Period Of Parental Care Research Articles

Brood Size, Male Fanning Effort and the Energetics of a Nonshareable Parental Investment in Bluegill Sunfish, Lepomis macrochirus (Teleostei: Centrarchidae)

AbstractWe present a model and an experimental test for a nonshareable parental‐investment behavior (fanning of eggs) using parental male bluegill sunfish. The model predicts that as brood size increases, nonshareable investment into the brood should increase if a parent is to maximize its remaining lifetime reproductive success. The experimental test manipulated the number of eggs in nests and quantified the frequency and tempo of fanning in the field using underwater video equipment. As predicted, male bluegill fanned larger broods more frequently than smaller broods. The fanning tempo (beats per min) did not change with changes in brood size. Parental males lost substantial amounts of body weight during the period of parental care, and lipid extractions revealed a loss in nonpolar lipids. The difference in fanning frequency between large and small broods did not result in differential weight loss for the parents, but parents that fanned more tended to lose more nonpolar lipids from the body tissue than males that fanned less.

Parental Care, Sibling Relationships and the Development of Aggressive Behaviour in Two Lines of Wild House Mice

Distinct behavioural strategies for dealing with environmental and social challenge are known to exist in the adults of a variety of mammalian species, but little is known about the developmental bases of these strategies. In an attempt to start to fill this gap in knowledge, the present study set out to describe and compare the development of males from two lines of wild house mice which are known to differ in their aggressive behaviour and response to challenging situations. Adult males from one line (Short Attack Latency = SAL line) are more aggressive, show less sensitivity to changes in their environment and behave in a more internally controlled, routine-like way, than do males from the other line (outbred = Control line). The parental care and development of eight litters of four male pups from each line was observed. Paternal care did not differ between the two lines, but SAL pups received higher levels of nursing and general maternal care than did Control pups, and they appeared to be weaned later. Despite these differences, SAL pups grew more slowly than Control pups, suggesting that their high levels of sucking behaviour were a reflection of high milk demand, perhaps due to a low milk supply, rather than high milk intake. SAL pups were also delayed in a number of measures of early behavioural development relative to Control pups. The apparent early retardation in certain measures of SAL pup behavioural development disappeared at the end of the parental care period. From day 32 onwards, SAL pups began to show higher levels of aggression towards each other than did Control pups, and also showed a reduced reactivity to tests involving changes to the home cage environment ; a characteristic of adult SAL males. As expected, SAL males developed into faster attackers than Control males and, in SAL litters, intra-litter variation in attack speed was strongly influenced by preceding experience of sibling aggression. The fastest attackers in each litter were more successful in fights occurring in their litter than their slowest attacking siblings. No such relationship was observed in the Control litters where levels of inter-sibling aggression were low. The results point to the potential significance of maternal care behaviour and pup fighting behaviour in the development of the fast-attacking phenotype. One hypothesis is that inadequate nutrition of young SAL pups, mediated through the mother, promotes increased competition for access to the mother's nipples and predisposes the pups to develop into more active/competitive individuals. Subsequent sibling-sibling aggression appears to influence intra-litter variation in adult attack latency.

Implications of the dental eruption sequence in Barbourofelis (Carnivora, Nimravidae) for the function of upper canines and the duration of parental care in sabretoothed carnivores

The eruption of the large deciduous upper canines in the nimravid sabretooth cat Barbourofelis was delayed until after the individual was eating meat. This inference is based primarily on the eruption sequence and dental wear displayed by seven specimens referred to this genus. It indicates that the sabres were not required for feeding and suggests that these teeth were primarily killing devices. The deciduous upper canines in Barbourofelis and the permanent canines in large felids probably erupted at similar stages of dental ontogeny. If the potential for independence from adults occurs with the eruption of canines that were large enough to serve as killing devices, the delayed eruption of the deciduous sabres in nimravids did not necessitate any significant extension to the long period of parental care that is typical of the extant Carnivora.SummaryThe eruption sequence of, and patterns of wear to, the dentition of Barbourofelis demonstrate that juveniles were processing meat before the eruption of the deciduous sabres and thus the upper canines were not necessary for feeding. This supports the view that the sabres were preferentially killing devices; any use of the sabres in dismemberment of the carcass by adults was probably secondary. The transfer of these inferences to felid sabretooths such as Smilodon may be unwise; however, arguments that Smilodon's sabres were inefficient slicing devices (Simpson, 1941), and the patterns of wear on its incisors and cheekteeth (Miller, 1969; Akersten, 1985), suggest that a similar scenario is likely. The marked modifications to the morphology and eruption sequence of the dentition in Barbourofelis may not have resulted in any significant increase in the length of parental care.

