Routine Formation and Flexibility in Social and Non-Social Behaviour of Aggressive and Non-Aggressive Male Mice

Abstract

To investigate the relationship between aggression and routine-like behaviour the response of male mice of bidirectionally selected lines for attack latency to a change in the social and non-social environment has been measured. In a non-social situation the extent of routine-like behaviour was measured in a Y-maze in which only one of the two arms gave access to the food compartments. The number of errors made in response to reversal of the arm that was blocked was taken as indicator for the degree of routine formation. Males of the short attack latency (SAL) line made significantly more errors, and hence were more routine-like in their performance, than mice of the long attack latency (LAL) line. Males of the LAL line that nevertheless had short attack latencies (i. e. aggressive LAL mice) turned out to be flexible in their behaviour; their response was similar to that of the non-aggressive LAL males. In a social situation SAL and aggressive LAL mice were used to investigate routine formation in attacking behaviour. The males were given different amounts of experience with male opponents after which their own female was introduced as opponent. The more extended the experience with male intruders was, the more SAL males subsequently attacked their female. In contrast, LAL mice appropriately changed their behaviour towards the female opponent. Thus, the attacking behaviour of SAL mice gets routine-like, whereas that of LAL males remains flexible. It is concluded that selection for attack latency generally coincides with selection for routine-like behaviour, suggesting that these two factors are influenced by many of the same genes. Regarding the fact that aggressive males of the LAL line show flexible behaviour, it may be proposed that with the phenotypic selection for attack latency there has in fact been selected for a mechanism that determines the organization (routine-like vs flexible) of behaviour.

Adrenocortical reactivity and central serotonin and dopamine turnover in young chicks from a high and low feather-pecking line of laying hens

“…The behavioral and physiological characteristics of birds of the HFP and LFP line show considerable analogy to the characteristics of respectively the proactive (active) and reactive (passive) coping strategy, known to exist in other species like rodents [2] and pigs [9,39]. In mice, it has been shown that proactive copers are more intrinsically driven.…”

“…They easily develop routines, a rather rigid form of behavior. In contrast, reactive copers are more flexible and react more to environmental stimuli [2,24]. There is a growing body of evidence that adopting a proactive coping strategy makes an individual more vulnerable to develop behavioral abnormalities than a reactive individual (see, for a review, Ref.…”

“…DA and 5-HT are known to be involved in the expression of (environmentally induced) behavioral disorders (e.g., stereotypies, obsessive compulsive disorder) in adult individuals of several species [2,9,30]. Stereotypies are generally defined as unvarying, repetitive behavior patterns that have no obvious goal or function [33].…”

Violent phenotype in SAL mice is inflexible and fixed in adulthood

“…SAL mice also attack anesthetized opponents in neutral environments [Natarajan et al, 2009]. The SAL mice additionally attack their female cage-mates in particular after cage cleaning or after repeated inter-male interactions in the resident-intruder paradigm [Benus et al, 1990]. This indiscriminate behavior was clearly different from the two other high-aggression mouse strains in that the latter displayed a rich agonistic repertoire of behaviors and aimed at neither the anaesthetized male opponents nor their female cage-mates [Caramaschi et al, 2008;Natarajan et al, 2009].…”

“…A large proportion of SAL mice routinely attacked unfamiliar male opponents upon repeated interactions [Benus et al, 1990;Caramaschi et al, 2008]. These intense agonistic interactions are relatively insensitive not only to the docile opponent but also to human interferences after the tests [personal observations].…”