Cheating (biology)

Cheating is a metaphor commonly used in behavioral ecology to describe organisms that receive a benefit at the cost of other organisms. Cheating is common in many mutualistic and altruistic relationships. Natural selection favors cheating, but there are mechanisms to regulate cheating.

Theoretical models
The producer/scrounger game contains cheaters. Producers search for their own food while scroungers take the food others have found. Producers benefit when scroungers are common. Scroungers benefit when scroungers are rare. If there are many scroungers and few producers, the producers are easily able to find food since there is much less competition. If there are few scroungers and many producers, the scroungers can easily cheat. The scroungers are no longer competing against each other to take the producer’s food. A bird can be a scrounger. Instead of foraging for its own food, the scrounger will wait until another bird comes back with food. The next day, the scrounger will follow the successful bird to the patch. The cheating bird reaps the benefits without putting in the effort that the producer put in to find the food.

Animal examples
Some examples of animals that are known to cheat include: cleaner fish, social insects, ungulates, and birds. Cleaner fish have a mutualistic relationship, a cleaning symbiosis, with their clients. The cleaners eat ectoparasites off their clients. The clients benefit from being cleaned, and the cleaners benefit from acquiring food. However, some cleaners cheat by eating tissue, scales, and mucus off their clients instead of only ectoparasites. This could be detrimental to the clients and possibly turn the mutualistic relationship into commensalism or parasitism.

As for social insects, such as bees, ants, and wasps, the queen is the only individual that is supposed to reproduce. In some cases, cheating workers reproduce also. This disrupts the altruistic relationship between the queen and the workers.

Vigilance is essential for many colonial animals. The animals on the outside of the group will be vigilant, while those on the inside forage. The animals within the group also monitor each other’s vigilance. A cheater may emerge in groups with vigilant animals. The cheater might try to forage the entire time, while the rest of the group switches between foraging and being vigilant.

Non-animal examples
The relationships between flowering plants and their animal pollinators and plants and fungi are generally mutualistic, but there are cheaters. Two species of yucca moths eat yucca seeds, but do not pollinate the yucca because they lack the necessary mouthparts. The animal pollinators are not the only cheaters though. Some flowers do not produce nectar. Many pollinators are not able to distinguish between which flowers produce nectar and which do not; therefore, some flowers cheat by not making nectar for the pollinator. Examples of nectarless plants include some species of orchids. Orchids are not just cheaters towards pollinators. Some orchids cheat by not providing fixed carbon to mutualistic fungi.

Solutions
There are ways to avoid cheaters, including: policing, changing partners, and pushing the cheater on the outside of a vigilant group.

In order to avoid cheating in polyandrous honeybees, worker policing is enforced, which entails the removal of eggs laid by selfish workers. To prevent cheating cleaner fish, the clients chase them or switch partners.