HATCHING ASYNCHRONY IN ALTRICIAL BIRDS

Summary1. The review aims to provide a simple conceptual framework on which to place recent studies of hatching asynchrony in altricial birds and to assess the evidence used in support of specific hypotheses.2. Hatching asynchrony arises bsecause parents start incubation before laying is complete, but the precision of parental control is largely unknown.3. Hypothesses concerning the functional significance of hatching asynchrony fall into four broad types. Hatching asynchrony might: (i) arise because of selection on the timing of events during the nesting period; (ii) facilitate the adaptive reduction in brood size; (iii) increase the energetic efficiency of raising the brood, or (iv) result from environmental or phylogenetic constraints.4. The incubation pattern could function to minimize the losses of eggs, nestlings or adults to predators (or climatic sources of mortality), particularly in species which cannot actively defend their nest. The best evidence comes from comparative studies of hatching asynchrony. Early incubation might also be favoured if the food supply declines sharply through the breeding season, although the evidence is weak and indirect, or if there is a risk of brood parasitism. In species in which only the female incubates, early incubation could ‘force’ the male to invest more in the nestlings, but this idea remains to be tested. Males may be constrained by the risk of cuckoldry to delay incubation until laying is complete.5. Hatching asynchrony could be adaptive by enabling the efficient reduction of brood size if food proves short after hatching (primarily because of a shortage of food in the environment or possibly because of a large proportion of ‘expensive’ nestlings in the brood in species which are sexually dimorphic). Observational evidence is often consistent with this hypothesis but few experimental studies provide adequate tests. Brood reduction could be adaptive in species (primarily eagles and pelecaniformes) which lay an extra egg to act as insurance against hatching failure, and again hatching asynchrony might facilitate brood reduction, although there are few experimental tests on such species. Hatching asynchrony might also enable sex ratio manipulation through selective brood reduction, although there is as yet no clear supportive evidence.6. Ins species in which young have a marked peak in energy demand during the period of parental care, hatching asynchrony can reduce the peak demand of the brood, which might allow the parents to raise more healthy young. In many species such savings are likely to be small or absent. There is some behavioural evidence that hatching asynchrony can reduce fighting amongst nestlings and therefore lead to the more efficient use of energy by the brood. In general this effect seems small and the only energetic study found no difference in the energy requirements of synchronous and asynchronous broods. Other possible energetic advantages to hatching asynchrony have not been tested.7. Environmental conditions during laying can influence both egg size and laying interval in aerial insectivores, and might directly influence incubation in this and other groups. Thus some variation in hatching asynchrony and the relative size of siblings is probably non‐adaptive. The variability of incubation pattern within and across species suggests that hatching asynchrony is not under strong phylogenetic constraint.8. The hypotheses about the adaptive significance of hatching asynchrony are complementary rather than mutually exclusive: within a species, several selective pressures could influence the optimal incubation pattern, and the relative importance of selective pressures will differ among species. Furthermore one should expect that the incubation pattern and parent–offspring interactions will be coadapted to maximize brood productivity.

Parental effort in the California gull: tests of parent-offspring conflict theory

Parental effort was studied among knownaged California gulls (Larus californicus) with a brood size of two. Results supported three of Triver's predictions from parent-offspring conflict theory. First, the amount of time parents withheld food from offspring increased with increasing offspring age. Second, older parents were less likely than younger parents to withhold food from offspring throughout the period of parental care. Third, older parents had a longer period of parental care compared to younger parents. Adult survival to future breeding seasons was inversely related to duration of parental care. Older parents, in association with their greater levels of parental effort, had a lower survival rate compared to that of younger parents.

