Strategic mate-guarding occurs when the male only guards the female during her fertile periods. This strategy can be more effective because it may allow the male to engage in both extra-pair paternity and within-pair paternity. This is also because it is energetically efficient for the male to guard his mate at this time. There is a lot of energy that is expended when a male is guarding his mate. For instance, in polygynous mate-guarding systems, the energetic costs of males is defending their title as alpha male of their community. Fighting is very costly in regards to the amount of energy used to guard their mate. These bouts can happen more than once which takes a toll on the physical well- being of the male. Another cost of mate-guarding in this type of mating system is the potential increase of the spread of disease. If one male has an STD he can pass that to the females that he's copulating with potentially resulting in a depletion of the harem. This would be an energetic cost towards both genders for the reason that instead of using the energy for reproduction, they are redirecting it towards ridding themselves of this illness. Some females also benefit from polygyny because extra pair copulations in females increase the genetic diversity with the community of that species. This occurs because the male is not able to watch over all of the females and some will become promiscuous.