Animal Behavior Exam 2

First order selection

Describes the geographic range of a species

Second order selection

The home range of an individual or group

Third order selection

Habitat use within the home range

Fourth order selection

Selection of specific resources at specific sites (e.g. berries from a bush)

Reproduction in kingdom Animalia asexually

• Asexual reproduction in some animals (such as budding in sponges)

• Parthenogenesis, or “virgin birth” (e.g. some sharks, reptiles (whiptail lizard), daphnia “water fleas”) - unfertilized egg develops into embryo

Reproduction in kingdom Animalia sexually

• Sexual reproduction - combination of sperm and eggs

• Androgenesis - rare, embryo develops using only genetic material from sperm (e.g. asian clams)

• Most animal

Ansiogamy

• Gametes differ in size and morphology

• Sperm (small): selected for motility, rapid production, mate competition

• Eggs (large): selected for nutrient investment and zygote viability

• Creates inherent asymmetry in parental investment between sexes

Ansiogamy vs isogamy

• Ansiogamy reversals toward isogamy possible via post-copulatory sexual selection

• Ansiogamy is the fusion of gametes in dissimilar sizes. Males and female gametes are present.

• Isogamy is the fusion of gametes in similar size. Male and female gametes are not distinguishable.

Fisherian runway

• Intersexual selection, female mate choice here, leads to positive feedback loop.

• Selected, conspicuous traits (e.g. tail length and bouncing behavior in long-tailed widowbird) increases in frequency

• Leads to an increase in preference for the conspicuous trait (and in the frequency of alleles associated with this preference), greater sexual dimorphism and the evolution of seemingly maladaptive traits (typically in males, but some exceptions such as two spotted gobies, dance flies, pipefish)

• Feedback loop continues until counterselection is strong enough to stop it (tails become so conspicuous and long that survival drops too low)

• Female genetic preference ←> male trait becomes genetically correlated

• Drives extreme trait elaboration

Intrasexual selection

competition over access to mates among same sex

pre-cop: contests, weapons, body size

e.g. beetle horns, elephant seal battles, female jacana territory defense

post-cop: sperm competition, mating plugs, mate guarding

Intersexual selection

mate choice by opposite sex

pre-cop: ornaments, courtship displays

e.g. manakin dances, bird song

post-cop: cryptic female choice, differential sperm storage or fertilization

Sexual conflict

• Coevolution of antagonistic behaviors/structures that increase fitness of one sex while reducing fitness of the other sex

Ex: Muscovy duck genital coevolution - male corkscrew phallus vs. female counter-clockwise vaginal tract

Monogamy

• 1 female + 1 male (may occur when offspring requires both parents, high degree of parental care)

• > 90% of birds

• <10% of mammals

• Social monogamy is not a good predictor of genetic monogamy

Monogamy H1 Mate assistance

Male care essential (canids)

Monogamy H2 Mate guarding

females scarce/dispersed (harlequin shrimp post-molt)

Monogamy H3 Female enforced

Female prevents her mate from mating with other females

Polyandry

• > 1 male per female

• Occurs where resources are patchy and briefly available, or predation is high

• Sequential polyandry - female clutch size is limited (phalaropes)

• Simultaneous polyandry - females defend males from other females, clutch size less restrictive (african tree frog, jacana)

Polyandry H1 Fertility insurance (genetic benefit)

Maximizing the number of female eggs fertilized

Polyandry H2 good genes (genetic benefit)

Mating with a male of higher social status or greater number of attractive features

Polyandry H3 genetic compatibility (genetic benefit)

Greater chance of some offspring having a superior combination of genes

Polyandry H4 more resources (material benefit)

Nuptial gifts or extensive male parental care

Polyandry H5 increased protection (material benefit)

Protection from harassment from other males

Polyandry H6 Infanticide reduction (material benefit)

Greater confusion about paternity of female’s offspring and lower rates of male killing their kids

Polygyny

• > 1 female per male

• > 90% of mammals

• Males defend females when they can

• Males disperse further, presumably to find a female group

• In some birds males defend food or nesting sites (oropendolas, grouse)

Polygyny H1 female defense

Males defend harems directly

Polygyny H2 resource defense

Males defend essential resources

Polygyny threshold model

• Female pairs with already-mated male on high-quality territory if fitness > unmated male on poor territory

