Parental care
[7] Parental care is seen in many insects, notably the social insects such as ants, bees and wasps; in certain fishes, such as the mouthbrooders; widely in birds; in amphibians; rarely in reptiles and especially widely in mammals, which share two major adaptations for care of the young, namely gestation (development of the embryo inside the mother's body) and production of milk.
[citation needed] The rise of paternal care in primates may be explained by the Mating Effort and Maternal Relief hypotheses.
[10][11] The Maternal Relief hypothesis proposes that males provide care to reduce the burdens associated with reproduction for the female, which ultimately generates shorter inter-birth intervals and produces more successful offspring.
[15] Females of some species of reptiles may remain with their clutch to provide care, by curling around their eggs for the duration of the incubation period.
[16] The general mammalian tendency for female parents to invest more in offspring was focused on in the development of early hypotheses to describe sex differences in paternal care.
It was initially suggested that different levels of investment by each sex in terms of gamete size and number may have led to the evolution of female-only care.
[17] Biparental care tends to be favoured when sexual selection is not intense, and when the adult sex ratio of males to females is not strongly skewed.
On one hand, it has been suggested that due to sexual conflict, parents should withhold the amount of care they provide and shift as much of the workload as possible to their partner.
Other experimental evidence contrasts this, and suggests that when both parents care for their mutual offspring, their individual contributions may have synergistic effects on the fitness of their young.
Due to their endothermy and small size at birth, there is a huge pressure for infant birds to grow up quickly to prevent energy loss.
Since both sexes are able to forage and provision offspring, it is therefore beneficial for parents to cooperate in care to meet the requirements of infant birds.
[26] The offspring that experience alloparental care may benefit from increased protection from predators and the learning of group dynamics through social interactions.
[25] It may be in the best interest of a worker to forgo her own personal reproduction and participate in alloparenting, or rearing drones, so that there is an enhanced likelihood that males from her colony will ultimately mate with a queen.
Mothers of the crab species Metopaulias depressus raises their young in water-filled bromeliads, cleaning them of debris, defending them against predators and feeding them with captured prey.
[40] Some fish such as pipefish, sea dragons and seahorses (Syngnathidae) have a form of male pregnancy, where the female takes no part in caring for the young once she has laid her eggs.
Mouthbrooding is the care given by some groups of fish (and a few other animals such as Darwin's frog) to their offspring by holding them in their mouth for extended periods of time.
For example, the male pouched frog of eastern Australia protects tadpoles in pouches on the lateral surface of their skin,[48] the gastric-brooding frog raised tadpoles (and potentially eggs) in their stomach[49] and the common Suriname toad raises eggs embedded in the skin on its back.
[51] Many species within this group produce offspring that are self-sufficient, and are able to regulate their body temperatures and forage for themselves immediately after birth, thereby eliminating the need for parental care.
[56] The major adaptation shared by all live-bearing mammals for care of their young after birth is lactation (the feeding of milk from the mammary glands).
[citation needed] Further, many mammals exhibit other parental care behaviors to increase the fitness of their offspring, for example, building a den, feeding, guarding, carrying, huddling, grooming and teaching their young.
[60] This goes far beyond anything found in other animals, including not only the provision of food, shelter, and protection from threats such as predators, but a prolonged period of support during which the child learns whatever is needed to live successfully in human society.
The evolution of male-only, female-only, biparental or alloparental care in different groups of animals may be driven by multiple factors.
[69] Explanations include the suggestion by Trivers (1972) that this depends on paternity certainty,[62] which may be less with internal fertilisation unless the male undertakes "mate guarding" until the female lays eggs or gives birth.
[70] A second explanation is Richard Dawkins and T. R. Carlisle's (1976) theory that the order of gamete release, and therefore the opportunity for each parent to desert, may influence which sex provides care.
With internal fertilisation occurring in the mother, the female parent is most closely associated with the embryo, and may be preadapted to care for the young.
In biparental care, the key theoretical prediction is that parents should respond to reduced partner effort with incomplete compensation.
Field experiments on a passerine bird species indicated that in areas where broods were fed with extra carotenoids, their mouths became redder.
[78] The act of eating one's own offspring, or filial cannibalism, may be an adaptive behaviour for a parent to use as an extra source of food.
[81] Further experimentation on mallard ducks has displayed that females lay larger eggs and increase their provisioning when paired with more attractive males.
By reducing the amount of care invested in these offspring, individuals may save resources for future reproductive attempts with a more attractive mate.
