Mating Systems & Parental Care; Communication

Question 1

Name and describe the four mating systems

Answer 1

1. Polygamy - males mate with multiple females
2. Polyandry - females mate with multiple males
3. Monogamy - one male and one female mate for life
4. Promiscuity - both males and females mate with multiple females and males, respectively

Question 2

Which of the four mating systems is surprising from the point of view of males? Why?

Is there anything else that is also surprising that we. have seen in some mating systems, in the POV of males?

Answer 2

Monogamy.

Why: males invest so little in reproduction, so they pass up the opportunity to spread their genes more and mate with more females by being monogamous. We learned from sexual selection that males would want to seek out as many female partners as possible

Another thing that is surprising: the formation of leks. Why willingly go and increase male-male competition for females?

Question 3

Which of the four mating systems is surprising from the point of view of females? Why?

Answer 3

Polyandry

Why; Females are limited by the number of offspring they can have, this is excessive energy wasting on something with high reproductive investment. We learned from sexual selection that females should only seek one male partner, that they choose.

Promiscuity

Why: two reasons, one, females are limited by the number of offspring they can have. Two, promiscuous species often have increased risk of STIs

(possibly) Polygyny

Why: Polygyny is only surprising IF males of the species often give resources to females they mate with, in which case they’d have to share resources with other females

Question 4

What were the two hypotheses given for why monogamy occurs in the perspective of males, and which hypothesis is the most supported one?

Answer 4

Hypothesis 1:

In some species, offspring need such intense levels of parental care that if both parents don’t contribute, they will not survive.

Hypothesis 2: (most supported)

Females are scattered in space, making them rare. This means once males have found a female, males are better off defending that one female, because looking for other females is uneconomical.

Question 5

Why is hypothesis 1 for why monogamy occurs for males not supported? Recall hypothesis 1: In some species, offspring need such intense levels of parental care that if both parents don’t contribute, they will not survive.

Answer 5

If this were true, we would see a correlation between monogamy and paternal care i.e. every monogamous species should show paternal care. Phylogenetically, we see no such correlation when we make phylogenetic independent contrasts.

Question 6

Why is hypothesis 2 for why monogamy occurs for males the most supported? Recall hypothesis 2: Females are scattered in space, making them rare. This means once males have found a female, males are better off defending that one female, because looking for other females is uneconomical.

Answer 6

This is because phylogenetic relationships show that species where females are gregarious (living together, close by) are rarely monogamous.

Question 7

True or false. Females being aggregated in space (gregarious/social females) leads to the evolution of polygyny

Answer 7

True

Question 8

What are the five hypotheses to explain why males form leks?

Answer 8

Hypothesis 1:
Aggregating males make it easier for females to find males. Females notice a large group of males easier than a solitary male

Hypothesis 2:
Males aggregating may reduce the chance of predation for males because of predator dilution

Hypothesis 3:
Female-preference hypothesis - females are attracted to leks because it gives them choice, which they wouldn’t have with a solitary male

Hypothesis 4: (not well supported)
Hotspot hypothesis: Males aggregate to where females frequent, and that’s why leks form.

Hypothesis 5:
Hotshot hypothesis: males aggregate around successful males that females find attractive, in hopes that that will increase their chances with females.

Question 9

Why is the hotspot hypothesis not well supported for why leks form?

Answer 9

Sometimes leks form where females do not necessarily frequent.

Question 10

True or false. females often mate with many males, even in systems that were originally thought to be monogamous. These matings are called extra-pair copulations

Answer 10

True

Question 11

Polyandry and promiscuity mean females mate with multiple males, which is surprising in the perspective of females. Name and describe the four hypotheses for why some females mate with multiple males.

Answer 11

Hypothesis 1:
Fertility insurance - females that mate more are more likely to get pregnant or have more eggs fertilized.

Hypothesis 2:
genetic benefits - females that mate with more males have more genetically diverse offspring, increasing the chance of having a son who is sexy or has good genes. Good for minimizing inbreeding.

