Chapter 13 reading

Cooperative behavior develops when two or more individuals integrate their activities to achieve a common goal that increases the inclusive fitness of both.

The second class of economic models ignores genetic similarities but assumes that all parties experience a net direct benefit by cooperating. → Mutualism

Mutualism: for all direct benefit cooperation models.

There will always be a temptation to cheat and do less of the work, since both actors and slackers will gain the same benefit. This type of situation is called by-product mutualism

Construction of a communal refuge, collaborative defense of a group territory, and group hunting of large prey are obvious examples . This form of mutualism, called synergism.

skew theory, that investigate just how inequitable the benefits and costs can be while still providing a marginally net benefit to all parties

Reciprocity is a third type of mutualism in which donors expend costs now to the benefit of recipients, but then must wait until the roles are reversed before they receive the benefits that compensate for those costs.

tit-for-tat rule of cooperating with a particular partner only if he cooperated on the previous occasion.

General Principles of Recognition

Recognition is the discrimination and identification of a target individual or group among a field of similar non-target individuals or groups.
- In the production component, the potential recipient of aid provides some information about its identity by producing a cue, signal, or label.
- In the perception component, the donor perceives the signal and assesses its similarity to a template of the target’s unique signature stored in memory.
- In the action component, the donor decides whether the potential recipient’s signal meets the criterion for a match

Recognition mechanisms

The mechanisms animals use for recognition: spatial location, familiarity, phenotype matching, and recognition tags.

Associating target individuals with a specific spatial location is the simplest mechanism of recognition.

Familiarity, or associative learning, is a recognition mechanism that requires prior experience from direct association with target individuals or groups, followed by the learning and memorization of their specific characteristics.

The phenotype matching mechanism functions to identify genetic similarity
- In contrast to the familiarity mechanism, recognition via phenotype matching is the ability to assign stimuli to classes of relatedness relative to the receiver or known parent

Recognition tag mechanism is associated with greenbeard models of cooperation.
- If the benefits of recognition (more food from true parents) outweigh the losses (less food from non parents), identity signals should be favored.

Recognition game, where there are two classes of senders—desirable and undesirable recipients of aid—whose phenotypes deviate from the receiver’s target phenotype template to different degrees.

Given that the phenotype distributions for the two types of recipients overlap to some degree, the receiver evolves a response threshold for accepting or rejecting the sender’s request for cooperation.

Signals designed to encode identity will employ the coding strategy of emergent multivariate signaling.

Male–Female Integration

Mate recognition at the most basic social level refers to the mechanism by which conspecific members of the opposite sex are recognized(species recognition)
At the next level, it refers to the mechanism by which good quality mates are identified, called mate-quality recognition
The third level of mate recognition, partner recognition, applies to species in which males and females form pair bonds for the purpose of reproductive cooperation.

According to ecological speciation models, when expanding populations encounter new ecological conditions or exploit new resources, population members undergo natural selection pressures that eventually lead to substantial genetic incompatibility and partial reproductive isolation from members of the original population.

behavioral speciation models, sexual selection for good genes or sexy sons, sexual conflict arms races, or sensory drive causes a reduction in cross attraction between members of different morphs or populations and eventually leads to reproductive isolation and speciation. In this case, rapid divergence in mating signals results from coupled evolutionary changes between male and female traits

A controversy exists concerning the presence of separate signal components functioning for species recognition versus mate quality assessment.

Hierarchical rule for mate choice, with the species-specific component setting primary limits on species recognition and the mate-quality component facilitating comparisons among potential conspecific mates.

multiple signal components are combined into a one dimensional preference function, and mating decisions are based on a threshold value or relative comparison along this single scale.

There are three main arguments for the evolution of distinct signals or signal components that function primarily in species recognition.

Reproductive character displacement, in which populations of two closely related species differ more in phenotypic traits where they occur together (in sympatry) than where each species occurs alone (in allopatry).

Mismating between heterospecific individuals results in hybrid offspring of low fitness, and selects for divergence of mating signals and receiver preferences that reduce the likelihood of heterospecific mating, a process called reinforcement.

Quantitative trait locus (QTL) mapping QTL is a region of DNA that contributes to variation in a phenotypic trait and can ultimately be related to candidate genes.

