social behaviors are species

that always live in groups in fact they

would be unlikely to survive away from

their group so examples include these

meerkats here on the bottom right you

sociality or extreme sociality is most

often observed in the order hinoptera

this is the arthropod order that

contains the bees the wasps and the Ants

however we do observe you sociality in

two species of mammals the African mole

rats including the adorable naked mole

rat pictured here as well as the

Tomorrowland mole rat so according to

the famous Dr EO Wilson three traits

characterized guys you social

organization number one

cooperation among individuals in the

colony in the care of young number two

use sociality is characterized by

reproductive castes a caste system with

non-reproductive members caring for

Reproductive Nest mates and then number

three overlap among Generations such

that offspring are going to assist

parents in raising siblings

so naked mole rats they form colonies

with a single reproductive active female

a queen whose monogamous with a single

breeder male and then they're surrounded

by these subordinate workers the workers

perform Offspring care they're taking

care of the babies construction and

defense of the burrow system and then

those workers are securing the food supply

supply

so why would natural selection favor

group living in mammals in 1974

Alexander wrote there is no automatic or

Universal benefit from group living

indeed the opposite is true there are

clearly automatic and Universal

detriments to living in groups those

Universal costs which I'll elaborate

more on here shortly are competition for

resources and increased transmission of

parasites because you're in close

proximity to your con specifics that

said there are benefits too or all

animals would be loners

most of the benefits of sociality can be

related to two ecological factors one

minimizing predation risk and two

foraging success like we see here it's a

bit gory but this is a pick a picture

that's a prime example of increased

foraging success these are chimpanzees

in Uganda these chimps are far more

successful when they work together when

they hunt together at catching and

killing red colibus monkeys one obvious benefit

benefit

bestowed to animals living in groups is

increased protection against predators

so in fact this herd of zebras it kind

of makes me dizzy I mean it is clearly

disorienting and this is a still shot a

imagine if this herd of Stripes was in motion

motion

so there are several different

hypotheses that have been put forth to

support this idea that group living is

going to increase uh an individual's

protection against predators the first

is the many eyes hypothesis and it

states that if I'm an individual living

in a large group with many other sets of

watchful eyes then I don't need to spend

as much time scanning my world watching

for predators and now I'm freed to do

other things that are going to increase

my fitness I'm going to have more time

to forage I'm going to have more time to

seek out mates

the dilution of a risk hypothesis

right here number two is clearly

exemplified uh by these zebras but it

proposes this idea that if a predator is

going to kill one animal then being in a

larger group reduces any one

individual's chance of being the one

that gets killed in other words zebras

that are in the middle of this

um you know

disorienting herd they're relatively

safe from lions

this has been coined the selfish herd

effect meaning an animal's position in a

group is going to reduce its exposure to predators

predators

individuals surrounded uh by other

individuals in the group they would be

relatively safer it then follows that

the safest place to be is in the center

of the group so an awesome anti-predator

strategy employed by these Musk Oxen

here is to surround their vulnerable

young so there's the wolves have to go

through this impenetrable wall to get to

those calves recall that an animal

society is a group of individuals of the

same species organized in a Cooperative

manner typically extending Beyond just

sexual and parenting Behavior there is

cultural knowledge stored in the minds

of the matriarchal Orca or elephant or

Pronghorn and Antelope about where to

find food resources when to migrate

which migratory routes to take

one of my old colleagues Dr Matt Kaufman

who's the unit leader at the Wyoming

Cooperative Fish and Wildlife Research

Unit up in Laramie Matt and his students

put GPS callers on a large sample size

of Pronghorn and it turns out that

Pronghorn in Wyoming they're going to travel

travel

120 mile long migration navigating

treacherous oil fields like the Pinedale

anticline gas patch uh it's an

intensively drilled piece of public land

in Western Wyoming they're also going to

navigate tricky Highway Crossings

subdivisions a 9 100 foot Mountain Pass

all to get to the Snake River in Grand

Teton National Park

it's a challenging journey and not all

are going to make it but they are

successful year in and year out because

they're Guided by these older does these

older females that have this stored

cultural knowledge of when to leave and

which routes to take what's so

astounding is that some of these routes

have likely been used since the

pleistocene for thousands of years

but we are rapidly transforming the

Western landscape this Pronghorn

migration one of the longest and most

dramatic land animal movements in the

United States is becoming increasingly

perilous please put me on pause and take

one minute and 45 seconds and check out

the embedded National Geographic video

entitled Pronghorn face modern

challenges uh this summarizes uh some of

Matt's work another tangible benefit of

