# data[].attributes.body
Why is it important?

The use of kin discrimination is important because it can prevent the use of inbreeding within species and it promotes the fitness of a species, both individual and populous. It also promotes better genes and larger gene pools.

# data[].attributes.headline
How species discriminate kin and non-kin: olfactory cues

# data[].attributes.subject
How species discriminate kin and non-kin: olfactory cues

# data[].attributes.body
Spermophilus beldingi or Belding's ground squirrel are a species that uses kin discrimination in order to carry out their nepotistic behaviors. Ground squirrels are able to differentiate between kin and non-kin via olfactory cues. Ground squirrels emit an odor from their oral and dorsal glands. This odor allows kin to recognize each other. Mateo (2003) found that ground squirrels spend significantly more time smelling the oral and dorsal glands of non-kin than they do kin. Mateo also reported that the amount of time spent investigating the smell of the other individual was inversely related to their relatedness. A ground squirrel will spend more time smelling the glands of their cousin and less time smelling the glands of their brother. This is due to the fact that the smell of their brother is more familiar to them than the smell of their cousin, which may be more novel (Mateo, 2003). Belding's ground squirrels use this tactic in order to recognize those close to them so that they can show nepotistic behaviors towards them, such as cooperative breeding and protection.

# data[].attributes.body
This video shows the Belding Ground Squirrels working cooperatively for predator protection. The ability for these ground squirrels to discriminate kin promotes this cooperative protection behavior.

# data[].attributes.headline
How species discriminate kin and non-kin: Prior Association

# data[].attributes.subject
How species discriminate kin and non-kin: Prior Association

# data[].attributes.body
Kin recognition via prior association seems to sufficient in species who interact with their relatives with the absence of non-kin. Direct association allows relatives to become familiar with one another. However, if non-kin are encountered during the learning phase, this can lead to mistakes in recognition in which case phenotype matching is favored because it allows kin recognition without prior association (Mateo, 2003). In juvenile mites or Phytoseiulus persimilis, kin recognition via prior association is favored because it allows constant updating in modification of kin, for example, being able to recognize their offspring as they grow up (Schausberger, 2007).

# data[].attributes.headline
How species discriminate kin and non-kin: Phenotype Matching (Genetic Selection)

# data[].attributes.subject
How species discriminate kin and non-kin: Phenotype Matching (Genetic Selection)

# data[].attributes.body
Some species are able to discriminate kin and non-kin via phenotype matching. Assuming genotypic similarity is correlated with phenotypic similarity, an individual is able to learn and recall specific phenotypes of relatives that are likely similar to their own. The individual is able to compare the phenotypes of an unfamiliar individual to a phenotype "template" that they use for recognition. Recognizing phenotypes is a learned behavior, likely coming from experience with others, and experience with one's own self ( Lacy & Sherman, 1983). Examples of this is seen in many species. For example, Campylorhynchus nuchalis or stripe-back wrens are able to distinguish kin from non-kin based on vocalizations and calls (Price, 1999).

# data[].attributes.body
The effect of being able to recognize and therefore select from your kin leading to cooperative behavior is beneficial, however these models show that ability to assess relatedness isn’t necessarily a requirement for cooperation. In many scenarios it is difficult to discern why the cooperative behavior is happening at all. For instance, imagine a situation in which individuals of low genetic relatedness decide to cooperate which in turn leads to the formation of a family, or group of more closely related individuals who interact with each other more frequently. This leads to a confounding variable when trying to discern whether the cooperative behavior happened due to the ability to recognize kin, or because the individual favors cooperative behavior and as such cooperates with those around them who are by default now more related because they’re family.

The linear and convex models describe scenarios in which though the high end or Z highis lower than the concave model, the ability to discriminate between individuals of higher genetic relatedness is expected an at least equal or greater effect on cooperation as compared to when the veil of ignorance model is favored. The linear model displays a situation where because levels of cooperation where discrimination is happening has just as much of an effect on cooperation as the ability to recognize relatedness, a choice made through either motivation will lead to higher levels of cooperation. Or in other words, the rate of cooperation is the same regardless of ability to recognize relatedness. Whereas the convex model shows us even though the levels of overall cooperation are lower by comparison to the other two models, cooperation happens more frequently due to the ability to recognize kin.

