Sexual behaviors of indochinese long-tailed macaque macaca fascicularis in comparison with sundaic long-tailed macaque

Regarding to the previous studies reported that the past hybridization event between rhesus (Macaca mulatta; Mm) and long-tailed (M. fascicularis; Mf) macaques was occurred by the southward introgression of male Mm into Mf population, thus the Mf originating from Indochinese region carried higher level of genetic admixture of Mm ancestry than the Mf living in Sundaic region. Since it was reported that Mf are non-seasonal breeder while Mm are seasonal breeder, thus, it is interesting to compare the sexual behaviors between Indochinese and Sundaic Mf. Mf populations at Wat Haad Moon Kra Beau, Pichit province (WHM; 16° 51′N) and Khao Noi/Khao Tangkuan, Songkhla province (KN/KTK; 7° 12′N) who carried 50% and 15% of Mm genetics were selected as representatives of Indochinese and Sundaic Mf. Ten adult females from each population were selected as focal animals and followed for 12 months (7 days/month/population) from January–December, 2018. Frequency of three sexual behaviors (proceptivity, attractivity and receptivity), number of newborn, changes of sex skin (scoring from 0 – 4) and salivary hormonal analysis collected by rope bait method were determined and recorded. Both populations showed three sexual behaviors throughout the year, but the peak period of the WHM (November–March) was one-month earlier than the KN/KTK (December–April). In association with a 24-week gestation period of Mf, though births were observed all year round, the birth peaks occurred in April-July for WHM and June-September for KN/KTK. Following the reproductive seasonality classification system of van Schaik and colleagues (1999), both populations were classified as moderately seasonal breeder that the birth count with a three-month period was 33-67% (56%; 5 out of 9 birth count for WHM, and 52%; 15 out of 29 birth count for KN/KTK). Sex skin swelling and reddening were consistent in both populations and thus no correlation with sexual behaviors. However, average score of sex skin reddening (Mm characters) in WHM (2.70±0.82) was higher than the KN/KTK (2.00±0.0), while the average score of swelling at the base of the tail (Mf characters) in WHM (0.70±0.48) was lower than the KN/KTK (1.50±0.85). Since the measurement of salivary estradiol levels was not succeeded, several interfering factors were predicted such as low estradiol levels in saliva. From these results, it indicates that autosomal genetic admixture of Mm has no effect on sexual behaviors of Mf, but it can intervene the fecundity and changes of sex skin. Thus, the reproductive seasonality was no differences between WHM Indochinese and KN/KTK Sundaic Mf, while the fecundity and sex skin reddening of WHM females were more prone to Mm’s pattern than the KN/KTK females.