group living which is especially evident

for carnivores is group living is going

to provide you and your group with

access to larger and more dangerous prey

that you couldn't take down by yourself

so this is actually another former

colleague this is the work of Dan

McNulty from Utah State University Dan

and his student Amy Talon demonstrated

that there is an optimal group size an

optimal pack size for the wolves in

Yellowstone National Park your pack

needs to be big enough to take down the

largest most energy rich prey in the

park the Buffalo or bison which can be

six feet tall at the shoulder and weigh

in excess of two thousand pounds

but your pack size can't be so large

that there's not enough meat to go

around to everyone in the pack if you

kill just a measly mule deer so another

Point worth noting is having a group of

hunters allows for more strategy in

terms of how you chase and secure that

prey item it allows for a division of

labor amongst the PAC members or the

pride members of for the carnivores so

female African lions for example they

have this winging formation it's a

hunting approach where the females are

going to form these wings along the

outside and they're going to keep the

prey contained

we also see hunting role specialization

in bottlenose dolphins in which one

individual is going to drive the fish

towards uh the group uh which has formed

a barrier they're closely spaced

together and you've got one individual

that pushes the fish into this wall of

uh pod mates for them to feed so again

these strategies would not be possible

if you're hunting solo

lastly by hunting in groups animals like

this bloody faced cheetah here they're

going to reduce the probability that

other larger animals are going to steal

their food which is called klepto

parasitism on the African Savannah there

is a lot of competition between cheetahs

and lions and spotted hyenas African

wild dogs so if you have one two three

four five cheetahs on a carcass you're

less likely to be pushed off of that

carcass by hyenas

and speaking of hyenas here's a great

shot of an epic battle between lionesses

we've got three of them and a group of

spotted hyenas that really want to get

at that cape buffalo carcass so there's

one study that's noted in your textbook

that said on average African carnivores

are forced to share their food Resources

with over 20 other species on the

Savannah so when you've made a kill it

helps to have friends to protect that

kill so this is one of my favorite

Topics in mammology that is social

learning and animal culture social

learning is the process of acquiring

knowledge by observation of or

interaction with another individual

usually of the same species for example

a orangutans are not born with the

innate knowledge that they can use

leaves to craft

umbrellas to keep them dry on rainy days

and nights in Borneo

they learn this early on by watching Mom

do it or older siblings

if we think about certain populations of

animals that have a specific Suite of

learned behaviors that are shared among

individuals living in that social group

but that those behaviors aren't

necessarily in other groups that group

specific knowledge that's passed down

from one generation to the next that's

culture that's animal culture so for

example another primate example some

populations of chimpanzees will fashion

sticks so that they can fish for

termites whereas other chimpanzee troops

don't appear to know how to do this

however I think the best example of

animal culture is the Pod specific

hunting Strategies employed by orcas or

killer whales so those old grandmother

matriarchs that live long beyond their

reproductive years those matriarchs are

very wise they're skilled this footage

here this is going to blow your mind I

beg of you take the three minutes here

and watch this now it is so good

another important benefit of group

living particularly for small bodied

animals is

thermoregulation so huddling together to

stay warm especially if you don't

hibernate during the winter so great

example of a bat Colony that's packed

together and they're trapping that body

heat using that body heat from their

colony mates

all right all that said there are always

trade-offs in nature there are costs

that are associated with various

strategies and one large and obvious

cost of group living is being forced to

compete for limited resources limited

resources like food like mates or shelter

shelter

if you have a large pride of lions with

lots of cubs one Thompson's gazelle is

just not gonna go very far this

publication cited at the end of this

lecture is an extensive

meta-analysis a meta-analysis of course

is a compilation and Analysis of

numerous published studies this study

definitively demonstrates that living in

close proximity to con specifics living

in groups is going to increase

transmission of a multitude of parasites

like these really disgusting uh deer ticks

ticks

animals living in groups have to compete

with calm specifics over limited

resources and they're swapping parasites

at much higher rates so why then does

social behavior even evolve

remember biology only makes sense when

we view it through an evolutionary lens

so sociality like all things in biology

it's all about Fitness

maximizing your reproductive success and

that of your Offspring our genes are

ultimately selfish and they only want to

propagate themselves

what this table is expressing is that a

mutualistic behavior is beneficial to

both the recipient of the behavior and

the actor who does the behavior so

mutualism is plus plus

beneficial for both recipient as well as

actor whereas an altruistic Behavior

benefits the recipient of the action but

comes at a cost to the actor

