Tradeoff between offspring mass and subsequent reproduction in a highly iteroparous mammal

When resources are limited, current maternal investment should reduce subsequent reproductive success or survival. We used longitudinal data on marked mountain goats Oreamnos americanus to assess if offspring mass at weaning affected maternal survival and future reproduction. Offspring mass was positively correlated with survival of old mothers, suggesting that mothers produced lighter kids, and hence reduced reproductive effort, in their last reproduction. Offspring mass at weaning did not affect survival of young and prime‐aged mothers, but females that had weaned heavy offspring had a reduced probability of subsequent reproduction in years of low population density. Because offspring survival is correlated with weaning mass, mothers’ allocation to reproduction involves a tradeoff between current and future fitness returns. We demonstrate for the first time that allocation to current offspring mass in an iteroparous mammal reduces the probability of subsequent reproduction.     

Parental effort of kestrels (Falco tinnunculus) in nest defense: effects of laying time, brood size, and varying survival prospects of offspring

We studied the nest defense behavior of Eurasian kestrels (Falcotinnunculus) towards a stuffed pine marten (Martes martes) througha 3-year vole cycle (1990–92) in western Finland. Survivalprobability of offspring decreases with a later start of breeding,and, therefore, early breeders should protect their offspringmore than late ones. We found this true for males during theincubation period, but not for females. In addition, we expectedthe nest defense intensity to increase with offspring number.During the incubation period, this was true for females, butnot for males. During the nestling phase, parents did not adjusttheir defense effort to natural or manipulated (by one to twoyoung) brood size. Survival prospects of kestrel offspring werehighest in the increasing vole year 1991 and lowest in the decreasingvole year 1992, and, therefore, we expected the defense activityof kestrels to follow the same trend. However, the oppositeresult appeared true for females with a similar tendency formales. Most hypotheses predicting avian nest defense behaviorwere not supported by our data. Temporally heterogeneous environmentand low degree of nest-site tenacity of migratory kestrels maymake them unfamiliar with environmental variation and survivalprospects of their offspring. Therefore, fitness benefits ofparental care are not predictable, and kestrels may thus adjusttheir parental effort to their own future reproductive potential(i.e., number of future breeding attempts), rather than to somecurrent investment indicator, like offspring age and number.     

Life-history analysis of the Trivers and Willard sex-ratio problem

Phenotypic quality, such as condition or size, often variesbetween individuals. For species with extensive maternal care,the quality of offspring may partially be determined by thequality of their mother. Trivers and Willard (1973) predictedthat high quality females should prefer offspring of the sexwhose reproductive success is most strongly influenced by maternalcare, which in many cases will be sons. Correspondingly, lowquality females should prefer daughters. However, this predictionis not based on a proper analysis of variation in reproductivevalue. Using state-dependent life-history theory, I show herethat high quality females should prefer offspring of the sexwhose reproductive value is most strongly influenced by maternalcare. I also show that when offspring quality is strongly determinedby their mother's quality, but not influenced by their father'squality, high quality females can have higher reproductive valuethan high quality males, even though their reproductive successmay be much lower. In such cases, high quality females shouldprefer daughters and, correspondingly, low quality females shouldprefer sons.[Behav Ecol 7: 316–325 (1996)]     

Brief Communication: Orphaned male Chimpanzees die young even after weaning

If a social‐living animal has a long life span, permitting different generations to co‐exist within a social group, as is the case in many primate species, it can be beneficial for a parent to continue to support its weaned offspring to increase the latter's survival and/or reproductive success. Chimpanzees have an even longer period of dependence on their mothers' milk than do humans, and consequently, offspring younger than 4.5–5 years old cannot survive if the mother dies. Most direct maternal investments, such as maternal transportation of infants and sharing of night shelters (beds or nests), end with nutritional weaning. Thus, it had been assumed that a mother's death was no longer critical to the survival of weaned offspring, in contrast to human children, who continue to depend on parental care long after weaning. However, in theory at least, maternal investment in a chimpanzee son after weaning could be beneficial because in chimpanzees' male‐philopatric society, mother and son co‐exist for a long time after the offspring's weaning. Using long‐term demographic data for a wild chimpanzee population in the Mahale Mountains, Tanzania, we show the first empirical evidence that orphaned chimpanzee sons die younger than expected even if they lose their mothers after weaning. This suggests that long‐lasting, but indirect, maternal investment in sons continues several years after weaning and is vital to the survival of the sons. The maternal influence on males in the male‐philopatric societies of hominids may be greater than previously believed. Am J Phys Anthropol, 153:139–143, 2014. © 2013 Wiley Periodicals, Inc.     

