I don't think they acquire the sun's energy directly.
The sun energy is absorbed by plants to make food (carbohydrate)by photosynthesis
Plant eating animals(herbivores)then get their energy from the plants they eat.
How do the ANIMALS in an ecosystem MAINLY acquire the sun’s energy?
Energy from the Sun reaches the Earth as the light. Plants use light for photosyntesis as their power source to grow. Herbivores-plant eaters- then eat the plants, which had grown due to the energy from the sun. Carnivores- meat eaters- eat the plant eaters, that has eaten the plants, that has grown because of sun light. A bit of energy- mainly warmth- the animals also gets by being in the sunlight directly.