Isolation Associated Aggression – A Consequence of Recovery from Defeat in a Territorial Animal

Abstract

Population density has profound influences on the physiology and behaviour of many animal species. Social isolation is generally reported to lead to increased aggressiveness, while grouping lowers it. We evaluated the effects of varying degrees of isolation and grouping on aggression in a territorial insect, the Mediterranean field cricket, Gryllus bimaculatus . Substantiating early observations, we show that dyadic contests between weight-matched, adult male crickets taken from groups rarely escalate beyond threat displays, whereas interactions between pairs of previously isolated crickets typically escalate to physical fights lasting several seconds. No significant differences were found between 1, 2 and 6-day isolates, or between individuals grouped for a few hours or lifelong. Unexpectedly, crickets grouped in immediate proximity within individual mesh cages that precluded fighting while permitting visual, olfactory and mechanical, antennal contact, were as aggressive as free isolates. This suggests that reduced aggression of grouped animals may be an acquired result of fighting. Supporting this notion, isolated crickets initially engage in vigorous fights when first grouped, but fighting intensity and duration rapidly decline to the level of life-long grouped crickets within only 10 min. Furthermore, grouped crickets become as aggressive as life-long isolates after only 3 hours of isolation, and on the same time course required for crickets to regain their aggressiveness after social defeat. We conclude that the reduced aggressiveness of grouped crickets is a manifestation of the loser effect resulting from social subjugation, while isolation allows recovery to a state of heightened aggressiveness, which in crickets can be considered as the default condition. Given the widespread occurrence of the loser effect in the Animal Kingdom, many effects generally attributed to social isolation are likely to be a consequence of recovery from social subjugation.

Assessment of fight outcome is needed to activate socially driven transcriptional changes in the zebrafish brain

“…There are at least two possible explanations for these results. Social isolation has been suggested to induce dominance-like status in different species including fish (45,46). If this is the case in zebrafish, than the behavioral state of winners is expected to be closer to that of socially isolated fish and that would explain the lower number of DE genes and gene modules in winners than losers, when using social isolation as a reference group.…”

Cumulative effects of body size and social experience on aggressive behaviour in a subsocial bee

“…Prior experience is another known predictor of future behaviours in many animal species (Hsu et al, 2006;Rutte et al, 2006;Seebacher & Wilson, 2007;Jeanson & Fewell, 2008;Wong & Balshine, 2011;Manfredini et al, 2013;Stevenson & Rillich, 2013), including social insects (van Doorn, 2008;Amsalem & Hefetz, 2010;Amsalem et al, 2013). The negative correlation between aggression and avoidance suggests two distinct behaviour outcomes, whereby those two behaviours are, in their extremes, mutually exclusive ( Figure 1).…”

Handling alters aggression and “loser” effect formation inDrosophila melanogaster

“…Loser and winner effects have been widely studied in many species, including insects (Stevenson and Rillich 2013), fish (Chase et al 1994), and mammals (Schwartzer et al 2013). Few studies, however, have reported such effects on Drosophila Cold Spring Harbor Laboratory Press on May 9, 2018 -Published by learnmem.cshlp.org Downloaded from (Yurkovic et al 2006;Penn et al 2010).…”