Maternal Manipulation Research Articles

Effects of pregnancy on body temperature and locomotor performance of velvet geckos

Pregnancy is a challenging period for egg laying squamates. Carrying eggs can encumber females and decrease their locomotor performance, potentially increasing their risk of predation. Pregnant females can potentially reduce this handicap by selecting higher temperatures to increase their sprint speed and ability to escape from predators, or to speed up embryonic development and reduce the period during which they are burdened with eggs (‘selfish mother’ hypothesis). Alternatively, females might select more stable body temperatures during pregnancy to enhance offspring fitness (‘maternal manipulation hypothesis’), even if the maintenance of such temperatures compromises a female's locomotor performance. We investigated whether pregnancy affects the preferred body temperatures and locomotor performance of female velvet geckos Amalosia lesueurii. We measured running speed of females during late pregnancy, and one week after they laid eggs at four temperatures (20°, 25°, 30° and 35°C). Preferred body temperatures of females were measured in a cost-free thermal gradient during late pregnancy and one week after egg-laying. Females selected higher and more stable set-point temperatures when they were pregnant (mean =29.0°C, Tset =27.8–30.5°C) than when they were non-pregnant (mean =26.2°C, Tset =23.7–28.7°C). Pregnancy was also associated with impaired performance; females sprinted more slowly at all four test temperatures when burdened with eggs. Although females selected higher body temperatures during late pregnancy, this increase in temperature did not compensate for their impaired running performance. Hence, our results suggest that females select higher temperatures during pregnancy to speed up embryogenesis and reduce the period during which they have reduced performance. This strategy may decrease a female's probability of encountering predatory snakes that use the same microhabitats for thermoregulation. Selection of stable temperatures by pregnant females may also benefit embryos, but manipulative experiments are necessary to test this hypothesis.

Effects of nutritional deprivation on development and behavior in the subsocial bee Ceratina calcarata (Hymenoptera: Xylocopinae).

By manipulating resources or dispersal opportunities, mothers can force offspring to remain at the nest to help raise siblings, creating a division of labor. In the subsocial bee Ceratina calcarata, mothers manipulate the quantity and quality of pollen provided to the first female offspring, producing a dwarf eldest daughter that is physically smaller and behaviorally subordinate. This daughter forages for her siblings and forgoes her own reproduction. To understand how the mother's manipulation of pollen affects the physiology and behavior of her offspring, we manipulated the amount of pollen provided to offspring and measured the effects of pollen quantity on offspring development, adult body size and behavior. We found that by experimentally manipulating pollen quantities we could recreate the dwarf eldest daughter phenotype, demonstrating how nutrient deficiency alone can lead to the development of a worker-like daughter. Specifically, by reducing the pollen and nutrition to offspring, we significantly reduced adult body size and lipid stores, creating significantly less aggressive, subordinate individuals. Worker behavior in an otherwise solitary bee begins to explain how maternal manipulation of resources could lead to the development of social organization and reproductive hierarchies, a major step in the transition to highly social behaviors.

Maternal manipulation of pollen provisions affects worker production in a small carpenter bee

Mothers play a key role in determining the body size, behavior, and fitness of offspring. Mothers of the small carpenter bee, Ceratina calcarata, provide smaller pollen balls to their first female offspring resulting in the development of a smaller female. This smaller female, known as the dwarf eldest daughter, is coerced to stay at the nest to forage and feed siblings as a worker. In order to better understand how this maternal manipulation leads to the physiological and behavioral differences observed in dwarf eldest daughters, we characterized and compared the quality of the pollen balls fed to theses females vs. other offspring. Our results confirm earlier studies reporting that there is a female-biased sex allocation in the first brood cell position and these daughters received mass provisions significantly smaller than other daughters. In addition to the smaller quantities of pollen provisioned, we found evidence for maternal control of the quality of pollen invested in the dwarf eldest daughters. Late brood cells receive pollen balls with significantly less floral diversity than early brood cells. This difference in floral diversity affects the protein content of the pollen balls; in that, older offspring receive less protein than their younger siblings. These results reveal that C. calcarata mothers manipulate not only the quantity but also the quality of the provision provided to her first offspring to create a small worker she is able to coerce to remain at the nest to help raise her siblings. This overlapping of generations and division of labor between mother and dwarf eldest daughter may represent the first steps in the evolution of highly social groups. One of the major transitions to the formation of highly social groups is division of labor. By manipulating resource availability to offspring, parents can force offspring to remain at the nest to serve as a worker leading to a division of labor between parent and offspring. In the small carpenter bee, C. calcarata, mothers provide their eldest daughter with less food resulting in a smaller adult body size. This dwarf eldest daughter (DED) does not have the opportunity to reproduce and serves only as a worker for the colony. In addition to overall reduced investment, we found that mothers also provide a different variety of pollen to her DED. By exploring the factors and mechanisms that influence maternal manipulation in a non-eusocial bee, we can begin to understand one of the major transitions in social group formation.

