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August 18, 2017
» Birds choose their neighbours based on personality
Birds of a feather nest together, according to a new study which has found that male great tits (Parus major) choose neighbours with similar personalities to their own. Oxford University researchers investigated whether the personality of birds influences their social lives – in particular who they choose to nest near. The study involved analysing social network structure in a population of wild great tits at Wytham Woods over six consecutive breeding seasons. Lead author and doctoral student Katerina Johnson explained: “We found that males, but not females, were picky about personalities, with males opting for like-minded neighbours. Our results emphasise that social interactions may play a key role in animal decisions.”
This tendency for males to associate with other males of similar personality may be particularly important during the breeding season when aggression peaks. Males fiercely defend their territories and compete for opportunities to mate with females and so shyer males may avoid setting up home near bolder, more aggressive individuals. Females, however, likely choose where to nest based on the attractive qualities of males.
The results also showed that this personality assortment amongst males was not affected by local environmental conditions. “Just like students choosing their flatmate”, Katerina commented, “birds may pay more attention to who they share their living space with than simply location.” She added: “Animal personalities can influence their social organisation and humans are likewise known to form social networks based on shared attributes including personality.”
Just like us, animals display individual behavioural differences that are consistent over time and stable across different situations and so may be thought of as personality traits. The researchers test the personality of great tits by introducing them to a novel environment and measuring how they respond. Whilst bold birds are keen to actively explore their new surroundings, shy birds tend to be more hesitant and cautious.
Katerina said: “This novel research finding may also help explain the evolution of personality and why individuals in a population differ in their behaviour. Rather than one particular personality type being favoured by natural selection as ‘the best’, different behavioural strategies may be equally good depending on who you choose to be your friends and neighbours.” Perhaps by nesting closer to others of similar character, this may improve a bird’s chances of survival and passing on their genes to the next generation. For example, although having bold neighbours may result in more skirmishes between males, they might also gain a shared benefit by more effectively repelling intruders. Link to paper here.
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August 18, 2017
» Pre- and postcopulatory sexual selection favour aggressive, young males in polyandrous groups of red junglefowl
Darwin recognised that in many species, males compete intensely for mating opportunities with females. He suggested that this competition is responsible for the evolutionary diversification and elaboration of male sexual characters. We now understand that in polyandrous populations, where females mate with multiple males, this competition continues after mating as the ejaculates of different males compete to fertilise ova. However, the way in which competition before and after mating interact to shape male reproductive success and drive evolutionary responses remains unclear. Using fine-grain behavioural observations and molecular parentage data in replicate, age-structured groups of red junglefowl (Gallus gallus) we show that males that were younger and more aggressive to other males had the most female partners. Moreover, younger and more aggressive males were also the most successful at fertilising ovabecause they are able to mate with the same females more often and produce more competitive ejaculates. These results show thatâ€”in these populationsâ€” intrasexual competition after mating reinforces competition before mating, consistently promoting younger and more aggressive males across pre- and post-mating episodes of sexual selection. Link to the paper here.
May 17, 2017
» Sperm and sex peptide stimulate aggression in female Drosophila
A new paper published in Nature Ecology & Evolution by Eleanor Bath, Nathalie Seddon, and Stu Wigby of the EGI, investigated how mating influences female aggression in fruit flies. Mating was found to double the amount of time females spent fighting each other over food. This increase in aggression after mating was stimulated by sperm, and in part by an associated seminal fluid protein, the sex peptide. Interestingly, this post-mating increase in aggression was not directly linked to the costs of egg production. These results suggest that male ejaculates can have a surprisingly direct influence on female aggression. Link to paper here.
September 19, 2016
» The socio-ecology of fear: How predators shape the social relationships of great tits
A new paper published in Scientific Reports by Bernhard Voelkl, Josh Firth & Ben Sheldon investigated how perceived predator pressure influences group composition and social relationships in flocks of British tits. In this experimental study the authors used model sparrowhawks to launch attacks on flocks of wild great tits and blue tits whilst monitoring their social dynamics. Non-lethal attacks caused instantaneous turn-over and mixing of group composition within foraging flocks. A single experimental ‘attack’ lasting on average less than three seconds, caused the amount of turn-over expected over three hours (2.0—3.8 hours) of undisturbed foraging, suggesting that nonlethal predator effects can greatly alter group composition within populations. This has implications for the birds’ social behaviour by increasing the number of potential interaction partners, as well as longer-term consequences for pair formation and emergent effects determined by social structure. This study provides the first evidence based on in depth monitoring of a social network that predators influence the social structure of groups, and it offers new perspectives on the key drivers of social behaviour in wild populations. Link to paper here.