Hypothesis 3:
Material benefits - females that mate with more males can obtain more resources from males, in the form of protection or parental care.

Hypothesis 4:
Mating with many males prevents infanticide, males aren’t sure of which offspring is theirs, so they don’t kill any.

Question 12

When is it surprising when females accept polygyny?

Answer 12

It’s surprising if males provide resources, because then females must share with other females, and that would be costly.

Polygyny is fine if males provide no resource, but if they do, it makes no sense.

Question 13

What are the two hypotheses for why females accept polygyny when males provide resources?

Answer 13

1. Females are deceived into thinking they are the only female the male has mated with, but has been deceived into mating polygynously because the male has hidden his mating status.
2. The Polygyny threshold model - females will choose a mated male compared to an unmated one if the mated one has superior resources or traits, the costs of sharing are outweighed by the benefits of having that mate.

Question 14

True or false. The type of parental care varies between species

Answer 14

true

Question 15

Which kind of parental care is most common…

a) in fish
b) in mammals
c) in birds

Answer 15

a) no parental care
b) female-only parental care
c) biparental care - both males and females

Question 16

True or false. 79 % of fish families have no parental care, which means this is likely the ancestral state

Answer 16

True

Question 17

In the fish families that do parental care, it’s mostly the ______that do parental care

Answer 17

the males

Question 18

In fish, the ratio of parental care (Male only: biparental: female-only) is…

Answer 18

9:3:1

Question 19

In fish, males care more for the offspring when fertilization is _________.

Females care for the offspring when fertilization is _________.

In fish, the most common form of fertilization is ________fertilization

Answer 19

males - external fertilization

females - internal fertilization

most common - external fertilization

Question 20

What are the three hypotheses for why, in fish, males care when fertilization is external, and why females care for offspring when fertilization is internal.

Which is the most supported hypothesis?

Answer 20

Hypothesis 1: paternity certainty - when fertilization is external, females can’t be sure of maternity (the eggs could belong to other females), but males that do external fertilization are often territorial, so they are sure of paternity. When fertilization is internal, females are sure of maternity, but males aren’t sure of paternity (the female could’ve been inseminated by other males).

Hypothesis 2: order of gamete release - the sex that releases the gametes second is the one stuck with the offspring because the one who released it first has greater chance of leaving - external: males release second, internal: females release second.

Hypothesis 3: association with offspring (most supported)

internal – females have greater association with the offspring because they develop inside her.

external - males are often territorial in this case, so they have to guard the eggs, and therefore have greater association than the females.

Question 21

The order of gamete release is a hypothesis for why, in fish, males care when fertilization is external and females care when fertilization is internal.
However, this hypothesis doesn’t work with what?

Answer 21

This hypothesis doesn’t work for fish species that release both male and female gametes at the same time.

Question 22

In mammals, majority of parental care is female-only, why?

Answer 22

females have greater association with the offspring, because in mammals babies develop within the body of the female.

Question 23

True or false. In birds, biparental care is the most common, so this is likely the ancestral state

Answer 23

True.

Question 24

In birds, the ratio of parental care (Biparental: female-only: male-only) is…

Answer 24

90:8:1

Question 25

Why is biparental care the most common in birds?

Answer 25

Two parents can find resources more efficiently than one parent by themselves, and this increases offspring survival

Question 26

Why is female-only care the second most common form of parental care in birds?

Answer 26

If resources are abundant, a single parent is often sufficient and the other parent is unnecessary. In this case the females will do parental care, because there’s a higher cost for males in not reproducing with others.

Question 27

Why do females often care more than males across taxa? What is the rule?

Answer 27

The rule:

The sex with the greatest cost and the lowest benefit from care should not be the one doing the parental care.

For males, parental care often means missed mating opportunities (huge cost) and they cannot be sure of paternity of offspring (little benefit).

