Seasonal variation in parental care, offspring development, and reproductive success in the burying beetle, Nicrophorus vespillo

1. Beetles of the genus Nicrophorus reproduce on small vertebrate carcasses that they bury in the soil to provide the larvae with food. Usually, both parents cooperate in brood care by feeding and guarding their progeny. 2. In pairs of the common European species N. vespillo, the duration of care depended on the time of year when the beetles reproduced. Both in 1990 and in 1991, male and female parents stayed longer with their broods when reproduction started in spring than when reproduction started in early or late summer. This was probably due to the longer development time of the larvae caused by lower temperatures in spring, because laboratory experiments suggested a strong influence of temperature on both the duration of brood care and offspring development. 3. The number of adult offspring produced by a beetle pair did not vary among different times of the year. 4. The median time required for offspring development, measured as time from burial of the carcass to emergence of young adults, was between 62 and 84 days. When the beetles reproduced in late summer, only about three-quarters of the offspring left the soil and hibernated as adults. The remaining offspring stayed underground and adults appeared on the soil surface the following spring. They still showed the flexible cuticle typical of newly-hatched beetles, suggesting that they may have overwintered in a pre-adult stage.     

A bibliography and categorization of bony fishes exhibiting parental care

Parental care occurs in a diversity of fishes, but predominantly among freshwater groups. Among the approximately 422 families of bony fishes (Osteichthyes), 89 are presently known to exhibit parental care. Grouping these families into eight categories, based on the sex of the care-giver(s), reveals male parental care is as common or more common than female parental care. Although unusual among vertebrates, parental care by males alone is very common among bony fishes. Lists of families, the forms of parental care exhibited, the modes of fertilization, the environments in which reproduction occurs, and the sources of documentation are presented. An extensive bibliography and index are provided.     

Interference competition among burying beetles (Silphidae, Nicrophorus)

Abstract. 1. This study investigated the impact of intraspecific and interspecific competition on the reproductive success of a biparental burying beetle, Nicrophorus defodiens Mannerheim.
2. Marked pairs or single females were placed on small and large mouse carcasses in the field in 1985 and 1986. Carcasses were exhumed after 9–10 days to determine the identity of the resident adult(s) and the production of young.
3. Competition was assessed by the prevalence of takeovers by intruders (unmarked adults). For N.defodiens , after the initial colonization of the carcass, interspecific competition from larger N.orbicollis Say and N.sayi Laporte was substantial and more intense than intraspecific competition. Competition was also greater in the middle of the breeding season and on large as opposed to small carcasses.
4. Successful takeovers resulted in the expulsion of the prior resident(s), killing of any offspring present on the carcass, and oviposition of a new clutch by the intruder.
5. Females aided by males were more likely than single females to avoid takeovers but did not produce larger broods or larvae of larger mass.
6. An additional laboratory experiment in 1985 and a field experiment in 1986 suggest that N.defodiens is able to reproduce on very small carcasses despite intense heterospecific activity.     

Human pair‐bonds: Evolutionary functions,ecological variation,and adaptive development

Stable mating relationships are widespread in our species, with important economic, social, and reproductive implications.¹ Pair‐bonds are part of the unique human mosaic, including very large brains, childhood, concealed ovulation, sexual intercourse in private, cultural symbols, and complex social groups. Yet we understand relatively little about the evolution of human pairing, its functions, and consequences for human diversity. We can define pair‐bonds as the long‐term affiliation, including a sexual relationship, between two individuals. The important point is that the union, whether monogamous or polygamous, is relatively enduring. Recent debate about human pair‐bonds highlights apparently conflicting hypotheses: Are pair‐bonds the evolutionary consequence of male mating competition^2,3 or are they an adaptation for paternal provisioning?^4,5 Unfortunately, a simple answer seems unlikely. The evidence indicates selective pressures from both mating competition and provisioning needs, suggesting different benefits of pair‐bonds in different contexts. Whether a bond emphasizes mating or parenting effort may depend on environmental cues. Childhood experience evidently affects pair‐bond development, suggesting further adaptive design for flexible life‐history strategies. © 2008 Wiley‐Liss, Inc.     

