Impacts of maternal characteristics and temperature on juvenile survival in the crocodile lizard: Implications for conservation

Abstract

Captive breeding is an important conservation measure that may restore and enhance wild populations of rare and endangered species. Multiple anthropogenic hazards have brought the crocodile lizard, Shinisaurus crocodilurus, to the brink of extinction. We initiated a captive breeding program and quantified female reproductive traits, including reproductive timing, litter size, litter mass, and neonate size. To identify the internal and external factors affecting female reproductive function, we then analyzed how maternal age is related to body size, temperature, and female reproductive traits. We found that larger female crocodile lizards produced more offspring than smaller ones, as both litter size and litter mass were positively related to maternal body size. In contrast, neonate size was independent of maternal body size. Maternal reproductive output varied among different age groups. Young and old females had significantly smaller living litter size and mass than middle‐aged females. Among captive females, one‐third exhibited early parturition in autumn and winter instead of the following spring, a pattern probably associated with higher ambient temperatures in captivity. Although female reproductive output and neonatal body size did not differ between early‐ and normal‐parturition females, offspring from the former group died earlier than those from the latter. Our study highlights the danger of climate change in hastening parturition, a phenomenon that could significantly hamper neonate survival and impede population recruitment.

The eggshell‐matrix protein gene OC‐17 is functionally lost in the viviparous Chinese crocodile lizard

“…The crocodile lizard was estimated to have an ancient origin of viviparity during the Cretaceous period, which is older than most Cenozoic origins of viviparity in squamates (Wright et al, 2015). In captivity, female crocodile lizards give birth to fully developed young after a gestation time of up to 10 months (Li et al, 2019), which is rare even in viviparous lizards (Olsson & Shine, 1998). Neonates are surrounded with a transparent, water‐rich membrane (Figure 1a), which is often broken during parturition.…”

Consumption of centipedes promotes growth and gut microbiome homeostasis in a lizard

“…Lizards were hand‐captured and labeled, and their positions were marked. Juveniles and adults were determined using a snout‐vent length (SVL) threshold of 121 mm, which was adopted from records in the captive population 29 . The lizards were then transported to the breeding center in an approximately 30‐min walk.…”

“…Juveniles and adults were determined using a snout-vent length (SVL) threshold of 121 mm, which was adopted from records in the captive population. 29 The lizards were then transported to the breeding center in an approximately 30-min walk. The stomach contents were flushed out with water following the method that had been formerly verified as effective and safe in a captive population.…”

Responses of gut microbiota in crocodile lizards (Shinisaurus crocodilurus) to changes in temperature

“…It is a class I protected animal in China and is listed as an endangered species on the IUCN Red List of Threatened Species ( Yu et al, 2009 ). This species is a semi-aquatic lizard, preferring mountainous streams within evergreen broadleaf forests and bamboo forests ( Li et al, 2019 ; Yang et al, 2020 ). The crocodile lizard is distributed in a few isolated sites in southern China (Guangdong Province and Guangxi Zhuang Autonomous Region) and northern Vietnam (Quang Ninh and Bac Giang provinces) ( van Schingen et al, 2014 , 2016 ).…”

“…According to previous studies, crocodile lizards prefer relatively low temperatures and they are able to thermoregulate better in the lower thermal quality environment ( Yang et al, 2020 ). In contrast, as a result of increasing temperatures, the offspring survival of crocodile lizards may be hampered ( Li et al, 2019 ). What’s worse, in a future global warming scenario, the potential range of crocodile lizards will continue to shrink ( Zhang X. et al, 2022 ).…”