the act itself could potentially be

detrimental to the bestower of the D

good maternal care of her infant by this

chimpanzee mother is mutualistic the

baby here is clearly benefiting it's

being nourished and cared for it's more

likely to survive but Mom is benefiting

as well certainly from an evolutionary

perspective because that baby represents

mom's genes it's survival and

reproductive success

increases mom's evolutionary Fitness

altruistic behaviors behaviors that cost

the actor but benefit the recipient I.E

plus minus behaviors are a little

trickier to understand at least on the

surface so consider the famous vervet

monkeys of Southeastern Africa they live

in troops when an individual vervet monkey

monkey

sees an eagle

or a snake or a leopard or some other

threat it's going to let out an alarm

call to alert the rest of the group

but in doing so it's gonna make its own

whereabouts known to that Predator it's

going to call attention to itself and

that's a risk so being snatched up and

gobbled up by an African crowned eagle

or a black Mambo or a python is

certainly detrimental to your

evolutionary Fitness

what's even more amazing about these

vervet monkeys is that their alarm calls

for different Predators Eagles snakes

leopards and baboons are acoustically

different they're distinct and they

respond to these distinct calls in

different ways they're going to seek

cover from birds of prey they're going

to stand up and scan uh to determine the

snake's location in this uh BBC video

embedded in canvas the researcher

clearly demonstrates the different calls

that these monkeys will use for

different predators and then their

appropriate response to that Potential

Threat no this is all learned behavior

infants are going to begin observing and

mimicking in these calls very early on

so take a one minute and check out this

video please so risking your life by

sounding the alarm call is this an

example of true altruism

well on the surface yes but when

examined from an evolutionary

perspective not so much the vervet

monkeys within those troops are all

closely related I.E they share many of

the same genes and by contributing to

the groups to the Troops survival

individuals are propagating the genes

that they share with their own kin

further there is reciprocity in these

groups meaning perhaps today I risk my

life by calling out an eagle because I

know that tomorrow you will call out an

eagle that I might not see

another example of superficially

altruistic Behavior are wolf

babysitters so oftentimes older siblings

or aunties they may stay back and care

for the young wolf pups while Mom and

Dad and the rest of the pack are out hunting

hunting

but in doing so the individual

caregivers are gaining parenting skills

that enhance their own ability to rear

their own offspring someday so learning

how to babysit is actually a direct

benefit to the actor also helping

sisters and brothers and cousins who

share a percentage of the actor's genome

also enhances an actor's overall

evolutionary Fitness which brings us to

arguably the most important Concept in

this lecture that idea of Inclusive

fitness Inclusive fitness is going to

think Beyond just the survival and

reproductive success of the individual

and its Offspring that's the Direct

Fitness the direct component within

Inclusive fitness Inclusive fitness is

also going to incorporate indirect

Fitness the indirect Fitness is the

reproductive success of one's relatives

so my brothers my sisters my cousins

they share my genes thus from an

evolutionary perspective their success

is my success in other words helping our

relatives to survive and reproduce

ultimately helps to spread shared genes

and therefore

cooperation should arise when the

combined propagation of those shared

genes is greater than the propagation of

the genes that result from Individual

survival and reproduction alone these

ideas were first clearly laid out by

William Hamilton in 1963 in his seminal

publication on Ken's selection Theory

Hamilton is really the first person to

take a Gene's point of view on the world

so a Gene's perspective our genes really

only care about us to the to the degree

in which we can benefit that Gene in a

way the genes are just using us they're

human vessels to propagate themselves

from a Gene's perspective if the

individual that benefited by the

altruistic Act is a relative of the

altruist then they're more likely than a

non-relative to be carrying that Gene

then ultimately the frequency of that

Gene is going to increase in the genes

of in the gene pool so from a genetic

perspective uh the altruistic Act is

really benefiting the gene a really nice

read on the topic is Richard Dawkins

famous and popular read the selfish Gene

which was published the year I was born

Robert trivers also contributed to these

ideas in 1971 with his concept of

reciprocal altruism

the idea that if you scratch my back

I'll scratch yours individuals may

cooperate and behave altruistically if

there's a chance that they will be the

recipients of such acts at a later time

so I've got a current events connection

for you on this topic in week six but in

short an amazing study came out in March

of 2020 that shows that the world's only

known blood-sucking mammal the vampire bat

bat

developed trust with unrelated

individuals first by grooming one

another and then eventually

regurgitating blood to share with that

unrelated individual it's an act of

altruism okay but this species has to

eat at least once every three days

so what's more blood sharing tends to be

reciprocal with bats more likely to

provide a meal to a partner that has

shared with them in the past

so according to Jerry Carter a

behavioral ecologist at Ohio State University

