Behavioral changes associated with introductions of male maned wolves (Chrysocyon brachyurus) to females with pups

Three male maned wolves were successfully introduced to their mates and 7‐ to 12‐week‐old pups at the Houston Zoological Gardens and Fossil Rim Wildlife Center in 1994 and 1995. The introductions took 3–7 weeks and had three stages: 1) allowing the male to see the female and pups through a chain‐link panel or a full chain‐link fence, 2) introducing the male and female without the pups present, and 3) introducing the male to the pups. For 7 days before Stage 2 and 7 days during Stage 3, the adults were observed for 150 hr. The amount of time they spent active and the amount of time they spent near the pups were recorded, as well as all behaviors they directed to the pups. After the males were introduced, the females' activity decreased, and the males' activity increased. The females spent less time near the pups after the introduction. The introduction did not affect the females' rates of affiliative or aggressive behaviors to the pups, and there was no difference between males' and females' rates of affiliative or aggressive behaviors. This introduction procedure offers an alternative to leaving the male with the pups from the time they are born. The adults' behavioral changes after the introduction show the benefits that occur when captive male maned wolves are allowed to help rear their pups. Zoo Biol 18:189–197, 1999. © 1999 Wiley‐Liss, Inc.     

Parental behaviour in the Lapwing Vanellus vanellus

Parental behaviour of monogamous and polygynous Lapwings was studied during incubation and brood care. Both parents attended the nest in 86% of monogamous pairs ( n = 29 pairs). In 14% of pairs, only the male parent continued incubation until the eggs hatched, whereas the female deserted the clutch before or at the end of incubation. There was a clear division of parental roles during incubation. Females spent more time incubating (64% of time) than their mates (27%), whereas males spent more time defending the nest (3%) than females (>1%). Time spent incubating did not differ between monogamous and polygynous males. However, polygynous females spent more time incubating (primary females: 95%; secondary females: 97%) than monogamous females. Biparental care was the most common pattern of post-hatching care, although in some broods either the male or the female parent deserted before the chicks fledged. Division of sex roles was less pronounced in brood care than during incubation. Females spent more time brooding (21%) than males (3%), and females attended their chicks more closely than males. Nevertheless, males and females spent similar amounts of time defending the brood from predators and conspecifics. We suggest that the apparent division of parental roles may be explained by sexual selection, i.e. the remating opportunities for male Lapwings might be reduced if they increase their share in incubation. However, the different efficiency of care provision, for example in ability to defend offspring, may also influence the roles of the sexes in parental care.     

How does a parent respond when its mate emphasizes the wrong role? A test using a monogamous fish

The convict cichlid fish, Archocentrus nigrofasciatus, is biparental: the male spends the majority of his time defending the territory and the female spends much of her time close to the offspring. Under natural conditions, this separation into sex-typical roles is somewhat blurred as males do spend some time with the offspring and females do attack intruders. Here we tested whether an individual selects a parental role based on the location (i.e. parental role) of its mate. For example, do females emphasize offspring care because the male is away from the offspring? Will males be more likely to care for the offspring when the female is away from the offspring? We manipulated the location of one parent by placing it in a transparent plastic box, either near the offspring or at the far end of the tank near a clear plastic compartment that held a conspecific male intruder. We tested both male and female parent under the following four conditions: boxed mate near offspring with no intruder present, boxed mate near offspring with intruder present, boxed mate near intruder compartment with no intruder present, and boxed mate near intruder compartment with intruder present. We found that both parents spent more time with the offspring and less time attacking the intruder when the mate was positioned near the offspring and more time away from the offspring and more time attacking the intruder when the mate was near the intruder. Males were more affected by the location of their mates than were females and we concluded that males were attracted both to their mates' location and their offspring while females were mostly attracted to their offspring. Overall, the location of the mate had little effect on the types of aggressive activities used against the intruder. We did find that males increased their aggression towards boxed females when they were positioned far from the offspring, whereas the aggressive behaviour of females towards boxed males when they were positioned near the offspring was ambiguous. We suggest that males in particular enforce the separation of sex-specific parental roles via this aggression.     

