Vampire Bats (Desmodus Rotundus) Meet the Conditions That Trivers (1971)

Vampire bats (Desmodus rotundus) meet the conditions that Trivers (1971) laid out that are favorable to the evolution of reciprocal altruism. For example,

A) blood is shared generously among bats regardless of their previous levels of association or their degrees of kinship.
B) on any given night, roughly 33% of juveniles less than two years old and 7% of older bats fail to feed and, thus, are likely to be in need of a favor.
C) the recipient of a blood meal may gain 12 hours of life, while the donor loses more than 36 hours of time until starvation.
D) all of the above.