The components of multivariate mate attraction signals can often be separated into two categories, static and dynamic

Static components are determined by the physical constraints of the signal production apparatus, show little variation within a species, and differ quantitatively between closely related species.→ They are subject to stabilizing selection by female preference for mean trait values, are more heavily weighted in preference decisions than other components, and presumably provide species identity information.

dynamic components are more variable within species and often correlated with sender condition. → These components are subject to strong directional selection by female preference for more extreme values, often above the normal species range, and they most likely provide mate quality information.

For animals that form male–female pair bonds or same-sex bonds for the purpose of extended cooperative behavior such as sharing of parental care duties or joint resource defense, distinctive signals are needed for rapid partner recognition.

The olfactory cue a female uses to distinguish her mate is a cuticular hydrocarbon associated with the male’s recent breeding status and experience with a carcass, a breeder’s badge, which an invader would typically lack.

Monogamous pair bonding (sometimes referred to as male– female partnerships) generally occurs in species where the male performs a critical role in parental care→Males are selected to remain with the female after mating because they benefit more from increasing the survival of their offspring than from maximizing the number of females fertilized

Mated pairs typically perform joint displays together, often highly synchronized and sometimes quite elaborate. The timing and context of these displays vary, suggesting different functions for these signals beyond the vague notion of pair bond maintenance

Some species engage in a long courtship period and use mutual displays as a means of continued mate evaluation. For example, great crested grebes (Podiceps cristatus) form pairs in mid-winter but don’t start breeding until spring many months later.

Mutual displays can serve a recognition and greeting function in cases where mates spend substantial periods of time apart. For example, many birds with long bouts of alternating incubation and foraging, such as herons and sea-birds, perform elaborate displays when the forager returns to the nest to relieve the incubator.

Cooperative territory defense is another context favoring mutual display. In some territorial monogamous species, especially those that retain the same territory throughout the year or in subsequent breeding cycles, the pair defends their territory as a team.

Mutual displays can serve a mate guarding function by revealing the mated status of each partner to same-sex rivals.

Tactile interactions such as allogrooming, huddling, hugging, kissing, and tail-twining are common forms of mutual display between monogamous pairs of birds and primates

Classic studies of doves, rats, and other species illustrate the mutually stimulating interactions between male and female signals, internal hormones, and external stimuli that synchronize hormonal cycles and coordinate the entire reproductive episode

(1) by influencing the development of special structures involved in the performance of a behavior such as male claspers or display structures, or by stimulating oviduct enlargement or lactation gland development; (2) by influencing the peripheral nervous system that controls sensory input to the brain; and (3) by triggering behavioral mechanisms in the brain directly.

Another model finds that evolutionarily stable negotiation rules can evolve that enable two parents to interactively arrive at a final allocation of effort

Parent–Offspring Integration

An inclusive definition of parental investment is: the time and energy devoted to offspring that increases the offspring’s survival while decreasing the parent’s ability to survive and invest in future offspring

The sophistication of parent–off- spring recognition mechanisms depends on the difficulty of the recognition task, which is affected by factors such as the development pattern of the young (altricial versus precocial), the existence of a fixed nest or roost site, family size, gregariousness of young from different families, and the duration of time young are left unattended while parents forage.

For territorial birds and mammals that have a small number of immobile young placed in a nest well-separated from adjacent broods, the nest location is the focus of parental recognition of offspring.

In species with unidirectional recognition systems, which party produces the distinctive signal that the other uses for recognition depends upon the ecological context.

For most colonial species in which young from many families aggregate and intermingle while parents leave on foraging trips, a mutual recognition mechanism is favored. The mere existence of such crèches implies a highly effective parent–offspring recognition mechanism. In swallows, many seabirds, and ground squirrels, young are ini- tially restricted to a nest or burrow site.

When brood size is very large, individual recognition of each offspring is not feasible, and a family identity signal is favored

Parent–offspring conflict

Parents provide food and protection to their offspring, and offspring fitness and survival increase as a result. Although both parties share an interest in the successful rearing of the young, parents and offspring disagree over the exact length and extent of parental care.