Experimentally-elevated testosterone, female parental care, and reproductive success in a songbird, the Dark-eyed Junco (Junco hyemalis)

In male dark-eyed juncos (Junco hyemalis), experimentally elevated testosterone (T) decreases male parental care and offspring survival, but results in higher overall fitness through greater mating success. To help address the ensuing question of what prevents selection from favoring higher levels of T in male juncos, we manipulated T in female juncos. A previous study demonstrated no effect of experimentally elevated T on female incubation behavior, suggesting that female parental behavior might be insensitive to T. In this study we asked whether experimentally elevated T mediates other female parental behaviors and whether variation in T-mediated parental behavior might influence reproductive success. We videotaped free-living control- and T-females during nesting to quantify brooding behavior when young were 3 days old and provisioning behavior when young were 6 days old. Nest defense was measured by quantifying responses to a mounted predator placed near the nest. Reproductive success was assessed via fecundity, nestling quality, and nest survival. T-females spent less time than control females brooding but did not differ in provisioning rate. T-females performed fewer dives at the predator mount and, unlike controls, failed to increase defense as nesting progressed. T-females also had lower daily nest survival and lower nest success (odds of producing at least one fledgling). We conclude that some aspects of female parental behavior are sensitive to experimentally elevated T while others are not and consider the implications for the evolution of T-mediated characters in both sexes.     

Do Male Desert Gobies Compromise Offspring Care to Attract Additional Mating Opportunities?

Males often play a critical role in offspring care but the time and energy invested in looking after young can potentially limit their ability to seek out additional mating opportunities. Recent studies, however, suggest that a conflict between male parental effort and mating effort may not always be inevitable, especially if breeding occurs near the nest, or if parental behaviours are under sexual selection. Accordingly, we set out to experimentally investigate male care and courtship in the desert goby Chlamydogobius eremius, a nest-guarding fish with exclusive paternal care. Despite courtship occurring near the nest, we found that when egg-tending males were given the opportunity to attract additional females, they fanned their eggs less often, engaged in shorter fanning bouts, and spent more of their time outside their nests courting. Our findings highlight the importance of understanding the circumstances under which reproductive tradeoffs are expected to occur and how these, in turn, operate to influence male reproductive decisions.     

Secret lives of maned wolves (Chrysocyon brachyurus Illiger 1815): as revealed by GPS tracking collars

The maned wolf Chrysocyon brachyurus is a nocturnal and shy species, which has proven difficult to study in the field; consequently, data about its behavioural biology are almost absent from the scientific literature. However, recent advances in global positioning system (GPS) technology mean that it is now possible to study the socio-spatial dynamics of this species in the field. In the present study three related maned wolves (an adult pair and their juvenile female offspring) were monitored by GPS tracking collars for a 6-month period, which included the birth of a litter of pups to the adult pair. The three GPS collars were programmed to record the position of the wearer every 2 h (simultaneously for all three individuals). Analyses of the data from the three individuals showed that the female had the largest home range, then the male and finally the juvenile. Furthermore, there was considerable overlap in home-range use by all three individuals. The home ranges of the adult pair also varied in relation to the birth of pups (decreasing dramatically and then showing a slow increase). During the night, which is the normal period of activity for this species, the three individuals avoided contact with each other. However, during the day, the adult pair usually slept together and their juvenile slept within a few hundred metres of their location. The distance travelled at night was greatest for the female, then the male and finally the juvenile. These data suggest that (1) the social bond between the male and female is strong, (2) maned wolves are highly tolerant of their juvenile offspring, even in the case of new pups being born, and (3) that maned wolves do not hunt together and, in fact, avoid each other when hunting.     