Cryptic male choice: experimental evidence of sperm sex ratio and seminal fluid adjustment in relation to coital rate.

The differential allocation hypothesis suggests that a mother should adjust the sex of offspring in relation to her mate's attractiveness, thereby increasing future reproductive fitness when her sons inherit the attractive traits. More attractive males have been shown to sire more sons, but it is possible that the sex ratio skew could be a result of paternal rather than maternal manipulation, which would be a more parsimonious explanation. We manipulated coital rate (an indicator of attractiveness) in laboratory mice and showed that males that mate more often have higher levels of glucose in their semen despite lower blood glucose levels. Since peri-conceptual glucose levels in utero increase male conceptus survival, this could result in male-biased sex ratios. The males that mated most also had more remaining X-chromosome-bearing-spermatozoa, suggesting depletion of Y-chromosome-bearing-spermatozoa during mating. We hypothesise that males may alter both seminal fluids and X:Y ratios in an ejaculate to influence subsequent sex ratios. Our results further support a paternal role in sex allocation.

Maternal effects and female manipulation: a response to comments on Paquet and Smiseth

about whether or not to help, which is likely to be influenced by lack of additional breeding opportunities. Alonzo (2016) finds our review a useful generalization of the manipulating androgens hypothesis (MAH) and argues that further work is needed to understand how sexual conflict shapes female life histories and how plasticity in maternal effects evolve in response to plasticity in male care and vice versa. We agree and emphasize that, because both the MAH and our review are based on verbal arguments, there is a need for more formal theoretical models on the coevolution of maternal effects and male (and female) parental care. Alonzo also argues that manipulation only would work in the short term as males should evolve a behavioral reaction that is adaptive from their perspective. We agree with this argument when applied to manipulation by deception. However, manipulation by incentivization could work in the long term because males make an optimal decision given the specific benefits and/or costs of care. Incentivization may provide an evolutionarily stable mechanism for female manipulation due to an asymmetry between the sexes with females making an initial decision adjusting the offspring’s phenotype, thereby moderating the benefit and/or cost functions of care that influences the male’s subsequent decision. Thus, even though males adjust their decision in a way that is optimal to them given the specific cost and benefit functions, their fitness might still be lower than it would have been in the absence of any female adjustment of the offspring’s phenotype.

Stable eusociality via maternal manipulation when resistance is costless.

In many eusocial species, queens use pheromones to influence offspring to express worker phenotypes. Although evidence suggests that queen pheromones are honest signals of the queen's reproductive health, here I show that queen's honest signalling can result from ancestral maternal manipulation. I develop a mathematical model to study the coevolution of maternal manipulation, offspring resistance to manipulation and maternal resource allocation. I assume that (i) maternal manipulation causes offspring to be workers against offspring's interests; (ii) offspring can resist at no direct cost, as is thought to be the case with pheromonal manipulation; and (iii) the mother chooses how much resource to allocate to fertility and maternal care. In the coevolution of these traits, I find that maternal care decreases, thereby increasing the benefit that offspring obtain from help, which in the long run eliminates selection for resistance. Consequently, ancestral maternal manipulation yields stable eusociality despite costless resistance. Additionally, ancestral manipulation in the long run becomes honest signalling that induces offspring to help. These results indicate that both eusociality and its commonly associated queen honest signalling can be likely to originate from ancestral manipulation.

