They are nocturnal scavengers and opportunistic predators. They are generalist scavengers and predators of small animals. Jackals are opportunistic omnivores, predators of small to medium-sized animals and proficient scavengers. However, many species feed as parasites, herbivores, scavengers and detritivores. Christmas Island red crabs are opportunistic omnivorous scavengers. Vultures are of great value as scavengers, especially in hot regions. Others are scavengers and feeders on detritus. It is thus likely that spinosaurids were also scavengers or hunters of larger prey. These chemicals are mostly oxygen scavengers and phosphates. The bird is adept at finding smaller carcasses before most other scavengers. Effects of oxygen radical scavengers and antioxidants on phagocyte-induced mutagenesis in bacteria. They often take the form of insects, reptiles, and desert scavengers. Most species will eat anything suitable that comes within reach and are also opportunistic scavengers. These smaller scavengers are often pests and disease vectors. Decomposers and detritivores complete this process, by consuming the remains left by scavengers.