Parental sex roles of Malaysian plovers during territory acquisition,incubation and chick-rearing

Shorebirds show high variability in parental care strategies among species, populations, and environments. Research on shorebird parental sex roles can help to understand the selective pressures that shape avian breeding strategies. Although several studies have examined parental care strategies in holarctic shorebirds, very little research has been conducted in the tropics. Here we examined parental sex roles during territorial defence, incubation, and chick-rearing in Malaysian plovers Charadrius peronii in the Gulf of Thailand. The costs and gains of particular parental behaviour may vary between the sexes and can be affected differently by environmental factors and chick age. Thus we also examined how temperature, prey availability, chick or embryo age, and time of day affected parental sex roles. Males spent more time defending territories and were further away from chicks whereas females spent more time incubating eggs. Both adults contributed to chick defence during disturbances throughout the entire chick-rearing period. Total nest attendance (sum of both sexes) was affected by the modelled temperature of an unincubated egg. Prey availability, embryo age, and time of day had no effect on total nest attendance. Males adjusted incubation effort in response to temperature only at high temperatures (>36°C) whereas females adjusted nest attendance at high and low temperatures. Chick age had no effect on the proportion of time adults spent defending territories or responding to disturbance. Pairs were more likely to fledge chicks if both the male and female spent more time defending territories. For Malaysian plovers, high cooperation between the sexes during parental care may help to achieve high quality breeding territories, maintain body conditions during hot days, protect offspring from predators and attacking conspecifics, and contribute to high lifetime reproductive success.     

Behavioral and physiologic responses to environmental enrichment in the maned wolf (Chrysocyon brachyurus)

The ex situ population of maned wolves is not self‐sustaining due to poor reproduction, caused primarily by parental incompetence. Studies have shown that environmental enrichment can promote natural parental behaviors in zoo animals. The objective of this study was to determine the effects of environmental enrichment on behavioral and physiological responses of maned wolves. During an 8‐week experimental period, daily behavior observations and fecal sample collection were conducted on four adult wolves (2.2) individually housed in environments without enrichment. After 2 weeks, the wolves were chronologically provided with 2‐week intervals of hiding dead mice around the exhibit, no enrichment, and introduction of boomer balls. Responses of the wolves to enrichment were assessed based on activity levels and exploratory rates, as well as the level of corticoid metabolites in fecal samples collected daily throughout the study period. Providing wolves with environmental enrichment significantly increased exploratory behaviors (P<0.05), especially when mice were hidden in the enclosure. Fecal corticoid concentrations were increased during periods of enrichment in males (P<0.05), but not in females. Overall, there were no correlations between behavioral responses to enrichment and fecal corticoid levels. Behavioral results suggest that environmental enrichment elicits positive effects on the behavior of captive maned wolves. There is evidence suggesting that providing animals with ability to forage for food is a more effective enrichment strategy than introducing objects. There is need for a longer term study to determine the impact of environmental enrichment in this species. Zoo Biol 26:331–343, 2007. © 2007 Wiley‐Liss, Inc.     

Individual Consistency in Parental Effort Across Multiple Stages of Care in the House Sparrow, Passer domesticus

In many avian species in which biparental care is provided to offspring, substantial variation exists within members of each sex in the level of effort contributed to various forms of parental care. Questions remain as to whether individuals that contribute more toward one parental activity also contribute more toward other activities in which they participate. We examined the contributions of male and female house sparrows (Passer domesticus) to three forms of parental care: incubation, nestling provisioning, and nest defense, and compared the investments made by individuals at each stage of care relative to other same‐sexed parents. In both males and females, nestling feeding rates were positively associated with time spent incubating, but no relationships were found between measures of nestling feeding and nest defense. The predictability of an individual's feeding behavior based on earlier incubation efforts may make incubation a good stage for individuals to evaluate the parental abilities of their partners.     

Why do Both Parents Incubate in the Kentish Plover?