Maternal postpartum corticosterone and fluoxetine differentially affect adult male and female offspring on anxiety-like behavior, stress reactivity, and hippocampal neurogenesis

Postpartum depression (PPD) affects approximately 15% of mothers, disrupts maternal care, and can represent a form of early life adversity for the developing offspring. Intriguingly, male and female offspring are differentially vulnerable to the effects of PPD. Antidepressants, such as fluoxetine, are commonly prescribed for treating PPD. However, fluoxetine can reach offspring via breast milk, raising serious concerns regarding the long-term consequences of infant exposure to fluoxetine. The goal of this study was to examine the long-term effects of maternal postpartum corticosterone (CORT, a model of postpartum stress/depression) and concurrent maternal postpartum fluoxetine on behavioral, endocrine, and neural measures in adult male and female offspring. Female Sprague–Dawley dams were treated daily with either CORT or oil and fluoxetine or saline from postnatal days 2–23, and offspring were weaned and left undisturbed until adulthood. Here we show that maternal postpartum fluoxetine increased anxiety-like behavior and impaired hypothalamic-pituitary-adrenal (HPA) axis negative feedback in adult male, but not female, offspring. Furthermore, maternal postpartum fluoxetine increased the density of immature neurons (doublecortin-expressing) in the hippocampus of adult male offspring but decreased the density of immature neurons in adult female offspring. Maternal postpartum CORT blunted HPA axis negative feedback in males and tended to increase density of immature neurons in males but decreased it in females. These results indicate that maternal postpartum CORT and fluoxetine can have long-lasting effects on anxiety-like behavior, HPA axis negative feedback, and adult hippocampal neurogenesis and that adult male and female offspring are differentially affected by these maternal manipulations.

Judicial Decision-Making in Family Law Proceedings

Judicial Family Law proceedings are peculiar; a large number of cases are never closed, until the children reach adulthood. We selected three variables to test whether they can explain the credibility of each party and agent in the proceedings: guiding principle that orients the court's decision, confirmation of maternal manipulation in the psycho-social report, and establishing credibility of the child's testimony. An incidental sample of 169 people was used. The three manipulated variables imply very different levels of credibility for each party to the proceedings. Finally, proposed modifications to court proceedings are suggested to ensure adequate protection of children.

Resource Effects on Solitary Bee Reproduction in a Managed Crop Pollination System.

Population density may affect solitary bee maternal resource allocation. The number of Megachile rotundata (F.), alfalfa leafcutting bee, females released for seed production of Medicago sativa L., alfalfa, may limit flower availability for nest provisioning. In turn, pollinator abundance also may affect crop yield. The M. sativa pollination system presents an opportunity to test for effects of density dependence and maternal manipulation on M. rotundata reproduction. A multiyear study was performed on M. sativa fields upon which M. rotundata densities were altered to induce low, medium, and high density situations. Numbers of adult bees and open flowers were recorded weekly; bee reproduction variables were collected once. Fields varied in plant performance for each site and year, and the intended bee densities were not realized. Therefore, the variable density index (DI) was derived to describe the number of female bees per area of flowers over the study period. As DI increased, percentages of pollinated flowers, established females, and healthy brood significantly increased, and the number of pollinated flowers per female and of dead or diseased brood significantly decreased. Sex ratio was significantly more female biased as DI increased. Overwintered offspring weights were similar regardless of DI, but significantly differed by year for both sexes, and for males also by field and year × field interaction. Overall, resource limitation was not found in this field study. Other density-dependent factors may have induced a bee dispersal response soon after bees were released in the fields that circumvented the need for, or impact of, maternal manipulation.

Kinship, parental manipulation and evolutionary origins of eusociality.

One of the hallmarks of eusociality is that workers forego their own reproduction to assist their mother in raising siblings. This seemingly altruistic behaviour may benefit workers if gains in indirect fitness from rearing siblings outweigh the loss of direct fitness. If worker presence is advantageous to mothers, however, eusociality may evolve without net benefits to workers. Indirect fitness benefits are often cited as evidence for the importance of inclusive fitness in eusociality, but have rarely been measured in natural populations. We compared inclusive fitness of alternative social strategies in the tropical sweat bee, Megalopta genalis, for which eusociality is optional. Our results show that workers have significantly lower inclusive fitness than females that found their own nests. In mathematical simulations based on M. genalis field data, eusociality cannot evolve with reduced intra-nest relatedness. The simulated distribution of alternative social strategies matched observed distributions of M. genalis social strategies when helping behaviour was simulated as the result of maternal manipulation, but not as worker altruism. Thus, eusociality in M. genalis is best explained through kin selection, but the underlying mechanism is likely maternal manipulation.

