In general, pornography use trended downward over the pandemic, for both men and women; problematic pornography use trended downward for men and remained low and unchanged in women

Porndemic? A Longitudinal Study of Pornography Use Before and During the COVID-19 Pandemic in a Nationally Representative Sample of Americans. Joshua B. Grubbs, Samuel L. Perry, Jennifer T. Grant Weinandy & Shane W. Kraus. Archives of Sexual Behavior, Jul 19 2021. https://link.springer.com/article/10.1007%2Fs10508-021-02077-7

Abstract: Of the many changes in daily life brought about by the COVID-19 pandemic, social distancing efforts and governmentally mandated lockdowns were among the most drastic. Coinciding with these changes, popular pornography websites made some previously premium content available for free, spurring dramatic increases in traffic to these websites. This increase in time spent at home and reported increases in traffic to specific pornographic websites led to some speculation that pornography use might generally increase over the course of the pandemic and that problematic use might also increase. To test these speculations and quantify the effects of the pandemic and its associated restrictions on social behaviors on pornography use, we analyzed data from a longitudinal sample of American adults. Baseline, nationally representative data were collected in August 2019 via YouGov (N = 2518). Subsequent data were collected in February 2020 (n = 1677), May 2020 (n = 1533), August 2020 (n = 1470), and October 2020 (n = 1269). Results indicated that, in May 2020, immediately following the height of the first wave of pandemic-related lockdowns, more people reported past-month pornography use than at other follow-up time points, but less did so than at baseline. Among those who reported use in May 2020, only 14% reported increases in use since the start of the pandemic, and their use returned to levels similar to all other users by August 2020. In general, pornography use trended downward over the pandemic, for both men and women. Problematic pornography use trended downward for men and remained low and unchanged in women. Collectively, these results suggest that many fears about pornography use during pandemic-related lockdowns were largely not supported by available data.

Discussion

At the outset of this work, we sought to examine whether or not there was evidence that pornography use had increased in response to the COVID-19 pandemic and associated restrictions on social behavior. Using a longitudinal study that started with a nationally representative sample of adults in the U.S., we examined the extent to which pornography viewing frequency and PPU changed from August 2019 to October 2020. Below, we summarize our findings and discuss the implications of the present work in the context of the ongoing COVID-19 pandemic and associated lockdowns.

Pornography in the Pandemic

As we noted earlier in this work, the world’s largest pornographic website made claims of increased pornography use at the outset of the COVID-19 pandemic during the height of the first wave of lockdowns and stay-at-home orders (Pornhub Insights, 2020). These increases in pornography use occurred in tandem with this same website offering a range of incentives for increased use. Similarly, analyses of internet search data suggested that interest in pornography peaked during the early stages of the pandemic (Zattoni et al., 2020). Collectively, this led to speculation in popular media (Grubbs, 2020) and peer-reviewed journals (Király et al., 2020; Mestre-Bach et al., 2020; Sinclair et al., 2020) about the possibility for pornography use to increase over the course of the pandemic. However, the present results indicate that, overall, changes seen in pornography viewing during the first several months of the pandemic were generally minimal and impermanent for both men and women.

Over the course of data collection, we found that the majority (86%) of our sample reported either decreases or consistency in their pornography use during the height of pandemic-related lockdowns (i.e., May 2020). It is important to note that a minority of our sample (5% of our May 2020, follow-up sample; corresponding with 14% of those who viewed pornography within one month of our May 2020, wave; 14.6% of men, 13.7% of women) did report increases in pornography use during the first COVID-19-related lockdowns. However, even for this group, by August 2020 and continuing into October 2020, their use had returned to levels indistinguishable from levels of those who reported decreases or that their use had stayed the same. Although a greater percentage of participants reported viewing pornography within the past month in May 2020 than did so at any other follow-up (38%), the percentages of people reporting past-month use in August 2020 (23%) and October 2020 (20.6%) were substantially lower than prior waves. Moreover, though May 2020 demonstrated the highest pornography use of any follow-up, rates of use were still lower than baseline rates in August 2019. In short, although it seems that, in May 2020, more people did indeed view pornography within the past month than at other follow-up points, this is better characterized as slight deviation from an otherwise clear downward trend.

