Editing Reciprocal altruism (section)

===Vampire bats===
[[Vampire bats]] also display reciprocal altruism, as described by Wilkinson.<ref name="Wilkinson1">{{cite journal | last1 = Wilkinson | first1 = G. | year = 1984 | title = Reciprocal Food Sharing in the Vampire Bat | journal = Nature | volume = 308 | issue = 5955| pages = 181–184 | doi=10.1038/308181a0 | pmid = 23282995 | pmc = 3574350 | bibcode=1984Natur.308..181W }}</ref><ref name="Wilkinson2">{{cite journal | last1 = Wilkinson | first1 = G. | year = 1988 | title = Reciprocal Altruism in Bats and Other Mammals | journal = Ethology and Sociobiology | volume = 9 | issue =2–4 | pages = 85–100 | doi=10.1016/0162-3095(88)90015-5 }}</ref>
The bats feed each other by regurgitating blood. Since bats only feed on blood and will die after just 70 hours of not eating, this food sharing is a great benefit to the receiver and a great cost to the giver.<ref>{{cite journal|last1=Carter|first1=Gerald|title=Food Sharing in Vampire Bats: Reciprocal Help Predicts Donations More than Relatedness or Harassment | journal=Proceedings of the Royal Society|volume=280|issue=1753|pages=20122573|date=January 2, 2013 |pmc=3574350|pmid=23282995|doi=10.1098/rspb.2012.2573}}</ref>
To qualify for reciprocal altruism, the benefit to the receiver would have to be larger than the cost to the donor. This seems to hold as these bats usually die if they do not find a blood meal two nights in a row. Also, the requirement that individuals who have behaved altruistically in the past are helped by others in the future is confirmed by the data.<ref name="Wilkinson1" /> However, the consistency of the reciprocal behaviour, namely that a previously non-altruistic bat is refused help when it requires it, has not been demonstrated. Therefore, the bats do not seem to qualify yet as an unequivocal example of reciprocal altruism.