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How does temperature affect the development time of reptile eggs?

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A painted turtle (Chrysemys picta) with a dark shell and red and yellow markings rests on a rock near water, surrounded by green aquatic plants. — reptile Painted turtle (*Chrysemys picta*).

Because reptiles are ectothermic, the development time of their eggs is directly influenced by the temperature of their surroundings.12

In general, warmer temperatures accelerate the rate of embryonic development, while cooler temperatures slow it down. Because of this sensitivity, incubation periods can be highly variable depending on environmental conditions. While extreme heat or cold can be lethal to developing embryos, moderate increases in temperature typically result in a shorter incubation period.23

In addition to affecting the speed of development, temperature plays a critical role in sex determination for many reptile species, a phenomenon known as temperature-dependent sex determination (TSD). For example, in many turtles, higher temperatures during the middle of the incubation period tend to produce females, while lower temperatures produce males.23