The logic of mate desertion

Since the fitness consequences of mate desertion are markedly affected by whether the partner also deserts, natural selection is expected to favour desertion decisions that take the mate's decision into account. A model for the evolution of mate desertion is described in which individuals make desertion decisions repeatedly during the period of parental care, choosing the option (desert or stay) that gives them the greater fitness, taking into account whether their mate has already deserted. If the partner still remains, the optimal decision is made assuming that the partner responds optimally in turn. Four patterns of time-dependent payoffs define all possible desertion decisions, three of which produce different kinds of stable evolutionary outcome: both parents stay with the young; both desert; and one deserts, one stays. The fourth pattern (‘pre-emptive desertion’) also results in both parents deserting but paradoxically, in this case, they sacrifice fitness by so doing. Such uncooperative parents are caught in the well-known Prisoner's Dilemma of game theory and provide a link with recent thinking on the evolution of cooperation. Under conditions of mate choice or repeated interaction between potential mates the payoff pattern that normally produces pre-emptive desertion may result instead in a ‘both stay’ outcome. When desertion decisions are conditional on the partner's decision, in the way assumed here, desertion outcomes cannot be predicted simply by comparing the costs and benefits of desertion for the male and female at any one time. Rather, one needs to know the way in which these payoffs vary for each partner over the whole of the parental care period. Applications of the model are discussed, with particular reference to uniparental care in fish and biparental care in birds.

Seasonal and Age-Related Changes in Plasma Testosterone Levels in Mountain White-Crowned Sparrows

Plasma levels of testosterone (T) were measured by radioimmunoassay in Mountain White-crowned Sparrow (Zonotrichia leucophrys oriantha) males of known age and natural history during four consecutive reproductive seasons in the Sierra Nevada of California. Because nesting occurred comparatively early in all of these seasons and mean schedules varied by only 11 days, data were lumped to show the seasonal pattern of T. This pattern was unimodal with a maximum coinciding with the period of competition for territories and mates and with mate guarding. This was followed by a decrease toward a minimum that coincided with the period of parental care and, eventually, postnuptial molt. When these data were analyzed by stage of the reproductive season (rather than calendar date) and by age, two unexpected results emerged. First, T levels decreased significantly between the stages of nest building and laying. Female mates should have been fertilizable and soliciting copulations during both of these stages and intermale conflicts associated with mate guarding should have been frequent. In both situations, high T levels would be predicted by current paradigms. Second, T levels were considerably lower in yearling males than in older males prior to the laying stage. Reasons for this age-related difference are unknown but it was observed that yearling males tended in all comparison intervals to have lower body masses, shorter wings, and shorter testis and cloacal protuberance lengths than older males--they were smaller birds. Yearling males were also less successful in obtaining mates than older males but, once paired, reared just as many offspring.

Parent-offspring relationships in wintering barnacle geese

The relationship between parent geese, Branta leucopsis, and their offspring was monitored in order to discover some of the possible costs and benefits resulting from their association. Compared with birds without young the amount of time parents devoted to feeding was restricted in autumn and winter when they spent significantly more time being vigilant and aggressive. Family goslings fed without interruption for longer periods in autumn, were victims of attacks less often and grew fatter than unattached goslings. By the time the geese migrated to the breeding grounds in spring over 60% of goslings were unattached. The appearance of unattached young was related to the frequency of parental attacks on them and to inter-sibling aggression. However, the majority of parents were still associating with at least some of their brood after 9–10 months. Birds with more breeding experience associated with offspring for longer. Maintaining association with offspring did not reduce a parent's chances of surviving to, or breeding in, the following year. In fact, birds that remained with young for the longest period bred more successfully the next year than those with shorter periods of parental care. It is suggested that extended association with goslings may increase a parent's chances of breeding in the future due to the ‘contributor’ effect of the goslings that stayed in the family. Such goslings spend more time being vigilant and repelling neighbours which enables parents to increase their feeding time.

