1. Energy Density:
* Lipids are much more energy-dense than carbohydrates. A gram of fat contains about 9 calories, while a gram of carbohydrate contains only 4 calories. This means an animal can store a lot more energy in a smaller volume of fat.
2. Water Conservation:
* Lipids are hydrophobic (water-repelling), meaning they don't bind water molecules. This allows migrating animals to carry a large energy reserve without carrying extra weight in the form of water.
* Carbohydrates, on the other hand, are hydrophilic (water-attracting). They bind water molecules, increasing their overall weight and making them less efficient for long-distance travel.
3. Storage Efficiency:
* Fat can be stored more efficiently than carbohydrates. Animals can store large amounts of fat in specialized tissues like adipose tissue, which can expand to accommodate the extra weight.
* Carbohydrates are not as easily stored in large quantities. They can be stored as glycogen in the liver and muscles, but these stores are limited.
4. Metabolic Flexibility:
* Lipids can be broken down slowly and steadily to provide energy over extended periods. This is crucial for long migrations where animals may not have access to food for days or weeks.
* Carbohydrates are quickly broken down and used for energy. This makes them less suitable for long-distance travel, where a steady energy supply is needed.
5. Insulation:
* Fat provides insulation, protecting animals from cold temperatures. This is particularly important for migrating animals that may encounter harsh weather conditions.
In summary, storing energy as lipids offers migrating animals a more compact, water-efficient, and long-lasting energy source that can sustain them through their journeys.