Correlations Among Rank,Hormone Levels And Intestinal Parasitic Infection In Adult Male Tibetan Macaques(Macaca Thibetana)

In nonhuman primates,dominance can affect the physiological and psychological stress of individual animals.Androgens,particularly testosterone,play a central role in shaping behavioral,morphological and physiological variation associating with alternative mating tactics,social status,dominance and even with reproductive success.Cortisol is the most potent metabolizing sugar in glucocorticoids which plays an important role in the body's stress response and affects parasites loads in the body along with testosterone.Therefore,understanding the relationship between hormone levels and intestinal parasites in non-human primates can help us to better understand the cost while non-human primates obtain dominance and rear offspring.In this study,we collected behavioral data in free-ranging Tibetan macaques(Macaca thibetana)at Mt.Huangshan,China(including mating season:August-November,2016 and non-mating season:March-May,2017)by using focal and behavioral sampling methods.Fresh fecal samples were collected from adult male individuals across mating and non-mating periods.We studied adult males'dominance rank,testosterone levels,cortisol levels,and intestinal parasite loads to explore potential correlations among dominance rank,testosterone,and health.The results showed that:(1)During the two periods,10 species of intestinal parasites have been detected:4 helminths,5 protozoans,and 1 mite.(2)In mating season,there was no difference between testosterone levels(Kruskal-Wallis H,P = 0.343)and intestinal parasite loads(Kruskal-Wallis H,P ?0.203)in adult males.Testosterone levels were not correlated with intestinal parasite loads(Spearman,N = 7,n = 42,P = 0.219).Furthermore,there was no correlation between dominance rank and intestinal parasite loads(Spearman,N = 7,n = 42,P ?0.796).However,there was a positive correlation between dominance rank and cortisol levels(Spearman,N = 7,n = 42,P = 0.013,rs = 0.379).Moreover,there was a negative correlation between cortisol level and intestinal parasite loads(Spearman,N=7,n=42,P = 0.046,rs =-0.309).(3)In non-mating season,there was a significant difference between testosterone levels(1.00±0.42 ng/g)and intestinal parasite loads(112.44 ± 83.62 EPG)in adult males(Kruskal-Wallis H,P<0.05).Testosterone levels were positively correlated with dominance rank(Spearman,N = 8,rs = 0.326,P<0.05),while protozoan loads were negatively correlated with dominance rank(Spearman,N = 8,rs=-0.345,P<0.05).We found no correlation between helminth loads and dominance rank(Spearman,N = 8,rs= 0.065,P>0.05).Testosterone levels were negatively correlated with protozoan loads(Spearman,N = 8,rs=-0.546,P<0.05),but there was no correlation between testosterone levels and helminth loads(Spearman,N = 8,rs=-0.013,P>0.05).This correlation was also not exist between dominance rank and cortisol levels(Spearman,N = 8,n = 39,rs = 0.169,P = 0.304).Social centrality was positively correlated with intestinal parasite loads(Spearman,N=8,n = 39,rs= 0.391,P = 0.014).Based on the results,we found that there were some correlations between hormone levels and intestinal parasite loads during different periods.We suggest that in mating season,cortisol levels can affect the dominance rank and intestinal parasite loads in male individuals.It's benefit for the maintenance of dominance and health when male individuals maintain a high level of cortisol.In non-mating season,the dominant males had higher testosterone levels,it suggests that testosterone has a stimulating effect on the maintenance of rank and that it inhibits protozoan infection.