Does gliding when pregnant select for larger females?

For terrestrial vertebrates, gliding imposes unique constraints on the interaction of body mass and structural size, particularly with reference to minimizing wing loading. Females of gliding animals experience increases in wing loading during pregnancy or gravidity, and selection may favour increased structural size to compensate for the added mass. We tested whether pregnant southern flying squirrels Glaucomys volans had similar wing loading as males, and whether females with lower wing loading bore heavier litters, than those with greater wing loading. Males had greater wing loading than females, regardless of the latter's reproductive state (males: 38.4±3.62 N m⁻², pregnant females: 30.7±4.21 N m⁻² and non-pregnant females: 26.8±5.13 N m⁻²). The slope of the linear relationship between planar surface area and body mass was similar between pregnant females and males, however ( F =0.383, P =0.322). Thus female flying squirrels may optimize their litter mass to minimize wing loading during pregnancy. Contrary to our prediction, females with greater wing loading had heavier litters than those with lower wing loading, which suggests reproductive output may be influenced by other ecological factors.     

The scheduling of spawning with the moult cycle in Northern krill (Crustacea: Euphausiacea): a strategy for allocating lipids to reproduction

Summary

Euphausiids moult and grow throughout their life, which implies sharing of resources between growth and reproduction for adult krill. In the Northern krill, Meganyctiphanes norvegica (M. Sars), female krill produce eggs cyclically. Spawning moult cycles alternate with vitellogenic moult cycles for lipid yolk accumulation. Histology shows that lipids are associated with the R cells of the digestive gland in both sexes, with the yolk platelets of mature oocytes and with the fat body cell membranes and blood lacunae in reproducing females. Mature female krill can have a total lipid content twice as high as males, mostly due to accumulation in the ovary, the fat body and the haemolymph. In contrast, in males, as well as in non-reproducing females, the highest percentage of lipids is found in the digestive gland and the haemolymph. In Meganyctiphanes norvegica, the most abundant lipid fractions are polar lipids and triglycerides, the latter being relatively low in reproducing female gonad and fat body. Triglycerides are believed to be a pure energy source and polar lipids are essential for membrane development in embryos. The fatty acid content and composition of the triglyceride and polar lipid fractions in females are different from males, related to both reproductive and dietary processes. Higher levels of polyunsaturated fatty acids (PUFA) in the polar lipid fraction were found in reproductive females. During the non-reproductive season, the converse was found, indicating the specific role PUFA and other fatty acids play in growth and egg production. Adaptive processes linked to reproduction were studied comparatively in three populations of the Northern krill—Clyde Sea (W, Scotland), Kattegat (E, Denmark), Ligurian Sea (Mediterranean)—all differing considerably in climatic and trophic conditions. Such adjustments in lipid synthesis and storage are viewed as reproductive strategies developed by the Northern krill in response to different environmental conditions.     

The reproductive biology of the Rock Partridge Alectoris graeca saxatilis in the southern French Alps: first evidence of double-nesting behaviour

Capsule: Double-nesting occurs frequently in Rock Partridges Alectoris graeca living in the southern French Alps.

Aims: To investigate reproductive parameters of a Rock Partridge Alectoris graeca population.

Methods: The reproductive behaviour of 62 radio-tagged birds was monitored during the breeding seasons 2012–16, to record breeding phenology, clutch sizes, hatching success, nest survival and parental care.

Results: Double-nesting behaviour in the Rock Partridge was confirmed for the first time. Participation in incubation was similar for males and females (86% versus 70%). Clutch size was larger for nests incubated by males (11.0?±?1.6 eggs) than by females (9.5?±?1.2). Male nest survival rate (0.37) tended to be lower than female nest survival rate (0.62), although the difference was not significant. No significant difference was detected between male and female hatching success. Nest failures were caused by mammals taking the eggs (78%) or predation of the incubating parent (13%). Some circumstantial evidence suggests that occurrence of double-nesting behaviour could depend on previous winter and spring weather influencing the body condition of females. The reproductive biology of the Rock Partridge contrasts in some breeding traits with Red-legged Partridge and natural partridge hybrids, possibly due to climatic differences between habitats.

Conclusion: Confirmation of double-nesting in Rock Partridges indicates that climatic constraints inherent to its mountain environment do not act as an impediment to this behaviour. Variation in weather conditions between years could influence the annual occurrence of double-nesting.     