Verhalten von Kranichfamilien (Grus grus) in Brutrevieren Nordostdeutschlands: Investition der Altv?gel in ihre Nachkommen

Zusammenfassung Junge Graukraniche haben einen weniger guten Jagderfolg bzw. eine geringere Rate bei der Nahrungsaufnahme als Altvögel. Dieses Defizit sollte durch die elterliche Investition bei der Jungenaufzucht kompensiert werden. Untersuchungen zum Zeitbudget und zum Aufwand aus dem Brutgebiet fehlen bisher. Mit Hilfe markierter Jungkraniche (Farbringe, Sender) wurde das Verhalten der Eltern und ihrer Nachkommen erfasst, um die Investitionen in Beziehung zum Reproduktionserfolg zu analysieren. Die Eltern sicherten mit 39,6% fast viermal so häufig wie Altvögel ohne Junge (Übersommerer). Bei Paaren mit zwei Nachkommen waren diese Aufwendungen höher als bei Paaren mit nur einem Jungvogel. Das Weibchen profitierte vom verstärkten Sichern des Männchens (Männchen: durchschnittlich 43,9%, Weibchen 35,3%) und konnte so vermutlich schneller seine Investition in die Gelegeproduktion ausgleichen. Die Revierverteidigung bzw. Feindabwehr übernahmen meist die Männchen. Die Beteiligung des Männchens förderte den Aufzuchterfolg, der auf zwei Junge begrenzt ist. Die Jungen profitierten von den Leistungen ihrer Eltern. Sie konnten mit geringem Sicherungsaufwand (11,9%) Nahrung suchen (67,7%, Eltern 42,8%) und so ihre geringere Aufnahmerate kompensieren. 77,9% der Jungkraniche überlebten vom Zeitpunkt des Markierens im Juni bis zum Abzug ins Überwinterungsgebiet im Oktober/November (84% der Einzeljungen und 75% bei Familien mit zwei Nachkommen).Junge Kraniche müssen einen wesentlichen Teil des Tages Nahrung aufnehmen, um den Energiebedarf für ein schnelles Wachstum sicherzustellen. Bei einer negativen Energiebilanz aufgrund zu vieler Störreize können die Erfolge bei der Jungenaufzucht sinken. Im Rahmen der Landschaftsplanung ist vor allem in Räumen mit einer hohen Siedlungsdichte des Kranichs auf eine stärkere Bebauung (z. B. mit Windkraftanlagen) oder Zerschneidung durch weitere Verkehrswege und Energieleitungen zu verzichten.

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Behaviour of Crane (Grus grus) families in their breeding territories in Northeast Germany: parental care and investment

Summary Juveniles and immature birds normally have less foraging ability and a lower food intake rate than adults. This — it has been presumed — is compensated for by parental care and investment during juvenile development. Studies of time budgets and parental investment of Common Cranes were carried out in the years 1995 to 1999 in Northeast Germany. Having first marked young Cranes (colour rings, radio transmitters), we analysed the behaviour of parents and offspring to correlate this with reproductive success. Parents with young (39.6%) were four times more vigilant than non-breeders. The investment of pairs with two young was significantly (p<0.001) higher than in pairs with only one young. Females profited from the high vigilance rate of their males (males mean 43.9%, females 35.3%) and were thus able probably to compensate for their investment in the clutch faster because of higher food intake. Defence of the territory against other cranes and defence against predators were tasks mostly undertaken by males. If the males participated in the rearing of the young, the pair were able to rear two juveniles to fleding.The young profited from parental care. They were able to feed most of the time (67.7%) with lower vigilance costs (11.9%; 27.7% less than parents), and thus possibly compensated for their lower feeding success. Rearing of two young, however, must be the upper limit of possible investment of adults. So far there has been no evidence of families with three grown-up young in a stopover region or on the wintering grounds. The survival of juveniles from the date of ringing in June up to the migration to the wintering sites in mid-November amounts to 77.9%, with 84% for families with one young and 75% for those with two young. Accordingly the reproductive success was higher for pairs with two young (1.32 juv./pair) than with one young (0.84 juv/pair).The long-term survival of the population in a man-made landscape is only possible with an appropriate reproductive success. The offspring of crane families have to feed throughout the major part of the day in order to gain their energy for the high metabolic rate during growth. With a negative energy balance because of too much disturbance, the reproductive success will decrease. Future landscape planning should avoid new traffic structures, buildings (e.g. wind turbines) or power lines at least in areas of high crane density.