Incubation by both parents is a common parental behaviour in many avian species. Biparental incubation is expected if the survival prospects of offspring are greatly raised by shared care, relative to the costs incurred by each parent. We investigated this proposition in the Kentish plover Charadrius alexandrinus, in which both parents incubate the clutch, but one parent (either the male or the female) usually deserts after hatching of the eggs. We carried out a mate‐removal and food supplementation experiment to reveal both the role of the sexes and food abundance in maintaining biparental incubation by removing either the male or the female from the nest for a short period of time. In some nests we provided supplementary food for the parent that remained at the nest to reduce the costs of incubation, whereas other nests were left unsupplemented. Although males spent more time on incubation after their mate had been removed, females’ incubation did not change. Notwithstanding the increased male incubation, total nest attentiveness was lower at uniparental nests than at biparental controls. However, incubation behaviour was not influenced by food supplementation. We conclude that offspring desertion during incubation is apparently costly in the Kentish plover, and this cost cannot be ameliorated with supplementary food.     

Sex Differences in Retrieval Behavior by the Biparental Convict Cichlid

Biparental species occasionally demonstrate a division of roles in which parents perform sex-typical tasks, with females offering direct care and spending the majority of their time with the offspring while males are more indirect in their care, providing the majority of defense against potential brood predators. To examine the flexibility in the sex-typical roles shown by convict cichlids ( Amatitlania nigrofasciata ), we displaced non-swimming young at three different distances from the nest and then analyzed the retrieval behaviors of each parent. Retrieval of altricial young is a behavior commonly used to measure parental care in mammalian studies, but has rarely been used in other taxa. We found sex differences in retrieval behavior: on average, females retrieved young close to the nest and males retrieved young far from the nest. This difference in parental contribution suggests a division of labor with sex-specific roles. Sex differences may be due to proximity to young and/or apparent risk of offspring predation. Additionally, we found that latency to first retrieval and total time spent retrieving young remained consistent across the various displacement distances, suggesting that retrieval is an essential parental behavior. Additionally, we include observations of wriggler retrieval by parents in a natural population of Costa Rican convict cichlids.     

Relative influence of male and female care in determining nestling mass in a migratory songbird

Biparental care is common in birds, with the allocation of effort being highly variable between the sexes. In most songbird species, the female typically provides the most care early in the breeding cycle with both parents providing care when provisioning young. Food provisioning should be directly related to offspring quality; however, the relative influence each parent has on offspring quality has rarely been assessed at the nest level. Consequently, we were interested in assessing the relative influence male and female provisioning has on one measurement of offspring quality, nestling mass, in the black‐throated blue warbler Dendroica caerulescens. Over a six year period, 2003–2008, we collected information on average nestling mass per brood on day 6 of the nestling cycle and parental provisioning rates on day 7 of the nestling cycle from 182 first brood nests on three different study plots. We found that average nestling mass was directly related to male provisioning rate, while it was not related to female provisioning rate. On the other hand, estimated biomass provisioned had little influence on average nestling mass, calling into question its utility in assessing parental quality. Finally, there was some indication that parental influence on average nestling mass was dependent on the other parent's provisioning rate, suggesting that parents work in concert to influence nestling quality.     

What makes a nest-building male successful? Male behavior and female care in penduline tits

Why do females increase parental effort when caring for theoffspring of attractive males? First, attractive males may bepoor fathers so that their females are compelled to increasetheir own contribution in order to fledge some young (the partner-compensationhypothesis). Second, females mated to attractive males may bewilling to increase their parental effort to reap high indirectbenefits for their offspring, and in turn males can decreasetheir own contribution (the differential allocation hypothesis[DAH]). We investigated these hypotheses in the penduline titRemiz pendulinus, a small passerine bird that has sequentialpolygamy by both sexes and strict uniparental care either bythe male or the female. We focused on two sexually selectedmale traits: nest size and nest-building behavior. We show thatmale care is unrelated to nest-building behavior, whereas femalesare more likely to care for the offspring of those males thatspend more time nest building. Females also more likely carefor the offspring of males that build large nests. Consequently,the reproductive success of males increases with nest size andnest-building behavior. Our results are consistent with theDAH and suggest that nest-building behavior and nest size areunder postmating sexual selection in penduline tits.     

