Final answer:
Migration in animals is a response to various environmental cues such as lowering temperatures, food scarcity, and shorter daylight hours, but not the absence of reproductive mates. This behavior is a survival strategy to find optimal conditions for living.
Step-by-step explanation:
The question pertains to migration as a phenotypically plastic response in animals, which is often triggered by environmental cues. Typical triggers for migration include seasonal changes such as lowering air temperatures, decreasing food supplies, and shorter day length. However, the absence of reproductive mates is not commonly a direct trigger for migratory behavior, but rather a factor that can influence the outcome or destination of migration. Animals often migrate to improve their chances for survival, moving between areas that offer optimal conditions for feeding, breeding, and raising offspring.
For example, the Arctic Tern undergoes an extensive migration to maintain a constant body temperature and access to food resources, while Monarch butterflies migrate to escape cold temperatures and find suitable locations to overwinter. These migrations are critical for the survival of these species as they adapt to changes in temperature and food availability. Yet, migration is also a high-energy cost activity and animals must weigh this against the benefits it brings.