Food limitation and starvation independently affect predator macronutrient selection

Area of Science:

• Ecology
• Animal Nutrition
• Behavioral Ecology

Background:

• Predators often face food limitations in their natural habitats.
• Specific macronutrient deficiencies (protein, lipid, carbohydrate) can also limit predators.
• The relationship between general food limitation and specific macronutrient limitation remains unclear.

Purpose of the Study:

• To investigate the connection between food and macronutrient limitation in predators.
• To determine how starvation affects macronutrient self-selection in carabid beetles.
• To understand the primary drivers of nutrient limitation in natural environments.

Main Methods:

• Studied macronutrient self-selection in the carabid beetle *Nebria brevicollis*.
• Assessed nutrient intake at three key time points: post-collection, post-satiation, and post-starvation.
• Analyzed dietary choices for protein, lipid, and carbohydrate content.

Main Results:

• In the field, both male and female beetles were limited by food, with females also limited by lipids.
• Following starvation, both sexes significantly increased their proportional carbohydrate intake.
• Starvation induced a distinct nutrient deficit compared to field conditions.

Conclusions:

• Food limitation can influence macronutrient limitation, but it is not the sole determinant.
• Nutritional imbalances in available food sources can be a more significant factor than general hunger.
• Dietary self-selection in predators is a complex interplay of food availability and specific nutrient needs.