Results from our LGC analyses generally support the above findings. Across five time points, we found no evidence that general symptoms of depression and anxiety trended either downward or upward, but rather remained stable over the course of our study. We found clear evidence that pornography use frequency trended toward less use over the course of the pandemic for both men and women. With regard to self-reported PPU, we found that it trended downward for men. For women, PPU neither increased nor decreased, on average. That is, PPU among women remained low and consistently flat without any fluctuations over the five time points.

In sum, although concerns were raised that pornography viewing (and possibly PPU) could increase during the early part of the pandemic (Grubbs, 2020; Turak, 2020), our results do not fully support this conclusion. That is, the above findings suggest that pornography use generally decreased for both men and women over the 15 months of data collection, and, even among those who experienced initial increases in pornography use, such increases were temporary. The general trends for both pornography use and PPU were downward, particularly for men, with little change in PPU for women who started with already low levels of PPU.

Implications

Despite the public-facing concerns that many public outlets, activists, and even some academic researchers shared, there is little evidence to support the notion that widespread increases in pornography use were a problem among U.S. adults during the early stages of the COVID-19 pandemic and its associated lockdowns. Although it is certainly possible that individual experiences may vary (i.e., some people may have experienced increased PPU), the general trend was for both pornography use and self-reported PPU to decrease over the course of this study. We suspect that the novelty effects of viewing pornography, even with a premium subscription offered to entice new viewers by Pornhub, likely wore off as people adjusted to new routines and allocated their time to working from home or taking on new demands caused by the pandemic (e.g., online schooling for children, caring for family members). Perhaps more simply, as promotional offers of free premium content expired, people may have simply stopped consuming as much pornography. Additionally, as the initial lockdown periods expired and the weather became more amenable to outdoor activities across the U.S., it is also possible that people were spending less time alone at home. Such conjecture is consistent with the previously discussed literature noting that boredom often motivates pornography use and suggests that, as people found alternate ways to spend their time, boredom-motivated pornography use likely decreased.

We have largely framed the results of the present work in the context of mandatory lockdowns, rather than in the context of the pandemic itself. Specifically, though lockdowns and restrictions have largely eased in the U.S. since their initial peak in April and May 2020, the SARS-CoV-2 virus has spread at a much greater rate in the times since those lockdowns expired. Accordingly, it is important to note that the trend of pornography use decreasing over the course of this work has occurred as the objective markers of the pandemic itself have increased. This suggests that, whereas lockdowns, restrictions, and stay-at-home orders in the Spring of 2020 did coincide to more people reporting pornography use in May of 2020 than at any other follow-up, pornography use has trended downward even as the spread of the SARS-CoV-2 has trended upward. In short, although speculative, the effects of the pandemic and associated social distancing measures on pornography use seem to have occurred as a result of lockdown efforts (i.e., more boredom, increased free time), rather than responses to the virus itself (i.e., increased use of pornography to cope with fears about the virus).

Of the many explanations for the trends described above, a particularly obvious explanation is that use of pornography trended downward because people were, in general, less likely to have time alone to view pornography. Although some people do report using pornography with their partners, pornography use is most often a solitary activity (Kraus & Rosenberg, 2014) and quite often hidden from partners (Willoughby & Leonhardt, 2020). Additionally, among individuals who live with others (e.g., family, roommates), some level of privacy is typically required for one to use pornography. That is, the majority of people are unlikely to regularly view pornography in the company others, particularly when those others are not prospective sexual partners. Given that social distancing measures and travel restrictions led to people spending more time at home with others, it is quite possible that such measures also led to general downward trends in pornography use, though our data do not allow us to directly test this hypothesis.

Finally, we note that pornography use decreased from baseline measures in August 2019 to February 2020 (before the spread of SARS-CoV-2 in the U.S.), suggesting that downward trends in use may have happened without the pandemic. In general, it may be that people use less pornography over time. Although we examined pornography viewing over five time points, we did not measure individuals’ motives for viewing pornography (e.g., enhancement of dyadic sexual activity, assistance in solitary masturbation, alleviation of boredom or stress); it is possible that individuals’ motives for viewing pornography may have changed or shifted throughout the pandemic, particularly as people have found themselves under growing stressors due to recent economic, employment, health, and caregiving challenges attributed to the ongoing COVID-19 pandemic and associated restrictions on activity.