The influence of the father on offspring development in the striped mouse

When males of a species follow different reproductive strategiesin different habitats, one might expect the strategy adoptedto maximize fitness payoffs under particular ecological conditions.Striped mice (Rhabdomys pumilio) males in the moist grasslandsof South Africa follow a roaming mating strategy, visiting severalreceptive females, and do not participate in parental care.In contrast, males in the arid succulent karoo are permanentmembers of social groups and help care for young. We predictedthat paternal care leads to fitness benefits in striped micefrom the succulent karoo but not from the grasslands. Experimentswere conducted simultaneously in both locations under captiveseminatural conditions to study offspring growth and survivalto weaning in two experimental groups: father absent and fatherpresent. In the succulent karoo, offspring development was fasterwhen the father was present, but the father's absence did notaffect offspring growth in the grasslands. The significantlylower night temperatures in the succulent karoo compared tothe grasslands negatively influenced offspring development duringthe first 3 days after birth, which in turn influenced offspringdevelopment until weaning. Exposure to low temperatures is energeticallycostly to free-living mice, as indicated by a greater loss ofbody weight during cold spring nights than warmer summer nights.We suggest that paternal care, particularly huddling of pups,improves offspring development in the succulent karoo, whereasthe presence or absence of the father does not appear to directlyinfluence offspring growth in the grasslands.     

The effect of partial brood loss on male desertion in a cichlid fish: an experimental test

There is little experimental evidence testing whether currentbrood size and past brood mortality influence mate desertion.In the cichlid Aequidens coeruleopunctatus both parents initiallydefend offspring. In a field study, all experimental broods,irrespective of initial brood size (222.9 ± 60.4, mean± SD), were manipulated to a size of 100 fry. Neitherthe duration nor investment of females in parental care differed between control and brood reduced pairs, even though care seemedcostly. On average, females lost 5.1 ± 4.8% of initialweight while guarding a brood until independence. In contrast,males with experimentally reduced broods guarded fry for significantlyfewer days before deserting their mate than did males fromcontrol pairs with natural-sized broods (20.5 ± 7.5 vs. 14.2 ± 6.2 days). In at least 20% of cases (n = 9/45),the deserting male immediately mated with another female. Maleswith experimentally reduced broods also spent less time guardingfry before deserting and attacked fewer brood predators thandid males with control broods. For broods manipulated to have100 fry, there was a significant negative relationship betweenthe days until male desertion and the proportion of the initialbrood removed. This indicates that male assessment of the futuresuccess of the current brood (hence its reproductive value)is based on past mortality and/or that there is variation amongmales in the expected size of future broods. Both current broodsize and brood size relative to initial brood size are thereforepredictors of male, but not female, parental behavior and matedesertion. Female care may be unaffected by brood reductiondue to limited breeding opportunities and partial compensationfor reduced male care.     

Costs of reproduction and terminal investment by females in a semelparous marsupial

Evolutionary explanations for life history diversity are based on the idea of costs of reproduction, particularly on the concept of a trade-off between age-specific reproduction and parental survival, and between expenditure on current and future offspring. Such trade-offs are often difficult to detect in population studies of wild mammals. Terminal investment theory predicts that reproductive effort by older parents should increase, because individual offspring become more valuable to parents as the conflict between current versus potential future offspring declines with age. In order to demonstrate this phenomenon in females, there must be an increase in maternal expenditure on offspring with age, imposing a fitness cost on the mother. Clear evidence of both the expenditure and fitness cost components has rarely been found. In this study, we quantify costs of reproduction throughout the lifespan of female antechinuses. Antechinuses are nocturnal, insectivorous, forest-dwelling small (20-40 g) marsupials, which nest in tree hollows. They have a single synchronized mating season of around three weeks, which occurs on predictable dates each year in a population. Females produce only one litter per year. Unlike almost all other mammals, all males, and in the smaller species, most females are semelparous. We show that increased allocation to current reproduction reduces maternal survival, and that offspring growth and survival in the first breeding season is traded-off with performance of the second litter in iteroparous females. In iteroparous females, increased allocation to second litters is associated with severe weight loss in late lactation and post-lactation death of mothers, but increased offspring growth in late lactation and survival to weaning. These findings are consistent with terminal investment. Iteroparity did not increase lifetime reproductive success, indicating that terminal investment in the first breeding season at the expense of maternal survival (i.e. semelparity) is likely to be advantageous for females.     