For these two reasons, it’s often females that do parental care across taxa.

Question 28

How do mating systems and parental care systems relate to each other?

a) female-only care is often, but not always, associated with ________
b) male-only care often, but not always, associated with ________
c) biparental care often, but not always, associated with ____________

Answer 28

a) polygyny
b) polyandry
c) monogamy

Question 29

Define communication

Answer 29

communication is when a sender sends out a signal meant to be picked up by a receiver, with the goal of wanting to affect the behaviour of the receiver.

Question 30

What is the difference between a cue and a signal?

Answer 30

Signals: a stimulus that is send out by the sender INTENTIONALLY, in order to benefit the sender

Cue: a stimulus that is send out by the sender UNINTENTIONALLY, and doesn’t necessarily benefit the sender.

Question 31

Define eavesdropper

Answer 31

An individual that receives the signal, but it was not meant for them

Question 32

What are some things signals can be used for?

Answer 32

• to advertise identity (I am species A, like in songbirds)
• to find mates
• to warn predators away
• to lure prey
• to advertise ownership of a territory
• to advertise need (nestlings)
• to warn of danger
• to call individuals to group up and assemble
• to attract symbiont species
• to advertise location of food

Question 33

Can you give an example of how signals can be used to advertise identity?

Answer 33

Songbirds often have complicated songs that are species-specific, females will not recognize males that sing different songs.

Firefly species also have species-specific light signals.

Question 34

Can you give an example of how signals can be used to find mates?

Answer 34

cicadas sing to attract mates. Frogs do a chorus to attract females.

Question 35

Can you give an example of how signals can be used to advertise ownership of a territory?

Answer 35

Woodpeckers knock on trees to tell you you’re in their territory. Dogs pee to mark their territory, the smell is used as a signal to say “this is my territory”

Question 36

Can you give an example of how signals can be used to assemble groups?

Answer 36

Tree-killing bark beetles release pheromones to attract other individuals to a tree.

Cellular slime molds produce a chemical signal that tells them to assemble into a slug-like formation, in order to move location.

Question 37

Can you give an example of how signals can be used to advertise location of food?

Answer 37

Honey bee waggle dance is used to advertise location of a particular good patch of flowers

Young ravens will call other young ravens to a carcass in order to overwhelm older territorial ravens

Question 38

Can you give an example of how signals can be used to warn of predators / danger?

Answer 38

Vervet monkeys have a different alarm call warning of three different predators; snakes, leopards and eagles

Question 39

Can you give an example of how signals can be used to warn predators?

Answer 39

Aposematism - some animals are brightly coloured, like the poison dart frog, to warn predators that they are toxic or nasty to eat.

Question 40

Can you give an example of how signals can be used to lure prey?

Answer 40

Angler fish have a bioluminescent organ that resembles little glowing fishes, which draws in their prey (who think the glowing fish is prey themselves!).

Question 41

Can you give an example of how signals can be used to attract symbiont species?

Answer 41

Flowers use smell and colours to attract pollinators.

Question 42

What are the five different categories of signal modalities

Answer 42

1. visual signals
2. acoustic signals
3. chemical signals
4. tactile / mechanical signals
5. electrical signals

Question 43

Name the disadvantages and advantages of visual signals

Answer 43

Visual signal:

Pros:

• can be species-specific
• can be permanent

Cons:

• Easily blocked by obstacles; only works short distance
• Can be seen by predators

Question 44

Name the disadvantages and advantages of acoustic signals

Answer 44

Acoustic signal:

Pros:
- can travel far, through obstacles

Cons:

• short-lived
• can alert predators to your location
• can be unintentionally distorted by the environment

Question 45

Name the disadvantages and advantages of chemical signals

Answer 45

Chemical signal:

Pros:

• very long-lasting
• can travel through obstacles
• if species-specific, it’s harder for predators to locate you

Cons:

• slow because it takes time for the chemical to diffuse
• travels shorter distance than acoustic

Question 46

Name the disadvantages and advantages of mechanical signals

Answer 46

Mechanical/tactile signal:

Pros:
- can travel through obstacles

Cons:

• short-lived
• can be unintentionally distorted by environment

Question 47

Name the disadvantages and advantages of electrical signals

Answer 47

Electrical signal:

Pros:
- no light needed

Cons:

• energetically costly
• only works in water
• short-lived

Question 48

True or false. Signals can be altered by the environment

Answer 48

True.