A selective trade-off for territoriality and non-territoriality in the polymorphic damselfly Mnais costalis

Males of the damselfly Mnais costalis occur as territorial orange-winged 'fighter' males or non-territorial clear-winged 'sneaker' males. Their morph life histories differ considerably but the estimated lifetime reproductive success is the same for the two morphs. In this study we compared the developmental and reproductive costs associated with the two morphs. Orange-winged male and female reproductive costs resulted in a decline in adult fat reserves with increasing age. In contrast, the fat reserves of clear-winged males remained constant with adult age. Body size was positively correlated with mating success in orange-winged males, but had no influence on the mating success of clear-winged males. The orange-winged male flight muscle ratios (FMRs) were significantly higher than the clear-winged male and female FMRs. However, there was no difference in the size-corrected fat reserves of the two morphs; both had higher fat reserves than females. The gain in mass between eclosion and reproduction in orange-winged males and females was almost double the mass gained by clear-winged males, suggesting that clear-winged male development is less costly. An experiment in which pre-reproductive levels of nutrition were manipulated confirmed this.     

Effect of larval food stress on male adult behaviour, morphology and reproductive investment in the butterfly Pararge aegeria

Males of several animals increase their reproductive success by territorial behaviour. In butterflies, males may defend a territory (i.e., territorial perching tactic), but this is assumed to be an energetically costly way to locate mates. Limitations of the energy budget may affect fight performance, and may, consequently, force males to adopt an alternative non-territorial searching behaviour (i.e., patrolling tactic) to maximize reproductive success. In this study, we tested to what extent behavioural tactics adopted by adult males of the butterfly Pararge aegeria (L.) were affected by the nutritional conditions during the larval stage. We compared the occurrence of territorial versus patrolling behaviour, lipid mass, flight muscle ratio, metabolic rate and spermatophore production of low quality males that were reared as a larva on drought-stressed host plants and control, high quality males. Low quality males were less likely to adopt the territorial perching tactic and emerged as adults with lower lipid mass than high quality males, but they were able to restore their lipid mass through adult feeding (and perhaps the breakdown of flight muscles). Host plant quality also affected spermatophore size. Independent of the larval food treatment, territorial perching males metabolised more lipids than non-territorial males, produced larger spermatophores and copulated for longer than males adopting non-territorial behaviour. We discuss the results relative to the co-existence of the behavioural tactics (perching and patrolling).     

Cryptic female choice predicated on wing dimorphism in decorated crickets

Male decorated crickets, Gryttodes sigllatus, normally lackbind wings and are incapable of flight (short-winged males),but occasionally exhibit fully developed hind wings that makerudimentary flight possible (long-winged males). Long-wingedmales bear a cost of flight in the form of decreased inseminationsuccess, which arises as a consequence of two interrelated factors:(1) long-winged males exhibit a lower reproductive investmentrelative to short-winged males, as measured by the mass of amale's spermatophore and reproductive organs and (2) the postcopulatorybehavior of females favors males that maximize their reproductiveinvestment. Of particular importance to male mating successis the spermatophylax, a large gelatinous mass forming partof the spermatophore and consumed by the female after mating.Consumption of the spermatophylax keeps the female preoccupiedwhile sperm are discharged from the remaining portion of thespermatophore (sperm ampulla) into her repro ductive tract.The spermatophylax of long-winged males is significantly smallerthan that of short-winged males and consequently requires lesstime to consume. As a result, the sperm ampulla of long-wingedmales is frequently removed before its complete evacuation andsignificantly sooner than that of short-winged males. Becausethe spermatophore-removal behavior of females mediates the relativeinsemination success of short-winged and long-winged males,it can be considered a form of cryptic female choice     

Fat and sassy: factors underlying male mating success in a butterfly

Theory predicts that male mating success depends on resource holding potential (RHP), which is reflected by proxies of condition, such as body mass, fat content, strength, or weaponry. In species lacking any physical means to inflict injuries upon combatants, such as butterflies, the factors determining mating success are less clear. Against this background, we explored the determinants of male mating success in the tropical butterfly Bicyclus anynana Butler (Lepidoptera: Nymphalidae: Satyrinae), by comparing physiological, immunological, and morphological traits between winning and losing males. Our results showed that successful males are characterized by a better flight performance, evidenced by having longer wings, a heavier thorax, a lighter abdomen, a higher fat content, and higher phenoloxidase expression levels than their unsuccessful counterparts, when being compared after their first mating. Males that won three consecutive trials against the same combatant were also characterized by a better flight performance, having larger forewings, a higher body mass, and a higher fat content. Thus, successful males were larger and in better condition than unsuccessful ones. Strikingly, many differences found indicated an enhanced flight performance for the former, which we suggest ultimately plays the key role for male mating success in B. anynana. As fat is the main energy source for flying insects, being crucial to flight endurance and in turn presumably to male mating success, it may represent a key determinant at the proximate level.     

