Female Body Condition Research Articles

Capital energy drives production of multiple clutches whereas income energy fuels growth in female collared lizards Crotaphytus collaris

Animals invest energy in reproduction that is obtained at two distinct times relative to the reproductive cycle. Energy obtained during egg production is referred to as income energy whereas stored energy acquired prior to reproduction is capital energy. Similar to most ectotherms, squamate reptiles are generally hypothesized to be capital breeders. Nearly all squamates in which income/capital energy investment has been examined thus far produce only one clutch per reproductive season. Although it is likely that squamates producing multiple seasonal clutches fuel first clutches with capital energy, either capital or income energy may be used to produce later clutches. We first monitored female eastern collared lizards over 14 reproductive seasons to confirm that the number of clutches females produce seasonally is a plastic response to variable environmental parameters, and to examine the effects of female body condition at the beginning of the reproductive season on clutch production. Clutch production varied annually and both the size and number of clutches were positively correlated with body condition. We then tested the competing predictions of the income and capital hypotheses experimentally by supplementing the diets of female collared lizards in situ for one season. Diet‐supplementation had no effect on the number of clutches produced but increased growth rates of gravid females. We further tested the competing predictions of these two hypotheses by examining variation in maternal energy investment per clutch using preserved specimens collected near our primary field site. Clutch size was highly correlated with female body size. Together, our results suggest that variation in reproductive output by female collared lizards is linked to stored capital energy rather than income energy, similar to most ectotherms.

Direct and socially-mediated effects of food availability late in life on life-history variation in a short-lived lizard

Food availability is a major environmental factor that can influence life history within and across generations through direct effects on individual quality and indirect effects on the intensity of intra- and intercohort competition. Here, we investigated in yearling and adult common lizards (Zootoca vivipara) the immediate and delayed life-history effects of a prolonged food deprivation in the laboratory. We generated groups of fully fed or food-deprived yearlings and adults at the end of one breeding season. These lizards were released in 16 outdoor enclosures together with yearlings and adults from the same food treatment and with food-deprived or fully fed juveniles, creating four types of experimental populations. Experimental populations were then monitored during 2 years, which revealed complex effects of food on life-history trajectories. Food availability had immediate direct effects on morphology and delayed direct effects on immunocompetence and female body condition at winter emergence. Also, male annual survival rate and female growth rate and body size were affected by an interaction between direct effects of food availability and indirect effects on asymmetric competition with juveniles. Reproductive outputs were insensitive to past food availability, suggesting that female common lizards do not solely rely on stored energy to fuel reproduction. Finally, food conditions had socially-mediated intergenerational effects on early growth and survival of offspring through their effects on the intensity of competition. This study highlights the importance of social interactions among cohorts for life-history trajectories and population dynamics in stage-structured populations.

Stable isotopes reveal inter-annual and inter-individual variation in the diet of female Australian fur seals

Understanding the temporal and spatial variation of foraging habits of apex predators is central to understanding their role in marine ecosystems and how their populations may respond to environmental variability. In the present study, stable isotope analysis (C and N) of blood was used to investigate inter-individual and inter-annual differences in the diet of adult female Australian fur seals Arctocephalus pusillus doriferus. Positive correlations were observed between red cell and plasma values for δ 13 C and δ 15 N (r 2 = 0.47 and r 2 = 0.66, respectively, p < 0.001 in both cases), suggest- ing relatively consistent individual prey choices over 3 or 4 foraging trips. Mean δ 15 N values (12.8 to 17.5‰) confirm the species occupies the highest marine trophic niche in the region. A significant decrease in plasma δ 15 N values, corresponding to two-thirds of a trophic level (ca. 2‰), was observed between the 1998 to 2000 and 2003 to 2005 sampling periods. This was associated with a significant decrease in adult female body condition and is consistent with a decline, previously documented by faecal analysis, of the proportion of red cod Pseudophysis bachus, barracouta Thyrsites atun and Gould's squid Nototodarus gouldi in the diet and an increase in redbait Emmelichthys nitidus. While substantial variation in δ 15 N was observed within each age cohort, a significant decrease was observed with age, suggesting individual specialisation for particular prey types is evident early in adulthood, but that its composition changes as females age. In addition, generalized linear models indicated body mass had a negative influence on δ 15 N, which may reflect larger total body oxygen