Question 49

Describe how acoustic signals can be altered by the environment and explain how bird songs differ in densely-vegetated forests vs. open woodland habitats.

Answer 49

Sounds can be changed because of …

a) other sounds (very noisy environment)
b) bouncing off of obstacles, like the surface of leaves.

For example, birds in densely-vegetated habitats have short and simple songs. Birds in open woodlands have longer more complex songs.

Question 50

Describe how visual signals can be altered by the environment and give the example of warbler plumage.

Answer 50

If you want to send out a visual signal, you don’t want to be camouflaged. Warblers that live in darker environments have lighter and brighter plumage than warblers living in lighter environments.

Question 51

True or false. Some species have been forced to modify their signals because they were being picked up by eavesdroppers (receivers they weren’t meant for)

Answer 51

True

Question 52

Can you give examples of how some species have modified their signals to deal with eavesdroppers?

Answer 52

Many bird species have modified their alarm call to a high-pitched seet call. It’s so high-pitched that the predator is unable to locate where it’s coming from.

Similarly, ground-nesting nestlings (that are more likely to be predated on) have higher pitched begging calls than tree-nesting nestlings, to prevent predators from locating them.

Question 53

What are dishonest signals?

Answer 53

Signals that a sender sends that are meant to trick the receiver. Not the same thing as eavesdropping, in which a signal is intercepted by an illegitimate receiver, but in this case we have an illegitimate SENDER

Question 54

According to the honest signalling theory, what are the three requirements denoting a signal as “honest”?

Answer 54

1. the sender and the receiver both have a common interest
2. The signal cannot be faked
3. The signals has to be a handicap / be costly to the sender.

Question 55

Explain why costly signals are expected to be honest (or how does the handicap principle relate to honest signalling theory?)

Answer 55

According to the honest signalling theory, only the highest quality individual can afford the cost of sending a signal, or individuals that send a signal are doing so because the benefits outweigh the costs (starved nestling begging calls)

Question 56

How would you determine if a signal is honest?

Is the angler fish bioluminscent organ honest?

Answer 56

See if it checks out all three requirements for whether a signal is honest.

No, the angler fish signal is dishonest. Sure the angler fish has a cost to producing the signal (energy and exposure to predators), but the sender and receiver do not have a common interest. The prey doesn’t want to be predated on.

Question 57

Are chick calls an honest signal of need? Explain using storm-petrels

Answer 57

Storm petrel chicks send out more calls the hungrier they are, so there’s evidence that you don’t call as much if you’re not hungry, showing it’s an honest signal.

Question 58

Other than the angler fish, what are some other examples of dishonest signallers?

Answer 58

Predatory fireflies mimic the flash patterns of females of other species to draw in the males and predate on them.

Cuckoo nestlings put in the nest of their hosts create calls that sound like a whole brood of nestlings of that host species, making them work harder to feed them more.

Batesian mimics signal unpalatability when they aren’t and this harms the actual model species because predators start to think they are palatable too.

Question 59

What are two ways dishonest signallers are dealt with?

Answer 59

1. Dishonest signals set up an arms race between signaller and receiver
2. Just like we talked about before with Batesian mimicry, constant dishonest signals leads to negative frequency dependent selection: when dishonest signallers are common, dishonest signallers are selected against.

Question 60

Define culture.

Answer 60

Behaviours shared by members of a group that are transmitted or learned.