Limitations

Although results in the current study are novel and shed light on unanswered questions around the possible effects of COVID-19 on pornography viewing behaviors among U.S. adults, they are not without limitations. First, we used a short measure, the Cyber Pornography Use Inventory-4 (CPUI-4; Grubbs & Gola, 2019), to assess for PPU in the current study. The use of a brief PPU measure for a longitudinal study is advantageous (i.e., reduces burden and time for participants), but it also lacks the diagnostic accuracy of a clinical interview or clinically validated measure. Further work using a validated clinical measure of PPU, such as the Problematic Pornography Consumption Scale (Bőthe et al., 2018), would likely provide a better diagnostic picture of PPU. Second, although it is beyond the scope of this paper, further work is also needed to identify factors (e.g., demographic, clinical, personality) that can predict the development of PPU or changes in PPU status over time, particularly during periods of significant stress or unrest due to the COVID-19 pandemic. Third, we did not examine the possible effects of moral incongruence on self-reported PPU as noted in prior works (e.g., Grubbs, Lee, Hoagland, Kraus, & Perry, 2020), which suggests that religiousness can moderate the relationships between pornography and self-reported PPU. Fourth, we did not examine the potential effects of pornographic content consumed or whether or not individuals felt as if their preferences in pornographic content shifted or became problematic over the course of the pandemic. We also note that our measure of symptoms of depression and anxiety, the PHQ-4, although widely used as a general screening measure of such distress, is not a diagnostically precise instrument and only briefly captures symptoms of depression and anxiety. Symptoms of loneliness, feelings of boredom, COVID-19 specific anxiety, and general stress levels associated with pandemic-related lifestyle changes were not assessed and may have demonstrated different trends than what we observed in PHQ-4 scores. More simply, general depression and anxiety may not have been the best measure of pandemic-related distress.

Behavioral Ecology of the Family: Harnessing Theory to Better Understand Variation in Human Families

Behavioral Ecology of the Family: Harnessing Theory to Better Understand Variation in Human Families. Paula Sheppard, Kristin Snopkowski. Soc. Sci. 2021, 10(7), 275; Jul 19 2021. https://doi.org/10.3390/socsci10070275

Abstract: Researchers across the social sciences have long been interested in families. How people make decisions such as who to marry, when to have a baby, how big or small a family to have, or whether to stay with a partner or stray are questions that continue to interest economists, sociologists, demographers, and anthropologists. Human families vary across the globe; different cultures have different marriage practices, different ideas about who raises children, and even different notions of what a family is. Human behavioral ecology is a branch of anthropology that is particularly interested in cultural variation of family systems and how these differences impact upon the people that inhabit them; the children, parents, grandparents. It draws on evolutionary theory to direct research and generate testable hypotheses to uncover how different ecologies, including social contexts, can explain diversity in families. In this Special Issue on the behavioral ecology of the family, we have collated a selection of papers that showcase just how useful this framework is for understanding cultural variation in families, which we hope will convince other social scientists interested in family research to draw upon evolutionary and ecological insight in their own work.

Keywords: human behavioral ecology; kinship; marriage systems; cross-cultural variation; family formation; cooperation and conflict; cooperative breeding; kin networks

3. Conclusions

In this Special Issue, we illustrate the benefits of applying a theoretical framework to create directed research that can complement data-driven methods so commonly used in other social sciences such as demography and quantitative sociology. Human Behavioral Ecology recognizes that the currency that people are trying to maximize is fitness5, not wealth or status, or even health, even though those things are often quite strongly associated with fitness. This insight is the grounding of all HBE hypothesis-testing and can be harnessed to explain the immense variation in human social behavior. It can also explain how apparently illogical behavior, such as life-threatening risk-taking, or not pursuing a high-education pathway, may be a logical choice for some people given their current circumstances.

