Thread by @realscientists

Today, I want to talk a bit more about sociality and health.
Life in social groups provides multiple benefits at the individual level such as dilution of predation risk and better access to or protection of mate, ressources, territory
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There are also individual costs of sociality: competition and dominance relationships triggering physiological stress, increased disease transmission... For sociality to be conserved, the benefits need to overcome the costs.
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In the last 2 decades there has been increasing focus on how sociality and health are intertwined. In particular, scientists including myself look at how social organisation, group size, connectivity & social behaviours influence health and on how being sick affects sociality 3/n

A lot of terms about sociality to define but basically
-Social organisation is how groups are composed and organised (e.g. pair-living, harem with 1♂️ and multiple ♀️, multi♂️-multi♀️groups...)
-group size: variation of group size in the same species or group
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Social behaviours are the behaviours directly involving 2 or more individuals. Ex: grooming, hugging, playing, mating, staying in contact or close proximity, fighting... in humans it can also be having a phone call, kissing, chatting, etc.
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Social connectivity refers to how individuals from the same group are connected together by their interactions or proximity. F.ex. in the gif below the hand shake connects all kids indirectly through their neighbours and directly only to the kid on their left & right
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Many studies show benefits of sociality on health and ultimately fitness. For example increased wound healing & survival of the offsprings in baboons, decreased glucocorticoids in Barbary macaques, effects counterbalancing smoking a pack of cigarettes/day in humans...
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In some species, we can see reduced connectivity & social behaviours in sick individuals. It can be because they divert their energy from sociality to fight the disease (ex. cricket, rat, human) or because others avoid them (lobster, ant, mandrill).
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In my PhD, I studied the link between sociality and health in 5 groups of red-fronted lemur in Madagascar. They are particularly interesting because they live in small (5-15 individuals) multi♂️-multi♀️groups & are quite egalitarian and tolerant
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But how to measure health in wild animals? This is where #PoopScience comes handy.
I collected hundreds of faecal samples to measure indicators of their metabolism, reproductive status and gastro-intestinal parasite infections.
I tried to develop an inflammation marker...
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...from faecal samples but this needs a bit more lab work to improve the method and I might change to saliva samples for it.
I also checked their weight change every 2nd week.
I used behaviour and samples from 42 individuals ranging from 1 to 23 y.o. over 18 months.
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What did we find and what does it bring to the general picture?
Stay tune tomorrow for the end of the story
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In red-fronted lemurs, there seem to be no short term benefits of sociality on health. Number of social partners, bond strength, group size, time spent in contact or actively engaged in social behaviour doesn't influence glucocorticoids & testosterone levels, weight loss...
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... But increased group size and time spent in contact with others increased parasite diversity and the occurrence of parasite infection, as predicted by theories on disease transmission.
And parasite infections were associated with higher inflammation marker levels
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Overall, we also found that all lemurs were indirectly connected to all other group members but only spent 18% of their time being social in average. They also seemed to be limited in the number of social partners (range: 2-5) whatever the group size (4-15).
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But we don't know if there are long-term social benefits on health and fitness like better reproductive success, increased survival and offsprings' survival. We have to go through the analysis of the genetic samples and demographic data in our population to work on this
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Interestingly, there are similar results in other lemur species living in small groups and with a relaxed dominance style.
Could it be an adaptation to life in Madagascar? To life in egalitarian small scales societies? I'd love to test it in other species including Humans
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