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From individuals to groups and back: interaction between individual variation in behaviour and group performance
Full text linkStark differences in individual behavioural responses are a well-known feature of animal diversity. Even within a social group many distinct strategies coexist, and this variation has been recently found out to play a significant role in resource exploitation, social learning and various collective behaviours. How the entire group performs can therefore depend on various characteristics, all linked to its members’ behaviour and the relationships that connect them. While there are theorical analyses focusing on the consequences of systems where individual variation and group environment influence each other by interacting through feedbacks, most of the assumptions and the effects hypothesized by these models have rarely been experimentally studied in controlled conditions.
My aim was thus to test if the interactions between variation in behavioural strategies and the social environment might have an effect on the performance of single individuals within the group and of the group itself. I approached the complex issue by performing a series of experiments on a captive population of House Sparrow (Passer domesticus). I started by examining the effect of predation on a potential proxy for life-history traits, i.e. relative telomere length, and the connection of the latter to various behavioural traits. In the second experiment I investigated if social connections between individuals within a group might have an influence on the measurable benefits obtained by its members. Expanding on this topic, I questioned if previous familiarity with a companion might be a factor strong enough to affect exploration of a novel environment, or if the presence of any conspecific would allow social facilitation. This investigation was also a necessary step to take before testing any group-related effect, as an attachment to one own’s group was a necessary prerequisite for the next experiment. In fact, I then assessed the performances of two flocks facing each other over limited resources. While there have been studies comparing groups’ performances, it has rarely been taken into account how two groups would interact together, even if in the natural environment groups sharing resources are quite common. For my last experiment I focused on one of the most well-studied dichotomous behavioural strategy, i.e. the leader/follower dynamic. I decided to investigate this variable strategy not only during exploration but also in a different situation, one of the most crucial in the life of any animal: the attack of a predator and the split-second reactions to it.
The first experiment showed no influence of predation on telomere dynamics: relative telomere length however changed with successive samples. In the second experiment results showed that social connections affected the rate of discovery of a novel food source, with individuals more closely connected to the first feeder foraging before the others. In the following experiment I discovered that averaging over familiarity and sex the presence of a companion strongly increased exploratory behaviour. Familiarity with the companion however had an influence on the social exploration of female sparrows: they explored faster and consumed more resources only when accompanied by a familiar individual.
In the experiment where two groups of sparrows faced each other we found out a that group membership affected the outcome of the confrontation, as the group that foraged first ended up almost always consuming more of the limited resource. This meant that whoever shared the group with a risk-averse individual, one that foraged first at a novel food source, gained benefits regardless of their own behavioural traits. Finally, individuals that led movements during exploration were followers during a simulated attack and vice versa, showing that social positions in this species are context dependent.
In conclusion, these experiments shed light on interactions between variation in behavioural strategies and the social environment. Our results underscored how various assumptions made by theoretical models on the potential role of complex feedbacks between individual traits and the performance of the entire group were indeed correct and testable in a controlled setting. In the future, in order to keep investigating how social animals trade off costs and benefits in crucial contexts such as novel environment exploration and predator attacks it will be imperative to account for the role of diversity within the social environment
Exploratory behaviour and sociality: the role of familiarity in House Sparrow (Passer domesticus).
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La percezione dell'odore in Passero domestico (Passer domesticus): viene usata per trovare una casa?
No full textEsplorazione e socialità: il ruolo dell'esplorazione nel Passero domestico (Passer domesticus).
No full textHouse sparrows' (Passer domesticus) behaviour in a novel environment is modulated by social context and familiarity in a sex-specific manner
Full text linkAbstract Background Exploratory behaviour is one of the best-investigated behavioural traits. However, little is known about how differences in familiarity, i.e. in the knowledge and previous experience with a companion can influence the exploration of a novel environment. However, to our knowledge, such a critical feature of the social environment has never been the target of a study relating it to exploratory behaviour in birds. Here we examined if familiarity with a conspecific could affect behavioural responses of individuals confronted with a novel environment. We recorded the latency to land on the ground, latency to feed, time spent feeding and number of sectors visited of 48 female and 48 male house sparrows (Passer domesticus) in an indoor aviary in three contexts: alone (individual context), with an unfamiliar and with a familiar same-sex companion. Results House sparrows landed sooner on the ground when in the familiar context than when in the individual context. Birds in unfamiliar pairs followed each other less than familiar birds, but this difference diminished with time spent exploring. Moreover, males and females differed in their behavioural responses in the unfamiliar context. Females with a familiar companion landed sooner than when they were paired with an unfamiliar conspecific, whereas only the presence of a companion but not familiarity reduced males latency to land on the ground. Finally, when considering the unfamiliar context males had shorter latencies to forage and thus spent more time eating than females. Conclusions The presence or absence of a companion and its familiarity with the focal individual influenced differently the behavioural responses of male and female house sparrows in a novel environment. As house sparrows are strongly sociable, the influence of the social environment is likely to be of paramount importance to understand the selective pressures acting on them, particularly in recently colonized areas with ephemeral food sources. Our results shed light on the complex influence that the social environment has on the behavioural responses of a cosmopolitan bird
Can house sparrows recognise familiar or kin-related individuals by scent?
