Study On The Influencing Factors Of Vocal Development In The Asian Parti-colored Bat, Vespertilio Sinensis

Similar to human vocal development,most early vocal signals in vocalizing animals undergo a series of changes that eventually develop into mature vocal signals for social communication or self-navigation.Studies have shown that the acoustic signals are influenced by genetic factors,maturation effect and vocal learning,which often interact with each other to affect vocal development.Earlier studies on animal vocal development and influencing factors mostly focused on birds.However,compared to birds,chiropteran have a closer relationship with humans.At the same time,the complexity of bat community and the diversity of acoustic signals make them as ideal species to study the factors affecting the vocal development and provide a scientific basis for the origin and evolution of human language.The research on the morphological development of Asianparti-colored bat has been carried out.They are a companion species that produces twins.They have strong ability to resist human interference and high survival probability in captivity.And they belong to Vespertilionidae and have the potential ability of vocal learning.Therefore,Asianparti-colored bat(Vespertilio sinensis)that belong to the Chiroptera,family Vespertilionidae and genus Vespertilio were selected as the research objects.Based on the separation of mother-infant,the young bats were artificially fed,and the acoustic data collection and the indoor playback experiments were used to study the factors affecting the vocal development.The main results were as follows:Genetic factors may account for the similarity of the early isolation calls in the twin bats.Spectrogram showed that twins are more similar in their isolation calls,and that the Euclidean distance between twins is smaller than that between non-twins.The paired t-test showed that there were significant differences in isolation calls between twin bats and non-twin bats at 3,5 and 7 days of age(3-day-old pups in 2018: t = 0.017;3-day-old pups in 2019: t = 0.021,5-day-old: t = 0.013,7-day-old: t = 0.009;all P < 0.05).In addition,discriminant function analysis(DFA)showed that the discriminant rate of isolation calls of young bats of each age was significantly higher than that of random discriminant rate(binomial test: all P < 0.001),indicating that the isolation calls of Asian parti-colored bat had individual characteristics in terms of statistics,which might be used for the acoustic recognition of mother-infant.The development of checked downward frequency modulation(cDFM)syllables in pups was affected by vocal learning.There was no significant difference in the body weight and forearm length between the two artificially fed groups at any stage(all P > 0.05),and no significant difference in the average body weight and forearm length between the two groups and the adult bat at last(P > 0.05).There was no significant difference in the fundamental frequency between the playback group and adult bats in the third stage(t = 0.237,P > 0.05).The fundamental frequency of the isolation group was always significantly different from that of adult bats(all P < 0.05).In addition,pearson's correlation analysis showed that the fundamental frequency of both groups decreased significantly with age(Playback group: r =-0.578,P = 0.000;Isolation group: r =-0.724,P = 0.000).Performing a discriminant function on the calls of the two groups with adults,combined with the calculation of euclidean distance,it can be seen that the playback group approaches the adult bats earlier and closer under various acoustic characteristics,indicating the development of cDFM syllables may be affected by vocal learning.The development of echolocation calls in V.sinensis was influenced by the maturation effect.The difference of fundamental frequency and bandwidth between two groups and adults was analyzed.The analysis results of fundamental frequency showed that there was no difference in fundamental frequency between the two groups at the age of 53 and 59 days(P > 0.05).The bandwidth analysis results showed that there was no difference between the playback group and the adult bats at the age of 53 days and 59 days(53-day: t = 0.072,P > 0.05;59-day: t = 0.117,P > 0.05).The isolation group also had no significant difference with adult bats at 59 days of age(t = 0.182,P > 0.05).The correlation analysis results showed that there was a significant positive correlation between fundamental frequency and age(Isolation: r = 0.670,P = 0.000;Playback: r = 0.638,P = 0.000),bandwidth and age(Isolation: r = 0.698,P = 0.000;Playback: r = 0.532,P = 0.000).In summary,this study found that the similarity of isolation calls in twins of V.sinensis was affected by genetic effect,and it was speculated that the individual characteristics of isolation calls were beneficial to the identification between mother and pups.The development of pups' communication calls was influenced by vocal learning,which suggests that the Asian parti-colored bat may have the ability of vocal learning.The results study added to the behavioral evidence to the studies on Chiropteras,and enriched the research on the influence of vocal development in mammals.It is further confirmed that Chiropteras can be used as a model for mammalian language research,providing important reference for the following similar studies.