Reproductive mode evolution in lizards revisited: updated analyses examining geographic, climatic and phylogenetic effects support the cold-climate hypothesis.

Viviparity, the bearing of live young, has evolved well over 100 times among squamate reptiles. This reproductive strategy is hypothesized to allow maternal control of the foetus' thermal environment and thereby to increase the fitness of the parents and offspring. Two hypotheses have been posited to explain this phenomenon: (i) the cold-climate hypothesis (CCH), which advocates low temperatures as the primary selective force; and (ii) the maternal manipulation hypothesis (MMH), which advocates temperature variability as the primary selective force. Here, we investigate whether climatic and geographic variables associated with the CCH vs. the MMH best explain the current geographical distributions of viviparity in lizards while incorporating recent advances in comparative methods, squamate phylogenetics and geospatial analysis. To do this, we compared nonphylogenetic and phylogenetic models predicting viviparity based on point-of-capture data from 20,994 museum specimens representing 215 lizard species in conjunction with spatially explicit bioclimatic and geographic (elevation and latitude) data layers. The database we analysed emphasized Nearctic lizards from three species-rich genera (Phrynosoma, Plestiodon and Sceloporus); however, we additionally analysed a less substantial, but worldwide sample of species to verify the universality of our Nearctic results. We found that maximum temperature of the warmest month (and, less commonly, elevation and maximum temperature of the driest quarter) was frequently the best predictor of viviparity and showed an association consistent with the CCH. Our results strongly favour the CCH over the MMH in explaining lizard reproductive mode evolution.

AN EVOLUTIONARY RESOLUTION OF MANIPULATION CONFLICT

Individuals can manipulate the behavior of social partners. However, manipulation may conflict with the fitness interests of the manipulated individuals. Manipulated individuals can then be favored to resist manipulation, possibly reducing or eliminating the manipulated behavior in the long run. I use a mathematical model to show that conflicts where manipulation and resistance coevolve can disappear as a result of the coevolutionary process. I find that while manipulated individuals are selected to resist, they can simultaneously be favored to express the manipulated behavior at higher efficiency (i.e., providing increasing fitness effects to recipients of the manipulated behavior). Efficiency can increase to a point at which selection for resistance disappears. This process yields an efficient social behavior that is induced by social partners, and over which the inducing and induced individuals are no longer in conflict. A necessary factor is costly inefficiency. I develop the model to address the evolution of advanced eusociality via maternal manipulation (AEMM). The model predicts AEMM to be particularly likely in taxa with ancestrally imperfect resistance to maternal manipulation. Costly inefficiency occurs if the cost of delayed dispersal is larger than the benefit of exploiting the maternal patch. I discuss broader implications of the process.

Distribución y viviparidad en especies de Liolaemus: el clima y cuando las hipótesis se ponen a prueba. Distribution and Viviparity in Liolaemus species: climate and when hypotheses need to be tested

Reptile' distributions, under the light of their strong dependence on particular temperature requirements, may be constrained as a consequence of climate. The relationship between reptile viviparity and climate yielded two previously proposed hypotheses (the cold climate and the maternal ma - nipulation hypotheses) that together with the climatic variability hypothesis; theoretically link climate, distribution and reproductive mode. The extensive variation in mean environmental temperature associated with changes in parity strategies has received much attention in this ectothermic group. Among Southamerican lizards, Liolaemus are distributed in cold and warm regions and more than 50 % of described species are viviparous. We stu - died 47 Liolaemus species considering climatic data where collected, preferred body temperature, its coefficient of variation and their thermal tolerance. Our results do not support the climate variability hypothesis, previously supported in other studies. We found a relationship between viviparity and elevation, but not between viviparity and thermal climatic variables. Finally, viviparous Liolaemus species showed more precise thermoregulatory behavior than oviparous ones, supporting the maternal manipulation hypothesis.

