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Research focus: How "Pay to Stay" functions in different animal species

Why we chose it: We chose to research this topic in part because the phrasing of it sounded quite interesting when listed on the guidelines document. We also wanted to see the difference between that and kin selection. From there, we found that the potential to link new information we learn to things we've covered in class sounded really interesting.

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We plan to define the pay-to-stay hypothesis and explain how it relates in cichlids. This includes how pay-to-stay affects or is affected by other mechanisms like kin selection, prestige, and group augmentation. We will also cover how the pay-to-stay functions similarly or and differently in different animal species.

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Josh DeVoogd

Kyliana Schipper

Bree Stemplewski

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How prevalent are pay-to-stay behaviors within cichlid populations?

If subordinates stay to help breeders, are they benefited in return?

Is the pay-to-stay hypothesis seen in different species, what are the different functions and behaviors?

Is pay-to-stay more prominent in cichlids compared to other mechanisms?

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The researchers in this article look at a species of cichlid in order to determine whether helpers will "pay" more in instances with a higher demand, and if they do so with behaviors that are considered cheap or expensive. They determined that kin selection alone did not account for the dynamics seen in this species due to the fact that helpers stay even when the breeding pair dies and is replaced with one not related to the helpers. The fish were divided into high density and low density concentrations in order to simulate situations of higher stress and lower stress. Helpers showed far more defensive behaviors in high stress environments than low stress environments, and that generally the larger a helper was (and, in turn, the higher their cost), the more helping behaviors they did. These findings are consistent with the pay-to-stay hypothesis. The limitations of this article with our project lies largely in the fact that most literature on the hypothesis seems to have been done on various species of cichlids, so we are seeing little variation in our research in order to compare different species. This may be something we need to discuss as a group--perhaps our focus should shift from comparison to a deep dive on cichlids specifically.

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Pay-to-stay hypothesis theorizes that lesser ranked members in a group will help higher ranked members in order to remain in the territory.

Kin selection theory proposes that an organism will more readily help a relative at their own expense due to the close genetic relatedness between them.

Signals of prestige are displays of a dominant individual that indicate and help solidify their rank to subordinate individuals. Prestige itself is just the social standing of an animal which can provide benefits if their rank is high enough.

Group augmentation is the building of group size in order to gain benefits. These benefits often come from collective help in resource gathering, defense, and sometimes care of young.

Because these four factors tend to be closely related at times. It has proven difficult for researchers to tease apart pay-to-stay's direct effect compared to other mechanisms.

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Cichlids are from the Cichlidae family, Neolamprologus Cichlids are the most studied species for the pay-to-stay hypothesis. This species is regularly occurring in eastern Africa, however the Neolamprologus Devosi is found in the Malagarasi River, in Lake Tanganyika. They often range from 3-5 inches in length, with a sleek brightly colored body.

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This article broke down the problem into three main questions; why do subordinates stay instead of dispersing to breed, why do subordinates forgo breeding with the group, and why do they help raise the young of the breeders?

The Neolamprologus pulcher was the species being focused on, found in Lake Tanganyika. The breeding male is usually the largest male in the group, with be breeding female being the next largest. Both the breeding pair and helpers defend and maintain the territory, as well as caring for the young. It was found that the helping females would produce eggs, leading to believe they might be helping in order to breed within the group. These results represented a step towards linking immediate reproductive benefits and helping behavior.

When looking at the benefits to the breeders, it was found that a breeding pair with helpers had higher rate of absolute breeding success than a breeding pair without helpers. Under natural conditions there was positive correlation between fry emerging and and the number of helpers. Fry had lower survival rates in groups where the helpers were removed. It was noted that territory size is a driving factor for breeding fitness, also that helpers being removed experimentally can disrupt the hierarchy of the social group, mothers may adjust their levels of investment due to amount of helpers present, and it is unsure which aspect of the helpers behavior leads to the proposed benefits.

Four possible hypotheses of why helpers help; Kin selection, pay-to-stay hypothesis, signals of prestige, or group augmentation hypothesis. In order to find which explanation could be responsible for helping, there are further evaluations of predictions and long term investigations that need to be conducted. There are many factors making it difficult to determine if the pay-to-stay hypothesis has the biggest impact on helpers.