Breeding success in cooperative meerkats: effects of helper number and maternal state

Studies of cooperatively breeding birds and mammals generallyconcentrate on the effects that helpers have on the number ofreproductive attempts females have per year or on the numberand size of offspring that survive from hatching/weaning toindependence. However, helpers may also influence breeding successbefore hatching or weaning. In the present study, we used anultrasound imager to determine litter sizes close to birth,and multivariate statistics to investigate whether helpers influencefemale fecundity, offspring survival to weaning, and offspringsize at weaning in cooperative meerkats, Suricata suricatta.We found that the number of helpers in a group was correlatedwith the number of litters that females delivered each year,probably because females in large groups gave birth earlierand had shorter interbirth intervals. In addition, althoughpup survival between birth and weaning was primarily influencedby maternal dominance status, helper number may also have asignificant positive effect. By contrast, we found no evidenceto suggest that helpers have a direct effect on either littersizes at birth or pup weights at weaning, which were both significantlyinfluenced by maternal weight at conception. However, becausedifferences in maternal weight were associated with differencesin helper number, helpers have the potential to influence maternalfecundity and offspring size within reproductive attempts indirectly.These results suggest that future studies may need to considerdirect and indirect helper effects on female fecundity and investmentbefore assessing helper effects on reproductive success in societiesof cooperatively breeding vertebrates.     

Behavioral correlations across breeding contexts provide a mechanism for a cost of aggression

Identifying correlations among behaviors is important for understandinghow selection shapes the phenotype. Correlated behaviors canindicate constraints on the evolution of behavioral plasticityor may reflect selection for functional integration among behaviors.Obligate cavity-nesting birds provide an opportunity to examinethese correlations because males must defend limited nest cavitieswhile also competing for mating opportunities and providingparental care. Here, I investigated the role of behavioral correlationsin producing a counterintuitive relationship between nest defenseand reproductive success in western bluebirds (Sialia mexicana)such that males that defended their nests most intensely hadthe lowest reproductive success, measured as the number of withinand extrapair offspring that fledged. By experimentally measuringaggression across contexts, I show that this cost of nest defensewas due to the correlated expression of aggression across thecontexts of nest defense and male–male competition coupledwith a trade-off between male–male aggression and parentalcare. In particular, more aggressive males provisioned theirfemales less during incubation and this led to disrupted incubationpatterns and fewer fledged offspring. However, aggressive malesdid not benefit from avoiding parental investment by gainingextrapair fertilizations, and thus, it is unclear how high levelsof aggression are maintained in this population despite apparentcosts. These results suggest that there are constraints to theevolution of plasticity in aggression and emphasize the importanceof considering the integrated behavioral phenotype to understandhow variation in behavior is linked to fitness.     

Why make daughters larger? Maternal sex-allocation and sex-dependent selection for body size in a mass-provisioning wasp, Trypoxylon politum

Mass-provisioning wasps package maternal investment into broodcells, sealed structures that contain all the provisions necessaryfor an offspring's growth and development. Optimal sex-allocationtheory predicts that if maternal provisions determine the sizeof each offspring, and the amount of provisions available toeach offspring varies, females should allocate well-stockedbrood cells to the sex that benefits most from being large.I tested this hypothesis using observations of organ-pipe wasps,Trypoxylon politum, and dissections of their nests. A Mississippipopulation of T. politum was intensively studied from 1993 to1995. This population fit the assumptions of optimal sex-allocationmodels by Green and Brockmann and Grafen. Female weight at emergencewas 1.29 times that of males, and wing length was 1.15 timesthat of males. This discrepancy in size occurred because thevolume of parental provisions strongly influenced adult bodysize, and better-stocked brood cells were preferentially allocatedto daughters. Brood-cell volume correlated with both wing lengthand weight at emergence in both sexes, and the chance that agiven brood cell contained a female offspring increased withincreasing brood-cell volume. Fitness was positively relatedto body size for females, but I found no evidence of an advantageto large males. Although there was evidence of stabilizing selectionfor male wing length in one year, there was no evidence of anincreasing relationship between body size and fitness (directionalselection) for males in either 1993 or 1994. Female fecunditywas positively related to body size in both years, indicatingthat larger females have increased reproductive success. Therate at which females provisioned brood cells was also correlatedwith body size. Observed patterns of investment in brood cellsare quantitatively consistent with the predictions of optimalsex-allocation theory, but certain aspects of female provisioningbehavior suggest females are not following a single "optimal"strategy. Patterns of provisioning were variable among differentfemales at the study site during the same year. Large femalestended to produce larger offspring. Although Brockmann and Grafen'smodel predicts a single, population wide "switchpoint" fromthe production of male to female offspring, there was no evidencefor such a switchpoint     

