Why do female mammals sometimes eat less during estrus?

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Two wild horses graze on tall grass in the open prairie of Theodore Roosevelt National Park, with rolling badlands visible in the background. — Feeding behaviour Wild horses graze in the Badlands of North Dakota.

In the context of feeding behaviour, female mammals may eat less during estrus because biological systems often prioritize certain functions over others. When an animal's body faces competing demands, it may suppress feeding to favor other critical processes, even if the animal is hungry.

This reduction in food intake is a form of caloric regulation distortion. Similar to how thirsty animals or mammals in hot environments suppress their feeding to avoid aggravating water shortages or heat stress, females during their fertile period may experience a marked loss of body weight due to this prioritized suppression of feeding.1