Social experience can modify the behavior of adult animals, and this type of behavioral plasticity associated with territorial aggression has been observed in several species including green anole lizards. Previously dominant animals were more aggressive to a novel stimulus in a new context than previously subordinate animals after 10 days of agonistic interaction. This behavioral shift could be beneficial to an animal by increasing survival and/or reproductive success to maximize its fitness. Behavioral modification through social experience can involve alteration in some physiological properties such as variations in hormone titer and hormone receptors. Steroid hormones such as testosterone (T) and corticosterone (Cort) and neurotrasmitters such as arginine vasotocin (AVT) are well known for their association with territorial aggression. Hormonal mechanisms underlying the control of this behavior are, however, context dependent, temporally dynamic, and evolutionarily very diverse. I performed experiments aimed at gaining insights into the proximate mechanisms underlying status-dependent behavioral differences in territorial aggression. First, steroid binding globulins of green anole lizards were analyzed and the presence of androgen-glucocorticoid binding globulins and sex-hormone binding globulins (SHBG) was established. Next, status differences in steroid hormone levels and the temporal pattern of hormone changes were assessed. We found that winners/dominants had elevated total T levels shortly after the onset of fighting and reduced SHBG after 10 days of agonistic interaction. These changes seemed to cause sustained increases in free T levels in winners/dominants throughout 10 days of agonistic interactions. Then, androgen receptor (AR) mRNA density levels were compared in dominant and subordinate animals. The result showed that the preoptic area (POA) and anterior hypothalamus AR mRNA density levels were higher in dominants than subordinates shortly after the agonistic interaction. Lastly, AVT immunoreactive cell counts were compared in dominant and subordinate animals. We found that subordinate animals had reduced AVT immunoreactive cell counts in the POA compared to that of dominants or control males. Findings from this dissertation suggest possible mechanisms that might be responsible for status dependent behavioral differences in territorial aggression: elevation in T and reduction in SHBG capacity, and sustained elevation of AVT immunoreactive cell counts in the POA. / text

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Thesis (M.S.)--University of Nevada, Reno, 2006. / "December 2006." Includes bibliographical references (leaves 23-27). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm.

Agonistic behavior and dominance are described for captive Townsend's chipmunks (Eutamias townsendii). A total of 10,739 encounters was recorded; 644l (59.9%) were agonistic. Chases (58.5%) and displacements (30.8%) were the predominant agonistic behaviors; threats (6.8%) and fights (4.l%) were relatively rare. Stable, non-triangular hierarchies were rapidly established in 11 of the 12 groups of chipmunks observed; the presence of individuals of equal rank in some groups precluded strict linearity. Dominance positions did not change within a group, but reversals in rank and changes from equal to dominant-subordinate reltionships occurred when the mebership of groups was changed. One hierarchy existed for both sexes; neither sex was consistently dominant. Experience and individual differences in activity and aggresiveness were more important determinants of an animal's position than were sex or size. No correlation was found between rank and encounter frequency, nor was closeness of rank strongly correlated with high numbers of agonistic encounters between any two chipmunks. The frequencies of recognitory and sexual behavior were inversely related to the frequency of agonistic behavior between the pairs of animals. Ritualized throats and appeasement behaviors did not replace overt aggression in established hierarchies. Members of hierarchies showed neither a reduction in numbers of asonistic encounters, nor temporal changes in froquency of the different types of agonistic behavior. Agonistic encounters increased in frequency from August to December, but seasonal variations wore much smaller than variations among the groups. Although dominance reduced neither the frequency of agonistic behavior nor the time and energy spent in chasing, it nay be advantageous in curtailing harmful confrontations and enhancing the establishment of tolerance among some individuals.

Title from title page of PDF (University of Missouri--St. Louis, viewed March 8, 2010). Includes bibliographical references.