Effects of a trematode infestation on body condition, reproduction and mating behaviors in a livebearing fish

AbstractMost studies of parasite-mediated sexual selection target organisms where female or male mate choice is the major driving force of sexual selection, leaving the effects of parasites on coercive mating systems understudied. Here, we investigated the role of a trematode infestation (black spot disease (BSD)) on female body condition, female fecundity, male coercion, and female resistance in a coercive livebearing fish (the western mosquitofish, Gambusia affinis). We tested the following predictions: (1) infected females are in poorer body condition and have lower fecundity than uninfected females; (2) males prefer to coerce uninfected females; (3) infected males coerce less frequently than uninfected males; and (4) infected females are less resistant to male coercion. In contrast to our first prediction, infected females had more energy reserves than uninfected females during one month and infected females had increased fecundity compared to uninfected females. In the behavior experiments, we found BSD influenced male coercion in two of our experiments supporting our third, but not second or fourth, prediction. These results suggest this parasitic infestation may play a minor role in sexual selection on G. affinis.

Individual optimization of reproduction in a long-lived migratory bird: a test of the condition-dependent model of laying date and clutch size

Summary 1. Optimality theory predicts that both timing of arrival and arrival state on the breeding area will determine reproductive timing and investment in migratory organisms. We tested this idea using a condition-dependent individual optimization model (Ardea 68, 1980, 225 and The American Naturalist 143, 1994, 698) in common eider ducks through descriptive data, path analyses and experimental manipulation. 2. Our results support the causal pathways drawn from the optimization model indicating that individuals adjust their reproductive decisions as a function of their arrival date and body condition at arrival. 3. Independent of body condition, early-arriving females had a longer pre-laying period, but still initiated their nests earlier, and produced larger clutches than late-arriving birds. Independent of arrival date, females in good condition laid earlier than those in poor condition. Manipulation of pre-laying female body condition confirmed that the relationship between condition and laying date was causal. 4. Female common eiders appear to optimize reproductive decisions in response to both their external (i.e. environmental conditions affecting the egg-value) and internal (i.e. body condition) states. These adjustments seem to minimize the fitness costs of reproduction, in which higher clutch size is not associated with an apparent lower survival or future breeding probability. 5. Our study emphasizes the importance of (i) simultaneously considering the timing of migration, the state of individuals and the seasonal change in egg-value to understand clearly birds’ breeding decisions and (ii) appreciating the potential proximate and ultimate factors explaining why some individuals delay breeding and ⁄ or produce small clutches.

Fit females and fat polygynous males: seasonal body mass changes in the grey-headed flying fox

When females and males differ in their timing of maximum reproductive effort, this can result in sex-specific seasonal cycles in body mass. Such cycles are undoubtedly under strong selection, particularly in bats, where they affect flying ability. Flying foxes (Old World fruit bats, Pteropus spp.) are the largest mammals that can sustain powered flight and therefore face critical trade-offs in managing body reserves for reproduction, yet little is known about body mass dynamics in this group. I investigated body mass changes in relation to reproductive behaviour in a large colony of grey-headed flying foxes (Pteropus poliocephalus). In this polygynous mammal, females were predicted to maximise reproductive effort during lactation and males during the breeding season. As predicted, female body condition declined during the nursing period, but did not vary in relation to sexual activity. By contrast, males accumulated body reserves prior to the breeding season, but subsequently lost over 20% of their body mass on territory defence and courtship, and lost foraging opportunities as they also defended their day roost territories at night. Males in better condition had larger testes, particularly during territory establishment, prior to maximum sexual activity. Thus, the seasonality of female mass reflected the high metabolic load that lactation imposes on mothers. However, male mass followed a pattern akin to the "fatted male phenomenon", which is commonly observed in large polygynous mammals with seasonal reproduction, but not in bats. This shows the importance of body reserves for reproduction in flying foxes, despite their severe constraints on body mass.