Human behavioral ecology is not only useful for understanding why people do the things they do but it has policy-relevant applications too. For instance, if we recognize that teenage pregnancy is often the product of limited choices and an unknown future that young women have in high-mortality neighborhoods (Geronimus et al. 1999) policymakers can focus attention on providing ways to improve young women’s health. Similarly, policy focused on reducing poverty, such as Universal Basic Income (Nettle 2018) can remove the insecurity of the future enabling people to prioritize long-term goals over short-term risks.

Here we have gathered an array of articles that demonstrate how the rich ecologies we inhabit as a diverse species can explain the myriad different family structures, reproductive outcomes, and social networks that we see across the world. We have also demonstrated the value of conducting cross-cultural research, not only because those cultures are intrinsically interesting but also because a global perspective can provide insights about societies and behavior in the global North.

Determinants of the Arab Spring Protests in Tunisia, Egypt, and Libya: The role of economic factors was inconsistent, whereas political grievances were more clearly related to the motive to participate in the uprisings

Determinants of the Arab Spring Protests in Tunisia, Egypt, and Libya: What Have We Learned? Zahraa Barakat, Ali Fakih. Soc. Sci. 2021, 10(8), 282; July 23 2021. https://doi.org/10.3390/socsci10080282

Abstract: This paper provides empirical evidence on the determinants of protest participation in Arab Spring countries that witnessed major uprisings and in which social unrest was most pronounced. Namely, this paper investigates the latter in Tunisia, Egypt, and Libya using a micro-level data survey, the Arab Transformation Survey (2015). The findings of our probit regression analysis reveal that gender, trust in government, corruption concern, and social media usage have influenced the individual’s perception of protest activism. We find evidence that the role of economic factors was inconsistent, whereas political grievances were more clearly related to the motive to participate in the uprisings. We then control for country-specific effects whereby results show that citizens in each country showed different characteristics of participation. The findings of this research would set the ground for governments to better assess the health of their societies and be a model of governance in the Middle East.

Keywords: Arab Spring; participation; protesting; probit model

6. Conclusions

This paper examines the factors behind participation in the Arab Spring demonstrations in Tunisia, Egypt, and Libya. Findings for all three countries reveal that set of socioeconomic and sociopolitical factors have established a motivation behind an individual’s decision to protest. The willingness to participate in uprisings was shown to be driven by political grievances rather than economic factors. The intention of such a result may reinforce the main determinant for conflict in weak MENA communities, suggesting that aspects of state fragility in MENA seem to be different than other societies in the world (Kivimäki 2021).

We find that the gender gap is significant in the examined sample, lack of trust in government showed to be a significant trigger towards protesting, social media played an essential role in influencing people to take part in protests, and governments’ attempts to combat corruption tend to decrease the probability of bringing people into streets. Indeed, each country had its roots for the uprisings; hence, our results show a substantial difference among the studied countries in citizens’ pattern toward rebellion. For instance, corruption and inequality seemed to increase the likelihood of protest participation in Egypt. We also find evidence that Egyptians with good health and who are satisfied with the economic development in their countries were engaged in political activism more often than those who are dissatisfied. As for Libyan citizens, males were more probable to join revolts. It was found that corruption, political freedom, lack of trust in government, and social media usage are the main drivers to prompt the protesting mechanism in Libya; however, satisfaction with the social security played a positive role in influencing people to join revolts. Lastly, Tunisia showed a gender gap difference in protest involvement. Regardless of the low magnitude, youth engagements tend to be significant, and usage of social media was correlated with a higher likelihood for political participation.

To further validate our findings, we can include other countries, increasing our sample size to helps us draw more accurate generalizations. Adding more economic indicators that were unfeasible to us and essential in having a better understanding whether participants were motivated by political change or economic grievances.

