Several species mitigate relationships according to their conspecifics’ parasite status. Yet, such strategy of defense comes with costs of depriving individuals from valuable social bonds. Animals therefore face a trade-off between costs of pathogen exposure and benefits of social relationships. According to models of social evolution, social bonds are highly kin-biased. However, whether kinship mitigates social avoidance of contagious individuals has never been tested so far. Here, we build on previous research to demonstrate that mandrills (Mandrillus sphinx) modulate social avoidance of contagious individuals according to kinship: individuals do not avoid grooming their close maternal kin when contagious (parasitized with oro-fecally transmitted protozoa), although they do for more distant or non-kin. While individuals’ parasite status has seldom been considered as a trait impacting social relationships in animals, this study goes a step beyond by showing that kinship balances the effect of health status on social behavior in a non-human primate.

Behavioral observations. During 54 months (October 2012-March 2017), we collected 1557 hours of behavioral observation from 71 individually-recognized mandrills (29 males, 42 females). We did not consider sub-adult and adult males (more than seven years old) because females are philopatric in mandrills and males are only temporary residents of the social group. They have therefore no kin in the group, except their own offspring that are generally still infants when co-residing with their father. We usually do not manage to collect fecal samples at this age. Trained observers, blind to the protozoa status of the studied animals, performed behavioral observations using 5-min focal sampling. All social interactions including grooming time were recorded. Female and male monthly dominance ranks were evaluated using the outcomes of approach-avoidance interactions. We attributed their mother’s rank to the studied males below 5 years of age. For both sexes, we considered three classes of dominance rank (low, middle, and high). In this study, we matched individual’s rate of grooming received with its parasitological status.

Parasitological analyses. We performed qualitative coprological analyses using a sedimentation protocol on fecal samples collected opportunistically since 2012 whenever a known animal was seen defecating. The study group is known to be infected by seven different protozoa taxa: Balantidium coli, Coccidian sp, Endolimax nana, Entamoeba coli, Entamoeba hartmanni, Entamoeba histolytica/dispar complex and Pseudolimax butschlii. Over the study period, we collected 860 fecal samples from 60 groomees (39 females, 21 males; mean number per individual ± SD=23.0 ± 13.6). We evaluated monthly protozoa richness of groomees for 507 groomee.month, by calculating the average number of protozoa taxa retrieved from all samples collected from one groomee in a given month (mean number per individual.month ± SD=1.6 ± 1.3).

Genetic analyses. This study includes 65 individuals trapped at least once using blowpipe intramuscular injections of anesthetics allowing collection of blood samples. DNA extractions from the buffy coat were performed using QIAamp DNA Blood Mini Kits (Hilden, Germany) and microsatellite genotyping was carried out using 12-36 primer pairs. Paternity analyses were performed using Cervus 3.0 software using previously described procedures. Among these 65 individuals, 14 of them were born in captivity and 51 were born into the wild. We reconstructed the full pedigree of individuals born in captivity going back as far as the generation of unrelated founder animals. We genetically determined both parents for 43 individuals out of the 51 individuals born into the wild. For the remaining eight animals, we only knew the mother’s identity because the genetic sample did not match any adult male of the genetic database. The study further included six young individuals, born into the wild but never captured, with an unambiguously known mother.

This dataset gives a compilation of behavioral data collected from October 2012 to March 2017. It gives the grooming time (‘Grooming_time’, in seconds) each groomee (i.e., the individual that is groomed (‘Groomee’) received from each groomer (i.e., the individual that groomed ‘Groomer’), for one month of one year (‘Year’, ‘Month’). The total observation of the groomee-groomer dyad for the considered month is also given (‘Observation-time’, in seconds). The kinship category of the groomee-groomer dyad is indicated (‘Dyad_category’: ‘Offsrping-Mother’, ‘Mother-Offsrping’, ‘Maternal HS’ and ‘Paternal HS’ referring to Maternal and Paternal half-siblings, Low-kin, Non-kin). Sex (‘Sex_groomee’, ‘Sex_groomer’) and dominance rank (‘Rank_groomee’, ‘Rank_groomer’: ‘HR’, ‘MR’, ‘LR’ corresponding to High, Middle and Low rank) of both individuals of the dyad is indicated. The absolute age difference between the groomee and the groomer is given in years (‘Age_difference’). Finally, the protozoa richness of the groomee for the considered month is indicated (‘Protozoa_richness’). It corresponds to the average number of protozoa species retrieved from all fecal samples collected from this individual this month.

We considered groomee-groomer dyads meeting the following criteria for each studied month:

1. The groomer was observed at least once grooming the groomee the corresponding year of the studied month. Indeed, mandrills socially interact only with a subset of social partners. This criterion allowed considering grooming dyads.

2. At least one fecal sample was collected from the groomee this month.

3. The total observation time of the groomee-groomer dyad reached at least 30 minutes for each studied month. To calculate the observation time of the dyad, we summed-up observation time of each partner when the other partner was co-resident (i.e, both individuals were present in the group the same day).

4. Kinship was unambiguously determined.