The effect of silt on the parental behaviour of the sea stickleback,Spinachia spinachia

The sea stickleback,Spinachia spinachia, lives in shallow coastal and estuarine waters where the male builds a nest and undergoes a protracted period of parental care. The accumulation of silt in the nest has been suggested as one of the environmental factors that regulate nest-directed activities during the parental phase. Experiments have quantified the behaviour of the male fish before and after the application of silt to the nest and shown that some behaviours are affected. The fanning activity, attendance at the nest and other nest-directed activities were examined and it was found that nest inspection and nest pushing increased significantly following the application of silt. Fanning activity, a major part of the parental behaviour of the sticklebacks, was unaffected by the experimental treatment and seems to be unresponsive to environmental changes. The results are discussed in relation to the functional significance of parental behaviour, and compared with a closely related species.

Intermale aggression in Padogobius martensi (Günther) (Pisces Gobiidae) during the breeding season: effects of size, prior residence, and parental investment

SUMMARY Resident males of Padogobius martensi (Gunther) (Pisces Gobiidae), which had experience of courtship and fertilization, were confronted with conspecific male intruders during the period of parental care. Dyadic encounters were conducted with different size relationships between residents (R) and intruders (I) as follows: resident larger (R > I), resident smaller (R < I) and resident equal (R = I) to the intruder. Results showed that size plays a crucial role in fighting assessment. On the contrary, the residence and associated parental investment (i. e. increased resource value), were ineffective in repelling intruders larger than the residents. At variance with previous accounts of conflict outside the breeding season (TORRICELLI et al., 1988), 100% fighting was observed in all three experimental situations and the increased resource value significantly augmented the residents likelihood of winning in matched size contests. Moreover, marked escalation was observed in terms of increased fighting d...

Environmental Variance in Lifetime Mating Success, Mate Choice, and Sexual Selection

The importance of chance variation in mate-encounter rates, and of sex differences in times, in generating sexual differences in the variance in success of polygamous species has been the subject of some discussion. Sutherland (1985a,b), for example, treated behavior as a time-budget problem within optimal foraging theory (foraging for mates) and noted a major difference in mating for males and females. Included in time are all matingrelated processes that reduce the ability of an individual to search for additional mates. Males typically have much shorter times than do females, which often delay remating until, for example, the end of an extended period of parental care. Sutherland (1985a) argued that random in a population in which the sexes differ in the length of the period before remating (hereafter, latency) results by itself in the observed asymmetry in the strategies of the sexes and that there is no need to invoke male-male competition or female choice. Bateman's (1948) data showing a higher variance in the success of Drosophila melanogaster males were consistent with such a random-mating model. In this paper, we develop Markovian models in which males and females are distinguishable, following Sutherland (1985a), by their differing postmating latencies. Using these models, we consider two problems. The first deals with the consequences of chance variation in life history for individual strategies. We analyze the evolutionarily stable strategies (ESS) for mate choice by males and females encountering a random stream of potential mates with two qualities. We answer the question of the evolution of choosiness as a function of survival rate, the duration of postmating latency, the probability of encountering potential mates, the proportion of high-quality potential mates, and the difference in quality of the potential mates. The second problem concerns the implications of chance variation in lifetime success (LMS) for the theory of sexual selection. We calculate LMS means and variances for males and females under a model of constant risk of death per unit of time. We examine a model in which the variance in

Plasma androgen levels during male parental care in a tropical frog ( Eleutherodactylus)

Males of the Puerto Rican frog Eleutherodactylus coqui practice parental care of terrestrial eggs throughout embryonic development (17–26 days). Parental care is associated with marked changes in male behavior, including the cessation of normal calling activity (necessary for mate attraction) and reduction of egg cannibalism. To analyze the relationship between parental behavior and androgens, blood was collected from male frogs in the field and plasma analyzed for total androgens. Parental males had significantly lower androgen levels than both nonparental, calling males, and amplectant (mating) males. The decline in circulating androgens between the sexually active state (calling and mating) and the parental care state was fairly rapid (<12 hr). Androgen levels did not differ among parental males at different stages of the parental care period.