Don'T put all your eggs in one nest: spread them and cut time at risk

Abstract In many egg-laying animals, some females spread their clutch among several nests. The fitness effects of this reproductive tactic are obscure. Using mathematical modeling and field observations, we analyze an unexplored benefit of egg spreading in brood parasitic and other breeding systems: reduced time at risk for offspring. If a clutch takes many days to lay until incubation and embryo development starts after the last egg, by spreading her eggs a parasitic female can reduce offspring time in the vulnerable nest at risk of predation or other destruction. The model suggests that she can achieve much of this benefit by spreading her eggs among a few nests, even if her total clutch is large. Field data from goldeneye ducks Bucephala clangula show that egg spreading enables a fecund female to lay a clutch that is much larger than average without increasing offspring time at risk in a nest. This advantage increases with female condition (fecundity) and can markedly raise female reproductive success. These results help explain the puzzle of nesting parasites in some precocial birds, which lay eggs in the nests of other females before laying eggs in their own nest. Risk reduction by egg spreading may also play a role in the evolution of other breeding systems and taxa-for instance, polyandry with male parental care in some birds and fishes.     

Mate desertion by male Great Reed Warblers Acrocephalus arundinaceus at the end of the breeding season

Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains.     

Reproductive behavior of the Amazonian dwarf cichlid Apistogramma hippolytae Kullander, 1982: offsetting costs and benefits

The reproduction trade-off for an animal is a conflicting choice in which resources (e.g., time and/or energy) allocated to one reproduction trait (e.g., parental care) become unavailable to other traits (e.g., future reproduction events). Here, we tested three hypotheses related to the parental care of the Amazonian dwarf cichlid Apistogramma hippolytae in its natural habitat of Central Amazonia: (1) brood-caring females have a lower feeding frequency than individuals that are not involved in this behavior; (2) females that spend more time on nest defense have lower feeding rates; and (3) females can recognize the species that present the greatest danger to its offspring and move farther from the nest to chase away these piscivorous fishes. We also described for the first time the reproductive behavior (including courtship) and parental care of this species. The results showed that maternal care produces a reduction in the rate of feeding of mothers, a greater amount of time is spent chasing invaders away from the nest, and reproductive females are able to distinguish species-specific predators. These observations support the hypotheses of this study and also suggest a trade-off between current and future reproduction events.     

Influence of Inter-Lake Variation in Natural Nest Predation Pressure on the Parental Care Behaviour of Smallmouth Bass (Micropterus dolomieu)

Predation risk has the ability to greatly influence the behaviour of reproducing individuals. In large long-lived species with low risk of predation for parents, reproductive behaviours often involve caring for offspring (i.e. defending broods from predators) and these behaviours are essential for offspring survival. Our objectives were to test for the presence of natural variation in nest predation pressure in an aquatic environment for a species that provides sole-paternal care, smallmouth bass ( Micropterus dolomieu ), and to determine if natural variation in predation pressure influences parental care behaviour. We used snorkeler observations and a series of metrics to assess predation pressure and parental care behaviour in six lakes within a narrow geographical range. Lakes differed in all predation pressure metrics: number of predators in proximity to nest when males were present, time to predator arrival and number of predators that consumed eggs when males were absent and total number of nests that was preyed upon. Similarly, parental behaviour varied between lakes. Parental smallmouth bass spent more time engaged in anti-predator defences in lakes with high predation pressure, while males from low predator pressure lakes remained close to their nest. Conversely, males from lakes with low and high predation pressure showed a similar willingness to defend their nests during simulated nest predation events. Our results show that natural variation in aquatic nest predation pressure across multiple lakes can be significant and has the ability to influence baseline parental care behaviour. Such variation provides opportunities to study the costs and consequences of parental care and to evaluate how this could influence demography and community interactions in aquatic systems.     