No full textAbstract: In the last decades, higher attention has been paid to olfactory perception in birds. As a consequence, a handful of avian species have been discovered to use olfaction in different contexts. Nevertheless, we still have a very limited knowledge about the use of odor cues in avian social life, particularly, in the case of songbirds. Here, we investigate if female house sparrows Passer domesticus show any preference for the odor of kin and nonkin conspecifics and we also test a possible role of familiarity based on male scent in female choice. We performed the experiment with captive birds twice, during the nonbreeding and breeding seasons. Our results show that female house sparrows strongly avoided the odor of unrelated familiar (UF) males, both in the breeding and nonbreeding seasons. Our results suggest recognition for olfactory stimuli related to familiarity and kinship. We suggest that avoidance for UF males is associated with previous experience in this species. Also, we provided further evidence to the use of olfaction in passerine species by using a new experimental setup
Genotype by Environment Interaction and Selection Response for Milk Yield Traits and Conformation in a Local Cattle Breed Using a Reaction Norm Approach
Full text linkLocal breeds are often reared in various environmental conditions (EC), suggesting that genotype by environment interaction (GxE) could influence genetic progress. This study aimed at investigating GxE and response to selection (R) in Rendena cattle under diverse EC. Traits included milk, fat, and protein yields, fat and protein percentage, and somatic cell score, three-factor scores and 24 linear type traits. The traits belonged to 11,085 cows (615 sires). Variance components were estimated in a two-step reaction norm model (RNM). A single trait animal model was run to obtain the solutions of herd-EC effect, then included in a random regression sire model. A multivariate response to selection (R) in different EC was computed for traits under selection including beef traits from a performance test. GxE accounted on average for 10% of phenotypic variance, and an average rank correlation of over 0.97 was found between bull estimated breeding values (EBVs) by either including or not including GxE, with changing top ranks. For various traits, significantly greater genetic components and R were observed in plain farms, loose housing rearing system, feeding total mixed ration, and without summer pasture. Conversely, for beef traits, a greater R was found for mountain farms, loose housing, hay-based feeding and summer pasture
The effect of social connections on the discovery of multiple hidden food patches in a bird species
Full text linkSocial foraging is thought to provide the possibility of information transmission between individuals, but this advantage has been proved only in a handful of species and contexts. We investigated how social connections in captive flocks of house sparrows (Passer domesticus) affected the discovery of (i.e. feeding for the first time from) two hidden food patches in the presence of informed flock-mates. At the first-discovered and most-exploited food patch social connections between birds affected the order of discovery and presumably contributed to a greater exploitation of this patch. However, social connections did not affect discovery at the second food patch despite its close spatial proximity. Males discovered the food sources sooner than females, while feeding activity was negatively related to patch discovery. Age had no effect on the order of discovery. Birds that first discovered and fed at the food patches were characterized by higher level of social indifference, i.e. followed others less frequently than other birds in an independent context. Our findings provide experimental evidence for the importance of variable social connections during social foraging in house sparrow flocks, and suggest that social attraction can contribute differently to the exploitation of different patches when multiple food sources are present
Improvement of Genomic Predictions in Small Breeds by Construction of Genomic Relationship Matrix Through Variable Selection
Full text linkGenomic selection has been increasingly implemented in the animal breeding industry, and it is becoming a routine method in many livestock breeding contexts. However, its use is still limited in several small-population local breeds, which are, nonetheless, an important source of genetic variability of great economic value. A major roadblock for their genomic selection is accuracy when population size is limited: to improve breeding value accuracy, variable selection models that assume heterogenous variance have been proposed over the last few years. However, while these models might outperform traditional and genomic predictions in terms of accuracy, they also carry a proportional increase of breeding value bias and dispersion. These mutual increases are especially striking when genomic selection is performed with a low number of phenotypes and high shrinkage value—which is precisely the situation that happens with small local breeds. In our study, we tested several alternative methods to improve the accuracy of genomic selection in a small population. First, we investigated the impact of using only a subset of informative markers regarding prediction accuracy, bias, and dispersion. We used different algorithms to select them, such as recursive feature eliminations, penalized regression, and XGBoost. We compared our results with the predictions of pedigree-based BLUP, single-step genomic BLUP, and weighted single-step genomic BLUP in different simulated populations obtained by combining various parameters in terms of number of QTLs and effective population size. We also investigated these approaches on a real data set belonging to the small local Rendena breed. Our results show that the accuracy of GBLUP in small-sized populations increased when performed with SNPs selected via variable selection methods both in simulated and real data sets. In addition, the use of variable selection models—especially those using XGBoost—in our real data set did not impact bias and the dispersion of estimated breeding values. We have discussed possible explanations for our results and how our study can help estimate breeding values for future genomic selection in small breeds
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