Weaning Age,Infant Care,and Behavioral Development in <Emphasis Type="Italic">Trachypithecus leucocephalus</Emphasis>

Primate infants are born in an altricial state and rely on the care of their parents for a relatively long period of time. Parental investment is critical to offspring survival and thus to the reproductive success of the parent as well. However, mothers and infants may experience a conflict of interest, in that infants may benefit by receiving prolonged maternal care but mothers may curtail such care in a tradeoff between investment in current versus future offspring. Documenting life history characteristics, such as age at weaning, is important not only for understanding the conflicts of interest and tradeoffs; such information can also provide insights about female reproductive rates and be valuable for conservation efforts. Little is known about the life history of white-headed langurs (Trachypithecus leucocephalus), despite their endangered status. We were the first to investigate mother-infant relationships and infant behavioral development in the species. We studied 3 wild mother-infant pairs throughout infancy. We used data from >460 h of focal subject sampling to calculate the proportion of time individuals spent in different behavioral states and the frequency of instantaneous events, such as maternal rejection. White-headed langur infants depended on their mothers for 19–21 mo, at which time they were weaned. Maternal rejection facilitated infant independence in the early stages of infant development, and mothers stopped investing in their infants when they resumed estrus. The weaning age of the wild white-headed langurs we studied was dramatically longer than that of captives, possibly as a result of the nutritional differences between wild and captive populations. Weaning age was also longer than for most other Asian colobines, and may be attributable to the degradation and fragmentation of their natural habitat.     

Determinants of reproductive success in female Columbian ground squirrels

Summary We studied the reproductive success of female Columbian ground squirrels (Spermophilus columbianus) in southwestern Alberta for nine years. We defined reproductive success as the number of offspring surviving their first hibernation, classified as yearlings. The number of weaned juveniles explained one third of the variance in number of yearlings at emergence from their first hibernation the following spring, and much of the variance in individual reproductive success originated after weaning. Weight of adult females at emergence from hibernation was correlated with annual reproductive success. The mother's survival beyond weaning and the subsequent winter's snow accumulation had positive effects on annual reproductive success, whereas population density and summer temperature had negative effects. We found no effects on annual reproductive success of date of litter emergence, weight at emergence as a yearling, presence or absence of adult kin, distance from the natal site, location within the study area, winter temperature or summer precipitation. Age of first breeding did not affect lifetime reproductive success, which ranged from 0 to 19 yearlings produced over a lifetime. The greatest source of variation in lifetime reproductive success for females surviving to breeding age was offspring survival, followed by reproductive lifespan.     

Fitness Consequences of Maternal Effects in Streblospio benedicti (Annelida: Polychaeta)

SYNOPSIS. The degree to which a female partitions resourcesbetween fecundity and per offspring investment is a centralquestion in life-history theory. Maternal effects may influencethe nature of this tradeoff through their effect on per offspringinvestment and subsequent offspring fitness. The purpose ofthis study was to determine the effect of female age and sizeon brood size (number of offspring), per offspring investment,and fitness in the polychaete Streblospio benedicti. Early stageembryos were collected from brooding females of known age andsize over a period of 100 days; these embryos were counted andanalyzed for their C and N content. Female size had a positiveeffect on brood size; larger females produced larger broods.However, brood size decreased with female age (females did notincrease in size after reaching sexual maturity). Brood sizedeclined 20–46% between 60 and 160 days of age. Duringthis same age period per offspring investment, measured in termsof C and N, increased by 25%. Offspring survivorship and sizeat two weeks post-release from the female were used as measuresof offspring fitness. Offspring survivorship increased 28% between60 and 160 days of age. Increased growth in offspring from olderfemales resulted in a 23% increase in offspring size at twoweeks. Including the maternal age effect in two population modelsfor S. benedicti increased population growth rate (). Populationgrowth was increased to a greater degree when the maternal effectwas modeled by enhancing offspring survival compared to whenfecundity was increased by the same proportional amount. Thissuggests that the maternal effect may be adaptive, particularlywhen conditions for offspring survival and growth are poor.     

