Question

Using Tinbergen’s framework explain how and why nonbreeding casts can persist in eusocial species?

Answer 1

Tinbergen's framework leads us to the four questions in animal biology. The four questions are:

1. How does a behavior occur in an individual? (Causation)
2. How the behavior is expressed and then develops in the individual? (Development)
3. Why this behavior is adaptive for the species? (Function)
4. How the behavior arises in species? (Evolution)

• Now, let us know what is eusociality: It is an advanced or extreme form of sociality, in which cooperative brood care, division of labor and multi-generational family groups are observed.

• So, we can answer the first question this way: An important characteristics of eusociality is cooperative brood care which includes taking care of offsprings from other individuals. Division of labor is another aspect, so, some individuals are needed to bring food, others are needed to maintain the habitat, some have to defend the entire society too. So, an individual can do these works and invest time and energy in it rather than in breeding.

• Second question can be answered like this: An individual who does not invest time and energy in breeding can take care of offsprings from other individuals or bring food or defend the society or maintain the habitat/home (e.g., bee-hives) instead. As time goes by, the individual becomes habituated and efficient in their specific work only. So, it does not develop behaviors that are required to find potential mates or to breed.

• Now let us come to the answer of the third question: The members which breed, only breed and produce offsprings. Neither they bring food, feed other members, nor do they defend and maintain their society or homes. So, the breeders only develop characteristics required for mating purposes. They produce more and more offsprings. Other members take care and feed the little ones, some others defend them and clean/maintain the hives. So, each member works for the entire society i.e., everyone is working for everyone. So, it is clear that if non-breeding members did not exist, the society would get collapsed. Hence, this is adaptive for the species.

• The answer of the fourth question can be given this way: As the above mentioned division of labor and cooperative brood care occurs in a society of a species, one does not have to look for potential mates or breed to exist in the community. One is working for the other so that everyone can exist in the society even without producing offspring. Besides, the ones who breed do not have to care about food, home, enemies or care of the offsprings. Because those works are being done by other members. As they are the breeding individuals, they become efficient in mating processes eventually and expend all their time and energy in producing offsprings only, while other members take care of them. It gradually happens in all the societies of the species because it is beneficial for all the members and for the existence of the society itself. So, this is how the behavior (of not breeding) arises in them, because the non-breeding members know that they can exist even without breeding.