Maximum Diving Duration And Its Influencing Factors Of Captive-reared Chinese Crocodile Lizard(Shinisaurus Crocodilurus) And Diving Lizards

Diving is an important locomotor performance for animals and the longest dive duration for voluntary diving is the best indicator to quantify diving ability.Due to climate change and human disturbance,the endangered Chinese crocodile lizard(Shinisaurus crocodilurus)has been released into captivity several times due to its narrow range,low numbers in the wild,high levels of inbreeding and reduced habitat.Captive-reared Chinese crocodile lizard can dive to avoid danger,and studying the maximum dive duration of captive crocodiles and the factors that influence it can provide a scientific basis for captive breeding and species conservation.At the same time,the proportion of lizards capable of diving is small and poorly studied,and single-species studies do not provide a broad interpretation of the entire diving lizard taxon.This study investigates the maximum dive duration of lizards and the factors that influence it,both from an intraspecific and interspecific study,contributing to a deeper understanding of the lizards'hypoxia tolerance and recovery capacity,and thus their ability to adapt to their environment.In this study,captive-reared Chinese crocodile lizard and lizards with maximum dive duration were used to investigate their maximum dive duration and its influencing factors.In the intraspecific study,from July to August 2021,the diving behavior of the captive-reared Chinese crocodile lizard in Daguishan Nature Reserve,Guangxi,China,was recorded on camera.Then the relationships between maximum dive duration and environmental factors,behavioral and morphological characteristics in 61 captive-reared Chinese crocodile lizards were investigated by Pearson's correlation analysis,analysis of variance(ANOVA),general linear model,one-dimensional linear regression and stepwise regression analysis.In addition,the interspecific study,the maximum dive duration of captive-reared Chinese crocodile lizard was included in the interspecific analysis.Phylogenetic generalized least squares,Markov Chain Monte Carlo GLMMs and Phylogenetic path analysis were used to investigate the relationships between maximum dive duration,environmental factors and life-history traits in 52 species of diving lizards.This study focuses on answering the following scientific questions:(1)Is the maximum dive duration of captive Chinese crocodile lizard influenced by environmental factors,behavioral traits and morphological characteristics?(2)Is the maximum dive duration of diving lizards influenced by environmental factors and life-history traits?(1)Maximum diving duration and its influencing factors of captive-reared Chinese crocodile lizard.The maximum dive duration for the sub-adult group(n=25)ranged from262.47 s?2048.20 s,with a mean of 775.61 s.The maximum dive duration for the adult male group(n=17)ranged from 247.17 s?2022.23 s,with a mean of 602.81 s.The maximum dive duration for the adult females(n=19)ranged from 224.83 s to 2169.77 s,with a mean value of 602.53 s.There were no significant differences in the maximum dive duration between captive-reared Chinese crocodile lizards of different ages and sexes(F_2,58=0.747,P=0.478).Results indicated that the diving behaviors of captive-reared crocodile lizards were repeatable.Air temperature(r=-0.239,P=0.199),water temperature(r=-0.172,P=0.962),to move or not to move(F_1,59=0.465,P=0.498)and is it near the stones(F_1,59=0.516,P=0.475)did not affect the maximum dive duration of the captive-reared Chinese crocodile lizard.The maximum dive duration of captive crocodile lizards was not significantly correlated with environmental factors or behavioral characteristics.Furthermore,the maximum dive duration of captive-reared Chinese crocodile lizard was positively correlated with tail loss(r=0.325,P=0.011)and was significant negatively correlated with tail length(r=-0.214,P=0.014)and tail volume(r=-0.326,P=0.012),while other morphological characteristics did not significantly affect the maximum dive duration of captive-reared Chinese crocodile lizard.(2)Maximum diving duration and its influencing factors of diving lizard.The maximum dive duration of 52 species of diving lizards ranged from 25.75 s to 16200.00 s,and Anoles lizards can rebreathe underwater.Longitude(r=0.628,P=0.764),latitude(r=0.628,P=0.812),insularity(n=52,Post.mean=-0.046,CI=-0.321?0.224,Pmcmc=0.742),water quality(n=52,Post.mean=-0.101,CI=-0.614?0.443,Pmcmc=0.692)and reproductive mode(n=38,Post.mean=-0.333,CI=-0.846?0.148,Pmcmc=0.197)were not significantly correlated with the maximum dive duration in diving lizards.The maximum dive duration of diving lizards was not significantly correlated with environmental factors.In addition,the maximum dive duration was positively correlated with body weight(r=0.780,P<0.001),head length(r=0.751,P<0.001),longevity(r=0.677,P=0.002),tail length(r=0.688,P=0.008)and clutch size(r=0.724,P<0.001)in diving lizards.After controlling for body size,the maximum dive duration of diving lizards was negatively correlated with tail length(r=-0.780,P=0.027)and positively correlated with clutch size(r=0.806,P=0.049).Body size(snout-vent length)not only directly influenced the maximum dive duration of diving lizards but indirectly increased the maximum dive duration of diving lizards by increasing clutch size.In summary,the diving performance of captive-reared Chinese crocodile lizard was influenced by morphological characteristics,while environmental and behavioral factors did not affect the maximum dive duration of captive-reared Chinese crocodile lizard.The diving performance of the diving lizards was related to life-history traits,while environmental factors did not affect the maximum dive duration of the diving lizards.The tail played an important role in the survival of the lizards,as the tail length of Chinese crocodile lizard was positively correlated with swimming speed,but was negatively correlated with maximum dive duration,this suggests a trade-off between swimming speed and maximum dive duration,with longer-tailed Chinese crocodile lizard choosing to swim faster to escape predators,and shorter-tailed Chinese crocodile lizard choosing to increase the diving duration to escape predators.The interspecific study found that the longer the tail length,the shorter the maximum dive duration for lizards after controlling phylogenetically,and that the negative correlation between tail length and lizard diving ability may be a unique anti-predator strategy for lizards.