• Mating system determined by differences in resource value of male territories

Scramble competition polygyny

• Males compete indirectly for fertilizations by spawning (releasing sperm) near spawning females (releasing eggs)

Lekking polygyny

• Males compete directly for mating by displaying for multiple females; do not defend resources

Hypothesis for Lekking - hotspot

Males cluster because females tend to travel along particular routes that intersect

Hypothesis for Lekking - hotshot

Males cluster around highly attractive males in order to encounter more females

Hypothesis for Lekking - female preference

Males cluster anywhere because females are attracted to the largest aggregation of males

Which mating system is most common?

• Polygynandry (promiscuity) is most common among all animals with both males and females mating with multiple partners

• Within vertebrates, polygyny is most common

• Within birds, social monogamy is far most common (around 90% bird species)

R strategists (many small offspring)

• Allocate energy into many small offspring

• Investing minimum into each one

• Have very little or no parental care (exceptions exist)

K strategists (few large offspring)

• Invest more into each offspring

• Far more likely to have HIGH parental care

• Amount of care varies greatly, can include: increased gestation, incubation of eggs, nest or young defense, young provisioning, etc)

continuous iteroparity reproductive strategy

Do not have set breeding seasons and may reproduce at any time of year (e.g. humans)

seasonal iteroparity reproductive strategy

Reproduce periodically

semelparity reproductive strategy

Reproduce once before death (like salmon and Antechinus males)

Patterns by taxon

• Patterns by Taxon

• Mammals: 100% maternal care, <5% paternal

• Birds: >90% biparental care

• Fish: ~25% show care; paternal > maternal (mouth brooding, egg aeration)

• Amphibians/Reptiles: <20% show care (croc nest protection, frog transport)

Investment hypothesis (maternal care) + counterargument

• Females invest more in gamete production so are less likely to abandon them

• Concorde fallacy. Parental care should depend on expected benefits not on whether past investment will be wasted.

• Not supported.

Paternal uncertainty hypothesis (maternal care)

• Males unsure of paternity

• Not supported (or weak)

Gamete order hypothesis (maternal care)

• Females are usually the last with gametes so are stuck with them

• Some support (most fish with simultaneous gamete release have paternal care ONLY)

Association hypothesis (maternal care)

Females are usually the sex nearest offspring when care is needed, so are more likely to be the caregiver

• Also supported (doesn’t explain fish with simultaneous gamete release since both are nearest fertilized egg)

Parent/offspring conflict

• Selection operates differently on parents vs offspring

• Young - maximize their own parental care

• Parents - distribute total resources equally among all offspring (lifetime offspring)

• Direct costs - physical costs. mouth brooding fish can’t eat while caring

• Indirect costs - current offspring care comes at expense of care for future young

Precocial/precocious offspring

More mobile and able to fend for themselves at birth

Altricial/altricious offspring

More reliant on parents for survival, less mobile

How to reduce costs of parenting?

• Sneaker males (e.g. cuttlefish)

• Extra pair copulations in birds

• Brood parasitism: cuckoos lay eggs in host nests - evolved multiple times independently

The sender

An individual that transmits a signal

The receiver

An individual whose probability of behaving a certain way is altered by the signal

The channel

The medium through which the signal is transmitted (visual, chemical, tactile, auditory, electrical)

The signal

The behavior of the sender (posture, display, vocalization)

Context

The setting in which the signal is transmitted and received

Noise

Background activity in the channel which is irrelevant to the signal being transmitted

Signal-to-noise-ratio

How easy the signal is to detect in the environment

Functions of signals (IDIAD)

• Identification (species, sex, position)

• Directions (food location, navigation)

• Intention (probable actions or state)

• Advertisements (mate attraction, dominance displays)

• Deceptions (false information)

Signals versus cues

• Signals evolved/intentional

• Cues influence behavior without being evolved to do so (unintentional)

Message versus meaning

• Message = sender’s encoding

• Meaning = receiver’s interpretation

Arbitrary versus nonarbitrary signals

• Arbitrary = no structural link

• Non-arbitrary = physical link (pitch ←> body size)

Discrete versus graded signals

• Discrete = signals operate in an on/off manner

• Graded = transmitted with varying intensity

Complex versus simple signals

Complex signals use multiple channels or convey multiple messages

What are rituals and steps in their evolution (SESR)

• Rituals are complex communication behaviors

• Originate from other functions: thermoregulation, maintenance behaviors, etc

1. Simplification (reduction in # of components)

2. Exaggeration of remaining components (as in peacocks)

3. Stereotype (behavior becomes invariable)

4. Repetition of signal

When do rituals arise?