One is brood sex ratio conflict between the queen and her worker offspring in the social Hymenoptera. The queen is equally related to her sons and daughters (r = 0.5) and prefers a 1:1 sex ratio, whereas the workers, her daughters, are more closely related to their sisters (r = 0.75), than to their brothers (r = 0.25), and there- fore prefer a 3:1 ratio. Workers have a great deal of power in this conflict because they control which eggs are reared.

The suppression of maternal alleles by paternal alleles, called genomic imprinting, has been proposed for the actions at several gene loci.

Phenotypic resolution models that examine the behavioral interactions between begging offspring and food-provisioning parents, with birds and insects in mind, have had some success in demonstrating the process of parent–offspring conflict.

Offspring begging models sort into two categories: honest signaling models and sibling scramble competition models

Honest signaling models view begging as an informative signal of offspring need to parents.

Scramble competition models, on the other hand, assume that offspring control food allocation by jostling for the best position when parents arrive with food, and that parents are passive providers of food to the closest or most active offspring.

A third modeling strategy, using tug-of-war models that let the degree of competitive asymmetry vary continuously, may hold more promise for evaluating the consequences of power asymmetries between relatives

Begging signals are remarkably similar among species, consisting of multimodal displays with vigorous postural movements, brightly colored gape (mouth), and repetitive vocalizations

Offspring are selected to give distress or alarm signals to elicit parental approach and protective behaviors.

Sibling negotiation is one proposed strategy, in which siblings communicate among themselves in the absence of the parent to assess each other’s relative hunger, and then modify their competitive behavior so that the hungriest sib is fed.

Collaborative begging occurs in a few species. In black- headed gulls (Larus ridibundus), chicks in increasingly larger broods (up to three) beg more synchronously and thereby both decrease their individual begging effort and increase the rate of parental provisioning

More closely related kin are expected to exhibit more cooperative, or at least less aggressive, behavior toward one another. This kin nepotism principle also applies to broods of siblings, which can vary in their relatedness from half to full sibs, depending on whether one or several sires fathered the brood.

In other contexts, parents give directive signals to offspring to elicit specific responses. For instance, parents usually possess a better knowledge of immediate environmental conditions, such as the presence and location of food, cover, and predators, than offspring do.

Parents can affect the development of their offspring in profound ways using strategies that sometimes qualify as communication signals. One strategy involves prenatal chemical signals.

Many organisms have the ability to develop along alternative pathways depending on environmental conditions, a phenomenon called phenotypic plasticity.

A second strategy by which parents can influence off- spring development involves teaching.→A broad operational definition of teaching requires that an individual, A, modifies its behavior only in the presence of a naive observer, B, at a potential cost to A; and as a result of A’s behavior, B acquires knowledge or skills more rapidly or efficiently than it would otherwise. This definition differentiates teaching from other forms of social learning, in which naïve animals acquire information by observing other individuals engaging in their usual behavior.

Group Integration

The mechanisms used for group-mate recognition depend on the size and stability of groups, whether or not group members are tied to a fixed site such as a nest or territory, and the importance of recognizing specific individuals or classes within groups.

Fission-fusion societies are those that exhibit flexible changes in group size by means of the merging and splitting of subunits, generally caused by spatial and temporal variation in the distribution of resources or by variation in group members’ needs and activities.

Some species embed their individual signature system within a group signature system. Group labels are usually acquired signal features, either learned acoustic signals or blended olfactory signals. Killer whales (Orcinus orca) provide one of the best acoustic examples. Calves learn by repeated signals

However, if there is competition for resources within such aggregations and individuals vary in fighting ability, then an ability to recognize relative dominance status is favored. Visual status badges evolve under these circumstances.

age badges reduce aggression of older individuals toward younger individuals.

Appeasement signals

Behavioral tactics and signals that maintain peace in groups are called appeasement signals.

Dominant individuals may also give specific conflict-avoidance displays if they wish to approach a subordinate with nonaggressive or benign intentions. In baboons, dominants that approach subordinates while uttering “grunts” are significantly less likely to attack and more likely to show affiliative behaviors such as grooming than dominants that approach without grunting

Dominants may also give reassurance displays, such as touching genitals and mock mounting, to young or fearful subordinates.

