When should a territory resident attack?

Abstract

Models of territorial defence tend to omit two characteristics of many territorial systems: repeated intrusions by the same individual and the learning processes of residents and intruders. Here we present state-dependent, dynamic models of feeding territories, designed to investigate temporal patterns of resident aggression towards intruders that are capable of spatial learning. We compare two types of models: (1) a nomadic intruder model, in which intruders never visit the same territory twice, and (2) a single, repeat intruder model, in which an intruder may repeatedly intrude into a given territory but is less likely to do so after being attacked. These two models produce qualitatively and quantitatively different patterns of aggression by residents. For instance, residents with intruders that may repeatedly intrude have high initial attack rates, regardless of initial probability of intrusion, but their attack rates decline over time. In contrast, residents in the nomadic intruder model do not attack intruders if intrusion rates are moderately high, and their attack rates are constant and high for most of the period of territory tenure. In addition, residents of both nomadic and repeat intruder scenarios stopped attacking intruders for a short period before voluntarily abandoning their feeding territories. The results of our models suggest that repeated intrusions and learning processes have a dramatic effect on territorial defence.  2001 The Association for the Study of Animal BehaviourFor many years, models have played an important role in advancing our understanding of the role of aggression in territorial species. However, a dichotomy has arisen between models investigating territories and models investigating aggressive behaviour. Most territory models focus on an individual versus the rest of the population, and consider such questions as when space should be defended, how much space should be defended, or what shape a territory should be (e.g.

Learning of Foraging Skills by Fish

“…Levels of aggression in contests between familiar individuals are lower than in contests between strangers, so that familiarity appears to reduce aggression and increase the foraging rate (Griffiths et al 2004). This is consistent with the hypothesis that individual recognition is used to reduce the costs of contesting resources: After an initial contest, encounters between familiar individuals should be settled with less aggression and a lower probability of status reversal than encounters between unfamiliar fish (Switzer et al 2001). However, this effect decays rapidly with time since previously familiar individuals are treated as strangers after 3 days of separation (Johnsson 1997).…”

Developmental perspectives on personality: implications for ecological and evolutionary studies of individual differences

“…However, niche-construction can also occur in many other situations, notably including social environments that are generated and maintained as a result of the behaviour of a focal individual. For instance, when aggressive behaviour by territorial animals discourages conspecifics from returning to the area where they were attacked, a focal individual who was highly aggressive at the time of territory establishment would have lower ongoing rates of social interactions for the rest of that season than a focal individual who was less aggressive during that same period (Stamps & Krishnan 2001;Switzer et al 2001).…”

What do territory owners defend against?

“…[34,35]). Specific aspects of the context the conflict happens in can, however, also be important, such as the likelihood of a repeated conflict [36], or the amount of knowledge an individual has about the opponents' strategy [37,38].…”

“…Furthermore, important aspects such as asymmetry of information between opponents [37], likelihood of a repeated conflict [36] and controllability of access [34] all vary dependent on which of these types of access to the territory individuals compete for. Each of these types of conflicts therefore has its own specific properties with specific evolutionary consequences for the individuals' behaviour.…”

“…While the first intruder's impact on the owner's foraging success is represented in the model, the effect of any further intruders is only taken into account as additional fixed defence costs. An interesting variation on this approach explores the effects of some simple optimizations of the intruders' behaviour on the owner's willingness to defend its territory [36]. In a slightly different context, Tao et al [83] use a similar type of model to investigate temporal dynamics of home range sizes.…”