Exposure to a novel male during late pregnancy influences subsequent growth of offspring during lactation

In mammals, allocation to reproduction can either be primed or suppressed in relation to cues from other individuals. Some conspecifics (e.g. potential mates) may enhance an individual's ability to reproduce but others may have a detrimental effect on reproductive success. One widely studied response to conspecific cues, the ‘Bruce effect’, occurs when pregnant females abort their pregnancies after exposure to a novel male. It has been suggested that this response has evolved as a counter‐tactic to the threat of infanticide posed by novel males. In some species, like mice, pregnancy termination will only occur if females are exposed to the unfamiliar male during a brief critical period early in pregnancy, which is surprising considering that an unfamiliar male threatens infanticide whenever present, and in particular near to birth. We demonstrate that female mice experiencing novel males during late pregnancy also alter their investment in progeny, but in a more subtle manner than previously observed. Females exposed to an unfamiliar male during late pregnancy give birth to offspring of a comparable weight to those produced by females exposed to the paternal male, but these offspring grow more slowly over lactation. As a consequence, offspring from these females weigh less at weaning. Modification of their growth trajectory, however, allows these offspring to catch up to normal weights by adulthood. Thus, cues of unfamiliar males, and possibly their associated threat of infanticide, can produce more wide‐ranging effects on maternal investment than previously recognized.     

Coadaptation in mother and infant regulated by a paternally expressed imprinted gene

This study investigates how a targeted mutation of a paternally expressed imprinted gene regulates multiple aspects of foetal and post-natal development including placental size, foetal growth, suckling and post-natal growth, weaning age and puberty onset. This same mutation in a mother impairs maternal reproductive success with reduced maternal care, reduced maternal food intake during pregnancy, and impaired milk let-down, which in turn reduces infant growth and delays weaning and onset of puberty. The significance of these coadaptive traits being synchronized in mother and offspring by the same paternally expressed imprinted gene ensures that offspring that have extracted 'good' maternal nurturing will themselves be both well provisioned and genetically predisposed towards 'good' mothering.     

Reproductive costs of sons and daughters in Rocky Mountain bighorn sheep

Differential maternal investment theory predicts that in sexuallydimorphic and polygynous species mothers should invest morein sons than in daughters. We tested the hypothesis that bighornewes that raise sons incur greater reproductive costs than ewesthat raise daughters. Although ewe mass gain during lactationand subsequent winter body mass loss were independent of lambsex, lambs born the year following the weaning of a son hadlower survival than lambs born after a daughter. The effectsof lamb sex on subsequent reproductive success of ewes becamemore evident at high population density. Lamb sex did not affectmaternal survival. Population density, weather, and ewe agedid not alter the relationship between lamb sex and subsequentreproductive success of the ewe. The year after weaning a son,ewes were more likely to have a daughter than a son, while ewesthat had previously weaned a daughter had similar numbers ofsons and daughters. Our results show that for bighorn sheepewes, sons have a greater life-history cost than daughters,suggesting a differential maternal investment in the sexes.     

Proximate and ultimate causes of natal dispersal in the great bustard Otis tarda

Between 1991 and 1997 we studied the offspring independenceand juvenile dispersal in a wild population of great bustards(Otis tarda). Young males were independent and began their juveniledispersal at an earlier age (6–11 months) than young females(8–15 months). The juvenile dispersal period was longerand the distances reached farther in males than in females.Natal dispersal distances were also longer in males, all ofwhich dispersed from their natal areas and established as adultsat 5–65 km from their natal nests. In contrast, most femaleswere strongly philopatric, settling at 0.5–5 km from theirnatal nests. These marked sex differences in offspring independenceand dispersal may have evolved originally to maintain geneticdiversity and are probably reinforced through male competitionfor mates. Young males that had fed at higher rates and receivedmore feedings from their mothers during the early maternal dependenceperiod became indepthdent and tended to disperse earlier. Theyalso integrated earlier into adult male flocks and settled earlierat their definitive leks, which were closer to their natal sites,in areas of higher adult male density. None of these correlationswas found among young females. These results suggest that enhancedfood intake and maternal care of male offspring are vitallyimportant in increasing their competitive ability during theimmature period and probably also in their fitness as breedingadults. These results are in accordance with the selective valueof large size in males and suggest how this species might havereached such a marked sexual dimorphism in size.     