To reach a more diversified understanding of the “Arab Spring” and its broader implications requires looking at their margins; hence, the narration of the “Arab Spring” employing a more in-depth approach. Although revolts used the same slogans calling for freedom and the fall of the “regime”, considering them as a single revolution indicates a misguided viewpoint given the differences between distinct Arab countries (Ventura 2016, p. 285). Many groups anticipated their movements such as the “Arab Spring” for recognition purposes. On the other hand, terms such as Arab awakening is linked to a “Neo-Orientalist” world-view calling for people’s awareness in the Arab world about the West’s approach to portraying them as oppressed, under-civilized, and lacking agency, to the idea of “Arab despotism” and the belief that Western philosophical theology is the only path towards modernity, or the “Islamist Winter”, which was employed to swing the focus of the social movement to political and security threats (Huber and Kamel 2015, p. 129; Al-Kassimi 2021). In this context, the representation of the events taking place in MENA seems to be generalized and associated with the myth of “Oriental despotism” (Ventura 2016, p. 286). The neo-orientalist approach can be recognized based on how rebellions were gendered by considering how Arab women were seen as victims of oppression and required saving (Al-Kassimi 2021). For instance, Western media deployed a gendered issue out of the uprisings and the continuous calls for women’s rights confirm their “Orientalism” (Mahmood 2006; Abu-Lughod 2013; Abbas 2014; Ventura 2016, p. 291). Moreover, to state that all Arab are Muslims represents a neo-Orientalist myth (Mahmood 2006; Abu-Lughod 2013; Abbas 2014). The participation of women in the protest challenges the neo-orientalist approach whereby a broad range of females were involved in the protests. Whether on the ground or their heavily online presence on social media platforms, such as Leila-Zahra, Esraa Abdel-Fattah, and Lina Ben Mhenne, they played a major role as activists in women empowerment agenda. Such a deterministic frame necessitates a deeper recognition and deconstruction (Khalid 2015, p. 163). Of note, Western modernity has refuted the ideology of Arab women as being rational and competent authors of their political lives by limiting the intricacy of Arab cultural heterogeneity across the Mashreq and Maghreb (Al-Kassimi 2021, p. 26).

7. Policy Implications

Understanding the factors that gave rise to the uprising helps to better assess the health of our society and to provide guidance for strategies ensuring political stability. Governments shall rely on two main pillars to build citizenship and minimize the risk of political instability. The first pillar is forming an anticorruption ecosystem by taking solid and firm actions to fight the existing corruption. Some measures include restructuring the judicial system to avoid bribes and irregular payments, investigating and penalizing those involved in corrupt acts within the public administration, and seizing assets where wealth cannot be explained, subject to judicial oversight (Morgan 1998). The second pillar is building transparency and trust between citizens and the government. Though efforts to earn public trust are limited, transparency is assumed to be crucial (Kettl 2017). A vital prerequisite for that is creating portals where government spending is published regularly allowing citizens to track all the ongoing projects and initiatives. It is worth noting that governments can adopt social media to provide complementary information broadcasting, communication, and participation channels whereby citizens can access government services and also government officials be able to make more informed decisions. Countries can also put citizens at the heart of policy making by offering them the opportunity to shape legislation in areas that they care most about by voting on policy proposals. Transparent, unbiased, and inclusive policy making helps in improving democratic performance (Shah 2007).

Lethal coalitionary attacks of chimpanzees on gorillas in the wild

Lethal coalitionary attacks of chimpanzees (Pan troglodytes troglodytes) on gorillas (Gorilla gorilla gorilla) in the wild. Lara M. Southern, Tobias Deschner & Simone Pika. Scientific Reports, July 19 2021. DOI: 10.1038/s41598-021-93829-x

[Popular version: https://www.mpg.de/17223684/0719-evan-lethal-attacks-by-chimpanzees-on-gorillas-observed-150495-x. Here, climate change shows up three times (also appears there as a keyword), while in the paper there is no occurence of climat*, warm*, or temperat*. Also, in the paper's 90+ references, the titles do not make mention of those three word stems.]