This study attempts to show cooperation levels as a function of relatedness independent from a species biology. Meaning they tried to display a result that isn’t influenced by the species biological or genetic ability to differentiate between members of the same species. They also assumed the cost and benefit functions of cooperation were the same across the board as well as the personal-fitness effects of a given amount of cooperation for the actor and recipient being independent of their relatedness to one another. With these variables held constant, the study did indeed show through both the linear and convex models that kin discrimination is shown to lead to increased or at least equivalent levels of cooperation when compared to the levels expected in the “veil of ignorance” scenario. (Faria & Gardner, 2020)

# data[].attributes.headline
How Genetic Relatedness Can Affect Discrimination Ability

# data[].attributes.subject
How Genetic Relatedness Can Affect Discrimination Ability

# data[].attributes.body
Though a lot of assumptions were made, that study still shows us that, independent of all other factors that have been observed to influence levels of cooperation otherwise positively, increased relatedness usually leads to increased cooperation between members of the same species. Prior association, olfactory cues, and the genetic ability to recognize phenotypes in a species have all been shown to lead to increased levels of cooperation, and in turn that cooperative behavior often comes with direct and indirect benefits to the individual’s reproductive fitness. Whether the cooperation manifest itself through shared parental burden, communal resource acquisition and allocation, or through increased group stability/protection, ultimately kin discrimination serves well to explain how cooperative behavior is beneficial to a species survival and therefore leads to their propagation.

# data[].attributes.body
One exception of animal behavior that falls slightly short of the traditional model of kin selection is the actions of the banded mongoose. In this species, dominant individuals in the group target female members who are of greater genetic relatedness for group eviction even when less related, but otherwise equivalent targets are available. Traditionally, the ability to recognize kin usually leads to an increase in cooperative behavior but that is not the case here. There are a few possibilities as to why this behavior occurs in this manner. (Thompson, Cant, and Marshall, 2017)

# data[].attributes.body
First is that local competition amongst kin can erode selection for local helping and instead favor indiscriminate harming or aggressive behavior. Second is that there is some confounding factor tied to genetic relatedness such as resource holding potential (RHP) or similar reproductive ability. This second theory however could be ruled out by the study linked above as they found no evidence to support the claim that closer related females were of higher RHP or any type of reproductive threat. In fact, younger females who reproduce less often and have low RHP are more often targeted for eviction.

# data[].attributes.attachment_caption
Evictees more related to the dominant member of the group, the more likely the eviction and also once evicted, less related individuals came back more frequent

# data[].attributes.body
The most widely accepted theory however is that targeting relatives for eviction could be part of an adaptive forced dispersal strategy by breeders to maximize the overall population fitness in an indirect way. This idea however is difficult to prove as it isn’t well studied and there are many confounding variables at play in any given eviction attempt. Moreover, dispersal entails direct costs for individuals who leave their kin but is nevertheless favored because it reduces local competition.

# data[].attributes.body
This video explains the violent eviction behavior towards older females by dominant individuals through the lens of kin discrimination. The desire to increase the number of their offspring that survive and thrive appears to be the driving force behind this negative kin discrimination.

# data[].attributes.attachment_link.title
Violent evictions: targeted females in mongoose family groups.

# data[].attributes.body
Kazem, A. J., & Widdig, A. (2013). Visual phenotype matching: cues to paternity are present in rhesus macaque faces. PloS one, 8(2), e55846. https://doi.org/10.1371/journal.pone.0055846

Lacy, R. C., & Sherman, P. W. (1983). Kin Recognition by Phenotype Matching. The American Naturalist, 121(4), 489–512. http://www.jstor.org/stable/2460977

Mateo, J. M. (2003). Kin recognition in ground squirrels and other rodents. Journal of Mammalogy, 84(4), 1163–1181. https://doi.org/10.1644/ble-011