One of the major costs of group living is increased competition due to social information. Social information allows foragers to gain information about the location and the quality of food patches from observing other group members. Ultimately, this allows social foragers to use resources more efficiently. However, the distribution and quality of food varies both spatially and temporally and social information may result in aggregations of foragers around favourable food patches when they are available. This results in individuals of various dominance ranks aggregating around food resources and competing for food. In order to understand how dominance and patch quality interact to determine foraging behaviour, various foraging models have been created. In particular, producer-scrounger social foraging models are used to understand foraging behaviour and patch choice under competitive conditions. In producer scrounger games, individuals can either find their own food patches (produce) or join other individuals at food patches (scrounge). This study focused on how the combination of patch holder dominance status and patch quality interacts to influence patch joining decisions by scroungers. According to producer-scrounger models scroungers only join patches held by subordinate individuals. However, I found that a scrounger will join any patch as long as the patch holder is not within the top five most ranked individuals in the herd. However, as patch quality increased, fewer of the top ranked patch holders were avoided at each patch quality. This suggests that foraging is a trade-off between the costs of an aggressive interaction and the benefits gained from each patch. Behavioural titrations found that the initial density of food at a patch needs to be 2.3 times greater for a scrounger to feed from the next dominant patch holder. At high patch qualities there was a threshold point where patch quality became the driving force behind patch joining decisions and no patch holders were avoided, no matter their dominance status. Scroungers that fed from the top ranked patch holders had the same intake rate when compared with feeding with subordinate patch holders. This could be due to an increased level of vigilance by the scrounger in order to avoid an aggressive interaction with the dominant patch holder. However, scrounger’s intake rate increased when they fed from dominant patch holders that were not the top ranked herd members. This suggests that only the top ranked herd members are aggressive enough to prevent scrounging attempts. A novel discovery of this study was that although the goats formed a linear dominance hierarchy, they did not forage in accordance with it, with lower ranking individuals avoiding dominant patch holders. This suggest that in social herbivores dominance hierarchies are not maintained to determine who has priority access to food. This study shows that even large differences in dominance are not sufficient enough to prevent scrounging decisions and only the top ranked patch holders have the ability to prevent joining attempts. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Network data, particularly social network data, is widely collected in the context of interactions between users of online platforms, but it can also be observed directly, such as in the context of behaviours of animals in a group living environment. Such network data can reveal important insights into the latent structure present among the nodes of a network, such as the presence of a social hierarchy or of communities. This is generally done through the use of a latent variable model. Existing network models which are commonly used for such data often aggregate the dynamic events which occur, reducing complex dynamic events (such as the times of messages on a social network website) to a binary variable. Methods which can incorporate the continuous time component of these interactions therefore offer the potential to better describe the latent structure present. Using observed interactions between mice, we take advantage of the observed interactions’ timestamps, proposing a series of network point process models with latent ranks. We carefully design these models to incorporate important theories on animal behaviour that account for dynamic patterns observed in the interaction data, including the winner effect, bursting and pair-flip phenomena. Through iteratively constructing and evaluating these models we arrive at the final cohort Markov-Modulated Hawkes process (C-MMHP), which best characterizes all aforementioned patterns observed in interaction data. The generative nature of our model provides evidence for hypothesised phenomena and allows for additional insights compared to existing aggregate methods, while the probabilistic nature allows us to estimate the uncertainty in our ranking. In particular, our model is able to provide insights into the distribution of power within the hierarchy which forms and the strength of the established hierarchy. We compare all models using simulated and real data. Using statistically developed diagnostic perspectives, we demonstrate that the C-MMHP model outperforms other methods, capturing relevant latent ranking structures that lead to meaningful predictions for real data. While such network models can lead to important insights, there are inherent computational challenges for fitting network models, particularly as the number of nodes in the network grows. This is exacerbated when considering events between each pair of nodes. As such, new computational tools are required to fit network point process models to the large social networks commonly observed. We consider online variational inference for one such model. We derive a natural online variational inference procedure for this event data on networks. Using simulations, we show that this online learning procedure can accurately recover the true network structure. We demonstrate using real data that we can accurately predict future interactions by learning the network structure in this online fashion, obtaining comparable performance to more expensive batch methods.

M. S.

This study explores the effect of changing ecological conditions on female social organization among free-ranging vervet monkeys (Cholorocebus aethiops pygerythrus) in the Klein Karoo, South Africa. Comparison was made between a previous study conducted during a period of drought in 2009, and my own study conducted when conditions were much wetter and hence, less ecologically stressful. In addition, animals in the present study also experienced conditions of low demographic stress. Compared to 2009, females displayed lower rates of competition and aggression, did not compete for access to grooming partners, and did not preferentially groom those of high rank, nor did they do so more frequently. Females did, however, preferentially associate spatially with those they groomed most; a finding in contrast to the previous study. Females did not groom those of adjacent ranks more frequently, nor was there any relationship between rank difference and spatial association. In addition, there were rank differences in vigilance were found between females, and vigilance costs overall were affected by total group size. Overall, these findings support some aspects of the socioecological model used to predict group structure in primates, but other aspects of social organization remain puzzling, and may reflect larger overall group sizes in the Samara population, which changes patterns of engagement between females in ways not fully captured by current models. / xi, 122 leaves ; 29 cm

The permanent coresidence of males within a troop is unusual but occurs in vervet monkeys. Several hypotheses have been projected to explain the coexistence of male vervets (predation risk, breeding season length) but these hypotheses fall short in explaining the multimale nature of vervet monkeys. In order to determine the explanation for coresiding males, I collected male behavioural data from two troops over the course of nine months. My dataset was divided into two categories, male-male interactions and female-male interactions. The male-male data indicate that breeding season is the most active time for migration, aggressions and wounds. Coalitions were described for the first time, and affiliative interactions between males highlighted coping tactics of males in regards to their coexistence. The female-male data indicate there was little indication for distinct male or female choice for mating. Specifically, olfactory information appears to lower successful copulations of males, and female resistance also decreased successful copulations. Grooming was not a commodity traded for mating access. Male dominance was not correlated with mating success, and females seem to express their preference for sexual partners. The large cohort of males of my troops appears to alter behaviours observed at other sites. The maintenance of male-female associations after breeding season suggests that males may be preparing for next breeding season, and males may co-reside for breeding purposes. / xiii, 123 leaves : ill. maps ; 29 cm