Abstract: Intraspecies violence, including lethal interactions, is a relatively common phenomenon in mammals. Contrarily, interspecies violence has mainly been investigated in the context of predation and received most research attention in carnivores. Here, we provide the first information of two lethal coalitionary attacks of chimpanzees (Pan troglodytes troglodytes) on another hominid species, western lowland gorillas (Gorilla gorilla gorilla), that occur sympatrically in the Loango National Park in Gabon. In both events, the chimpanzees significantly outnumbered the gorillas and victims were infant gorillas. We discuss these observations in light of the two most widely accepted theoretical explanations for interspecific lethal violence, predation and competition, and combinations of the two-intraguild predation and interspecific killing. Given these events meet conditions proposed to trigger coalitional killing of neighbours in chimpanzees, we also discuss them in light of chimpanzees’ intraspecific interactions and territorial nature. Our findings may spur further research into the complexity of interspecies interactions. In addition, they may aid in combining field data from extant models with the Pliocene hominid fossil record to better understand behavioural adaptations and interspecific killing in the hominin lineage.

Discussion

Here, we report the first observations of two lethal coalitionary attacks of chimpanzees on another hominid species, gorillas. In both events, the chimpanzees considerably outnumbered the gorillas, however in the second event, the lethal attack started when the silverback had abandoned his group. In both events, the victims were gorilla infants, but the consumption of the victim was observed in one event only.

Recent studies59 were able to distinguish genetically distinct gorilla groups within the study area; when overlaid against the Rekambo chimpanzee community home range there was clear overlap with seven distinct gorilla groups (see Supplementary Fig. S1 in the Supplementary information). However, further data are needed to clarify whether our rare observations are due to lack of data or indeed mirror true frequencies of interspecies interactions in the study area.

In the following paragraphs, we will present and discuss several possible explanations that may account for the two lethal coalitionary encounters observed.

One explanation may be that the observed events represent cases of predation with the chimpanzees hunting and opportunistically targeting the smaller-bodied gorilla infants as prey. Although differences in behaviours accompanying hunting and hunting patrol patterns have been observed across sites, the behaviors observed at Loango were similar to the patterns reported for Taï41,60 and Ngogo38. For instance, the chimpanzees showed conspicuous behaviours prior to hunting such as being extremely attentive to any arboreal movements, scanning, changing directions several times without vocalizing, and performing specific call types—hunting calls38,45. Post-hunting behaviour is characterized by the prevalence of high-ranking males as the primary prey possessors and consumers, high levels of attention, arousal and excitement of party members, as well as begging and food sharing13,40,41,41,61. However, the behaviours observed during the two events were very different to those reported during hunting: The chimpanzees were noisy, emitted alarm barks and screams and performed displays long before the infants were killed. The excitement levels dropped immediately following the death of the infant gorillas. In addition, the observed feeding behaviours during the two events also differed from patterns expected during conventional hunting for the purpose of gaining nutritional benefits through the consumption of prey27. In the first encounter no feeding behaviour was observed, and in the second event the gorilla infant was almost entirely consumed by a single adult female. In contrast to species-typical hunts, in the second event the majority of individuals present, including adult males, showed almost no interest in the carcass, and only small amounts of meat were exchanged between low ranking individuals.

Another explanation may be that the two cases are the product of interspecific competition such as IGP and IK. So far, studies investigating interspecific competition in gorillas and chimpanzees have provided evidence for dietary niche differentiation and mutual avoidance to limit competition e.g.,62,63,64,65,66,67. All previous accounts of interspecies interactions as well as co-feeding events have been reported as peaceful despite a relatively high potential for feeding competition concerning key resources or during certain periods e.g.,68,69,70. Thus far, aggressive interference competition, including infanticide, has been observed between monkey species (e.g., Cercopithecus nicitans stampflii, Cercopithecus diana diana71; Ateles hybridus, Alouatta seniculus72) but not between chimpanzees and gorillas. Such interactions are however frequent in carnivore species and have been suggested as key determinants of their abundance and distribution33,73 (but see for an overview of other taxa31). As in the lethal interactions discussed here, carnivores tend to attack their closest dietary competitors31, most agonistic encounters occur in seasonal environments when food is scarce27, and killings decrease abruptly when dietary overlap is reduced73. Gorillas and chimpanzees show considerable dietary overlap and have a relatively high potential for dietary competition45,74. Across study communities, the degree of dietary overlap ranges between: 50% Kahuzi-Biega; Gorilla beringei graueri, Pan troglodytes schweinfurthii75 and 60–80% Loango, Lopé, and Ndoki; Gorilla g. gorilla, Pan t. troglodytes66,74,76. The two lethal encounters we observed occurred at times characterized by food scarcity and a period of high dietary overlap (for fruit resources)45,74—February and December 2019. In contrast, the two previously observed peaceful co-feeding events took place in April, a month characterized by relatively low dietary overlap between the two species45,74.