Male-caused failure of female reproduction and its adaptive value in alpine marmots (Marmota marmota)

We studied reproductive performance of free-living alpine marmots (Marmotamarmota) for 14 years in the National Park of Berchtesgaden, Germany.Female reproduction was influenced by body condition and social factors.Reproduction depleted fat reserves, and only females emergingfrom hibernation with sufficient body mass were able to reproducesuccessfully. Marmots lived in social groups in territoriesdefended by a dominant male and female. Subordinate femalesnever reproduced, regardless of body mass. Territory takeoversby males impaired reproduction of dominant females, but onlyif the takeover occurred after the mating period. Reproductivefailures occurred despite clear signs of pregnancy such enlargednipples or late molt. Decreasing progesterone levels after themating period and the lack of evidence for direct infanticideby new territorial males suggest a block of pregnancy as a likelyexplanation for reproductive failures in groups with male takeoversduring gestation. Rendering female reproduction impossible increasedfuture reproductive success of new territory owners. Nonparous femalessaved the energetic cost of maternal investment and thus emergedwith higher body mass in the following spring. In line withthis, females failing to wean young had higher reproductivesuccess in the subsequent year.     

Lasting effects of conditions at birth on moose body mass

Whether cohort effects can be retrieved in adult phenotypes depends on the possibility for individuals to compensate for a good or bad start in life. This ability to compensate may itself depend on the environment and on individual sex. In large polygynous ungulates, male reproductive success relies more on body size than the reproductive success of females, which makes them more sensitive to a bad start in life. Based on current theories of life history evolution and sexual selection, we tested the following predictions in a moose population: 1) cohort effects and year effects occur in both male and female adult body mass, but due to 2) compensatory growth, cohort effects tend to fade away with the individual's age; and 3) males are more sensitive to cohort effects than females. In support of the first prediction, we found that density and climate during the year-of-birth and the year-of-harvest affected moose body mass in both sexes. However, the magnitude of the effects of environmental conditions at birth on adult body mass decreased with increasing age, but less so in males than in females. Thus, as expected based on our third prediction, environmental conditions early in life were more influential on adult body mass of males compared to females. Such a result supports the existence of sex-specific life history tactics, with males maximising growth rate and females rather trading-off growth for reproduction.     

Biochemical content, energy composition and reproductive effort in the broadcasting sea star Asterias vulgaris over the spawning period

To assess sex differences in reproductive effort, we examined the biochemical composition and energetic content of the principal body components of the broadcast spawning sea star Asterias vulgaris in the Mingan Islands in the northern Gulf of St. Lawrence, eastern Canada. The body wall was the most stable body component, showing no variations in mass or in lipid and protein content (and total energetic content) between sexes or during spawning. Patterns in the gonads differed between sexes and with spawning. The lipid, protein and carbohydrate content of the ovary dropped during spawning, while only the protein content of the testis decreased significantly. Reproductive effort, expressed as loss of energy in the gonads during spawning for an individual weighing 10 g in underwater mass (8.2 cm in radius), was six times greater in females (49.5 kJ) than males (7.9 kJ). The energetic content of the pyloric caeca also decreased during spawning, by 17.7 kJ in females and 21.5 kJ in males, mainly due to a decrease in lipids. If this decrease is included as reproductive effort, it lessens the gender difference. The caecum decrease possibly represented expenditures due to formation of aggregations or the expulsion of gametes during spawning. Effectively, we observed aggregations during a massive spawning in this population. The sex ratio did not differ from 1:1 in all size classes sampled. This suggests that, unless males suffer higher mortality, females manage to allocate as much energy to somatic growth as males, possibly by feeding at higher rates to compensate for their higher reproductive effort. Stomach protein content tended to be higher in females than males and may indicate greater muscular development to facilitate digestion.     

Winter territoriality and its implications for the breeding ecology of White-throated Dippers Cinclus cinclus

Capsule: Pairs of White-throated Dippers Cinclus cinclus which defended winter territories bred earlier than non-territorial individuals, but there was no difference in reproductive success.

Aims: The effect of winter territoriality on breeding ecology has rarely been studied in resident birds. We carried out a preliminary investigation of whether winter territorial behaviour and territory size affect the timing of reproduction, breeding territory size and reproductive success in a riverine bird, the White-throated Dipper.

Methods: We monitored an individually marked population of White-throated Dippers in the UK. Wintering individuals were classified as either territorial or ‘floaters’ according to their patterns of occurrence and behaviour, and their nesting attempts were closely monitored in the subsequent months. Winter and breeding territory sizes were measured by gently ‘pushing’ birds along the river and recording the point at which they turned back.