• Often in conflict situations (threat, territoriality, reproduction)

• Reduces ambiguity of signal → message is standardized, efficient

• e.g. piloerection (goosebumps) originally for thermoregulation, co-opted for communication

Properties of channels (RCOLC)

• Range: how far will the signal carry?

• Change: how much does the signal degrade or change from the point of release?

• Obstacle: how well does the signal move around obstacles?

• Locate: how easy is it for the receiver to find the signaler?

• Cost: how much does it cost to produce the signal?

Auditory channel (acoustic communication)

Advantages

• long distance, works at night, rapid starting/stopping

Disadvantages

• attenuation in vegetation, eavesdroppers, environmental masking

Mechanics of acoustic communication

• Stridulation (running two body parts together, crickets)

• Tymbal organ (cicada)

• Vocal organ (larynx, syrinx) (mammals)

• Swim bladder (toadfish)

• Other more complex ones (rattlesnakes)

Chemical channel (scent + taste)

Advantages

• long distances via wind or water, works at night, low energy to produce, persists in environment

Disadvantages

• can be difficult to locate, old messages may linger, causing confusion or alerting predators, few messages can be conveyed

Mechanics of chemical communication

• Oldest form evolutionarily

• Pheromones - most common, intraspecific (female armyworm calling)

• Allomones - defensive chemicals that benefit sender, harm receiver, interspecific (bombardier beetle)

• Kairomones - chemical eavesdropping, benefit receiver, harm sender, inter or intra specific (tracking in wolves)

• Synomones - mutualistic attraction signals. Plant/pollinators.

When are signals likely to be dishonest?

1. If signaler and receiver have different goals

Ex: Begging calls of baby birds are usually honest, but chicks can sometimes try to manipulate to get more than their share of food

2. If signal is costly to assess or to challenge

Ex: Stomatopods bluffing after molting

Zahavi’s honest signaling hypothesis (handicap principle)

• Signals are reliable because they are costly to produce and maintain. Only high quality males can bear the cost

• There should be a direct link between signal design and the quality being signaled (honest signals should be nonarbitrary)

• Conspicuous displays/weapons = reliable quality indicators

Tactile channel

Advantages

• Increasing privacy/avoiding inadvertent receivers, helpful at night, instantaneous feedback

Disadvantages

• Signals can’t travel very far, in a group signal has to be repeated, limits spatial awareness increasing risk of predation

Mechanics of tactile communication

• All animals but sponges which rely on cilia, diff receptors diff tactile signals

• Vibrissae (whiskers) are stiff hairs in mammals used for sensing textures, detecting changes in air currents.

• Antennae (combo touch and chemical) in insects and many arthropod with rhythmic touching for direction, identify, resource info

• Substrate/seismic receptors. Lateral lines in fish, corpuscles in elephants which are low range due to adaption for detecting low frequency vibrations)

Bat mating and sociality

• Most bat species are polygynous (through the spectral bat is monogamous)

• They form complex social groups displaying fission-fusion dynamics

• Unique communal care - young are left behind in creches while adults forage (sometimes a “nanny bat” remains behind to babysit)

Bat foraging strategies (via echolocating)

• Aerial hawking - catching prey mid flight

• Trawling - picking insects off the surface of water

• Gleaning - picking insects off of other surfaces (active = echolocating, passive = listening)

Reciprocal altruism

• Bats will regurgitate blood and share with non-kin. However, they preferentially share with those who have donated blood to them in the past. This is similar to the long term optimal solution to the ultimatum game as the behavior is based on trust built of repeated interactions

Bat behavior

• Chiropteran powered flight: elongated phalanges + patagium membranes

• Echolocation: high-frequency ultrasonic vocalizations (distance calculated via echo delay, target size via frequency modulation and doppler shifts)