Influence of Spring Temperatures and Individual Traits on Reproductive Timing and Success in a Migratory Woodpecker

ABSTRACT. We investigated the effect of spring temperatures, female age, and female body condition on the timing of laying in a migratory woodpecker, the Northern Flicker (Colaptes auratus), and looked at the relationship between laying date and reproductive success. Average annual laying dates in the population, recorded over 12 years, were not related to the North Atlantic Oscillation or the Pacific-North American climate indices but were earlier when average daily temperatures along the migration route of Northern Flickers along the Pacific coast of North America were warmer. However, the strongest negative correlation between laying dates and ambient temperatures occurred after the arrival of most birds on the breeding site, which suggests that the ability of females to accumulate resources for egg laying on the breeding site was an important determinant of laying times. At the population level, egg laying advanced by 1.15 days for every degree warmer on the breeding grounds. At the level of individua...

Adult predation risk drives shifts in parental care strategies: a long-term study

1. Grouping provides antipredatory benefits, and therefore aggregation tendencies increase under heightened predation risk. In socially breeding groups, however, conflicts over reproductive shares or safety tend to disintegrate groups. Group formation thereby involves a balance between the antipredatory benefits of aggregation and the destabilizing effect of reproductive conflict. 2. We study the grouping behaviour of a facultatively social precocial sea duck with uniparental female care, the eider (Somateria mollissima Linnaeus). Females tend their young solitarily or in groups of 2-5 females. Here, we focus on the effect predation on adults has on group-formation decisions of brood-caring females. 3. By modifying an existing bidding game over care, we model the effects of predation risk on the width of the window of selfishness, which delimits the reproductive sharing allowing cooperation within brood-rearing coalitions, and generate predictions about the relative frequencies of solitary versus cooperative parental care modes. Furthermore, we model the dilution effect as a function of female group size and predation risk. 4. The window of selfishness widens with increasing predation risk, and the dilution of predation risk increases with both female group size and increasing predation risk, yielding the following predictions: (i) cooperative brood care becomes more prevalent and, conversely, solitary brood care less prevalent under heightened predation risk and (ii) group sizes increase concomitantly. 5. We tested these predictions using 13 years of data on female grouping decisions and annual predation rates, while controlling for the potentially confounding effect of female body condition. 6. Our data supported both predictions, where heightened predation risk of nesting females, but not changes in their condition, increased the relative frequency of cooperative brood care. Increased female nesting mortality also resulted in larger groups of cooperative females. 7. The predation risk of incubating females has long-term implications for later parental care decisions. We discuss the potential consequences of predation-induced shifts in group size on per capita fitness and population-wide productivity.

Sex-, morph- and size-specific susceptibility to stress measured by haematological variables in captive common wall lizard Podarcis muralis

In polymorphic species of animals, colour morphs may show alternative physiological properties, and hence evolve or be maintained as an indirect response to selection exerted on these physiological attributes. In this study, we investigated if different colour morphs (white, red and yellow) of the polymorphic common wall lizard differed in their physiological responses to a long-term stress by determining variation between capture and release in leukocytes profiles, haemoparasite loads and body condition of male and females maintained in captivity throughout the breeding season. We found that most blood parameters of lizards varied significantly following captivity, and this variation was sex-, morph- and size-dependent. In particular, the heterophil:lymphocyte ratio (H:L), a sensitive measure of immunodepression and long-term stress, varied significantly among yellow females, larger individuals significantly increasing and smaller individuals decreasing their H:L ratio after captivity. This trend was reversed in red females, where smaller individuals presented raised H:L index at release. Our study indicated that response to long-term stressful conditions, such as those induced by captivity, differed among common wall lizard colour morphs, implying a sex-, size-(i.e. age) and morph-specific sensitivity to stress, and hence a different physiological profile of colour morphs, which may contribute to the maintenance of colour polymorphism in this species.

Influence of female nutritional status on mating dynamics in a sexually cannibalistic praying mantid

The classical paradigm of sexual selection is that of advertising males and choosy females; however, male mate choice may be more common than previously thought. Unlike visual and acoustic cues, females rather than males usually emit long-distance chemical signals for mate attraction, thus providing an excellent opportunity to examine male mate choice further. Here, I used the sexually cannibalistic praying mantid Pseudomantis albofimbriata to determine the effect of female body condition on male mate choice via chemical cues in a natural scenario. Female body condition is positively correlated with fecundity and negatively correlated with the propensity to cannibalize in this system, so I predicted strong male mate choice for good-condition females to maximize male reproductive fitness. Results of field-based choice tests showed differential male attraction to good-condition females: all males were found on the cages of good-condition females and none on those of poor-condition females. In a second series of choice tests conducted in large field enclosures, I found that some poor-condition females attracted males in the absence of good-condition females, and that these females had significantly more eggs in their ovaries than the unattractive poor-condition females. Furthermore, when egg number was controlled but female body condition varied, males no longer had a significant preference for good-condition females. I therefore propose that the male preference for fecund females is a result of egg-bearing females producing a greater quantity/quality of pheromone than egg-free females, and that chemical cues are likely to be an honest indicator of female fecundity in this system.

