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"Aggressive behavior in animals."
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Lethal aggression in Pan is better explained by adaptive strategies than human impacts
A meta-analysis of studies on chimpanzees and bonobos across Africa shows that their conspecific aggression is the normal and expected product of adaptive strategies to obtain resources or mates and has no connection with the impacts of human activities.
Chimpanzees born to get wild
Studies of our closest living relatives, chimpanzees and bonobos, have been influential in efforts to understand the evolution of aggressive behaviour in our own species. In recent years, however, the validity of these studies has been questioned by proponents of the human impacts hypothesis, which argues that the occurrence of violence in chimpanzees is mainly the result of human activities. Now a meta-analysis of studies on chimpanzees and bonobos across Africa reveals that aggression between chimpanzees is the normal and expected product of adaptive strategies to obtain resources or mates, and has no connection with the presence or otherwise of human beings.
Observations of chimpanzees (
Pan troglodytes
) and bonobos (
Pan paniscus
) provide valuable comparative data for understanding the significance of conspecific killing. Two kinds of hypothesis have been proposed. Lethal violence is sometimes concluded to be the result of adaptive strategies, such that killers ultimately gain fitness benefits by increasing their access to resources such as food or mates
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. Alternatively, it could be a non-adaptive result of human impacts, such as habitat change or food provisioning
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. To discriminate between these hypotheses we compiled information from 18 chimpanzee communities and 4 bonobo communities studied over five decades. Our data include 152 killings (
n
= 58 observed, 41 inferred, and 53 suspected killings) by chimpanzees in 15 communities and one suspected killing by bonobos. We found that males were the most frequent attackers (92% of participants) and victims (73%); most killings (66%) involved intercommunity attacks; and attackers greatly outnumbered their victims (median 8:1 ratio). Variation in killing rates was unrelated to measures of human impacts. Our results are compatible with previously proposed adaptive explanations for killing by chimpanzees, whereas the human impact hypothesis is not supported.
Journal Article
12 super-dangerous animals you need to know
Features 12 super-dangerous animals found around the world and includes facts such as life cycles, habitats, and traits.
Book
Topography of violent intraspecific aggression in a subset of dogs from directionally selected lines of Canis familiaris
We extended well-established animal models of human violence paradigms to domestic dogs ( Canis familiaris ) seized from organized dogfighting operations (n = 137). Using standard metrics of frequency, latency, duration, and severity of physical attack and social behavior, we found a pattern of severe intraspecific aggression and alterations in species typical social behavior comparable to that described in the models of violence literature. Behavior was coded from archival video footage of a model conspecific screening test by a technician blind to the categorical behavior severity rating assigned to the dogs on intake. Biting attacks were initiated with short latencies and a dramatically higher prevalence in dogs rated as severe for dog-directed aggression. Furthermore, high intensity attacks involving crushing and shearing bites and guttural growl vocalizations (a heretofore unreported vocalization) were exclusively exhibited by those subjects, and their attacks were directed to vulnerable body regions of the model, including the throat. Social investigation was absent or abbreviated; many individuals in this category failed to investigate the anogenital region of the model conspecific and spent a significantly smaller proportion of the test sniffing the model. Conversely, the comparator group from the same lines of domestic dogs showed normal social behavior toward the model conspecific despite their directional selection and life history. Our findings are the first to quantify the topography of extreme intraspecific aggression in domestic dogs, broadening our understanding of the social behavior of C. familiaris . In addition to contributing to basic science, our findings also support the use of expert ratings to categorize extreme intraspecific aggression in fight-bred lines. That finding is of applied value to shelter professionals making outcome decisions, and to legal professionals who require objective evidence grounded in accepted scientific paradigms when considering the prosecution of organized dogfighting cases.
Journal Article
Functional identification of an aggression locus in the mouse hypothalamus
Electrical stimulation of certain hypothalamic regions in cats and rodents can elicit attack behaviour, but the exact location of relevant cells within these regions, their requirement for naturally occurring aggression and their relationship to mating circuits have not been clear. Genetic methods for neural circuit manipulation in mice provide a potentially powerful approach to this problem, but brain-stimulation-evoked aggression has never been demonstrated in this species. Here we show that optogenetic, but not electrical, stimulation of neurons in the ventromedial hypothalamus, ventrolateral subdivision (VMHvl) causes male mice to attack both females and inanimate objects, as well as males. Pharmacogenetic silencing of VMHvl reversibly inhibits inter-male aggression. Immediate early gene analysis and single unit recordings from VMHvl during social interactions reveal overlapping but distinct neuronal subpopulations involved in fighting and mating. Neurons activated during attack are inhibited during mating, suggesting a potential neural substrate for competition between these opponent social behaviours.