Question 61

Give an example of animals with cultural behaviours

Answer 61

Capuchin monkeys learn to break nuts with rocks. This behaviour is both individually and socially learned.

Songbird males learn their complex songs from older males.

Bighorn sheep learn migration routes from other individuals.

Question 62

Cultural transmission is done through ______ _______

Answer 62

social learning.

Question 63

What is social learning?

Answer 63

Learning through either…

a) watching other individuals and then copying or imitating. Local enhancement also falls into this category
b) being actively taught something

Question 64

What is the difference between social learning and individual learning?

Answer 64

Individual learning is when you learn behaviours on your own, through trial and error, habituation to stimuli or sensitization to stimuli.

Social learning is all about the social aspects, it involves learning only because you’re in a social setting, and you’re learning from others.

Question 65

Is utilizing local enhancement done by other individuals a form of social learning?

Answer 65

Yes, other scavengers learn that vultures fly over carcasses (an unintentional cue). This is a form of social learning.

Question 66

What is the difference between imitation and copying?

Answer 66

Copying often has to do with choice i.e. “oh that female chose that male, I will choose him too.”

Imitation is much more complex, for example the capuchin monkeys imitate their elders in several steps - they look for nuts, they leave the nuts in the sun, they find good rocks, they find a good anvil surface.

Question 67

Define teaching, and how it differs from imitation.

What are the four requirements for social learning via teaching?

Answer 67

In teaching, the model that one is learning from has an active role and is trying to get you to learn. In imitation, the model isn’t necessarily trying to get you to learn, you do that yourself.

The four requirements for whether we have social learning through teaching:

1. The students must be naive
2. The teacher imparts information faster than the students themselves would receive it.
3. Teacher is providing a benefit by teaching the student
4. There is no benefit to the teacher

Question 68

give examples of animals teaching.

Answer 68

Meerkat adults gradually introduce pups to dangerous prey by feeding them dead prey at first, showing them how to take the tails off. As the pups get older, they introduce live scorpions and how to subdue them.

bird songs: male singing rates decline during nest incubation but generally males start singing again when chicks have hatched, just so the chicks learn the songs. These species-specific songs cannot be sung by young birds if they did not have a tutor.

Question 69

True or false. Cultures evolve through a process parallel to organic evolution (evolution we’ve always talked about thus far), using Darwin’s four postulates

Answer 69

True

Question 70

Can culture evolve through selection and drift?

Answer 70

Yes! It follows processes analogous to organic evolution

Question 71

What conditions are required for cultures to evolve? (hint: Darwin’s four postulates in terms of cultural evolution)

Answer 71

1. There needs to be a variety in the different practices, both within and between populations
2. Some cultural practices increase your chances of proliferation and survival more than others
3. There has to be some degree of loyalty to the practices, such that they are passed on to other generations.
4. There needs to be a turnover of practices over time, some practices are replaced by others

Question 72

True or false. Cultural evolution can influence organic evolution. If true, give examples

Answer 72

True.

Lactose intolerance is the ancestral state in human adults. But some population adopted dairy traditions, that selected for mutations that allowed the consumption of lactose in adulthood.

Bird songs are socially learned, but the songs are also how you attract mates, so they are important in sexual selection and recognition by females.

Question 73

Compare and contrast organic and cultural evolution

Answer 73

Similarity:

• they both follow Darwin’s 4 Postulates
• in organic evolution, certain genetic traits are chosen due to natural selection or drift. Similarly, in cultural evolution, certain practices could increase survival/reproductive success more than other practices and be “selected” for, or certain practices could have simply been chosen due to chance (drift).

Differences:

• cultural evolution is the evolution of behavioural practices that are taught, copied, mimicked, or learned from local enhancement.
• organic evolution the evolution of genetic genes through reproduction.
• focus of the survival / reproduction of the cultural practice rather then the individual itself
• Cultural evolution can happen within or across generations. Organic only happens across.