Price J. J. (1999). Recognition of family-specific calls in stripe-backed wrens. Animal behaviour, 57(2), 483–492. https://doi.org/10.1006/anbe.1998.1018

Schausberger, P. (2007). Kin Recognition by Juvenile Predatory Mites: Prior Association or Phenotype Matching? Behavioral Ecology and Sociobiology, 62(1), 119–125. https://doi.org/10.2307/25511674

Faria, G. S., & Gardner, A. (2020). Does kin discrimination promote cooperation? Biology Letters, 16(3), 20190742. https://doi.org/10.1098/rsbl.2019.0742

Thompson, F. J., Cant, M. A., Marshall, H. H., Vitikainen, E. I., Sanderson, J. L., Nichols, H. J., Gilchrist, J. S., Bell, M. B., Young, A. J., Hodge, S. J., & Johnstone, R. A. (2017). Explaining negative kin discrimination in a cooperative mammal society. Proceedings of the National Academy of Sciences, 114(20), 5207–5212. https://doi.org/10.1073/pnas.1612235114

# data[].attributes.body
Mateo, J. M. (2003). Kin recognition in ground squirrels and other rodents. Journal of Mammalogy, 84(4), 1163–1181. https://doi.org/10.1644/ble-011

Jill Mateo explains the kin discrimination among Belding's ground squirrels or Spermophilus beldingi as well as other rodents. This is an in-depth review of how they use olfactory cues in order to discriminate kin from non-kin and potentially why kin discrimination is important in their species. Although ground squirrels are able to discriminate their kin by phenotype matching and prior association, the author focused on their olfactory cues. Ground squirrels emit an odor from their oral and dorsal glands. They are able to recognize this smell and discriminate kin from non-kin. One reason that kin discrimination is important to them is because they exhibit nepotistic behaviors. If they are able to recognize kin as "theirs", then they are able to display these nepotistic behaviors towards them. These behaviors include territory defense and the production of alarm calls. The results of their odor tests in the ground squirrels were that they produce more similar odors among close kin than distant kin. The ground squirrels also inversely spent more time investigating an odor as the level of relatedness decreased. I think that this article is really good information about the specifics of one species' ability to discriminate. There is also good surface level information about other species that can be used to learn more. I also think that this article explains a lot of information about kin discrimination in general in its background and introduction. Overall, I think this article is a great start, gives us a lot of background on the topic and will gives ideas for further research.

# data[].attributes.body
Sex Differences in Offspring Discrimination in the Biparental California Mouse (Peromyscus Californicus)

Nguyen, C. T. Y., & Saltzman, W. (2021). Sex differences in offspring discrimination in the biparental California mouse (Peromyscus californicus). Journal of Ethology, 39(3), 309–318. https://doi.org/10.1007/s10164-021-00705-2

The researchers of this study focused on the California mouse or the  California deer-mouse, and wanted to look into whether or not there are sex differences regardings discrimination amongst kin. The study presented a total of 12 mated pairs (N=24). Each parent was presented with two pups ( kin v. non-kin) during postpartum days (referred to as PPD in the study; days examined 3,7, 16, and 28) and each pair were presented the same. They did this to test and see if there was any kin discrimination occuring between the sexes. They primarily believed that mothers would have higher rates of discrimination in comparison to the father. The presentation of the pups to the parents were randomized, however the pups appeared to be relatively close in size and shape. The idea was to see if the parents would go to their “kin” or not. When the data was compared regarding the pups (kin and non-kin), no major differences were found when analyzed. The only significant finding during this analysis was that fathers would spend less time sniffing or being around the pup that was not related to them. A lot of observed behaviors that the male mice or fathers conducted were inconsistent and were not of any significance.