Seasonal Tradeoffs in Reproductive Investment in a Multi-Brooded Passerine

Abstract. Because investment in eggs is costly for birds, a female's body condition is expected to influence that investment. Moreover, resource availability can fluctuate by year, and older and younger females may acquire or allocate resources differently. Additionally, in multi-brooded species, females may make tradeoffs in investment in first and second clutches. Because environmental conditions often change through the breeding season and early maturity of second broods can increase females' fitness, patterns of females' allocation to each clutch may change with the season. Here, we investigate associations between females' quality (body condition and age) and pre-hatching investment (clutch size, average egg mass per clutch, and total clutch mass) in adults of the Eastern Bluebird (Sialia sialis), a multi-brooded cavity-nesting passerine. In the two years of the study, relationships differed; in 2003, females that were heavier relative to their body size produced larger eggs and invested in greater o...

Seasonal clutch size decline and individual variation in the timing of breeding are related to female body condition in a non-migratory species, the Upland Goose Chloephaga picta leucoptera

Several studies have shown that waterfowl females in good condition lay larger clutches and start egg-laying earlier in a breeding season. However, most of these studies lack corresponding data on individual condition and timing of breeding in different years. We analysed data on clutch size, egg size, hatching date and female body condition of a non-migratory species, the Upland Goose Chloephaga picta leucoptera, recorded in three seasons on New Island, Falkand Islands. We found a strong seasonal decline in both egg and clutch size. Egg size increased with clutch size. The mean egg volume and total clutch volume increased with female body condition and hatching date was earlier for females in higher body condition. Chicks hatched from nests with higher mean egg volume had higher early body condition. We also compared individual females between different study years and found that individual body condition showed a significant repeatability between years, whereas hatching date did not. While female aging did not systematically affect hatching date, females produced clutches that hatched earlier in years of higher body condition. We could thus show for the first time that the frequently reported negative relationship between female condition and hatching date also holds true on an individual basis. To our knowledge, this is the first study on seasonal clutch size decline in sheldgeese and one of a few in waterfowl comparing condition and timing of breeding within individuals between different years.

Does egg colouration reflect male condition in birds?

How colouration provides information about individuals in birds has been a central issue in recent decades. Although much information has been derived, little is known about the adaptive significance of egg colouration in birds. A recent idea suggests that biliverdin- and porphyrin-pigmented eggs may act as a post-mating sexual signal for males to assess female quality. In birds, it is common for males to influence prelaying female condition by courtship feeding. Using Eurasian kestrels, a species that lays protoporphyrin-pigmented eggs, we descriptively assessed the influence of male feeding on egg pigmentation by considering female phenotype, condition, breeding parameters and male body condition. We found that older females and females with greyer tails (an index of individual quality) produce highly pigmented eggs. However, male body condition was the only variable that explained egg colouration when considered together with the female-related variables. Therefore, females that mated with males in better condition laid highly pigmented eggs. With the same species, we also explored the cost of producing protoporphyrin-pigmented eggs using a food-supply experiment before the laying period. Food supplementation did not increase egg pigmentation, but hatching success and egg mass were positively related to egg colouration only in food supplied pairs. We suggest that egg colouration might be costly to produce and probably suggests egg quality. However, this cost cannot be explained by female quality, but by male condition instead. In general, our results do not support the theory that egg colouration is a post-mating sexual signal in species where males determine female condition at the time of laying.

