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1. Damage from intraspecific combat is costly

   https://doi.org/10.1093/beheco/arab090  

   Emberts, Zachary; Somjee, Ummat; Wiens, John J (August 2021, Behavioral Ecology)

   Briffa, Mark (Ed.)

   Abstract When individuals engage in fights with conspecifics over access to resources, injuries can occur. Most theoretical models suggest that the costs associated with these injuries should influence an individual’s decision to retreat from a fight. Thus, damage from intraspecific combat is frequently noted and quantified. However, the fitness-related costs associated with this damage are not. Quantifying the cost of fighting-related damage is important because most theoretical models assume that it is the cost associated with the damage (not the damage itself) that should influence an individual’s decision to retreat. Here, we quantified the cost of fighting-related injuries in the giant mesquite bug, Thasus neocalifornicus. We demonstrate that experimentally simulated fighting injuries result in metabolic costs and costs to flight performance. We also show that flight costs are more severe when the injuries are larger. Overall, our results provide empirical support for the fundamental assumption that damage acquired during intraspecific combat is costly. 

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2. Weapon performance drives weapon evolution

   https://doi.org/10.1098/rspb.2020.2898  

   Emberts, Zachary; Hwang, Wei Song; Wiens, John J. (January 2021, Proceedings of the Royal Society B: Biological Sciences)

   Many sexually selected traits function as weapons, and these weapons can be incredibly diverse. However, the factors underlying weapon diversity among species remain poorly understood, and a fundamental hypothesis to explain this diversity remains untested. Although weapons can serve multiple functions, an undeniably important function is their role in fights. Thus, a crucial hypothesis is that weapon diversification is driven by the evolution of weapon modifications that provide an advantage in combat (e.g. causing more damage). Here, we test this fighting-advantage hypothesis using data from 17 species of coreid bugs. We utilize the fact that male–male combat in coreids often results in detectable damage, allowing us to link different weapon morphologies to different levels of damage among species. We find that certain weapon morphologies inflict much more damage than others, strongly supporting the fighting-advantage hypothesis. Moreover, very different weapon morphologies can inflict similarly severe amounts of damage, leading to a weapon performance landscape with multiple performance peaks. This multi-peak pattern could potentially drive different lineages towards divergent weapon forms, further increasing weapon diversity among species. Overall, our results may help explain how sexually selected weapons have evolved into the diversity of forms seen today. 

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3. Drosophila mutants lacking the glial neurotransmitter-modifying enzyme Ebony exhibit low neurotransmitter levels and altered behavior

   https://doi.org/10.1038/s41598-023-36558-7  

   Pantalia, Meghan; Lin, Zhi; Tener, Samantha J.; Qiao, Bing; Tang, Grace; Ulgherait, Matthew; O’Connor, Reed; Delventhal, Rebecca; Volpi, Julia; Syed, Sheyum; et al (December 2023, Scientific Reports)

   Abstract Inhibitors of enzymes that inactivate amine neurotransmitters (dopamine, serotonin), such as catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO), are thought to increase neurotransmitter levels and are widely used to treat Parkinson's disease and psychiatric disorders, yet the role of these enzymes in regulating behavior remains unclear. Here, we investigated the genetic loss of a similar enzyme in the model organismDrosophila melanogaster. Because the enzyme Ebony modifies and inactivates amine neurotransmitters, its loss is assumed to increase neurotransmitter levels, increasing behaviors such as aggression and courtship and decreasing sleep. Indeed,ebonymutants have been described since 1960 as aggressive mutants, though this behavior has not been quantified. Using automated machine learning-based analyses, we quantitatively confirmed thatebonymutants exhibited increased aggressive behaviors such as boxing but also decreased courtship behaviors and increased sleep. Through tissue-specific knockdown, we found thatebony’s role in these behaviors was specific to glia. Unexpectedly, direct measurement of amine neurotransmitters inebonybrains revealed that their levels were not increased but reduced. Thus, increased aggression is the anomalous behavior for this neurotransmitter profile. We further found thatebonymutants exhibited increased aggression only when fighting each other, not when fighting wild-type controls. Moreover, fights betweenebonymutants were less likely to end with a clear winner than fights between controls or fights betweenebonymutants and controls. Inebonyvs. control fights,ebonymutants were more likely to win. Together, these results suggest thatebonymutants exhibit prolonged aggressive behavior only in a specific context, with an equally dominant opponent. 

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4. Determinants of hyena participation in risky collective action

   https://doi.org/10.1098/rspb.2023.1390  

   Montgomery, Tracy M; Lehmann, Kenna_D S; Gregg, Samantha; Keyser, Kathleen; McTigue, Leah E; Beehner, Jacinta C; Holekamp, Kay E (November 2023, Proceedings of the Royal Society B: Biological Sciences)

   Collective action problems arise when cooperating individuals suffer costs of cooperation, while the benefits of cooperation are received by both cooperators and defectors. We address this problem using data from spotted hyenas fighting with lions. Lions are much larger and kill many hyenas, so these fights require cooperative mobbing by hyenas for them to succeed. We identify factors that predict when hyena groups engage in cooperative fights with lions, which individuals choose to participate and how the benefits of victory are distributed among cooperators and non-cooperators. We find that cooperative mobbing is better predicted by lower costs (no male lions, more hyenas) than higher benefits (need for food). Individual participation is facilitated by social factors, both over the long term (close kin, social bond strength) and the short term (greeting interactions prior to cooperation). Finally, we find some direct benefits of participation: after cooperation, participants were more likely to feed at contested carcasses than non-participants. Overall, these results are consistent with the hypothesis that, when animals face dangerous cooperative dilemmas, selection favours flexible strategies that are sensitive to dynamic factors emerging over multiple time scales. 

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5. How Does Past Performance of Competitors Influence Designers’ Cognition, Behaviors, and Outcomes?

   https://doi.org/10.1115/1.4054604  

   Shergadwala, Murtuza N.; Panchal, Jitesh H.; Bilionis, Ilias (October 2022, Journal of Mechanical Design)

   Abstract Existing literature on information sharing in contests has established that sharing contest-specific information influences contestant behaviors, and thereby, the outcomes of a contest. However, in the context of engineering design contests, there is a gap in knowledge about how contest-specific information such as competitors’ historical performance influences designers’ actions and the resulting design outcomes. To address this gap, the objective of this study is to quantify the influence of information about competitors’ past performance on designers’ belief about the outcomes of a contest, which influences their design decisions, and the resulting design outcomes. We focus on a single-stage design competition where an objective figure of merit is available to the contestants for assessing the performance of their design. Our approach includes (i) developing a behavioral model of sequential decision making that accounts for information about competitors’ historical performance and (ii) using the model in conjunction with a human-subject experiment where participants make design decisions given controlled strong or weak performance records of past competitors. Our results indicate that participants spend greater efforts when they know that the contest history reflects that past competitors had a strong performance record than when it reflects a weak performance record. Moreover, we quantify cognitive underpinnings of such informational influence via our model parameters. Based on the parametric inferences about participants’ cognition, we suggest that contest designers are better off not providing historical performance records if past contest outcomes do not match their expectations setup for a given design contest. 

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