Gonadal Hormones And Their Relationship With Sexual Behavior In Captive Female Tibetan Macaques (Macaca Thibetana)

In multi-male multi-female primate populations,although sexual behavior is not limited to the female ovulation phase,it was proposed that females are most attractive during the time of ovulation,which has been proved in a large number of species that female estrous with obvious sexual signal.However,the distribution of sexual behavior in the menstrual cycle of species with females concealed estrus is still unclear.Macaca thibetana(Macaca thibetana)camp lives in groups with many males and many females,which is a typical mixed mating system.Mating occurs throughout the year,but the frequency is higher from July to January,and the litters are born from January to April.Adult females have a slightly swollen skin on the perineum,but the size and color of the skin do not vary with either the breeding period of the group or the individual female’s cycle.Due to the complex habitat of Tibetan macaques in the wild,it is difficult for researchers in the field to collect continuous physiological samples to measure the menstrual cycle and infer the ovulation day.This study on October 2,2019 to January 14,2020,during the non-invasive sampling method is used to collect Tongling city zoo of 6 adult female fecal samples of 490,estrogens were extracted by ethanol heating method and measured by radioimmunoassay.Solicited copulations,copulatory and Post-copulatory grooming were recorded by focal animal sampling and behavioral sampling method.In order to understand the secretion pattern of bracket estrogen and analyze the menstrual cycle of adult female macaques,we analyzed the fecal estrogen of female macaques in order to elucidate the sex hormone secretion status of adult female macaques in different physiological states.We combined behavioral and physiological data to explore the relationship between behavioral indicators of proceptivity(female presentation)and attractivity(male sexual-inspection),copulatory and Post-copulatory grooming,and mating strategies of female macaques.The main research results are as follows:1.Estradiol secretion levels in adult female Tibetan macaques fluctuated periodically,with an average cycle length of 31.1 ± 1.8 d(N = 7,range: 23-37 d).The estradiol concentration increased slowly 5 ± 0.74 d(N = 11,range: 1-9 d)before reaching the peak,and increased rapidly the day before.The average peak estradiol concentration was 16960.7 ± 722.9 pg/g(N= 11,range: 12240.2-20532.2 pg/g),2.43 times higher than the baseline value.The peak rapidly reached its lowest point 2.5 ± 0.39 d after the peak(N = 11,range: 1-5 d).There was a slight secondary increase followed by a small peak at 6.5 ± 0.6 d(N = 11,range: 4-10 d).2.The mean absolute difference of peak estradiol in feces of 4 adult female Tibetan macaques was 9.47,which was much higher than the expected absolute difference of 5.5.Indicating that the menstrual cycles of female macaques were out of sync.The mean absolute difference of the peak value was 9.75,which was much higher than the expected absolute difference of 5.5,indicating that the adult females in adjacent cages did not have menstrual synchronization.3.The analysis of the relationship between frequency of female presentation,frequency of male sexual-inspection and ovulation period in the menstrual cycle showed that females had a significantly higher presentation frequency in the prefertile phase compared with fertile phase and postfertile phase(T =-1.215,df = 12,P = 0.044).There was no significant difference in the frequency of male sexual-inspection in the three stages.To test the correlation between the frequency of female presentation and the frequency of male sexual-inspection and estradiol level,The results showed that there was a significant negative correlation between the frequency of female presentation and the level of estradiol in the three stages of the menstrual cycle(r =-0.616,N = 15,P = 0.015).There was no significant correlation between the frequency of male sexual-inspection and the mean estradiol.This because estrogen no longer has a strict control over sexual behavior in Tibetan macaques,and female macaques concealed estrus.4.This study analyzed the relationship between the frequency of female individual copulatory(Total copulations,copulations solicited by males and copulations solicited by females)and ovulation day.There were no significant differences between the three stages of total copulations and copulations solicited by males,and there was no significant correlation between daily total copulations,copulations solicited by males and copulations solicited by females frequency and the mean estradiol concentration.The fact that copulations in Tibetan macaques is not focused on the fertile period indicates that male Tibetan macaques cannot accurately identify the fertile period of the female.5.This study analyzed the relationship between the frequency of post-copulatory grooming behavior and ovulation days.During the 15 days associated with ovulation,the frequency of female active grooming after mating was significantly higher in the prefertile phase than fertile phase(T = 1.155,df = 12,P = 0.04),The frequency of male grooming after mating was significantly higher in fertile phase than prefertile phase(T =-1.115,df = 12,P = 0.04).There was no significant difference between the three stages of menstrual cycle in the frequency of grooming after mating.There was a significant positive correlation between the frequency of male grooming behavior after mating and the average daily hormone value in the three stages of the menstrual cycle(r = 0.524,N = 15,P = 0.045).Post-copulatory grooming is a conditional mating strategy,and many factors may influence post-copulatory grooming strategies in primates.In this study,the menstrual cycle length of female Tibetan macaques was 31.1 ± 1.8 d(N= 7,range: 23-37 d),and the menstrual cycle of female Tibetan macaques was not synchronized.During the menstrual cycle,estradiol concentration was only negatively correlated with female presentation behavior,and positively correlated with the frequency of male post-copulatory grooming behavior,but not with other sexual behaviors.Sex in Tibetan macaques is also not concentrated during the fertile period of the female.The results showed that the sexual behavior of caged macaques was free from the strict control of estrogen,and the male macaques could not accurately identify the fertile period of the female macaques,which provides a theoretical basis for further research on the behavioral mechanism and mating strategy of wild macaques.