# data[].attributes.body
Reference: Patel, M., West, S. A., & Biernaskie, J. M. (2020). Kin discrimination, negative relatedness, and how to distinguish between selfishness and spite. Evolution Letters, 4(1), 65–72. https://doi.org/10.1002/evl3.150

The authors of this study aim to distinguish spitefulness and selfishness using mathematical models and the relationship between those behaviors and kin discrimination. Spiteful behavior involves an individual harming itself for the intention of inflicting harm on another individual. It had been argued that spite and kin discrimination go hand and hand while specifically being favored when the harming is taking place on an individual of lesser similarity. The argument is whether indiscriminate spite is possible. Given the evolution of spite, many had come to the conclusion that indiscriminate spite is impossible. However, several studies have predicted that spiteful behavior directed at others indiscriminately could be favored in smaller populations. The focal actor (C) will be portrayed as negative due to the automatic cost of being spiteful. The two types of recipients of spiteful behavior, one who is harmed primary recipients (B1) and the unharmed secondary recipients who benefit from reduced competition (B2), result in the equation of –C+B1+B2=0 where if the fitness of C decreases then that is an automatic increase for the recipients. Using more mathematical models, the authors explain the conditions for a harming trait and if it can be classified as spiteful or selfish. Mathematical models suggest that negative relatedness will only arise if the harm can be directed to primary recipients who have less genetic similarity than secondary recipients which explains that indiscriminate spite cannot evolve but will be favored when it is done out of selfishness with a positive direct fitness benefit. Previous studies have misclassified indiscriminate harming as spite hen indiscriminate harming traits are rather selfish. While this article does not correlate kin discrimination with cooperation, the article does steer into a direction of how kin discrimination leads to the opposite. I found the data and hypothesis to be interesting and seemed to be helpful navigating scenarios using mathematical models. I would recommend this article to someone who is looking to do more research on aggressiveness and how kin discrimination is portrayed to kin and non-kin.

# data[].attributes.body
Thompson, F. J., Cant, M. A., Marshall, H. H., Vitikainen, E. I. K., Sanderson, J. L., Nichols, H. J., Gilchrist, J. S., Bell, M. B. V., Young, A. J., Hodge, S. J., & Johnstone, R. A. (2017). Explaining negative kin discrimination in a cooperative mammal society. Proceedings of the National Academy of Sciences, 114(20), 5207–5212. https://doi.org/10.1073/pnas.1612235114

Thompson and fellow authors state that traditionally when kin selection is possible, animals will typically act more favorably toward individuals that are closely related genetically to themselves, and more aggressively towards those who’re less related. In opposition to the norm however is a study of the wild banded mongoose, or Mungos mungo. In this species, females who’re closely related to the dominant individuals of a group are often targeted for eviction which results in injury and sometimes death in extreme cases. The negative kin discrimination displayed here in this species is restricted almost entirely to eviction behavior towards females capable of resistance, and the dominant mongoose also doesn’t exhibit kin discrimination when attempting to evict younger females or when carrying out infanticidal attacks on defenseless young. This is behavior is in contradiction to the normal model of kin discrimination and the behavior can’t be explained by inbreeding avoidance or local kin competition. So, this research team used game theory to show how negative kin discrimination can be explained by selection for unrelated targets to invest more effort in resisting eviction. Through an examination of a two-step game in which the first step asses the decision made by the aggressor, and the second step involving the resistance decision, the variables were cost of selfish act by aggressor, cost of resisting by evictee, benefit of aggressor, benefit of evictee, and a relatedness coefficient between aggressor and evictee. With all of these factors in mind and the results obtained, the research team concluded that it seems relatedness does indeed play a factor in this decision-making process. Which is to be expected in cases where kin discrimination applies, however, for mongooses the relatedness coefficient between the evictee and dominant females of the group was more important than almost any other factor. This study shows that in some species, kin selection theory doesn’t fully explain preferential altruistic behavior towards individuals of higher genetic relatedness. So, further exploration of subsequent social interactions proceeding selfish behavior will most certainly be of great benefit for a better understanding of the “why” behind this behavior. It seems aggressive and cooperative behavior within animal groups can be more subtle, variable, and nuanced than capable of explanation by traditional kin selection theory.