Study On Cochlea Structure And Long Call Signal Of Plateau Pika

Vocal communication of animal plays important role in the behaviors in term of mating,foraging and defense,etc.in their life.Plateau pika(Ochotona curzoniae)is a keystone species in the alpine grassland ecosystem of the Qinghai-Tibet Plateau and plays an important role in maintaining food webs and biodiversity maintenance.But,plateau pika is regard as the pest because they compete with domestic animals for foragin and dig tunnels that cause soil erosion when their population is high.Plateau pika is known as "sounding rat because of its unique chirping.Vocal communication plays an important role in mating,defense and alarm behavior.So far,a few papers have reported the the types of plateau pikas' calls and their biological meanings.However,compared with other studies of behavior in plateau pika,there are few papers on vocal communication of plateau pika.In this study,we caught plateau pika living alpine meadows in Maqu County,Gansu Province,eastern edge of the Qinghai-Tibet Plateau,for dissecting their cochlea.After that,we studied the temporal distribution,types,and acoustic characteristics of their long call.Moreover,the internal factors(testosterone and progesterone)and external factors(temperature and wind speed)that affect long call were analyzed.The purpose of the study is to supply the basic research of vocal communication in plateau pika and to clarify the reproductive strategies are important.The main findings are as follows:(1)The cochlea of plateau pika has a 2.5-circle bony spiral structure.There are 3 rows of outer hair cells on the basement membrane and only 1 row of inner hair cells from the bottom of the cochlea to the top of the cochlea.The scala tympani,cochlear duct and scala vestibuli are relatively short,the number of hair cells is relatively few,and the thickness of the basilar membrane is relatively thin to rats(Rattus norvegicus),guinea pigs(Cavia porcellus)and plateau moles(Eospalax fontanierii).The number of the helix ganglions from the bottom to the top of cochlea gradually decreases.(2)The long call of plateau pika mainly occurred in the breeding period from March to May,which was significantly higher than in other months.The duration of long call ranges in each individual male but was 130~180 seconds per day and mainly uttered 2 hours after sunrise and 1.5 hours before sunset throughout the year.The occurrence of long call uttered by male plateau pika throughout the year is closely related to pikas' testosterone levels which peak in the warmer months.The long call in plateau pikas during the non-breeding period was negatively correlated with air temperature and wind speed.(3)Used the voice analysis software Wavesurfer to analyze the recorded long call,combined with the behavior of the long calls,the male plateau pika long call were divided into alarm calls,mating calls and defence calls.All the long calls with 30 syllables were sounded by male pika.the long call of male plateau pikas has a strong complexity,which the mating and defense of long calls had the similar acoustic characteristics.