Possible link between aggression and mating behaviour
Certain regions of the hypothalamus are known to be important in aggression. Until recently, it has not been possible to learn much more than that because it was difficult to stimulate specific cell types within a mixed population of cells. David Anderson and colleagues have used optogenetics to solve this specificity problem, and find that optogenetic stimulation of neurons in a subdivision within the ventromedial hypothalamus can elicit inappropriate attack behaviours — but that electrical stimulation does not produce the same result. Additional analysis of genetic and electrophysiological activity revealed overlapping neuronal subpopulations involved in fighting and mating, with potential competition between these behaviours, as neurons activated during aggression are inhibited during mating.
Certain regions of the hypothalamus are important in aggression, but until recently, it has been difficult to specifically stimulate specific cell types within a mixed population of cells. Here, optogenetics is used to solve this specificity problem, finding that optogenetic stimulation of a subdivision within the ventromedial hypothalamus can elicit inappropriate attack behaviours in mice, but electrical stimulation does not produce the same result. Additional analysis of genetic and electrophysiological activity revealed overlapping neuronal subpopulations involved in fighting and mating, with potential competition between these behaviours, as neurons activated during aggression are inhibited during mating.
Journal Article
Triple threat : thrillers
Cross kill: Along Came a Spider killer Gary Soneji has been dead for over ten years. Alex Cross watched him die. But today, Cross sees him gun down his partner. Is Soneji alive? A ghost? Or something even more sinister?
Book
Wild gelada monkeys detect emotional and prosocial cues in vocal exchanges during aggression
Recognizing vocal behaviours intended to benefit others is a crucial yet understudied social skill. Primates with rich vocal repertoires and complex societies are excellent models to track the evolution of such capacity. Here, we exposed wild geladas ( Theropithecus gelada ) to vocal exchanges between unfamiliar female victim screams and male affiliative calls. The stimuli were arranged in sequences either simulating vocal affiliation towards victims (scream-affiliative call) or violating such order (affiliative call-scream), with varying emotional arousal conveyed by the affiliative call type. Measuring gazing activity towards the loudspeaker and the interruptions of feeding, we show that monkeys were sensitive to the sequential order in vocal exchanges as well as to the emotional arousal conveyed by affiliative calls. Our field study suggests a prosocial use of vocalizations in wild monkeys and reveals that foundational cognitive elements for processing vocal exchanges as meaningful third-party interactions may have existed in our common ancestors with monkeys.
Journal Article
Social mates dynamically coordinate aggressive behavior to produce strategic territorial defense
Negotiating social dynamics among allies and enemies is a complex problem that often requires individuals to tailor their behavioral approach to a specific situation based on environmental and/or social factors. One way to make these contextual adjustments is by arranging behavioral output into intentional patterns. Yet, few studies explore how behavioral patterns vary across a wide range of contexts, or how allies might interlace their behavior to produce a coordinated response. Here, we investigate the possibility that resident female and male downy woodpeckers guard their breeding territories from conspecific intruders by deploying defensive behavior in context-specific patterns. To study whether this is the case, we use correlation networks to reveal how suites of agonistic behavior are interrelated. We find that residents do organize their defense into definable patterns, with female and male social mates deploying their behaviors non-randomly in a correlated fashion. We then employ spectral clustering analyses to further distill these responses into distinct behavioral motifs. Our results show that this population of woodpeckers adjusts the defensive motifs deployed according to threat context. When we combine this approach with behavioral transition analyses, our results reveal that pair coordination is a common feature of territory defense in this species. However, if simulated intruders are less threatening, residents are more likely to defend solo, where only one bird deploys defensive behaviors. Overall, our study supports the hypothesis that nonhuman animals can pattern their behavior in a strategic and coordinated manner, while demonstrating the power of systems approaches for analyzing multiagent behavioral dynamics.
Journal Article