Predators significantly influence amphibian larval development. Predator-induced plasticity is often studied independently from conspecific density effects, but these environmental factors may interact. We conducted two-factor factorial experimental design to manipulate conspecific density and predator cues, aiming to investigate the independently or interactive impacts of these two factors on the development of Chinhai spiny newt larvae (Echinotriton chinhaiensis). Our findings reveal that both high and low conspecific densities constrain spiny newt larval growth and predators also limit growth. Interestingly, high conspecific density restricts predator-induced growth plasticity without interacting effects. Only lower density groups exhibit slower growth responses to predators. Our study investigates how density mediates predator-induced plasticity in the endangered Chinhai spiny newt larvae, providing insights into their intricate life history. These results contribute to the understanding of predator-induced plasticity in amphibians and provide insights into the adaptive strategies of endangered species like Chinhai spiny newt. Such knowledge informs the development of effective conservation strategies for their protection.

Amphibians are the most threatened vertebrates, yet their resilience in relation to growth and locomotor performance with rising temperatures remains poorly understood. Here, we chose a critically endangered amphibian—the Chinhai spiny newt (Echinotriton chinhaiensis)—as the study species and set four water temperature gradients (20 °C, 24 °C, 28 °C, and 32 °C) to simulate climate changes. The thermal performance to climate warming was quantified by measuring morphometric parameters, basal metabolic rate (oxygen consumption rate), and the locomotor performance of Chinhai spiny newt larvae. We found that the optimal temperature range for Chinhai spiny newt larvae is 24–28 °C. Within the temperature range of 24–28 °C, the growth, oxygen consumption rate, and locomotor performance of the larvae were positively correlated with temperature. High temperatures inhibited larval growth, oxygen consumption rate, and locomotor performance, and the temperature threshold was 32 °C. In addition, Chinhai spiny newt larvae are more sensitive to acute temperature changes, meaning that climate-driven extreme events (e.g., heatwaves and droughts) pose significant threats to their larvae. The optimal temperature range obtained from this study could guide artificial breeding and early warming; future studies should integrate controlled temperature fluctuations in order to understand the thermal adaption of this threatened species.