Amphibians and lizards undergo aestivation/hibernation during winter months .

Explanation

**Step-by-Step Solution:**

1. **Understanding the Terms**: First, we need to clarify the terms "aestivation" and "hibernation". Aestivation refers to a state of dormancy that occurs during hot or dry periods (usually in summer), while hibernation is a state of dormancy that occurs during cold periods (usually in winter).

2. **Identifying the Organisms**: The question specifically mentions amphibians and lizards. Both of these groups of animals are ectothermic (cold-blooded) and rely on external environmental conditions to regulate their body temperature.

3. **Behavior During Winter**: During winter months, many ectothermic animals, including amphibians and lizards, cannot maintain their body temperature due to the cold environment. As a result, they enter a state of dormancy to conserve energy.

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