Results: All birds defending winter territories did so in pairs, but some individuals changed partners before breeding. Territorial pairs that were together throughout the study laid eggs significantly earlier than pairs containing floaters and those comprising territorial birds that changed partners. However, there were no significant differences in clutch size, nestling mass or the number of chicks fledged. There was no relationship between winter territory length and lay date or any measure of reproductive success, although sample sizes were small. Winter territories were found to be significantly shorter than breeding territories.

Conclusion: Winter territoriality may be advantageous because breeding earlier increases the likelihood that pairs will raise a second brood, but further study is needed. Territories are shorter in winter as altitudinal migrants from upland streams increase population density on rivers, but this may also reflect seasonal changes in nutritional and energetic demands.     

Wing morph-related physiological differences in adults of temperate population of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae)

The reproductive and diapausing adult females of brachypterous morph and macropterous females with reproductive arrest of non-diapause type, originating from the laboratory cultures of Pyrrhocoris apterus, were studied for their feeding and drinking behaviour, digestive enzyme activities, and carbohydrate and lipid contents. The highest feeding and drinking activities were observed in reproductive brachypters, the lowest in macropters. Macropters also differed from brachypters by lower activities of gut lipase, peptidase and protease, lower concentration of haemolymph sugars, and lower weight of fat body, which probably reflects their low feeding activity. The total content of fat body lipids was also lower in macropters (0.6 mg) than in reproductive and diapausing brachypters (4.6 and 7.5 mg, respectively) on day 14. A very high amount of glycogen was found in the fat body of diapausing brachypters, 363 μg on day 14, as opposed to 15 and 80 μg in macropterous and reproductive brachypterous females, respectively. The obtained data indicate that the most important difference between macropterous and brachypterous females with different types of reproductive arrest consists of an enhanced mobilization of lipids for dispersal in macropters and accumulation of energetic reserves for hibernation in brachypters.     

Effects of habitat use on food acquisition and food caching during a nonbreeding season in a winter-breeding,food-storing passerine

ABSTRACT

Capsule: Wintering male Bull-headed Shrikes Lanius buchepalus preferred vegetable fields with perch sites to search for and detect terrestrial prey, and males occupying territories with large areas of vegetable fields acquired more prey and cached more food.

Aims: To better understand effects of habitat use on food acquisition and food caching of the Bull-headed Shrike, we investigated relationships between habitat quality (measured through foraging-site selection and foraging success) and food caching during the non-breeding season.

Methods: We monitored 66 territorial male shrikes during the non-breeding season from 2014 to 2016, and collected data on foraging-site selection, foraging success, and food caching.

Results: Our field observations showed that male shrikes preferred to forage over vegetable fields and that males occupying territories incorporating large areas of that habitat were able to acquire more food items and store more food caches in their territories during the nonbreeding season.

Conclusion: We suggest that for male Bull-headed Shrikes, a winter-breeding food-storing passerine, the quality of habitat in the nonbreeding season has the potential to affect their subsequent fitness.     

STOPOVER AND FAT DEPOSITION BY BLACKCAPS SYLVIA ATRICAPILLA FOLLOWING SPRING MIGRATION OVER THE SAHARA

Maitav, A. & Izhaki, I. 1994. Stopover and fat deposition by Blackcaps Sylvia atricapilla following spring migration over the Sahara. Ostrich 65:160-166.

Length of stopover and rate of weight change were studied in Blackcaps that stopover in Eilat (southern Israel) in spring after a trans-Saharan flight. The birds studied had already completed 2000 km of desert crossing and faced just 200 km more. The potential predicted flight range for these transients suggests that the fat depleted Blackcaps (fat class=0) could not reach the east Mediterranean scrublands, which offer more extensive foraging opportunities than the desert area around Eilat, without refueling. However, 46% of the Blackcaps had sufficient fat (fat class > 0) to reach central or northern Israel in a single flight in still air. Recaptured birds stayed in Eilat for 2,4±1,9 days. Although the body mass of an average recaptured bird increased by 0,27±1,44 g/day, which was an increase of 0,8%±7,0% of its body mass per day during stopover, these results were not significantly different from zero. Stopover length, mass change during stopover, and the rate of change in mass did not differ between males and females and between those who stopped over for only one day to those which stayed > 1 day. However, there was a tendency of these lean birds to stay for a shorter period in Eilat than relatively fat birds. There was also some tendency for lean birds to gain more mass during their stopover than fat birds. It seems that in spring, when less time is allotted for the whole migration program, the migrants resume their journey before fat reserves have been replenished.     