Sex differences in biparental care as offspring develop: a field study of convict cichlids (<Emphasis Type="Italic">Amatitlania siquia</Emphasis>)

Parental investment theory states that parents should contribute more to older offspring. Differences between the sexes also influence how each parent contributes to offspring in biparental species. Here, we examined a naturally occurring population of biparental convict cichlids in Costa Rica to determine how each parent cared for offspring during two distinct offspring development stages. Consistent with the predictions of the reproductive value hypothesis, we hypothesized that the levels of parental contribution would be relative to the value that each parent places on a brood. We predicted that female parents would contribute more than male parents because female convict cichlids have lower future reproductive success than males. Additionally, we predicted that both parents should contribute more to older offspring, either due to the young’s increased susceptibility to predation (i.e., the vulnerability hypothesis) or because of the longer period of time parents have been interacting with older offspring (i.e., feedback hypotheses). This increase in investment by males should coincide with a change in the coordination of care between parents. Detailed observations of parental pairs in their natural habitat supported these predictions. Females contributed more to broods than males and were relatively unaffected by offspring age while males spent significantly more time with older, free-swimming fry. Additionally, males tended to leave younger offspring more than females did, and were more likely to do so consecutively with younger offspring. This suggests that the coordination of duties between parents changes as parental investment changes. Overall, these data support both the reproductive value and the vulnerability hypotheses, but not necessarily the feedback hypothesis.     

The pay‐offs of maternal care increase as offspring develop,favouring extended provisioning in an egg‐feeding frog

Offspring quantity and quality are components of parental fitness that cannot be maximized simultaneously. When the benefits of investing in offspring quality decline, parents are expected to shift investment towards offspring quantity (other reproductive opportunities). Even when mothers retain complete control of resource allocation, offspring control whether to allocate investment to growth or development towards independence, and this shared control may generate parent–offspring conflict over the duration of care. We examined these predictions by, in a captive colony, experimentally removing tadpoles of the strawberry poison frog (Oophaga pumilio) from the mothers that provision them with trophic eggs throughout development. Tadpoles removed from their mothers were no less likely to survive to nutritional independence (i.e. through metamorphosis) than were those that remained with their mothers, but these offspring were smaller at metamorphosis and were less likely to survive to reach adult size, even though they were fed ad libitum. Tadpoles that remained with their mothers developed more slowly than those not receiving care, a pattern that might suggest that offspring extracted more care than was in mothers’ best interests. However, the fitness returns of providing care increased with offspring development, suggesting that mothers would be best off continuing care until tadpoles initiated metamorphosis. Although the benefits of parental investment in offspring quality are often thought to asymptote at high levels, driving parent–offspring conflict over weaning, this assumption may not hold over natural ranges of investment, with selection on both parents and offspring favouring extended durations of parental care.     

Maternal obesity-impaired insulin signaling in sheep and induced lipid accumulation and fibrosis in skeletal muscle of offspring

The prevalence of maternal obesity is increasing rapidly in recent decades. We previously showed that maternal obesity affected skeletal muscle development during the fetal stage. The objective of this study was to evaluate the effects of maternal obesity on the skeletal muscle properties of offspring. Ewes were fed a control diet (100% energy requirement, Con) or an obesogenic diet (150% energy requirement, OB) from 2 mo before pregnancy to weaning. After weaning, the offspring lambs were fed a maintenance diet until 19 mo of age and then ad libitum for 12 wk to measure feed intake. At 22 mo old, the longissimus dorsi (LD) muscle was biopsied. The downstream insulin signaling was lower in OB than Con lambs as shown by reduction in the phosphorylation of protein kinase B, mammalian target of rapamycin, and 4-E binding protein 1. On the other hand, the phosphorylation of protein kinase C and insulin receptor substrate 1 was higher in OB compared to Con lambs. More intramuscular adipocytes were observed in OB compared to Con offspring muscle, and the expression of peroxisome proliferator-activated receptor gamma, an adipocyte marker, was also higher, which was consistent with the higher intramuscular triglyceride content. Both fatty acid transport protein 1 and cluster of differentiation 36 (also known as fatty acid translocase) were increased in the OB group. In addition, higher collagen content was also detected in OB compared to Con offspring. In conclusion, our data show that offspring from obese mothers had impaired insulin signaling in muscle compared with control lambs, which correlates with increased intramuscular triglycerides and higher expression of fatty acid transporters. These data clearly show that maternal obesity impairs the function of the skeletal muscle of offspring, supporting the fetal programming of adult metabolic diseases.