University

in vampire bat relationships we saw that

the history of interactions mattered and

the social environment mattered so great

example of reciprocal altruism we're all

hungry for blood if you regurgitate a

blood meal for me today I'm more likely

to regurgitate a blood meal for you down

the line when you might need it okay so

we'll finish this lecture by surveying

means by which mammals communicate so

the social interaction that I've

described thus far really rests on the

ability of animals to communicate or

convey information from one individual

to another communication is going to

rest on some form of a signal some

building the sender uses to transmit

information to the receiver

this signal could be behavioral it could

be a morphological structure like we see

here in this female gelata baboon these

are uh bright fluid filled blisters that

form this necklace around the females

when they're in estrus when they're ovulating

ovulating

communicating to the males that now is

the appropriate time to mate

communication can occur in an array of

forms in mammals from visual auditory

tactile and olfactory so let's take a

closer look at each of those forms

the primary olfactory system the sense

of smell is located within the nasal

cavity which is enlarged and complex in

most mammals the dorsal or the top part

of the nasal cavity is lined with

olfactory epithelium that contain

chemoreceptors that can detect over a

thousand different volatile molecules

that are going to dissolve in the mucus

that covers the epithelium and create

nerve impulses that are transmitted to

the olfactory bulbs that are on the

bottom side of each of the brain's hemispheres

hemispheres

the ursids or the Bears are thought to

have the keenest sense of smell of any

animal on planet Earth so the area

inside of a bear's nose the nasal mucosa

is over a hundred times greater than

ours resulting in just an incredible

sense of smell uh in this grizzly bear

so even Bloodhounds right the dogs that

are so famous for their sense of smell

tracking criminals right

um they don't smell as well as the Bears

do it's estimated that a bear's sense of

smell is about seven times more powerful

than that of the Bloodhound mammals have

a second

chemosensory system the vomero nasal or

Jacob substance organ is located between

the nasal passages and the mouth it

opens up to the roof of the mouth

while the primary olfactory system which

we covered on the last slide is going to

detect volatile molecules meaning

molecules that vaporize

the Jacobson's organ detects

non-volatile chemical compounds that

dissolve in liquids like urine or other

bodily secretions

these secretions are composed of pheromones

pheromones

pheromones are animals chemical

messaging molecules that are released

specifically to signal to con specifics

and elicit responses in other

individuals so you can tell when

ungulates or felids are using their

Jacobson's organ because they're going

to retract that upper lip like this

tiger here and what's known as the

flemen response here's another example

of the fleamen response that curled

upper lip exposing the Jacobson's organ

this time in a Beard's tape here so it's

catching the pheromones dissolved in

droplets of urine from a con specific

and a horse showing its fleeman response

pheromones are especially important in

social communication amongst the mammals

they're influential in mate

identification and attraction

pheromones are used for spacing

mechanisms in territorial species there

are even pheromone alarm smells sources

of these products include urine feces

the sexual accessory glands and a number

of specialized skin glands so if you've

ever carefully observed a white-tailed

buck when it's rubbing The Velvet off of

its antlers onto a rub tree you may have

noticed that they'll also rub their

forehead along the scrape so this is purposeful

purposeful

they're rubbing the secretions from

these two glands uh the gland in the

forehead and the pre-orbital glands so

uh these glands are used uh by the box

to communicate with the females the does

also a gland called the inter-digital

gland which is located between the

Hooves on each foot and it's going to

emit secretions that are going to allow

individuals to determine herd identity

and then further with every step a deer

leaves scent via this inter-digital

gland allowing deer to not only identify

each other but they can determine how

long ago a deer passed through here

when multiple deer travel the same Trail

at different times they're not

necessarily following uh visual cues

they're following the scent that's left

by the inter-digital gland of previous

deer that have walked along that trail

there's also the very ripe uh tarsal

glands here these produce a fatty oil

that's going to mix with the Tufts of

hair and it's going to capture the urine

that the deer purposefully excrete and

runs down their legs pheromones allow

for the identification of an

individual's sex their reproductive

status they're also used for marking

territories for example all hyenas will

scent mark their territories by smearing

grass stems with a paste that's secreted

by their subcodile scent glands or anal

glands and is deposited along with feces

at these latrines latrines are used by

Badgers and otters and hyenas so all of

the hyenas in the clan are going to

defecate in these specific spaces in

these latrines

the substances that are associated with

a species urinary and digestive systems

they're highly specialized as you would

probably imagine but they're also going

consider your pet dog who may very much

enjoy scooting his butt along your

carpeted floor why does he do this your

dog is scratching his anal glands so all

