Adaptive Value (also known as Survival Value) refers to the ways in which the behavior affects the survival and lifetime fitness of the individual organism. While it may seem fairly intuitive why established dominance hierarchies would be valuable for dominant males (i.e., they get access to females without having to constantly fight off subordinate males), it is less clear what advantages there are, if any, for the subordinate male. Some potential benefits for subordinates, while mostly theoretical, will nevertheless be presented and discussed.

Benefits for dominant males: Increased reproductive success

Although data for differential reproductive success between dominant and subordinate rats is not readily available, a comparison of offspring produced between dominant and subordinate zebrafish, which have a social hierarchy that operates similarly to that of rats, indicates that dominant males produce more offspring than subordinate males.

Increased reproductive fitness of dominant male zebrafish relative to subordinate male zebrafish. Reprinted from Paull et al., 2010.

Further taking into account the fact that individuals higher up on the ladder tend to have longer lifespans than lower-ranking individuals (Marmot et al., 1991), it is apparent that if an individual rat has the opportunity to be dominant, then it is likely in their best interests (both in terms of their lifespan and their reproductive fitness) to do so.

Benefits for subordinates: Prevents death by fighting

As discussed at greater length in Silk et al., 2007, while a subordinate male will likely be less reproductively fit than a dominant male, they still enjoy greater fitness than if the dominance hierarchy was not present at all. The major speculation for this conclusion is that while the hierarchy may prevent a subordinate from mating in most occasions, it does at least discourage the sort of violent conflicts over females that might very well result in the death of a subordinate male if no hierarchy was present. Additionally, reproductive tactics such as subordinate males covertly mating with females allow them to produce offspring without the need to directly challenge a larger dominant male.