Because time and resources are no longer being devoted to the offspring, infanticide often stimulates the female to return to sexual receptivity and fertility sooner than if the offspring were to survive. Furthermore, while lactating, females do not ovulate and consequently are not fertile. Infanticide therefore has the potential to increase the incoming male's reproductive success. Harems are beneficial social structure for the dominant male, as it allows him access to several reproductively available females at a time. Harems provide protection for the females within a particular harem, as dominant males will fiercely ward off potential invaders. This level of protection may also, such in the case of the common pheasant, reduce the energy in female expended on remaining alert to, or fleeing from, invading males. Harems allow bonding and socialization among the female members, which can result in greater control over access to females as determined by the females' preferences. Harems also facilitate socialized behavior such as grooming and cooperative defense of territory. Harems can prove energetically costly for both males and females. Males spend substantial amounts of energy engaging in battles to invade a harem, or to keep hold of a harem once dominance has been established. Such energy expenditure can result in reduced reproductive success such in the case of red deer. This is especially true when there is high turnover rates of dominant males, as frequent intense fighting can result in great expenditure of energy. High turnover rate of dominant males can also be energetically costly for the females as their offspring are frequently killed in harems where infanticide occurs. Harems can also negatively affect females if there is intra-harem competition among females for resources. A lower-cost alternative mating strategy, useful to bachelors without a harem, is kleptogyny or the "sneaky fucker strategy", sneaking in to mate while the harem owner is distracted: in the case of red deer, when the harem stag is involved in a fight with another older stag. The strategy is also recorded in the elephant seal. Animals that form harems include: