Parental Care in Animals: Who Cares, Why, and at What Cost

Topic: Animal Behaviour & Ethology Subject: Parental Care, Family Conflict, and Cooperative Breeding Last verified: 2026-09-23

Parental care covers any behaviour by which a parent improves the survival and growth of its offspring, from a frog guarding a clutch of eggs to a mother orangutan carrying and suckling her infant for years. It is extraordinarily varied: in some species only the male cares, in others only the female, in others both parents, and in some societies helpers who are not parents at all raise the young [Clutton-Brock 1991; Royle et al. 2012; Cockburn 2006]. Because care is costly to the parent and valuable to the offspring, it is also a source of evolutionary conflict, between parents and young, among siblings competing for food, and between parents and the brood parasites that exploit their devotion [Trivers 1974; Kilner & Johnstone 1997; Davies 2011]. Research on parental care now spans comparative surveys of thousands of species, long-term field studies, experiments with insects, and the mapping of the brain circuits that switch parenting on and off [Furness & Capellini 2019; Eggert et al. 1998; Dulac et al. 2014].

This article looks at what parental care is and which sex provides it, how conflicts within the family are expressed through begging and sibling rivalry, how cuckoos turn host care against itself, why some animals help to raise young that are not their own, and what is known about the hormones and neurons behind parenting. It closes with the practical relevance of parental care for conservation and animal welfare.

What Counts as Parental Care

Tim Clutton-Brock's 1991 book The Evolution of Parental Care set out the modern framework for studying care. It treats care as a form of investment: it increases the fitness of the offspring that receive it but costs the parent time, energy and future opportunities to reproduce [Clutton-Brock 1991]. Two decades later, an edited volume by Nick Royle, Per Smiseth and Mathias Kölliker drew together research on the evolution of care across the animal kingdom, including the conflicts that care generates within families [Royle et al. 2012].

Care takes many forms. It can begin before offspring even exist, with nest building or the provisioning of eggs, and continue through guarding eggs, carrying young, feeding them and defending them after independence [Clutton-Brock 1991; Royle et al. 2012]. It is not confined to birds and mammals. Burying beetles (Nicrophorus spp.) defend a small vertebrate carcass that is the sole food source for their larvae, prepare and manipulate the carcass, and regurgitate pre-digested carrion directly to their young [Eggert et al. 1998]. In an experimental study of Nicrophorus vespilloides, Anne-Katrin Eggert and colleagues found that larval survival and mass were significantly higher in broods that received parental care than in broods that developed without adults. Parental presence immediately after hatching greatly improved survival, and continued presence over several days led to heavier larvae [Eggert et al. 1998].

Even within one class of animals, the diversity can be striking. Alexander Furness and Isabella Capellini used phylogenetic comparative methods and data on over 1,300 amphibian species to ask how different kinds of care evolve [Furness & Capellini 2019]. Egg attendance, arguably one of the simplest forms of care, was gained and lost faster than any other. More complex adaptations such as brooding and viviparity were lost at very low rates, if at all. Biparental care proved evolutionarily unstable, regardless of whether the two parents performed similar or complementary duties [Furness & Capellini 2019]. Care, in other words, is not a single trait that a lineage either has or lacks, but a collection of behaviours that can be assembled and dismantled over evolutionary time [Furness & Capellini 2019].

Who Cares? Fathers, Mothers and Pairs

Which parent provides care differs sharply between major groups. In fishes, male-only care is widespread. Mart Gross and Craig Sargent argued that parental care brings one benefit, the increased survival of young, but can carry three kinds of cost: lost mating opportunities, reduced adult survival, and reduced future fertility [Gross & Sargent 1985]. They proposed that male care predominates in fishes because, although both sexes gain the same benefit from caring, males pay smaller future fertility costs than females [Gross & Sargent 1985]. Their analysis also suggested that biparental care can arise from male-only care, that female-only care can arise from biparental care when males desert, and that the origin of female-only care directly from no care is rare in externally fertilising fishes [Gross & Sargent 1985].

The most extreme form of paternal care is found in the seahorses and pipefishes (family Syngnathidae). In these fishes, the male incubates the developing embryos in a specialised brooding structure where they are aerated, osmoregulated, protected and probably provisioned [Stölting & Wilson 2007]. Kai Stölting and Anthony Wilson reviewed physiological, morphological and genetic evidence that this male incubation is a highly specialised form of reproduction comparable to other forms of viviparity, and that male pregnancy evolved in parallel in the two major syngnathid lineages [Stölting & Wilson 2007].

Birds show a very different pattern. Andrew Cockburn re-examined the incidence of six modes of avian care in the light of modern phylogenies: use of geothermal heat to incubate eggs, brood parasitism, male-only care, female-only care, biparental care and cooperative breeding [Cockburn 2006]. Biparental care by a pair-bonded male and female was the most common pattern, at 81% of species, but it was less common than once believed. Female-only care occurred in about 8% of species and cooperative breeding in about 9%, both more often than previously recognised [Cockburn 2006].

In mammals, internal gestation and lactation mean that mothers provide care in every species, whereas care by fathers is much less common [Clutton-Brock 1991]. Why one sex rather than the other ends up caring is closely tied to mating systems and sexual selection, a topic covered elsewhere on this site. The key point here is that the costs and benefits of care differ between the sexes and between lineages, and these differences shape who stays with the young [Gross & Sargent 1985; Clutton-Brock 1991].

Parent–Offspring Conflict and Sibling Rivalry

It might seem that parents and offspring share the same interests. Robert Trivers showed in 1974 that they do not. Because a parent is equally related to all its offspring, while each offspring is more closely related to itself than to its siblings, parents and young are expected to disagree [Trivers 1974]. Trivers identified disagreements over how long parental investment should last, how much should be given, and how altruistically or selfishly the offspring should behave towards other family members [Trivers 1974]. He predicted that conflict would be expected throughout the period of care and that offspring would use "psychological weapons" in competing with their parents [Trivers 1974]. He noted that data on mother–offspring relations in mammals were consistent with these predictions [Trivers 1974]. This framework, known as parent–offspring conflict, remains central to the study of family life in animals [Royle et al. 2012].

Conflict among siblings can be even more direct. In some seabirds, sibling competition ends in death. The masked booby (Sula dactylatra) usually lays two eggs, but only one chick is raised: the older chick eliminates its younger sibling soon after it hatches, a pattern known as obligate siblicide [Anderson 1990]. David Anderson tested the "insurance-egg" hypothesis, which proposes that the second egg is laid as a back-up in case the first fails to hatch or the first chick dies early. His results supported the idea that the second egg provides insurance against the failure of the first [Anderson 1990]. The case illustrates how an apparently wasteful behaviour, laying an egg whose chick will almost always die, can make sense once the risks of hatching failure are taken into account [Anderson 1990].

Begging: Signalling Need or Scrambling for Food?

Young animals in many species solicit food from their parents with conspicuous displays, such as the gaping mouths and loud calls of nestling birds. Rebecca Kilner and Rufus Johnstone reviewed the evidence for a prominent theory that begging is an honest signal of need: that begging advertises how hungry offspring are, that parents provision young in relation to begging intensity, and that the cost of begging keeps the signal reliable [Kilner & Johnstone 1997]. They found some support for these predictions. They also noted that empirical studies had revealed complexities, such as the use of multiple signals, that the theoretical models had only begun to address [Kilner & Johnstone 1997].

Experimental work on reed warblers (Acrocephalus scirpaceus) illustrates this complexity. Kilner, David Noble and Nicholas Davies showed that reed warbler parents integrate visual signals (the area of gape displayed by the brood) and vocal signals (begging calls) to adjust how often they bring food. The two signals together conveyed more accurate information about offspring need than either did alone [Kilner et al. 1999].

Begging may also have originated from something simpler than signalling. Larvae of the burying beetle N. vespilloides both beg for food from their parents and feed themselves on the carcass, a condition Per Smiseth and colleagues called "partial begging" [Smiseth et al. 2003]. In their experiments, begging ceased when the larvae became efficient enough at feeding themselves to grow just as well without parental food. The parent did not change its behaviour over time, whereas the larvae reduced their begging, so the transition to nutritional independence was under the offspring's control [Smiseth et al. 2003]. The authors suggested that models of the origin of begging should be built as scramble-competition models, because in this system the offspring control how food is allocated [Smiseth et al. 2003].

Brood Parasitism: Exploiting Parental Care

Wherever parents reliably care for young in a nest, there is an opportunity for other animals to exploit that care. The common cuckoo (Cuculus canorus) lays its eggs in the nests of other bird species and plays no part in raising its young [Davies 2011]. Nicholas Davies described the cuckoo's adaptations as being of two kinds. Trickery consists of adaptations that allow adult cuckoos, their eggs and their chicks to evade host defences, and it has co-evolved with those defences. Tuning consists of adaptations that allow the parasitic chick to exploit its hosts' parental provisioning [Davies 2011].

Egg mimicry is a classic example of trickery. Different populations of female cuckoos, known as gentes, specialise on different host species. Michael Brooke and Nicholas Davies found that the eggs of British cuckoo gentes differed statistically from one another [Brooke & Davies 1988]. Using model eggs placed in host nests, they showed experimentally that hosts discriminate against eggs that match their own poorly. This discrimination acts as a selective force maintaining the gentes, and cuckoos lay better-matching eggs in the nests of host species that are more discriminating [Brooke & Davies 1988]. The result is a co-evolutionary arms race, in which improvements in host defence select for better cuckoo mimicry [Brooke & Davies 1988; Davies 2011].

Once hatched, the cuckoo chick is reared alone, without the host's own young, and it must persuade its foster parents to feed it as much as they would feed a whole brood [Kilner et al. 1999; Davies 2011]. Kilner and colleagues found that a lone cuckoo chick in a reed warbler nest presents a deficient visual display, because a single gape cannot match the combined gapes of a brood. It compensates with an exaggerated vocal display, eliciting the same amount of care as a reed warbler brood [Kilner et al. 1999]. The cuckoo succeeds not by mimicking host begging signals but by tuning into the sensory predispositions of its hosts, a clear example of how the signals that normally help parents allocate care can be hijacked [Kilner et al. 1999; Davies 2011].

Helpers at the Nest: Cooperative Breeding

In cooperatively breeding species, individuals other than the parents help to raise the young. In birds, this system occurs in about 9% of species [Cockburn 2006]. At first sight, helping to raise another animal's offspring looks like a paradox. W. D. Hamilton's theory of inclusive fitness offered a solution: a gene that causes an individual to help relatives can spread, because those relatives are likely to carry copies of the same gene [Hamilton 1964]. On this view, a helper raising its younger siblings can gain "indirect" fitness benefits even if it does not breed itself [Hamilton 1964; Clutton-Brock 2002].

Ben Hatchwell's review of avian cooperative breeding found that a large majority of cooperatively breeding birds live in kin-based groups [Hatchwell 2009]. This is consistent with the idea that cooperative breeding arises through delayed dispersal, where young birds stay at home and form family groups, or through limited dispersal that creates neighbourhoods of relatives [Hatchwell 2009]. Hatchwell also argued that comparative analyses had not produced robust predictions about which ecological constraints matter. He suggested that a broader view, including life history and demographic processes, may give fresh insight into the evolution of bird societies [Hatchwell 2009].

Kinship is not the whole story. Tim Clutton-Brock reviewed evidence from cooperatively breeding vertebrates showing that helpers are sometimes unrelated to the young they raise [Clutton-Brock 2002]. He argued that the indirect, kin-selected benefits of helping may often have been overestimated and the direct benefits to the helper's own fitness underestimated, and that in some species direct benefits alone may be enough to maintain cooperative breeding [Clutton-Brock 2002].