Multimodal mate assessment by male praying mantids in a sexually cannibalistic mating system

The traditional view of sexual selection has been that of competing males and choosy females; however, more recently it has been recognized that males mayexhibit mate choice when females vary in quality and when males suffer costs associated with mating. Sexually cannibalistic mating systems provide an opportunitytoexaminemalematechoicefurther:thehighcostspotentiallyinvolvedinthematingprocess for males, as well as variation in female quality, predict male mate choice. We used the praying mantid Pseudomantis albo! mbriata to determine the effect of female body condition on male mate choice in a system with frequent precopulatory sexual cannibalism. Female body condition is positively correlated with fecundity and negatively correlated with the propensity to cannibalize, so we predicted males would strongly prefer females in good condition to maximize their reproductive potential. Results of our simultaneouschoicetestsshowedthatmalesusechemicalandvisualcuesformatelocationandassessment,and that theycan use eitherof these sensory modalities to distinguish and choose between females differing in body condition, with a signi! cant preference for good-condition females. However, surprisingly, males rarely rejected poor-condition females in the more ecologically relevant scenario of only one immediate potential mate and both sensory modes available to them, which may be explained by the strong scramble competition known for praying mantid systems. These results show that even when female quality varies and the cost of mating for males is substantial, male mate rejection does not always evolve. Crown Copyright ! 2010. Published on behalf of The Association for the Study of Animal Behaviour by Elsevier Ltd. All rights reserved.

Seasonal effects of Pacific‐based climate on recruitment in a predator‐limited large herbivore

1. Climate is an important factor influencing the population dynamics of large herbivores operating directly on individuals or through its effect on forage characteristics. However, the seasonal effect of climate may differ between forage- and predator-limited populations because of a climatic influence on predation rates. The influence of climate on predator-limited large herbivores is less well known than on forage-limited populations. Further, the effect of Pacific-based climate on large herbivore populations has been rarely assessed. 2. We investigated the effect of the Pacific Decadal Oscillation (PDO), across different seasons, on recruitment in 10 populations (herds) of mountain-dwelling caribou Rangifer tarandus caribou L. in the Yukon Territory, Canada. These low-density populations occur in highly seasonal environments and are considered predator-limited with high neonatal calf mortality. Hence, in most years females do not spend resources through lactational support during the summer and resource intake is devoted to self-maintenance. We predicted that climate affecting environmental conditions at calving would have a strong effect on recruitment via its influence on predation rates. We also predicted that climatic conditions prior to conception could have an effect on recruitment through its influence on female fecundity. We modelled recruitment (n = 165) by seasonal PDO values using generalized linear mixed-effects models with herd-varying coefficients. 3. We found that recruitment variability was best explained by variation in winter climate (beta = 0.110, SE = 0.007) prior to birth (in utero) and May climate (beta = 0.013, SE = 0.006) at calving. There was little support for a pre-conception climate effect influencing female body condition and hence fecundity. These results confirm that recruitment in these populations is limited by predation and that forage-limitation is not a significant factor in their population dynamics. There was considerable variability in herd-specific relationships between the PDO and recruitment. Incorporating herd-specific characteristics, such as variable predator densities or terrain characteristics within a herd range, may shed greater light on the complex relationship between climate and ungulate population dynamics.

Mutual mate choice by mountain pine beetles: size‐dependence but not size‐assortative mating

1. Mutual mate choice may be rare, occurring when both sexes invest heavily in reproduction, mating opportunities are abundant, and individuals differ in quality.2. Mountain pine beetles, Dendroctonus ponderosae (Curculionidae: Scolytinae) appear to meet the conditions for mutual mate choice. We introduced males to females in breeding sites and observed the occurrence and speed of a male entering a female's gallery. We tested for consequences of mutual mate choice, namely condition‐dependent choosiness and assortative mating.3. Males were more likely to enter a female's gallery when the gallery was in a smaller tree with less resin production and when the gallery was larger. Female body size and condition did not influence the probability of entry. Larger males were less likely to enter a gallery than were smaller males, probably because of size‐dependent choosiness rather than physical limitations.4. Small males took longer to enter galleries of large females than of small females, whereas large males entered as quickly into galleries of large females as small females. This suggests size‐dependent choosiness by females.5. No assortative mating by body size was detected, probably because males appeared to choose on the basis of female‐associated resources rather than on female traits.