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Balshine-Earn, S., Neat, F. C., Reid, H., & Taborsky, M. (1998). Paying to stay or paying to breed? Field evidence for direct benefits of helping behavior in a cooperatively breeding fish. Behavioral Ecology, 9(5), 432-438.

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Zöttl, Markus, et al. “Kinship Reduces Alloparental Care in Cooperative Cichlids Where Helpers Pay-To-Stay.” Nature Communications, vol. 4, no. 1, 8 Jan. 2013, pp. 1–9. Google Scholar, www.nature.com/articles/ncomms2344, https://doi.org/10.1038/ncomms2344. Accessed 4 Apr. 2024.

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Of the four mechanisms that referred to in this presentation, pay-to-stay has both empirical and theoretical support despite being much less researched compared to kin selection. However, most of the empirical data gained has come almost exclusively from cichlids. This seemed a little strange at first because most of the time when a nonspecific trait in an animal is researched, researchers tend to branch off and observe the trait in different animals. Upon further investigation the reason cichlids are so popular is likely because of the supporting data they provide. Many field and laboratory studies show that pay-to-stay is especially strong in cichlids. Direct evidence appears to have been hard to find in other species with pay-to-stay seeming more like it is just speculation. For this reason cichlids seem like the clear choice for resource.

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Pay-to-Stay vs. Other Mechanisms (Concepts) 

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Pay-to-Stay vs. Other Mechanisms (Concepts) 

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In this article pay-to-stay is recognized as just one of many mechanisms related to why there are cooperative behaviors at the helping individual's expense. Kin selection is a mechanism where relatives help each other in order to benefit their own indirect fitness. This is because of the close genetic relatedness.

There are three other proposed mechanisms to explain this which benefit direct fitness. The first of them is group augmentation. Simply by the members of a group collectively helping out, the survival rate of the group is exponentially higher. This also leads to more reproductive opportunity as they get to live longer than otherwise, but also may get additional benefits. This can include territory inheritance or learned skills that allow for more successful mating attempts.

The second proposed mechanism is social prestige. By helping out dominants, their own rank can potentially rise. Eventually this may lead to them becoming dominant or gaining access to mates.

The last of these mechanisms is pay-to-stay. If the cost of a subordinate being in a group is too high, then they can offset this by helping out, so they remain needed. High costs that force helpers into these scenarios include resource and reproduction competition. On the other hand, helpful tasks to offset this include territory defense and brood care.

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This article questions if helpers are paying to stay or paying to breed, specifically direct benefits of helping behaviors in cooperative breeding fish. Reporting on Two experiments that tested the territory inheritance and pay-to-stay hypotheses in cichlids. Many studies showed that helpers are often prevented from breeding due to an environmental factor, why they stay is the main question. Helpers might benefit by receiving the same help in the future, gaining protection and feeding benefits, gaining experience in parental care, increasing the probability of survival through group augmentation, and increasing the probability of finding a mate or territory. Of the 74 families of cichlids studied, the average family had five helpers. Helpers that were separated then reintroduced were either passively accepted back or were subject to harassment, nine returning helpers were attacked by the other helpers.the proposed explanations for these actions are finely tuned visual recognition allows them to know what helpers are theirs, acceptable presence of helpers and unwelcome strangers, breeders largely ignored helpers and removed helpers were recognized.Lazy helpers might be attacked for their lack of help. Why did the returning helpers actually help more, theorized to reduce the likelihood of eviction and attacks, or to signal commitment to the group.

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Paying to stay or paying to breed? Field evidence for direct benefits of helping behavior in a cooperatively breeding fish

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Abstract. Several hypotheses aim to explain the evolution of helping behavior, but conclusive experimental support for evaluating the relative importance o

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Koenig, W. D., & Walters, E. L. (2011). Age-related provisioning behaviour in the cooperatively breeding acorn woodpecker: testing the skills and the pay-to-stay hypotheses. Animal Behaviour, 82(3), 437–444. https://doi.org/10.1016/j.anbehav.2011.05.028

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Pay-to-Stay vs. Other Mechanisms (Experiment)

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Pay-to-Stay vs. Other Mechanisms (Experiment)

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In different groups of cichlids various members were removed, then reintroduced. This was to observe how other cichlids (namely dominant ones) would respond to the absence, then reintroduction of helpers. Before all else the researchers would observe to identify a fish as a focal helper. In other words, a fish that seemed more helpful than its peers. Each treatment was done on multiple families and groups.