Meerkats (Suricata suricatta) of the Kalahari show how sophisticated alloparental care can be. Alex Thornton and Katherine McAuliffe combined observations and experiments to show that helpers teach pups prey-handling skills by giving them opportunities to handle live prey [Thornton & McAuliffe 2006]. As pups grow older and their begging calls change, helpers alter the way they provide prey, speeding up learning without the need for complex cognition [Thornton & McAuliffe 2006]. Begging, once again, is the signal that parents and helpers use to adjust their care [Kilner et al. 1999; Thornton & McAuliffe 2006].

Hormones, Neurons and the Parental Brain

Parental behaviour is regulated by hormones and specialised brain circuits. In birds, prolactin has long been known as the "parental hormone" [Angelier et al. 2016]. Frédéric Angelier and colleagues reviewed evidence that changes in prolactin levels can mediate, at least in part, how breeding birds adjust their parental effort to environmental conditions [Angelier et al. 2016]. They examined how environmental conditions and stressors influence circulating prolactin, and to what extent prolactin levels predict breeding success in wild birds. They also noted that the hormone's role in this context had been surprisingly overlooked [Angelier et al. 2016].

In mammals, research on laboratory mice has begun to map the neural circuits of parenting at the cellular level. Catherine Dulac, Lauren O'Connell and Zheng Wu reviewed studies showing a striking antagonism between the brain systems that underlie parental care and those that drive aggression towards infants, in both males and females [Dulac et al. 2014]. They also highlighted a wide range of internal and environmental influences that modulate these circuits [Dulac et al. 2014].

A key discovery came from work on the medial preoptic area (MPOA) of the hypothalamus. Virgin male mice typically attack pups, whereas virgin females and sexually experienced males and females care for them [Wu et al. 2014]. Wu and colleagues found that virgin males unable to sense pheromones through the vomeronasal organ did not attack pups and behaved parentally [Wu et al. 2014]. They identified galanin-expressing neurons in the MPOA that were specifically activated during parenting in both sexes. Destroying these neurons markedly impaired parental responses in males and females, while activating them in virgin males suppressed aggression towards pups and induced pup grooming [Wu et al. 2014]. The same brain can therefore produce care or infanticide, depending on which circuits social experience and physiology bring into play [Wu et al. 2014; Dulac et al. 2014].

Conservation and Welfare Relevance

Parental care has direct consequences for how populations grow and recover. Species with long periods of care reproduce slowly, which limits how quickly they can rebound from losses. Maria van Noordwijk and colleagues combined birth data from seven long-term field sites on wild orangutans (Pongo spp.) and found an average interbirth interval of 7.6 years, with very high survival of infants before weaning [van Noordwijk et al. 2018]. Female survival to first birth, at around 15 years of age, was 94%, higher than reported for any other mammal under natural conditions [van Noordwijk et al. 2018]. The authors noted that such a slow life history can be viable only when unavoidable mortality is kept low [van Noordwijk et al. 2018]. It follows that any additional mortality, particularly of mothers, is difficult for such a population to absorb [van Noordwijk et al. 2018].

Losing a mother can have effects that go beyond the loss of milk or food. In Samburu, northern Kenya, an African elephant (Loxodonta africana) population experienced high adult mortality from drought and intense ivory poaching. Shifra Goldenberg and George Wittemyer compared the social partners of orphaned and non-orphaned females [Goldenberg & Wittemyer 2017]. Orphans had as many social partners as non-orphans, but different kinds. While resting in scarce shade, they had markedly less access to mature adults and associated instead with sisters, bulls and age mates [Goldenberg & Wittemyer 2017]. The authors suggested that this lack of interaction with adult females may reduce orphans' access to resources and carry fitness costs in a matriarchal society [Goldenberg & Wittemyer 2017]. The role of older elephants as social leaders is discussed further in this site's article on dominance hierarchies.