Furthermore, age, size and patterns of grouping seem to play a significant role in the outcome of IGP’s and IK’s (see e.g.,27). While relative body size of the opponents is the primary determinant of lethal interactions and results in favour of the larger species, in interactions involving adults, smaller species frequently kill the young of larger species27,73. There are cases where smaller species were able to kill or deter larger species such as wolves (Canis lupus) killing adult black bears (Ursus americanus)77 and hyenas (Crocuta Crocuta) killing lions (Panthera leo)27, however, these outcomes were only possible when individuals of the smaller species formed coalitions27,77. The grouping style of a species was found to strongly influence the outcome of IGP’s resulting largely in favour of species that form groups78. This is in line with our current observations, where the chimpanzees were at an advantage even against the larger gorilla species, given their ability to cooperate. Additionally, specific adaptations to prey-capture also influence the outcome of IGP’s, resulting in favour of species more adapted for vertebrate predation73 where the successful species, here, the chimpanzee, has adaptations to vertebrate predation13,39,41. Hence, as in IGP food webs (with specific emphasis of species classification) portrayed by Arim and Marquet79, the two reported killings may represent cases of IGP and IK between an intermediate omnivorous species (i.e. broad diets comprising both animal and plant foods80), the chimpanzee, and a herbivorous species (feeding mainly on plant foods81), the gorilla.

Lastly, both of the lethal encounters reported here also showed similarities to behaviours observed during chimpanzee intercommunity encounters. For instance, similar to territorial patrols, where chimpanzees move to the periphery and beyond their territorial boundaries to search for neighbours e.g.,11,13,82,83, the observed events took place in the peripheries of the territory before and during territorial patrols. In both events, infants were targeted and adult males were the main attackers and played the most active roles. Similarly, in lethal chimpanzee intercommunity encounters, infanticide is common and adult males are the main participants11,83,84,,83,84 (but see for female roles51). It has been proposed that in chimpanzees, adult males may kill infants of other communities to reduce competition for food by inducing foreign females to avoid contested regions84. The observed interspecies killings of gorilla infants by chimpanzees could have similar motivations85. We also observed behaviours before and during the encounters characteristic to coalitionary intercommunity encounters such as aggression (e.g., charges, chases, threatening displays, contact aggression), high levels of arousal and the use of loud vocalizations13,14,15,51. The imbalance-of-power hypothesis postulates that the function of unprovoked intercommunity aggression (such as deep incursions into other chimpanzee communities’ territory and coalitionary attacks) is a drive for dominance over neighbours resulting in fitness benefits for the attackers through improved access to resources such as food, females, or safety6,13. Two conditions are proposed to be required to trigger coalitional killing of neighbours: (i) a state of intergroup hostility, and (ii) sufficient imbalances of power between interacting parties resulting in impunity from aggressors. Thus, it may be possible that at Loango, which is characterized by relatively high dietary food overlap in specific months45,74, gorillas are perceived as competitors, for both space and resource use, similar to members of other chimpanzee communities. Lastly, we cannot rule out that the presence of human observers, in both events, may have had an effect on the unhabituated silverback’s departure and may have tilted the imbalance of power in favour of the habituated chimpanzees.

In sum, the observed events show similarities to patterns reported in IGP’s, IK’s and intraspecies agonistic encounters. Ultimately, additional observations in combination with isochronous assessments of fruit availability and dietary overlap are needed to differentiate whether coalitionary attacks are indeed the output of interspecific predation spurred by opportunistic hunting, interspecies competition for food resources or whether these interactions are merely a non-adaptive by-product of the “xenophobic nature” of chimpanzees. Finally, analyses of long-term phenological data could aid in investigating if potential high levels of feeding competition may be a more recent phenomenon caused by a collapse in fruit availability as observed in other tropical forests in Gabon86.