Why is blood meal sharing in vampire bats considered to have evolved via reciprocal altruism?

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Blood meal sharing in vampire bats is considered to have evolved via reciprocal altruism primarily because individuals share food with individuals from whom they have received food. This behavior fits the concept of reciprocal altruism, where an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, with the expectation that the other organism will act in a similar manner at a later time.
The key aspects of reciprocal altruism, as observed in vampire bats, include:
1. **Non-random sharing**: Vampire bats tend to share blood meals with specific individuals that have shared with them in the past, rather than sharing randomly. This suggests a tit-for-tat strategy, which is a fundamental component of reciprocal altruism.
2. **Cost and benefit**: While there is a cost to the donor in sharing a blood meal (reducing its own food intake), the benefit to the recipient (who might otherwise starve) is significant. The donor bats are more likely to receive food from others on days when they are unsuccessful in finding food themselves, which can be a critical survival factor.
3. **Memory and recognition**: Vampire bats demonstrate the ability to remember past interactions and recognize other individuals, which is necessary for reciprocal altruism to evolve. They keep track of who has shared with them and are more likely to share with those individuals in the future.
4. **Enforcement**: There is evidence that vampire bats enforce the reciprocal arrangement by punishing individuals who do not reciprocate. Bats that do not share blood meals may find themselves excluded from future sharing by others.
The other options provided do not adequately explain the evolution of blood meal sharing via reciprocal altruism:
a. Blood meal sharing occurs both in captivity and in the wild, and its occurrence in the wild is essential to the argument for reciprocal altruism.
c. There is a cost to blood meal sharing for the donor, as it gives up some of its food resources.
d. While cooperation between males and females may occur, reciprocal altruism specifically refers to the exchange of resources between individuals, which can occur regardless of sex.
e. Blood meal sharing in vampire bats does not only involve relatives; it can also occur between unrelated individuals, which is a key point in the argument for reciprocal altruism rather than kin selection.

Why Is Blood Meal Sharing in Vampire Bats Considered to Have