Captive breeding programmes often have to replace or supplement natural parental care through hand-rearing or fostering. Noel Snyder and colleagues warned that captive breeding has significant limitations, including poor success in reintroductions, domestication, and the genetic and phenotypic changes that occur in captive environments [Snyder et al. 1996]. They argued that it should be treated as a last resort rather than a long-term solution, and that programmes should operate with careful genetic and behavioural management [Snyder et al. 1996]. Because parents in many species shape the skills of their young, as helpers do when meerkats teach pups to handle prey [Thornton & McAuliffe 2006], and because the effects of early social experience on later behaviour can be profound (see this site's article on filial imprinting), the way young animals are reared in captivity is a behavioural and welfare question as well as a husbandry one.

Finally, the relationship between brood parasites and their hosts has an unexpected conservation use. Federico Morelli and colleagues showed that sites where the common cuckoo is present in Europe and Asia have greater bird species richness, while the cuckoo is absent from sites with low richness [Morelli et al. 2017]. They also reported that the cuckoo's population trend in Europe mirrors the average trend of bird communities as a whole [Morelli et al. 2017]. A bird that depends entirely on the parental care of other species may therefore serve as a practical indicator of healthy bird communities [Morelli et al. 2017].

References

[Anderson 1990]     Anderson, D.J. (1990). Evolution of obligate siblicide in boobies. 1. A test of the     insurance-egg hypothesis. The American Naturalist, 135(3), 334–350.     https://doi.org/10.1086/285049

[Angelier et al. 2016]     Angelier, F., Wingfield, J.C., Tartu, S. & Chastel, O. (2016). Does prolactin mediate parental     and life-history decisions in response to environmental conditions in birds? A review.     Hormones and Behavior, 77, 18–29.     https://doi.org/10.1016/j.yhbeh.2015.07.014

[Brooke & Davies 1988]     Brooke, M. de L. & Davies, N.B. (1988). Egg mimicry by cuckoos Cuculus canorus in relation     to discrimination by hosts. Nature, 335(6191), 630–632.     https://doi.org/10.1038/335630a0

[Clutton-Brock 1991]     Clutton-Brock, T.H. (1991). The Evolution of Parental Care. Princeton University Press,     Princeton, NJ.     https://doi.org/10.1515/9780691206981

[Clutton-Brock 2002]     Clutton-Brock, T. (2002). Breeding together: kin selection and mutualism in cooperative     vertebrates. Science, 296(5565), 69–72.     https://doi.org/10.1126/science.296.5565.69

[Cockburn 2006]     Cockburn, A. (2006). Prevalence of different modes of parental care in birds. Proceedings of     the Royal Society B: Biological Sciences, 273(1592), 1375–1383.     https://doi.org/10.1098/rspb.2005.3458

[Davies 2011]     Davies, N.B. (2011). Cuckoo adaptations: trickery and tuning. Journal of Zoology, 284(1),     1–14.     https://doi.org/10.1111/j.1469-7998.2011.00810.x

[Dulac et al. 2014]     Dulac, C., O'Connell, L.A. & Wu, Z. (2014). Neural control of maternal and paternal behaviors.     Science, 345(6198), 765–770.     https://doi.org/10.1126/science.1253291

[Eggert et al. 1998]     Eggert, A.-K., Reinking, M. & Müller, J.K. (1998). Parental care improves offspring survival     and growth in burying beetles. Animal Behaviour, 55(1), 97–107.     https://doi.org/10.1006/anbe.1997.0588

[Furness & Capellini 2019]     Furness, A.I. & Capellini, I. (2019). The evolution of parental care diversity in amphibians.     Nature Communications, 10, 4709.     https://doi.org/10.1038/s41467-019-12608-5

[Goldenberg & Wittemyer 2017]     Goldenberg, S.Z. & Wittemyer, G. (2017). Orphaned female elephant social bonds reflect lack of     access to mature adults. Scientific Reports, 7, 14408.     https://doi.org/10.1038/s41598-017-14712-2

