<P> Reproduction is costly . Individuals are limited in the degree to which they can devote time and resources to producing and raising their young, and such expenditure may also be detrimental to their future condition, survival, and further reproductive output . However, such expenditure is typically beneficial to the offspring, enhancing their condition, survival, and reproductive success . These differences may lead to parent - offspring conflict . Parental investment can be provided by the female (female uniparental care), the male (male uniparental care), or both (biparental care). Parents are naturally selected to maximize the difference between the benefits and the costs, and parental care will tend to exist when the benefits are substantially greater than the costs . </P> <P> Penguins are a prime example of a species that drastically sacrifices their own health and well - being in exchange for the survival of their offspring . This behavior, one that does not necessarily benefit the individual, but the genetic code from which the individual arises, can be seen in the King Penguin . Although some animals do exhibit altruistic behaviors towards individuals that are not of direct relation, many of these behaviors appear mostly in parent - offspring relationships . While breeding, males remain in a fasting - period at the breeding site for five weeks, waiting for the female to return for her own incubation shift . However, during this time period, males may decide to abandon their egg if the female is delayed in her return to the breeding grounds . This is an interesting case, as it shows that these penguins initially show a trade - off of their own health, in hopes of increasing the survivorship of their egg, but there comes a point where the male penguin's costs become too high in comparison to the gain of a successful breeding season . In a study, Olof Olsson investigated the correlation between how many experiences in breeding an individual has and the duration an individual will wait until abandoning his egg . He proposed that the more experienced the individual, the better that individual will be at replenishing his exhausted body reserves, allowing him to remain at the egg for a longer period of time . The males' sacrifice of their body weight and possible survivorship, in order to increase their offspring's chance of survival is a trade - off between current reproductive success and the parents' future survival . This trade - off makes sense with other examples of kin - based altruism and is a clear example of the use of altruism in an attempt to increase overall fitness of an individual's genetic material at the expense of the individual's future survival . </P> <P> A study found that male dunnocks tend to not discriminate between their own young and those of another male in polyandrous or polygynandrous systems . However, they increase their own reproductive success through feeding the offspring in relation to their own access to the female throughout the mating period, which is generally a good predictor of paternity . This indiscriminative parental care by males is also observed in redlip blennies . </P> <P> In iteroparous species, where individuals may go through several reproductive bouts during their lifetime, a tradeoff may exist between investment in current offspring and future reproduction . Parents need to balance their offspring's demands against their own self - maintenance . This potential negative effect of parental care was explicitly formalized by Trivers in 1972, who originally defined the term parental investment to mean any investment by the parent in an individual offspring that increases the offspring's chance of surviving (and hence reproductive success) at the cost of the parent's ability to invest in other offspring . </P>

When is unequal parental involvement in caring for offspring is likely