Factors That Affect Renesting in Mallards (Anas platyrhynchos)

ABSTRACT. Renesting is an important strategy for coping with nest loss in many species of birds. We investigated renesting behavior of radiomarked Mallards (Anas platyrhynchos) breeding in the Canadian Prairie Parklands and found that females were persistent renesters, replacing >57% of 4,112 destroyed nests. Renesting propensity was most affected by nest initiation date, with ∼90% of unsuccessful females renesting if destroyed clutches had been initiated in April but <10% renesting for clutches initiated after 20 June. Probability of renesting declined with successive number of nesting attempts, but this was primarily an effect of initiation date. Renesting propensity increased with female age and body condition and declined for birds that had invested more time tending their previous clutch, but the latter effect was pronounced only among late-nesting females. The amount of time required to produce a replacement clutch was primarily a function of whether females were engaged in rapid follicle growth whe...

Using time‐dependent models to investigate body condition and growth rate of the giant gartersnake

AbstractIdentifying links between phenotypic attributes and fitness is a primary goal of reproductive ecology. Differences in within‐year patterns of body condition between sexes of gartersnakes in relation to reproduction and growth are not fully understood. We conducted an 11‐year field study of body condition and growth rate of the giant gartersnake Thamnophis gigas across 13 study areas in the Central Valley of California, USA. We developed a priori mixed effects models of body condition index (BCI), which included covariates of time, sex and snout–vent length and reported the best‐approximating models using an information theoretic approach. Also, we developed models of growth rate index (GRI) using covariates of sex and periods based on reproductive behavior. The largest difference in BCI between sexes, as predicted by a non‐linear (cubic) time model, occurred during the mating period when female body condition (0.014±0.001 se) was substantially greater than males (−0.027±0.002 se). Males likely allocated energy to search for mates, while females likely stored energy for embryonic development. We also provided evidence that males use more body energy reserves than females during hibernation, perhaps because of different body temperatures between sexes. We found GRI of male snakes was substantially lower during the mating period than during a non‐mating period, which indicated that a trade‐off existed between searching for mates and growth. These findings contribute to our understanding of snake ecology in a Mediterranean climate.

Incidence of climate on common frog breeding: Long-term and short-term changes

In Brittany (northwest France), the climate is showing a trend toward warming. This change is increasingly suspected to have a role in driving amphibian decline, but it is very difficult to determine at what level the climate affects the future of species. Recently, some studies have detected some direct effects on breeding phenology and indirect effects on energy allocation. The present study explores some of these effects on the common frog ( Rana temporaria) from 1984 to 2007. The results show two trends: a long-term change in breeding activities and a short-term influence due to the 2003 climatic anomaly. For the period of study, the start of egg-laying shows a precocity that was correlated with thermal conditions during the preceding 40 days as well as milder springs during the previous year. This degree of precocity is currently the highest found in Europe (+26.6 days). As a result of the 2003 heat wave, the clutch mean fecundity in 2004 was smaller than for other years, the fecundity rates were reduced and abortions were numerous (unlike other years). Moreover, young females were the smallest observed in recent years and some females seemed to exhibit a trade-off between fecundity and growth. Before or after egg-laying, female body condition and mean weight of mature ovules were both lower. The year 2005 appears as a transition period before the recovery in 2006–2007. The results show that climate warming endangers the vital rates of the common frog, while the 2003 climatic events seem more detrimental than the long-term warming trend.

Evidence that plumage bacteria influence feather coloration and body condition of eastern bluebirdsSialia sialis

Parasites influence the expression of secondary sexual traits and the health of infected individuals. We set out to test the influence of reputed exogenous parasites, plumage bacteria, including feather‐degrading bacteria (FDB), on secondary sexual characteristics and body condition of wild adult eastern bluebirdsSialia sialis. Previous work has shown that FDB alter the coloration of structurally‐colored bluebird feathersin vitro(Shawkey et al. 2007). In a correlational study of how bacteria affect birds in the wild, we found that female plumage got duller with increasing FDB intensity. Males tended to get brighter with increasing FDB intensity, but the relationship was not significant. We also found significant associations between plumage bacteria intensity and body condition, but, again, with gender‐based differences. Female body condition was negatively associated with plumage bacteria intensity, while male body condition was positively associated with plumage bacteria intensity. Interestingly, plumage bacteria intensity of males and females in nesting pairs was significantly positively correlated. We also report the highest prevalence of FDB measured in a wild bird population, with FDB detected on 67/68 (99%) of individuals. Further work is needed to fully understand the relationships between plumage bacteria and birds, but our data indicate that plumage bacteria may have sex‐dependent effects on multiple phenotypic traits.