     

Size-Based Variation in Somatic Energy Reserves and Parental Expenditure by Male Smallmouth Bass, Micropterus dolomieu

Male smallmouth bass show size-based variation in both probability and timing of reproduction. The objective of this research was to determine seasonal and size-based patterns of depletion of energy reserves and determine if parental defense is related to males' energy reserves. We sampled male smallmouth bass in the spring, during the parental care period and in the fall to measure energy reserves (lipid stores in muscle and viscera tissue) over a two year period. Energy stores, which were not built up before nesting, declined to a minimum level by the end of the parental care period. Small males had consistently lower energy reserves than larger males and did not utilize these reserves at the same rate during the parental care period. All parental males complimented endogenous energy reserves by feeding during parental care, however, small males appear to rely proportionately more on exogenous energy intake than do larger males. Parental defense by all sizes of males declined over the parental care period, the decline being the most obvious by small males. Small males' lower energy budget may make them less effective parents and decrease their probability of survival over the following winter relative to larger males.     

The influence of brood loss on nest abandonment decisions in largemouth bass Micropterus salmoides

Largemouth bass Micropterus salmoides broods were experimentally reduced in size to test whether brood size (BS) and simulated brood depredation affect the decision by a male to continue providing care for its brood or to abandon that brood prematurely before its offspring reach independence. The highest ranked of the generalized linear models predicting brood abandonment was based on the number of offspring remaining in a nest following brood devaluation, indicating that parental male fish reassess the value of a brood following perturbation. Paternal M. salmoides were more likely to abandon their broods if initial BS was small before devaluation, and if there was a greater decrease in BS, indicating a threshold for both the amount of brood loss and remaining BS. Larger, older males were also less likely to abandon their brood than smaller, younger conspecifics. These results have broad implications for determining drivers of parental care trade‐offs and how individuals assess the value of a brood.     

Short‐term dynamics of nest occupancy in an allopaternal species,the tessellated darter Etheostoma olmstedi

To inquire how male size interacts with alloparental behaviour and mating success in the tessellated darter Etheostoma olmstedi, males were given a choice of nests with or without eggs; subsequent nest occupancy, takeovers and egg deposits were monitored. Subordinate males readily occupied available nests with eggs but were often evicted by dominant males, suggesting that males of all sizes compete for the opportunity to provide allopaternal care in this species.     

Will male advertisement be a reliable indicator of paternal care,if offspring survival depends on male care?

Existing theory predicts that male signalling can be an unreliable indicator of paternal care, but assumes that males with high levels of mating success can have high current reproductive success, without providing any parental care. As a result, this theory does not hold for the many species where offspring survival depends on male parental care. We modelled male allocation of resources between advertisement and care for species with male care where males vary in quality, and the effect of care and advertisement on male fitness is multiplicative rather than additive. Our model predicts that males will allocate proportionally more of their resources to whichever trait (advertisement or paternal care) is more fitness limiting. In contrast to previous theory, we find that male advertisement is always a reliable indicator of paternal care and male phenotypic quality (e.g. males with higher levels of advertisement never allocate less to care than males with lower levels of advertisement). Our model shows that the predicted pattern of male allocation and the reliability of male signalling depend very strongly on whether paternal care is assumed to be necessary for offspring survival and how male care affects offspring survival and male fitness.     

Effects of testosterone on song, aggression, and nestling feeding behavior in male great tits, Parus major