The costs of male parental care and its evolution in a neotropical frog

Parental care is practiced exclusively by males of the Puerto Rican frog, Eleutherodactylus coqui. Males brood clutches of direct-developing eggs in non-aquatic nest sites and defend eggs against cannibalistic nest intruders. Here, I report on energetic and mating costs incurred by males that provide parental care, and suggest how these proximate costs affect male fitness and the evolution of male parental care in this species. Energetic costs are small for brooding males in comparison to non-brooding, calling males. Brooding males had a higher frequency of empty stomachs and lost small, but significant, fractions of their initial body mass during parental care. Abdominal fat bodies of brooding males during the middle third of parental care were significantly smaller than those of calling males; those of males brooding eggs in earlier or later stages were not different. The mating cost of parental care is greater. Most brooding males cease calling during parental care. However, gravid females are available (i.e., known to mate) on most nights during the principal breeding season; hence non-calling males miss potential opportunities to mate. A mating cost was estimated by calculating nightly mating probabilities for calling males in a plot where nightly calling male densities and daily oviposition schedules were known. On average, a male exhibiting normal calling behavior would be expected to obtain a new mate once every 35.7 days. Hence a brooding male that ceased calling for a 20-day parental care period would miss, on average, 0.56 additional mates. Males that were more successful than average in attracting mates could miss up to 1.63 matings. A marginal value model (Fig. 1) is used to analyze the net effect on male fitness of parental care benefits and costs in E. coqui (Fig. 3). The model indicates that males garner the highest reproductive success by providing care from oviposition through hatching. There is no stage during the pre-hatching period at which a desertion strategy would yield higher reproductive success. In fact, the model suggests that males should provide full parental care even in the face of much higher mating costs than currently obtain in the system.

Sex Ratio, Differential Cost of Rearing Young, and Differential Mortality between the Sexes during the Period of Parental Care: Fisher's Theory Applied to Birds

Fisher (1930) argued that the overall parental expenditures on the male and on the female progeny are fixed at equality by natural selection. Taking the primary sex ratio, the parental costs of rearing young of each sex, and the possible existence of differential mortality rates into account, we have constructed a model to test this theory, using data obtained for the Rook Corvus frugilegus and other bird species to illustrate the properties of the model. The metabolic rates of nestling Rooks of both sexes at rest were dependent on their ages and body weights. The parent Rooks were found to have to invest about 10% more energy in a male than a female offspring during the period of parental care. Nevertheless, in support of Fisher's theory, an average pair of Rooks seems to invest an equal proportion of their energy resources in progeny of both sexes, because the total energy investment in their progeny by a population is evened out by a skewing in the mortality rate, whereby more male than female offspring die before independence and at a later age.

Variation in the Mating System of a Biparental Cichlid Fish, Cichlasoma Panamense

Abstract Cichlasoma panamense is a biparental, substrate-spawning cichlid which breeds during the dry season in Panamanian streams. In one population some males helped to defend their offspring throughout the period of parental care but many deserted their mates to achieve additional spawnings leaving females to guard alone. The proportion of C. panamense guarding in pairs increased throughout the breeding season. This was associated with an increase in the rate with which parental cichlids attacked potential brood predators and an increase in brood size. The increase in attack rate was due to the crowding of fishes as water levels receded during the dry season and especially to the increasing numbers of newly independent cichlids which congregated in the shallow water areas where C. panamense brood. The sex ratio in the population was strongly biased towards females. Males spent more time away from the brood than females which enabled them to find and spawn with unmated females. The attack rate of females brooding alone was not significantly higher than that of those with mates and their foraging rate not significantly lower although they spent less time away from their brood. In a more productive stream where population density was high, breeding was almost entirely in monogamous pairs. The rate at which parents attacked potential predators was higher, the sex ratio was 1:1 and brood size was large. The male's decision to guard or desert appears to depend on his opportunities for further matings, the ability of the female to guard alone and the value of a current brood. These results agree with the predictions of game theory models of parental care.

The Breeding Biology of the Red-Vented BulbulPycnonotus Caferin Fiji

SUMMARYWATLING, Dick, 1983. The breeding biology of the Red-vented Bulbul Pycnonotus cafer in Fiji. Emu 83: 173–180.In Fiji, the Red-vented Bulbul Pycnonotus cafer has a distinct breeding season which occurs during the rains. The Bulbul has a mean clutch size of 2.5. There is a high rate of egg and nestling loss; 72% of eggs laid do not hatch and 53% of nestlings do not survive. Bulbuls have an extended period of parental care of fledglings and are unlikely to raise more than one brood in a season. Fledgling survival appears to be good and the annual recruitment rate is probably about 30%, although in one year it was considerably less.