Patient Parents: Do Offspring Decide on the Timing of Fledging in Zebra Finches?

Parent–offspring conflict over parental care is predicted to become most pronounced during offspring transition to independence when offspring are predicted to attempt to extend care for longer than parents are selected to provide it. However, on the proximate level, it is difficult to determine who plays the most important role in this process, parents or offspring. For several vertebrate taxa, it has been documented that parents end brood care by abandoning offspring after a fixed period or else show high flexibility in the duration of care, but teasing apart the role of offspring and parents underlying this flexibility has been difficult. Here, we studied the decision to fledge in captive zebra finches (Taeniopygia guttata), an altricial songbird. We experimentally delayed the time of fledging to determine who decides about the end of feeding inside the nest, parents or offspring. The experiment indicates that parents do not primarily rely on phenotypic offspring traits in their decision to feed offspring in the nest, but appear to adjust the duration of parental care as long as offspring are in the nest which parents may take as an indicator of offspring need and locomotor abilities. Delayed‐fledging offspring appeared not to suffer a disadvantage in terms of age at the onset of independent feeding. Our study suggests that, in zebra finches, offspring play a major role in determining the time of fledging and leave the nest on their own, possibly to reduce the risk of nest predation, or to evade sibling competition in the nest.     

Flexible communication within bird families—The consequences of behavioral plasticity for parent–offspring coadaptation

Offspring are selected to demand more resources than what is optimal for their parents to provide, which results in a complex and dynamic interplay during parental care. Parent–offspring communication often involves conspicuous begging by the offspring which triggers a parental response, typically the transfer of food. So begging and parental provisioning reciprocally influence each other and are therefore expected to coevolve. There is indeed empirical evidence for covariation of offspring begging and parental provisioning at the phenotypic level. However, whether this reflects genetic correlations of mean levels of behaviors or a covariation of the slopes of offspring demand and parental supply functions (= behavioral plasticity) is not known. The latter has gone rather unnoticed—despite the obvious dynamics of parent–offspring communication. In this study, we measured parental provisioning and begging behavior at two different hunger levels using canaries (Serinus canaria) as a model species. This enabled us to simultaneously study the plastic responses of the parents and the offspring to changes in offspring need. We first tested whether parent and offspring behaviors covary phenotypically. Then, using a covariance partitioning approach, we estimated whether the covariance predominantly occurred at a between‐nest level (i.e., indicating a fixed strategy) or at a within‐nest level (i.e., reflecting a flexible strategy). We found positive phenotypic covariation of offspring begging and parental provisioning, confirming previous evidence. Yet, this phenotypic covariation was mainly driven by a covariance at the within‐nest level. That is parental and offspring behaviors covary because of a plastic behavioral coadjustment, indicating that behavioral plasticity could be a main driver of parent–offspring coadaptation.     

Male parental care and its adaptive significance in a neotropical frog

In the Puerto Rican frog Eleutherodactylus coqui, parental care is performed exclusively by males, and consists of attending the eggs and hatchlings at a terrestrial oviposition site. The two major behavioural components of parental care are egg brooding and nest defence against conspecific egg cannibals. Defence behaviour includes aggressive calling, biting, sustained biting, wrestling, and blocking directed against nest intruders. Parental care lasts from oviposition to hatching (17–26 days) and often for several days after hatching. During pre-hatching development, males are present in their nests 97.4% of the time during the day and 75.8% of the time at night. A large portion of this time is spent brooding eggs. In a field experiment, males were removed from their nests and the fate of clutches was monitored. Compared to control clutches (males not removed), experimental clutches had significantly lower hatching success and suffered significantly greater mortality from desiccation and cannibalism. Hence, parental care yields significant benefits to male fitness via increased offspring survival.