dogs have a unique scent it's a bit like

a human fingerprint only smellier and

it's formulated inside of these anal

sacs these anal sacs or anal glands are

located on either side of the anus and

the idea is when the dog defecates the

anal sphincter squeezes the anal glands

which expresses this smelly uh blob uh

this excretion along with the droppings

so this is kind of the equivalent of a

dog social media because that secretion

then uh gives the

um you know whoever cares to come along

and read uh that post read that smell

it's going to give them a message about

the dog uh that left that feces so again

it's sex it's reproductive status

um specific information about that individual

individual

moving on to the auditory sensory

Channel mammalian hearing

penne the pin a is the external part of

the ear the pen a are going to direct

the sound waves down into the middle ear

which we've talked a fair amount about

the three ossicles in the mammalian

middle ear

uh we've got some impressive uh penne

here exhibited on uh one of my son's uh

other favorite animals the Finnick Fox

so with those three ossicles mammals are

capable of detecting a surprisingly wide

range of sounds but the ability of most

mammals to hear high frequency sounds

and by that I mean sounds that are

greater than 10 kilohertz

so that's going to set mammals apart

from other vertebrates like reptiles and

amphibians who can't hear in that high

frequency range ultra Sonic

vocalizations that is to say

vocalizations that have sound waves that

are greater than 20 kilohertz are

produced by mammals for example howling

wolves or Echo locating bats to which we

will return and discuss in more detail

when we talk about the order chiroptera

in module six and then one more example

of ultrasonic vocalizations are singing

mice yep you heard that right singing mice

mice

so please take just the one minute and

watch this little guy just really belt

it out although we can't hear much of it

ultrasonic vocalizations are above the

range of human hearing

on the other side of the spectrum

elephants are going to produce very low

frequency Rumbles

infrasonic sounds that are going to

travel great distances on the order of

several kilometers

which brings us to this week's

assignment a Howard Hughes Medical

Institute bio interactive that walks you

through the amazing research of

biologist Caitlin O'Connell's

experimental field work that

demonstrates that elephants can sense

low frequency vibrations in the ground

and will behaviorally respond

differently at their water hole

depending upon whether they hear a high

frequency alarm call or they're feeling

low frequency vibrations this is a

really engaging assignment and I hope

you enjoy it visual communication is

accomplished via displays which are

usually defined as a subset of signals

that involves structure pictures like a

swollen baboon rump or ritualized

behaviors with visual components think

about the alpha male silverback gorilla

thumping his chest so interestingly

while a male mountain gorillas hearty

chest beats would seem to Signal

aggression new research suggests that

the behavior may actually prevent

violence between these massive animals

which can top out at nearly 500 pounds

mountain gorillas live in these tight

knit family groups that are led by these

Silverback males whose authority is

constantly being challenged by other

males so by advertising visually their

size their mating status their fighting

ability these silver backs are signaling

to would-be Challengers that they better

think twice before starting a Ruckus the

sense of touch in mammals is activated

by pressure responsive nerve cells near

the surface of the skin

further most mammals have whiskers or

the brisay which provide that tactile

sense touch is really important in many

primate species as grooming is an

important social activity that functions

not only to remove

ectoparasites but it also serves as this

social cement that reaffirms social

bonds within the troops remember

Trevor's reciprocal altruism if you grew

me today I'll groom you tomorrow so

before you go I have to tell you about

the most sensitive touch organ in the

animal kingdom and that is the

22 tentacled Ultra sensitive snout

called the tactile male phobia of the

star-nosed mole so this organ features

more than a hundred thousand nerve

endings that are packed into an area

that's barely more than a centimeter in diameter

diameter

each of the Stars 22 tentacles is

covered by these small Dome structures

called imer's organs the average snout

has some 30 000 in total so by way of

contrast an entire human hand contains

roughly 17

000 touch fibers which is analogous to

these imers organs on the star nose mole

snout but this snout is smaller than a

single human fingertip so it's got more

than thirty thousand on an organ the

size of a fingertip compared to 17 000

on an entire human hand so it's

considerably more sensitive than our hands

hands

as we discussed in our last module we

already know that duck-billed platypuses

recognize electrical Potentials in a

highly directional manner as opposed to

the electric fish that can only migrate

linearly to the electric Source this

ability is attributed to the large

number and variety of Electro receptors

found on their bills

so that concludes this lecture some

really big names in this reference list

that I hope you recognize Edward O Wilson

Wilson Hamilton

Hamilton

trivers okay so those are some big names

in ecology

tune in next time when we examine the

elephants hyraxes dugongs and manatees

thank you so much for your attention and

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Lecture 3.1_Mammalian Social Behavior and Communication