捕食 and 天敵: predator, prey and a natural-enemy relationship
Read the active 捕食する and passive 捕食される alongside 天敵. Separate observed predation, a relationship looked up in a guide and a bird's role in a story.
捕食する and the large fish
捕食 (ほしょく) means predation. 「水槽で大きな魚が小魚を捕食する様子を観察した。」 means “We observed a large fish preying on a small fish in the tank.” The large fish is the predator and the small fish the prey; the observers watched the action in the tank.
大きな魚が marks the acting subject and 小魚を the object. Preserve those roles when reading the observation of predation.
捕食される and the preyed-on side
「捕食される側の動物は周囲に溶け込む色をしている。」 means “Animals that are preyed upon have colors that blend into their surroundings.” The passive 捕食される側 identifies the animals on the preyed-on side, rather than the predators.
The sentence describes those animals' colors blending into their surroundings. This statement does not supply a universal color rule for all prey or the time of an actual predation event.
天敵 as a relationship and a story role
天敵 (てんてき) means natural enemy or predator. 「この昆虫の天敵を図鑑で調べた。」 means “I looked up this insect's natural enemies in an illustrated guide.” Looking up this relationship in a guide is not a report of directly observing predation.
「物語では小さな鳥が森の害虫の天敵として登場する。」 means “In the story, a small bird is a natural predator of forest pests.” The bird appears in the story as a natural enemy of forest pests. Naming that role does not report that the pests were actually eaten.
How do the roles differ in 捕食される側 and 大きな魚が小魚を捕食する?
Show the answer and why
The first names the preyed-on side; the second describes a large fish preying on a small fish. Looking up 天敵 concerns the natural-enemy relationship, distinct from the tank example's direct observation of predation.