Evolution of Manipulated Behavior

Many social behaviors are triggered by social partners. For example, cells in a multicellular organism often become soma via extrinsically regulated differentiation, while individuals in a eusocial colony often become helpers via extrinsic caste determination. One explanation for social triggering is that it informs when it is beneficial to express the behavior. Alternatively, social triggering can represent manipulation where social partners partially or completely control the focal individual's behavior. For instance, caste determination in primitively eusocial taxa is typically accomplished via differential feeding or dominance hierarchies, suggesting some manipulation. However, selection would favor resistance if manipulation is detrimental to manipulated parties, and the outcome of the manipulation conflict remains intricate. We analyze the coevolution of manipulation and resistance in a simple but general setting. We show that, despite possible resistance, manipulated behavior can be established under less stringent conditions than spontaneous (i.e., nonmanipulated) behavior because of resistance costs. The existence of this advantage might explain why primitive eusocial behavior tends to be triggered socially and coercively. We provide a simple condition for the advantage of manipulated behavior that may help infer whether a socially triggered behavior is manipulated. We illustrate our analysis with a hypothetical example of maternal manipulation relevant to primitive eusociality.

Various factors influencing birth weight in animal production

This is a review article that looks at various factors that influence birth weight in animal production. Birth weight is an important indicator of potential growth of an animal and is affected by both genetic and non-genetic factor, and the birth size depends on their interaction. Environmental conditions such as kind and quality of feed and details of management may have an influence on birth weight in livestock production. In order to minimize the adverse effects of factors that influence birth weight, it is perhaps important to understand the implications of different mechanisms, how and why they affect birth weight. Low birth weight than optimum is the main factor that determine the pre weaning losses of young ones and large birth have been associated with difficult birth. Traditional measures to ameliorate birth associated negative effects should also focus on maternal dietary manipulation which may influence optimum birth weight. Nutritional programs designed to improve dam’s body condition during pregnancy will have a positive influence on birth weight of progeny. A good knowledge of genetic parameters is essential to develop accurate selection indices and to optimally design breeding programs and performance recording systems for maximum economic gain or profit from growth traits. Estimates of genetic parameters for birth weight is model dependent and ignoring of maternal genetic effect in the model leads to overestimation of direct heritability for birth weight. Estimates of direct and maternal heritability for birth weight in different species have been reported and vary from low to high. The review article therefore, concludes that the large variability of birth weight in livestock species suggests that many factors or conditions may be responsible for this variation. The reported low heritability estimates for birth weight may be explained by the poor nutritional levels of dams creating a large environmental variation.

The effects of maternal dietary lysine intake on offspring performance to 21 days of age

SUMMARY The CP and amino acid requirements for broiler breeder hens have historically been determined by assessing the response of these birds in terms of egg production. However, based on increasing evidence on the effects of maternal nutrient intake on offspring performance, this should be revised. In addition, the nutrition management of broiler breeder hens during lay is very controversial, and managers and nutritionists resort to the manipulation of feed allocation to improve egg production in these flocks. In this study, broiler breeder hens were fed diets differing in digestible lysine concentration from 26 to 60 wk of age. Fertile eggs were collected at 38, 48, and 60 wk and incubated. Broilers hatched were reared in commercial conditions and their performance was measured to 21 d of age. Based on this study, the feeding of the hens has a significant effect on offspring performance, and this should be considered when maternal requirements are investigated. Furthermore, we demonstrated the effects of maternal nutrient intake manipulation on the performance of broilers hatched from hens at different stages of the productive cycle.

ПРИРОДНЫЕ АНТИОКСИДАНТЫ В ЭМБРИОГЕНЕЗЕ КУР И ЗАЩИТА ОТ СТРЕССОВ В ПОСТНАТАЛЬНОМ РАЗВИТИИ (обзор)

Evidence is accumulating indicating that a maternal diet can have a profound effect on the hatching egg quality and health status, growth and development of newly hatched chick. Several points are important to outline. Maternal diet determines chicken development during egg incubation and for the first few days post-hatch. Vitamin E and carotenoids accumulation in the chicken liver during embryonic development is considered as an adaptive mechanism to deal with stress conditions of the hatching process. In postnatal development a strategy of antioxidant defence is changed from antioxidant accumulation to the synthesis of antioxidant enzymes with more sophisticated and effective regulation at the gene level. Immune and digestive systems of the chicken are not mature at hatch and are actively developing during first 2 weeks post-hatch and are at risk of oxidative stress and need effective antioxidant protection. Increased vitamin E/carotenoid/Se supplementation of the maternal diet is proven to be beneficial for the embryonic and early postnatal development of the chick. However, maternal dietary manipulation is not able to prevent oxidative stress in early postnatal development and there is a need to address this issue. Therefore, a new antistress composition provided with drinking water is developed and successfully tested in commercial conditions of Ukraine and Russia.

