Detrivores are certain animals that are an extremely important part of the food chain. There are numerous types, with the most being insects, fish, some crustaceans, and birds, reptiles or mammals that are primarily scavengers. Their role in the food chain is to eat dead organic material, but they usually have little role in killing the organic material. They are recyclers to a degree, consuming this material, but not completely breaking it down in their digestive systems.
For example, oceans, streams and lakes have fish (and sometimes crabs) that eat dead organic materials present on the floor of the water source. Such material can include already dead animals, fish scales, excretions from fish, and dead plant material. Detrivores typically consume these, helping to keep the aquatic environment cleaner and removing detritus.
Once detrivores have fed on this material, they’ve also left it vulnerable to decomposers, who break down detritus even further. Decomposers can include certain animals and fish, but are more likely to include various forms of bacteria and fungi. Decomposers can be said to be responsible for cleaning up and breaking down the end stage of decay, while detrivores take the role of first pass at the cleaning but still contribute to decay.
You’ll find a variety of these first stage cleaners in the insect world. Termites, for instance, eat wood (unfortunately some of it in our houses) that is no longer living. Woodlice also feed on dead plant matter, typically from trees. Wasps, yellow jackets and even butterflies can be found gathering on carcasses. Worms consume dead plant material and essentially work as wonderful composters.
Even in fish bowls and aquariums you may find detrivores, which may also be called bottom feeders by some. They serve a useful role in small aquariums because they help to keep detritus from gathering at the bottom of the tank. A few bird species are considered detrivores since they feed on dead animals alone. In particular, most vultures tend to scavenge only, rather than hunting.
There are animals that can sometimes scavenge, but may also hunt. Foxes, lions, hyenas and numerous other animals are opportunistic feeders. They won’t necessarily reject a dead animal as a good source of food, but they will also hunt for food when they can’t scavenge enough to get the necessary nutrients they need. In some respects, especially in advanced human cultures, humans are similar. Most of the food we consume is dead organic material; however, some human had to harvest it or slaughter it to make it available to us.