As outlined in the trade-off hypothesis of testosterone (T) secretion, fluctuations in T during the breeding season might reflect how males allocate their time and energy to competitive behaviors for mates and territories, associated with high T levels, and parental activities, associated with low T levels. In the present study, great tit, Parus major, males were implanted with T-filled or empty silastic capsules at the start of the breeding season and the behavior of these two male categories was compared during the entire breeding season. As a measure of competitive behavior we looked at song behavior and territorial responsiveness to a male decoy, during the three main stages of the breeding period (the egg-laying, incubation, and nestling stages). As a measure of parental care we looked at feeding behavior during the nestling stage. Our results only partly supported the trade-off hypothesis. T implants increased plasma androgen levels and enhanced spontaneous song activity and the production of aggressive vocalizations in response to a decoy. However, our results suggest that the degree of physical aggression might be less than fully coupled with T. First, approach to the decoy was not affected by the treatment. Second, although T levels are known to vary from high during egg laying to low while feeding young, control and T-treated males spent similar amounts of time close to the decoy in the three breeding stages. Our results thus suggest that vocal and physical aggression might be regulated differently in the great tit. Furthermore, in contrast with most other studies on temperate bird species but in agreement with a previous study on the great tit, T treatment did not affect male feeding rates. As the dose of T we used was lower than that typically used in other studies, we cannot at present completely exclude the possibility that the latter result reflects this lower dose of T rather than the species used.     

Developmental stress increases reproductive success in male zebra finches

There is increasing evidence that exposure to stress during development can have sustained effects on animal phenotype and performance across life-history stages. For example, developmental stress has been shown to decrease the quality of sexually selected traits (e.g. bird song), and therefore is thought to decrease reproductive success. However, animals exposed to developmental stress may compensate for poor quality sexually selected traits by pursuing alternative reproductive tactics. Here, we examine the effects of developmental stress on adult male reproductive investment and success in the zebra finch (Taeniopygia guttata). We tested the hypothesis that males exposed to developmental stress sire fewer offspring through extra-pair copulations (EPCs), but invest more in parental care. To test this hypothesis, we fed nestlings corticosterone (CORT; the dominant avian stress hormone) during the nestling period and measured their adult reproductive success using common garden breeding experiments. We found that nestlings reared by CORT-fed fathers received more parental care compared with nestlings reared by control fathers. Consequently, males fed CORT during development reared nestlings in better condition compared with control males. Contrary to the prediction that developmental stress decreases male reproductive success, we found that CORT-fed males also sired more offspring and were less likely to rear non-genetic offspring compared with control males, and thus had greater overall reproductive success. These data are the first to demonstrate that developmental stress can have a positive effect on fitness via changes in reproductive success and provide support for an adaptive role of developmental stress in shaping animal phenotype.     

The evolution of human biosocial behaviour

The analysis of human behaviour can be approached from three different but complementary perspectives: the first includes the eternal debate about the degree of environmental or genetic determinism of social behaviour; the second, in the context of evolutionary ecology, concerns the evaluation of behavioural responses to morphological and/or environmental changes that have been the key to success in our species; the third, in the context of the analysis of the biology of the health of modern day populations, deals with the biological consequences of social behavioural changes. The secret of the success of a species resides in its capacity to respond behaviourally to the morphological and environmental changes produced during its biological history. What is unique about humans concerns our brains and their derived function: flexible behaviour. The morphological, physiological and behavioural changes that allow thecreation and maintenance of such a large brain are intimately connected to reproduction and therefore to the biosociology of women, the members of the speciesHomo sapiens in whom are combined, with notable success, a prolonged life-cycle, some anatomical and physiological traits and flexible reproductive behaviour, which together confer a decisive demographic advantage on them over other hominids. In summary, as well as contributing to the spread of this information by which women can make informed decisions based on a knowledge of causes, with the aim of optimizing our health it is necessary to consider the possibility of approaching some aspects of our biology and behaviour as patterns fixed by evolution. Three factors would be the most easily adjustable for this purpose: a) to delay the age of sexual maturation, b) to bring forward the age of first maternity, and c) to encourage breastfeeding on demand without substitutes and for a 3–5 month period.     

Sex differences in resource utilization by the peacock blenny

This paper presents data on the seasonal variation of gonadosomatic, hepatosomatic and feeding indices in nesting males, females and female-like males of the blenniid fish Salaria pavo . Eviscerated condition factors, female fecundity and feeding rates are also presented. The results are consistent with the hypothesis that females maximize their feeding rates during reproduction, converting food into eggs through repeated spawning. Nesting males feed at a very low rate during the breeding season. It is argued that one major component of the reproductive costs in these males is the reduction of feeding opportunities. Female-like males present lower reproductive costs, which probably reflects the compromise between fertilizing some eggs and growing.