In some group-living species, however, such conflicts are often followed by reconciliation, or friendly post conflict reunion.

A smaller number of species also exhibit third-party consolation after conflicts, defined as the intervention of an individual not involved in the conflict to console the loser.

ALLOGROOMING

Allogrooming is the grooming or preening of another individual. It is nearly ubiquitous in primates and also occurs in some ungulates, a few rodents, carnivores, bats, cooperatively breeding birds and mammals , and social insects.

Allogrooming is a classic multiple function act.

First, it obviously serves a hygienic function. This claim is supported indirectly by the fact that allogrooming is directed toward parts of the body that the self-groomer cannot reach, such as the back, neck, and head

Allogrooming has a calming, tension-reducing effect on the recipient, releasing beta-endorphin in monkeys and lowering heart rate in horses. It is a major stress reduction strategy in primates and rats →reduction in aggression received from other group members.

Allogrooming also functions as a commodity that can be traded in a biological market for other goods → reciprocal grooming; access to resources controlled by the recipient; a mating opportunity; tolerance or reduced aggression if the recipient is a dominant; or agonistic support, in which the recipient assists the groomer during an aggressive conflict.

biological market model, individuals do not compete over access to trading partners in an agonistic manner, bur rather outcompete each other by offering a valuable commodity, such as grooming

Finally, allogrooming serves a signaling function.→The mere act of offering to groom another individual communicates the message that the target recipient is a valuable partner

GREETING DISPLAYS

Signals are clearly important for managing interactions in these communal species, the most prominent being greeting ceremonies during fusions. Greeting ceremonies typically combine recognition signals, signals of approach with benign intentions, and expressions of mutual affiliation, reassurance, or assessment.

Group movement coordination and decision making

The decision-making process for groups is different from the process for individuals because it requires reaching consensus.

If the interests of group members conflict, then some group members will pay a consensus cost if they abide by the group decision.

DEMOCRATIC DECISIONS AND QUORUM SENSING

By pooling the knowledge and information of a larger number of individuals, more accurate decisions can often be made by democratic groups than by individuals. This concept has been called the wisdom of the crowd.

Quorum sensing, whereby animals increase their probability of exhibiting

Similar consensus- building departure signals have been documented in gorillas, capuchin and sifaka monkeys, and elephants→ In many monkey and ungulate species, any animal may be the first to initiate the movement— there is no consistent leader—but this individual pauses and looks around to make sure others are following, and if there are not sufficient followers, it will return to the group

DESPOTIC DECISIONS

Conditions under which it might pay to follow a single despotic leader include: (A) the potential for significant errors in assessing the best timing and direction of travel, (B) a large difference inexperience or knowledge between the leader and all other group members, so that the leader’s average decision error is lower than the average error of other members, and (C) small group size → Known examples of despotic groups are indeed relatively rare, as predicted, and do meet these types of conditions. For instance, chacma and hamadryas baboons (Papio ursinus and P. hamadryas), which inhabit harsh environments (dry mountains and deserts, respectively), have fission-fusion social systems in which the basic “fission unit” is a single male plus several females

GROUP COHESION

In more densely vegetated habitat, visual contact is quickly lost and acoustic contact signals are required.→ Flocks of birds foraging through foliage keep up a constant twitter with repeated soft peep, tick, or chip vocalizations that reveal the location of the flock.

Cooperative breeding

Cooperative breeding is a social system in which individuals care for offspring that are not their own. Cooperative systems vary along a continuum of reproductive sharing from egalitarian mutual care of several females’ offspring in a joint brood to highly skewed care of a single female’s offspring by non reproductive helpers.

The colonies of advanced eusocial insects, such as army and leaf-cutter ants, honeybees, yellow-jacket wasps, and fungus-growing termites, have been likened to superorganisms because the activities of colony members are so well integrated and show little evidence of internal conflict

However, to avoid anarchy and wasteful searching and repetition, there is a basic organization with division of labor among the workers. Task allocation is determined primarily by age, with newly emerged workers

Specific inside tasks are allocated based on perception of cues and a self-organizing system, which we shall describe in detail in