Reproductive strategies in female Mountain and Dorcas gazelles (Gazella gazella gazella and Gazella dorcas)

Observations of reproduction in four gazelle populations in the semi–arid and arid habitats of Israel during three years have revealed intra– and interspecific differences. In the eastern Lower Galilee of northern Israel, female Mountain gazelles (Gazella gazella gazella) reproduce during every month of the year, conceive first at six months of age and exercise long parental care. Females of a population 80 km to the north (Upper Galilee) maintain a seasonal reproductive pattern, conceive first at 18 months of age and have a short parental care period. The latter pattern is similar to the Dorcas gazelle (Gazella dorcas) females of the southern Negev Desert. Interspecific similarities in reproduction of these two populations is attributed to the lack of free water during lactation in both environments where females rely on water available in plant tissue only. The importance of the daily accessibility to water during lactation in female gazelles is discussed. It is suggested that the timing of births and the ability of female gazelles to conceive while lactating are not species‐specific characteristics but simply a matter of short‐term adaptation to changing environmental conditions common understanding today that animal reproductive strategies are a function of prevailing environmental conditions.

Serum prolactin levels and crop-sac development in ring doves during a breeding cycle

Using a turkey prolactin radioimmunoassay, the serum prolactin levels of male and female ring doves ( Streptopelia risoria) during the breeding cycle were measured and their circulating prolactin levels were compared to crop-sac weight on a within-bird basis. During the early phase of the incubation period, crop weight showed a delayed response to prolactin stimulation and there was no correlation; during the midincubation period when prolactin and crop-sac weight were increasing, there was a strong positive correlation; around hatching, when prolactin was at its peak, there was no correlation. There were again strong positive correlations at later samples, when squabs were developing and both prolactin and crop-sac weight were declining. Thus, it appears that the correlation between the circulating prolactin level and crop-sac development depends on the stage of the breeding cycle. While males and females showed similar pattern of circulating prolactin during the period of incubation and parental care, only females consistently showed a postovulatory rise of prolactin. These results were discussed in the context of the role of prolactin in the breeding cycle.

Brood success in variable environments: Implications for parental care allocation

A model is developed which makes predictions about intraspecific variation in parental care patterns. The model assumes that animals can respond to predictable changes in conditions for rearing offspring, and can adjust the amount of parental care they provide. The following predictions are made: (1) Where the environment or the parent's condition varies predictably, animals should provide more care to successive broods under improving conditions, and less care under deteriorating conditions. (2) In stochastic environments, variation in brood success during the period of parental care should have a predictable effect on subsequent brood-care. (3) In non-uniform environments or populations, parents facing higher than average mortality risks of types independent of parental effort should increase care provided for current offspring. Parents whose mortality risks result from parental effort should provide less care for their offspring. These predictions are assessed in relation to the available empirical evidence. Much of this suggests that parental care patterns vary within species and may often be adjusted by individuals according to prevailing and projected conditions. Data could not be found to test all aspects of the theory, however, so further field studies would be valuable.

Bionomics and Sociology of Tancho, Grus japonensis

Territoriality of Tancho or the Japanese Crane, Grus japonensis was studied in Kushiro marshlands from March 1971 to June 1972. Two types of social patterns are recognized: The permanent territorial pattern and the segregation of breeding and wintering areas. The difference of these two social patterns seems to be correlated with availability of winter food supply. Daily life of a pair is confined within a territory. The territory involves three important places for: nesting, roosting and feeding. The daily home range markedly varies, in the period of early parental care, its minimum size being as small as 1/1600 of the largest one. But the territory remains almost constant through breeding season. The alternation of guarding chick and searching food may be most responsible for the reduction of daily home range. To raise their chicks in huge open and bioeconomically poor marshlands, the reduction of daily home range is advantageous for Tancho. The territory occupants exhibit territorial defense at the invasion of alien birds. The sequence of invasion and defense varies considerably according to age of invaders, season, time and weather conditions. Duetting decreases the chance of invasion and increases the withdrawal of invaders. Social units found in Tancho in the breeding seasons are classified as territorial pairs, families, non-territorial two associated yearlings, solitary yearlings and solitary adults.