LACTATION BIOLOGY SYMPOSIUM: Maternal nutrition during early and mid-to-late pregnancy: Comparative effects on milk production of twin-born ewe progeny during their first lactation1,2

Studies using sheep models indicate that the fetal mammary gland is sensitive to maternal nutrition during gestation; however, results have been inconsistent and do not identify critical feeding periods. This study aimed to clarify previous findings by partitioning the period of maternal nutritional manipulation into 2 stages: early and mid-to-late pregnancy. Sixty-six twin-born, twin-bearing ewes, born to dams that were fed either submaintenance, maintenance, or ad libitum during early pregnancy (d 21 to 50 of pregnancy; SmP21-50, MP21-50, or AdP21-50, respectively) and then either maintenance or ad libitum during mid-to-late pregnancy (d 50 to 140 of pregnancy; MP50-140 or AdP50-140, respectively) were milked once a week, starting from d 7 ± 1 postpartum, for 7 subsequent weeks to enable estimation of daily milk yield and composition. Their lambs were weighed weekly. Ewes born to dams fed MP21-50 tended to have greater accumulated milk (P = 0.10), fat (P = 0.07), and NE (P = 0.06) yields over 50 d compared with ewes born to dams fed SmP21-50 and AdP21-50. In contrast, ewes born to dams fed AdP50-140 tended to have greater accumulated milk (P = 0.10) and lactose (P = 0.09) yields compared with ewes born to dams fed MP50-140. Grandoffspring birth weights were unaffected by granddam nutrition during pregnancy. Ewes born to dams fed AdP21-50 weaned lighter lambs (P = 0.05) than ewes born to dams fed AmP21-50 and tended to wean lighter lambs (P = 0.07) than ewes born to dams fed MP21-50 whereas there were no differences between the weaning weights of lambs (P = 0.43) from ewes born to dams fed AdP50-140 and MP50-140. Maintenance nutrition of dams during early pregnancy appears to be associated with an improved lactation performance of ewe offspring. Higher levels of nutrition during mid-to-late pregnancy also appears to improve the first-lactation performance of ewe offspring. Interestingly, although grandoffspring birth weights were unaffected, weaning weight appears to be influenced by granddam early pregnancy nutrition in a manner discordant with the lactational performance of their dam. Results from this study indicate that dam nutrition during early pregnancy can influence the lactational performance of ewe offspring and the BW at weaning of their grandoffspring, which may ultimately affect farmer profits. This highlights the importance of nutritional management of breeding ewes during this period.

Are Females Maternal Manipulators, Selfish Mothers, Or Both? Insight from Pythons

Abstract During reproduction, females often modify their behavior relative to the nonreproductive condition. These changes are frequently attributed to maternal efforts to optimize offspring development and survival (i.e., the maternal manipulation hypothesis). However, Schwarzkopf and Andrews (2012) recently challenged this concept as oversimplified, emphasizing that females should optimize their own lifetime fitness, and therefore maternal efforts may be directed at the female's future reproductive effort in addition, or even in contrast, to current reproductive effort. To provide insight into the relative importance of current versus future reproductive effort in shaping maternal behavior, we systematically explore a single study system—pythons. Pythons show distinct maternal behaviors during gravidity (modified basking effort), peri-oviposition (nest site selection), and postoviposition (egg brooding). By examining each component, we reveal that python maternal effort is predominantly aimed at current...

“Selfish Mothers” Use “Maternal Manipulation” To Maximize Lifetime Reproductive Success

Abstract Females should behave in ways that maximize lifetime reproductive success (the “selfish mother” hypothesis [SMH]). Very often, this will mean that female behavior during reproduction maximizes fitness of the current batch of offspring. In some cases, however, females may maximize lifetime reproductive success by behaving in ways that are neutral, or even detrimental, to current offspring fitness. The “maternal manipulation hypothesis” (MMH), proposed by Shine (1995), argues that females should behave in ways that maximize fitness of the current batch of offspring. We argued, however, that if researchers focus solely on measuring benefits to offspring of female behavior during reproduction, they will not consider the possibility that female behavior is neutral or even detrimental to offspring fitness, thereby missing an important facet of behavior during reproduction. Here we reply to comments by Shine (2012) and DeNardo et al. (2012), mainly to emphasize our point that contrasting the MMH and the...