Gregarious Behaviour of Evasive Prey

Lecture on the first SFB/TR 15 meeting, Gummersbach, July, 18 - 20, 2004We model the formation of a herd as a game between a predator and a prey population. The predator receives some information about the composition of the herd when he chases it, but receives no information when he chases a solitary individual. We describe situations in which the herd and its leader are in conflict and in which the leader bows to the herd’s wish but where this is not to the benefit of the herd

Exploring the evolution of a trade-off between vigilance and foraging in group-living organisms

Despite the fact that grouping behavior has been actively studied for over a century, the relative importance of the numerous proposed fitness benefits of grouping remain unclear. We use a digital model of evolving prey under simulated predation to directly explore the evolution of gregarious foraging behavior according to one such benefit, the "many eyes" hypothesis. According to this hypothesis, collective vigilance allows prey in large groups to detect predators more efficiently by making alarm signals or behavioral cues to each other, thereby allowing individuals within the group to spend more time foraging. Here, we find that collective vigilance is sufficient to select for gregarious foraging behavior as long there is not a direct cost for grouping (e.g., competition for limited food resources), even when controlling for confounding factors such as the dilution effect. Further, we explore the role of the genetic relatedness and reproductive strategy of the prey, and find that highly related groups of prey with a semelparous reproductive strategy are the most likely to evolve gregarious foraging behavior mediated by the benefit of vigilance. These findings, combined with earlier studies with evolving digital organisms, further sharpen our understanding of the factors favoring grouping behavior.Comment: 26 pages (double-spaced, single column), 6 figures, 2 SI figure

The evolution of gregariousness in parasitoid wasps

Data are assembled on the clutch-size strategies adopted by extant species of parasitoid wasp. These data are used to reconstruct the history of clutch-size evolution in the group using a series of plausible evolutionary assumptions. Extant families are either entirely solitary, both solitary and gregarious, or else clutch size is unknown. Parsimony analysis suggests that the ancestors of most families were solitary, a result which is robust to different phylogenetic relationships and likely data inadequacies. This implies that solitariness was ubiquitous throughout the initial radiation of the group, and that transitions to gregariousness have subsequently occurred a minimum of 43 times in several, but not all lineages. Current data suggest that species-rich and small-bodied lineages are more likely to have evolved gregariousness, and contain more species with small gregarious brood sizes. I discuss the implications of these data for clutch-size theory

Gregarious Behaviour of Evasive Prey

Lecture on the first SFB/TR 15 meeting, Gummersbach, July, 18 - 20, 2004We model the formation of a herd as a game between a predator and a prey population. The predator receives some information about the composition of the herd when he chases it, but receives no information when he chases a solitary individual. We describe situations in which the herd and its leader are in conflict and in which the leader bows to the herd’s wish but where this is not to the benefit of the herd.

Gregarious Behaviour of Evasive Prey

Gregarious behavior of potential prey was explained by Hamilton (1971) on the basis of risk-sharing: The probability of being picked up by a predator is small when one makes part of a large aggregate of prey. This argument holds only if the predator chooses its victims at random. It is not the case for herds of evasive prey in the open, where prey’s gregarious behavior, favorable for the fast group members, makes it easier for the predator to home in on the slowest ones. We show conditions under which, gregarious behavior of the relatively fast prey individuals leaves slowest prey with no other choice but to join the group.Failing to do so would signal their vulnerability, making them a preferred target for the predator. Analysis of an n + 1 player game of a predator and n unequal prey individuals clarifies conditions for fully gregarious, partially gregarious, or solitary behavior of the prey.

Cow welfare aspects in automatic milking systems

This paper deals with the aspects of cow welfare in automatic milking systems, using literature and observations from the Suitia research farm and the first Finnish private farms. The welfare of a cow is largely dependent on her stockperson, also in automatic milking systems. Cow traffic arrangements are decisive in the cow's welfare

Gregariousness, interactive jobs and wages

Gregariousness is an important aspect of human life with implications for labour market outcomes. The paper examines, to the best of our knowledge for the first time for Germany, gregariousness and social interaction at the workplace and associated wage differentials. Our empirical findings with samples from the German Socio-Economic Panel (SOEP) demonstrate that gregarious people more often work in jobs with social interaction. Furthermore, females tend to work more often in interactive jobs compared to males. There is evidence that working in an interactive job is associated with a compensating negative wage differential of 7 percent for women and non for men. Implications for wage policy are discussed. --Gregariousness,social interactions,labour markets,sorting,wage differentials

Gregariousness, Interactive Jobs and Wages

Gregariousness is an important aspect of human life with implications for labour market outcomes. The paper examines, to the best of our knowledge for the first time for Germany, gregariousness and social interaction at the workplace and associated wage differentials. Our empirical findings with samples from the German Socio-Economic Panel (SOEP) demonstrate that gregarious people more often work in jobs with social interaction. Furthermore, females tend to work more often in interactive jobs compared to males. There is evidence that working in an interactive job is associated with a compensating negative wage differential of 7 percent for women and non for men. Implications for wage policy are discussed.Gregariousness, social interactions, labour markets, sorting, wage differentials