[Gross & Sargent 1985]     Gross, M.R. & Sargent, R.C. (1985). The evolution of male and female parental care in fishes.     American Zoologist, 25(3), 807–822.     https://doi.org/10.1093/icb/25.3.807

[Hamilton 1964]     Hamilton, W.D. (1964). The genetical evolution of social behaviour. I. Journal of Theoretical     Biology, 7(1), 1–16.     https://doi.org/10.1016/0022-5193(64)90038-4

[Hatchwell 2009]     Hatchwell, B.J. (2009). The evolution of cooperative breeding in birds: kinship, dispersal and     life history. Philosophical Transactions of the Royal Society B: Biological Sciences,     364(1533), 3217–3227.     https://doi.org/10.1098/rstb.2009.0109

[Kilner & Johnstone 1997]     Kilner, R. & Johnstone, R.A. (1997). Begging the question: are offspring solicitation     behaviours signals of need? Trends in Ecology & Evolution, 12(1), 11–15.     https://doi.org/10.1016/S0169-5347(96)10061-6

[Kilner et al. 1999]     Kilner, R.M., Noble, D.G. & Davies, N.B. (1999). Signals of need in parent–offspring     communication and their exploitation by the common cuckoo. Nature, 397(6721), 667–672.     https://doi.org/10.1038/17746

[Morelli et al. 2017]     Morelli, F., Møller, A.P., Nelson, E., Benedetti, Y., Liang, W., Šímová, P., Moretti, M. &     Tryjanowski, P. (2017). The common cuckoo is an effective indicator of high bird species     richness in Asia and Europe. Scientific Reports, 7, 4376.     https://doi.org/10.1038/s41598-017-04794-3

[Royle et al. 2012]     Royle, N.J., Smiseth, P.T. & Kölliker, M. (Eds.) (2012). The Evolution of Parental Care.     Oxford University Press, Oxford.     https://doi.org/10.1093/acprof:oso/9780199692576.001.0001

[Smiseth et al. 2003]     Smiseth, P.T., Darwell, C.T. & Moore, A.J. (2003). Partial begging: an empirical model for the     early evolution of offspring signalling. Proceedings of the Royal Society of London B:     Biological Sciences, 270(1526), 1773–1777.     https://doi.org/10.1098/rspb.2003.2444

[Snyder et al. 1996]     Snyder, N.F.R., Derrickson, S.R., Beissinger, S.R., Wiley, J.W., Smith, T.B., Toone, W.D. &     Miller, B. (1996). Limitations of captive breeding in endangered species recovery.     Conservation Biology, 10(2), 338–348.     https://doi.org/10.1046/j.1523-1739.1996.10020338.x

[Stölting & Wilson 2007]     Stölting, K.N. & Wilson, A.B. (2007). Male pregnancy in seahorses and pipefish: beyond the     mammalian model. BioEssays, 29(9), 884–896.     https://doi.org/10.1002/bies.20626

[Thornton & McAuliffe 2006]     Thornton, A. & McAuliffe, K. (2006). Teaching in wild meerkats. Science, 313(5784),     227–229.     https://doi.org/10.1126/science.1128727

[Trivers 1974]     Trivers, R.L. (1974). Parent-offspring conflict. American Zoologist, 14(1), 249–264.     https://doi.org/10.1093/icb/14.1.249

[van Noordwijk et al. 2018]     van Noordwijk, M.A., Utami Atmoko, S.S., Knott, C.D., Kuze, N., Morrogh-Bernard, H.C., Oram,     F., Schuppli, C., van Schaik, C.P. & Willems, E.P. (2018). The slow ape: high infant survival     and long interbirth intervals in wild orangutans. Journal of Human Evolution, 125, 38–49.     https://doi.org/10.1016/j.jhevol.2018.09.004

[Wu et al. 2014]     Wu, Z., Autry, A.E., Bergan, J.F., Watabe-Uchida, M. & Dulac, C.G. (2014). Galanin neurons in     the medial preoptic area govern parental behaviour. Nature, 509(7500), 325–330.     https://doi.org/10.1038/nature13307