Control: The focal helper was placed in a plastic cylinder which was relocated nearby it's home and territory. This fish was only held for five minutes before being released. The researchers left and returned 24 hours later to observe them for 10 minutes. When possible, this was done alongside the prevented help treatment. This was mainly done just to see how the fish react to the manipulations of the researchers.

Prevented help treatment: The focal helper was placed in a plastic cylinder that was attached to a custom shelter. This was also placed nearby the fish's home and territory. When in the custom shelter they seemed to swim around not under any stress. One of the cichlids returned to the shelter after being released. The purpose of this treatment was to have the fish present, but unable to participate in help. Researchers returned 24 hours later, released the cichlid, and then observed for 10 minutes.

Helper removal treatment: The focal helper was trapped in a mesh cage and removed from the colony. It was reintroduced 24 hours later where the researchers then observed behaviors for 10 minutes. The researchers would return an additional 24 hours later to see if the reintroduced fish was accepted back into the family.

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Pay-to-Stay vs. Other Mechanisms (Results) 

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Pay-to-Stay vs. Other Mechanisms (Results) 

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In small groups, they were much more defensive in response to the control than larger groups. In the preventative help treatment, the reintroduced helper exhibited heavy submission toward other group members. They also received much more aggressive behavior compared to the cichlid from the control. Larger groups also translated to more submissive behavior from the reintroduced member as well as higher aggression from other members.

After release, all treatment groups (not including control) were less defensive. Helpers were much less defensive in large groups, while breeders were much less defensive in small groups. In these small groups breeders were also the primary aggressors. In large groups the aggressors tended to be other helpers of similar size.

While there were families that existed within the groups, they were not all closely related like in certain other social animals. The helpers often helped out more than their own family showing that kin selection wasn't nearly as strong as pay-to-stay. The main motivation for the fish to help out seemed to be the avoidance of ostracization of when they don't help out. This lines up with the pay-to-stay hypothesis where if they don't contribute enough for their cost of living, then they get put in their place.

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Josh DeVoogd - Kinship reduces alloparental care in cooperative cichilds where helpers pay-to-stay

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Josh DeVoogd - Kinship reduces alloparental care in cooperative cichilds where helpers pay-to-stay

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The article primarily focuses on the relationship between kinship theory, alloparenting, and pay-to-stay behavior. Between different vertebrates it was found that multiple of conducted studies didn't follow what was expected in regard to kinship theory. Different animal groups studied include mammals, fish, birds, and insects. Help that was deemed substantial would not only appear between kin, but was also given by unrelated individuals. This led to a hypothesis. If these unrelated individuals are helping out substantially, then they must be benefitting in their own direct fitness somehow. A big key point in direct fitness is simply being alive to reproduce. The main benefit in pay-to-stay behavior seems to be basic survival, but can also include reproductive access. However, it still seems to follow a similar set of rules set by kin selection. For an individual to engage in pay-to-stay behavior, the benefit of being part of a larger group has to outweigh the cost of helping out. The benefit doesn't have to just be a communal benefit (like being part of a big group). The benefit can come in the form of limited resources and additional protection from predators. Sometimes it may be direct access to reproduction. On the other hand, the more dominant members of the group may coerce subordinates to help if the cost of having them around is high. Such as an increase in resource consumption. The help subordinates give often comes in the form of helping raise dominant members' young. This doesn't sound very different from kin selection, but the key difference is the lack of relatedness. The benefit of unrelated individuals tends to be closer to direct fitness as opposed to indirect fitness seen often in kin selection. Pay-to-stay and kin selection go hand in hand. If paying attention to just one, they would imply the opposite of what the other does. For example, kin selection assumes that high relatedness translates to a high amount of help due to indirect fitness. However, pay-to-stay implies that unrelated individuals would help more than related individuals due to benefits in direct fitness. For this reason, kinship is taken into account in the pay-to-stay hypothesis. This allows different levels of relatedness and help to be analyzed. A problem I have in this article is that although they demonstrate how all of these things are intertwined. It doesn't really give a clear idea on how relatedness actually affects help. The article introduces different ideas that go hand in hand, but also somehow directly oppose each other.

