| Many warm-blooded mammals and birds need to adjust their body temperature in order to adapt to changes in their environment.Huddling behavior is often adopted as the most direct way of thermoregulation in warm-blooded animals.Thermoregulation is a key feature in maintaining homeostasis.Thermoregulation is closely related to energy balance,and animals are constantly looking for ways to limit energy expenditure in normothermic states.The Yunnan snub-nosed monkey(Rhinopithecus bieti)is the highest-altitude primate in the world,only distributed in the narrow area between the Lancang and Jinsha Rivers.The harsh environmental conditions limit the field research of the Yunnan snub-nosed monkey.At present,the research on its huddling behavior mainly focuses on the relationship between huddle and social function.There is no specific caloric data to verify the hypothesis that huddling behavior can maintain body temperature and preserve heat.From July 2020 to August2021,we used the focal animal sampling and continuous recording method to study the huddling behavior of a group of habitual Yunnan snub-nosed monkey living in the Baimaxueshan National Nature Reserve in Yunnan with the range of activity of 2400 m to 3300 m.During the study,we observed 8 One Male Unit(OMU)and 1 All Male Unit(AMU)composed of 65 Yunnan snub-nosed monkeys.Data on huddling behavior was collected using an infrared thermal imager.By studying the huddling behavior of Yunnan snub-nosed monkeys,we hope to explore the factors that affect the huddling behavior,explore the relationship between the huddling behavior and heat loss,and reveal the adaptation strategies of the Yunnan snub-nosed monkeys to the high-frigid environment.The main results of this study are as follows:1.The body temperature of the Yunnan snub-nosed monkey had seasonal differences.In this study,the facial temperature of the Yunnan snub-nosed monkey was used to represent the body temperature.Through the analysis of infrared thermal imaging data,it was found that the facial temperature of the Yunnan snub-nosed monkey was significantly different in spring,summer,autumn and winter(Krukal-Wallis H test,H=443.349,df=3,P<0.001).The facial temperature was35.19±1.25℃ in spring,35.25±1.88℃ in summer,34.94±1.23℃ in autumn and32.09±1.84℃ in winter.The difference of face temperature between summer and winter is the largest,and the difference between them is 3.16℃.However,there was no significant difference in facial temperature between male and female Yunnan snub-nosed monkey in the four seasons(Mann-Whitney U test,Z=-0.146,P=0.884).These results indicate that the Yunnan snub-nosed monkey reduced the heat loss by lowering the body surface temperature in the cold season and maintains the balance of the body.2.The huddling behavior of Yunnan snub-nosed monkeys could maintain body temperature.By comparing and analyzing the heat loss of Yunnan snub-nosed monkeys in different seasons when resting in a group or without resting in a group,the results show that:(1)The heat loss value of Yunnan snub-nosed monkey when they were grouped in spring was significantly lower than that when they were not grouped in spring(Mann-Whitney U test,Z=-4.518,P<0.001),and the difference between the two was 54.43 k J/mbm.(2)The heat loss value of Yunnan snub-nosed monkey when they were grouped in summer was significantly higher than that when they were not grouped in summer(Mann-Whitney U test,Z=-6.182,P<0.001),the difference between the two was-37.81 k J/mbm.(3)The heat loss value of Yunnan snub-nosed monkey when they were grouped in autumn was significantly lower than that when they were not grouped in autumn(Mann-Whitney U test,Z=-7.764,P<0.001),the difference between the two was 584.09 k J/mbm.(4)The heat loss value of Yunnan snub-nosed monkey when they were grouped in winter was significantly lower than that when they were not grouped in winter(Mann-Whitney U test,Z=-7.762,P<0.001).The difference between the two was 631.66 k J/mbm.These results indicated that the huddling behavior of Yunnan snub-nosed monkeys could maintain body temperature and reduce heat loss in spring,autumn and winter when the temperature was lower.As the ambient temperature drops,the greater the thermal gains from its huddling behavior.3.The heat loss of Yunnan snub-nosed monkey in a group is affected by the ambient temperature and the size of the group.(1)In terms of ambient temperature: comparing the heat loss of Yunnan snub-nosed monkey resting in a group and not in a group at different temperature ranges,the results showed that at 0-5℃,the heat loss of resting in a group was significantly lower than that of resting without a group(Mann-Whitney U test,Z=-9.134,P<0.001),and the difference between the two was 1024.9 k J /mbm,the difference between the two was 1024.9 k J/mbm.The heat loss at 5-10℃ was significantly lower than that without resting(Mann-Whitney U test,Z=-5.946,P<0.001),and the difference between the two was 670.56 k J/mbm.At 10-15°C,there was no significant difference of resting in a group and resting without a group(Mann-Whitney U test,Z=0.000,P>0.05),and the difference in heat loss between the two was 1049.63 k J/mbm.At 15-20℃,the heat loss of resting in a group was significantly lower than that of resting without a group(Mann-Whitney U test,Z=-22.298,P<0.001),and the difference between the two was 163.52 k J /mbm.At20-25℃,the heat loss of resting in a group was significantly higher than that of resting without a group(Mann-Whitney U test,Z=-19.339,P<0.001),and the difference between the two was-428.21 k J/mbm.At different temperatures,there are differences in heat loss and thermal insulation effects between resting in groups and without resting in groups,indicating that the ambient temperature would affect the benefits of thermal insulation of Yunnan snub-nosed monkey in groups.(2)In terms of the size of the group: when the different sizes of the groups of the Yunnan snub-nosed monkeys appeared,there was a significant difference in the ambient temperature(Kruskal-Wallis H test,H=61.406,df=5,P<0.001),With the decrease of the ambient temperature,the size of the clumps showed an overall increasing trend.Comparing the heat loss generated by different clump sizes in the same season,the results showed that: 1)In spring,there were significant differences in heat loss between groups of 2 groups,3 groups,and 4 groups and more group sizes(Kruskal-Wallis H test,H=165.263,df=2,P<0.001).2)In summer,there were significant differences in heat loss of different clump sizes(Kruskal-Wallis H test,H=10925.730,df=2,P<0.001).3)In autumn,there were significant differences in heat loss of different clump sizes(Kruskal-Wallis H test,H=536.937,df=2,P<0.001).4)In winter,there were significant differences in heat loss of different clump sizes(Kruskal-Wallis H test,H=53.911,df=2,P<0.001).These results indicate that the different sizes of the group would affect the heat loss of Yunnan snub-nosed monkey in different seasons.This study verified the hypothesis that the huddling behavior of Yunnan snub-nosed monkey had an thermal insulation effect,which helped researchers to understand the adaptation strategy of Yunnan snub-nosed monkey to the high-frigid environment from the perspective of heat loss,and provided a reference basis for behavioral ecology research of Yunnan snub-nosed monkey. |
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