Paternal care
Exclusive paternal care has evolved multiple times in a variety of organisms, including invertebrates, fishes, and amphibians.
[13][14] For example, mammalian fathers that care for their young may undergo changes in body mass and an increase in production of a number of costly hormones (e.g. androgens, glucocorticoids, leptin).
However, one recent study concluded that fathers generally report higher levels of happiness, positive emotion, and meaning in life as compared with non-fathers.
Numerous studies have documented negative consequences of being raised in a home that lacks a father, including increased likelihood of living in poverty, having behavioral problems, committing crimes, spending time in prison, abusing drugs or alcohol, becoming obese, and dropping out of school.
Paternal certainty is high in monogamous pair-bonded species and males are less likely to be at risk for caring for unrelated offspring and not contributing to their own fitness.
[24][25] In contrast, polygamous primate societies create paternity uncertainty and males are more at risk of providing care for unrelated offspring and compromising their own fitness.
[31] Shortening inter-birth intervals, which is theorized to be a possible outcome of increased male care, is not beneficial for Strepsirrhine mothers and can decrease infant survival.
[31] Studies also show that paternity can be highly skewed in Strepsirrhines, with only one or few male members being the only biological father within a single group.
[27] Male care in this group of primates is often portrayed through actions such as grooming, carrying, tolerance of the infant, as well as protection against agonistic interactions and infanticide.
[34] Direct care such as grooming and playing is not as common compared to male intervention on behalf of the infant when it is being harassed by conspecifics.
Studies have shown that male Savannah baboons selectively choose to remain in closer proximity to their own offspring and engage in long-term investment beyond early infancy, when the infant is at greatest risk for infanticide.
Long-term care and investment beyond early infancy is better linked to paternity in this species and affecting infant growth and development.
Relationships created by male and female members are significant for infant survival in Chacma baboons (Papio ursinus) because the risk of infanticide in early infancy is higher in this species.
[39][40] More research needs to be done addressing how reproductive skew affects paternal care and infant-male relationships in non-human primates including chimpanzees and bonobos.
[44] Scientists believe that future research on kin recognition needs to be done on capuchins to determine if males choose to bias their care as well as in other non-human primates relying on phenotypic matching to distinguish biological offspring.
[29] Paternal uncertainty is high in multimale-multifemale primate groups so males must use these cues to recognize and bias care towards their own offspring.
The Maternal Relief hypothesis: Males provide care infants to help reduce reproductive burdens of the female, ultimately resulting shorter inter-birth intervals and more successful offspring.
[27] This stems from the male alleviating the female from her parental duties in order to keep her resources from becoming depleted and subsequently allowing her to produce high quality milk for the infant.
Several species of rodents have been studied as models of paternal care, including prairie voles (Microtus ochrogaster), Campbell's dwarf hamster, the Mongolian gerbil, and the African striped mouse.
The California mouse (Peromyscus californicus) is a monogamous rodent that exhibits extensive and essential paternal care, and hence has been studied as a model organism for this phenomenon.
[5] The unusually high incidence of paternal care in birds compared to other vertebrate taxa is often assumed to stem from the extensive resource requirements for production of flight-capable offspring.
By contrast, in bats (the other extant flying vertebrate lineage), care of offspring is provided by females (although males may help guard pups in some species[48]).
In contrast to the large clutch sizes found in many bird species with biparental care, bats typically produce single offspring, which may be a limitation related to lack of male help.
[53] Paternal care is rare in arthropods,[54] but occurs in some species, including the giant water bug[55][56] and the arachnid Iporangaia pustulosa, a harvestman.
In this view, paternal care is an evolutionary achievement that compensates for the higher energy demands that reproduction typically involves for mothers.
[60][61] Other models suggest that basic life-history differences between males and females are adequate to explain the evolutionary origins of maternal, paternal, and bi-parental care.
Mechanisms underlying such effects may include protecting offspring from predators or environmental extremes (e.g., heat or cold), feeding them or, in some species, direct teaching of skills.
It was found that their fledging period, the time between a chick's first trip to sea and its absolute independence from the group, was longer than other penguins of the same genus.
In vertebrates, at the level of hormonal control, vasopressin apparently underlies the neurochemical basis of paternal care; prolactin and testosterone may also be involved.
As with other behaviors that affect Darwinian fitness, reward pathways[67] in the brain may reinforce the expression of paternal care and may be involved in the formation of attachment bonds.
