>Depends on what you call "infidelity". Some species are promiscuous,
>mate for life. In those species where promiscuity is the norm, it's
>perfectly "acceptable" behavior. Promiscuity is not infidelity, since no
>long-term bond of trust is expected. Individuals of species with a
>tradition of "marriage" OTOH are seldom observed to violate the bond--and
>those who practice infidelity often face sanctions.
>The article included geese (long thought to mate for life) and found that
>they in fact didn't. They just hid it very well (it used genetics to
>parentage and found it wasn't what it should have been).
This is a case where the initial theory - that geese are strictly monogamous - turned out to be wrong. So the existence of "infidelity" is largely illusory.
>It also looked at
>primate (I think chimpanzees) and found that some of them were expert at
>arranging assignations. One particularly amusing example was of two
>chimpanzees pretending to forage with their top halves while having sex
>their bottom halves, both of them surpressing the normal chimpanzee mating
>noises (which are rather loud).
Chimps have long been known to be promiscuous. The main constraint is the fact that dominant males try to reserve the females to themselves, causing the subordinate males to be sneaky about mating opportunities. Again this is not an instance of "infidelity". Fornication is not (necessarily) adultery.