Knowing just how complex this all is, for out group our focus could shift to analyzing a specific animal species and how the many factors affect pay-to-stay behavior in that species.

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Seen in Other Species: Acorn Woodpeckers

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Seen in Other Species: Acorn Woodpeckers

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This article is testing both the skills and pay-to-stay hypotheses by examining acorn woodpeckers and the relationship between provisioning behavior of helpers and where they end up. If there is evidences that by provisioning, helpers stay in the group longer in a way that benefits them later, which was proposed by the pay-to-stay hypothesis.

They studied a color-marked population at the Hastings Reservation in California, between 1979 and 2010. During this time the population was monitored continuously. when testing the skills hypothesis they examined the age related feeding rates of the helpers, the dependent variable being the feeding rate per hour. When testing the pay-to-stay hypothesis they expected more useful helpers to stay in the native populations longer than less useful helpers. However, there was a potential confound, the birds that remained as helpers were more likely to inherit the territory, not because of their behavior but for being around for longer.

The findings are consistent with the two key pay-to-stay predictions, the more useful helpers remain as helpers for longer and by doing so they gained fitness benefits. However, the pay-to-stay hypothesis assumes helpers that are not preforming at the expected rate are potentially evicted from the group. The acorn woodpecker population did not show this behavior, helpers maintain access to resources despite their provisioning rate of the groups young. Some of the helpers that feed less have more time to look for reproductive opportunities.

The pay-to-stay behavior may not have been the only one seen but there are aspects of it along with kin selection and environmental factors that lead to these behaviors. As discussed in class there are many benefits to these Acorn Woodpeckers behaviors, from increased awareness and learning, having supply for slow seasons, increasing relative fitness of other young and access to resources.

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Example of Acorn Woodpecker behaviors

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Acorn Woodpecker Family Guards Their Stash

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Researchers Trapote et al (2020) examined the details of cooperative breeding in carrion crows (Corvus corone). Their initial hypothesis was that these crows would act in accordance with Pay-To-Stay behaviors, and the data they found supported this theory.

They focused on a series of populations located in an agricultural region of northern Spain. In these groups, there was often a dominant breeding pair, female offspring, male offspring, and immigrant males present. A clear social hierarchy is also displayed through their prioritized access to food: the dominant breeding male is at the top, followed by male immigrants, male offspring, the dominant breeding female, and the female offspring in that order.

This social hierarchy was found to be a factor in the degree to which they intentionally displayed caretaking behaviors for new offspring in the nest. Researchers observed instances in which non-breeding individuals visited the nests of breeding individuals specifically while the dominant individuals were present. The relevance of this in regards to the study being conducted lies in the idea that, in a pay-to-stay society, the more an individual has been observed helping the breeding pair, the less likely they are to be kicked out of the group.

The results of this study did indeed support this idea: non-breeding individuals of lower social standing were more likely to visit the nests of the breeding pair while they were present, likely due to an increased risk of being kicked from the group.

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S;, W. M. (n.d.). The evolution of cooperative breeding in the African cichlid fish, Neolamprologus Pulcher. Biological reviews of the Cambridge Philosophical Society. https://pubmed.ncbi.nlm.nih.gov/20849492/

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Trapote, E., Canestrari, D., & Baglione, V. (2021). Female helpers signal their contribution to chick provisioning in a cooperatively breeding bird. Animal Behaviour, 172, 113-120.

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The pay-to-stay hypothesis is just one minor piece of cooperative breeding and cooperation within animal species. Many different factors and pressures lead to behaviors of those in the group, the pay-to-stay hypothesis expects those that do not provide the minimum expected rate of help to be removed from the group, or resource access become limited. Many studies do not show these specific behaviors, more testing on the hypotheses is required.

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We have a lot of data from cichlids to the point that we can more easily understand what pay-to-stay looks like in different animals. Now we should be able to more readily explore this mechanism in other species.

Broadly pay-to-stay is now understood, but knowing this we can maybe more easily tease apart different components of it. It may also be much easier now to develop research opportunities where the other mechanisms can be compared in species alongside it.

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Fischer, S., Zöttl, M., Groenewoud, F., & Taborsky, B. (2014). Group-size-dependent punishment of idle subordinates in a cooperative breeder where helpers pay to stay. Proceedings of the Royal Society B: Biological Sciences, 281(1789), 20140184.