Sexual dimorphism and growth trade‐offs in Blue Tit Cyanistes caeruleus nestlings

The outcome of sibling competition for food is often determined by variation in body size within the brood and involves trade‐offs; traits that enhance competitive ability within the nest may be developed at the expense of traits that enable effective flight at fledging, or vice versa. We quantified growth of skeletal, body mass and feather traits in male and female Blue Tit Cyanistes caeruleus nestlings. Males were significantly heavier, had longer tarsi and tended to have greater head–bill lengths than females, whereas females were similar to males in wing flight feather growth. These differences in growth may result from sexual differences in selection of the traits. Females are likely to prioritize feather growth to facilitate synchronized fledging with the rest of the brood, and to enhance escape from predators. We suggest that males are heavier and develop longer tarsi because body size is an important determinant of male reproductive success.     

Non-breeding fæder Ruffs Philomachus pugnax associate according to sex,not morphology

Capsule Fæders (males that are female look-alikes) associate with males rather than females, at several different spatial scales.

Aims To test the prediction that the occurrence in space and time of fæders on ecological grounds should track that of females.

Methods The fraction of fæders was estimated in five morphometric data sets that were collected over four decades in four different countries in three different seasons (comprising 9133 Ruffs). The regression of fæder–female fractions was tested against the null model assuming that the number of fæders is 1.0% of females.

Results The fraction of fæders in catches averaged 1.03%, varying between 0.3% in autumn in the UK up to 0.85% in Sénégal in winter and 1.04% in The Netherlands in spring. On a stopover in The Netherlands the fraction decreased from 1.3% to 0.7% when the females started to arrive. At all four spatial and temporal scales the regression of fæder–female fractions deviated from the null model: we found high fractions of fæders in catches with low fractions of females, indicating that fæders rather associate with the larger-sized ‘normal’ males.

Conclusion We suggest that fæders spend the winter, and migrate with, the larger-sized lekking males, and we propose that any survival costs associated with the use of suboptimal habitats is compensated by higher reproductive success as sneakers on leks.     

Optimal progeny body size in a solitary bee,Osmia bicornis (Apoidea: Megachilidae)

1. Females of solitary, nest‐constructing bees determine both sex (haplo‐diploidy) as well as body size (by amount of provision) of each single offspring. 2. According to the Optimal Allocation Theory, females should allocate resources in portions that maximise fitness returns. A key fitness component in bees is body size that is determined solely by the provisions supplied by the mother. 3. The optimal progeny body size relies on different factors in both sexes. In females, provision efficiency is crucial for reproductive success. In males, however, fitness depends primarily on mating success. 4. Provision efficiency of Osmia bicornis L. females depends on the capacity to stow pollen (scopa) and their ability to carry the packed loads. Scopa capacity increases isometrically with body size whereas indices of flight performance (EPI, free lift) decrease. These complementary effects substantially contribute to the adjustment of optimal body size in daughters. 5. The impact of body mass on fitness of males is determined by the mating system. Owing to the opportunistic polygyny in O. bicornis, there was no detectable correlation between body size and male mating success. Consequently, mother bees distribute their provisions to many, but small sons to increase the number of descendant competitors in the race for matings. Optimal body size in sons is a trade‐off between a large male advantage in rare scrambles over receptive females and small‐size‐related disadvantages in viability.     

Lipid dynamics in the viperine snake, Natrix maura, from the Ebro Delta (NE Spain)

Body reserves play a major role in several aspects of vertebrate biology. Accurate identification and quantification of body reserves constitute a useful contribution to the better understanding of the energetic costs of reproduction and the implication of food availability in life history traits of organisms. In this study, lipid content in fat bodies, liver and muscle of the viperine snake (Natrix maura) were measured along an active season. Samples were collected monthly from a natural population of the Ebro Delta Natural Park (NE Spain). This methodology pointed out that lipids stored in fat bodies were the main energetic source during reproduction. In addition, lipids stored in liver appeared to be critical for vitellogenesis, while lipids stored in muscle turned out to be a supplementary energetic resource to fuel reproductive effort. Relationships between changes in body reserves and prey availability in canals of the Ebro Delta were also considered. In males, lipid reserves presented a positive correlation with food availability. On the contrary, lipid reserves in female viperine snakes decreased during vitellogenesis even though food availability increased in this period, which suggests a quick transfer of body lipids to clutch. In April, when rice fields of the Ebro Delta were dry and aquatic prey was scarce for viperine snakes, males and females presented a lower lipid content in fat bodies, liver and muscle than they did in other months, showing a clear link between prey availability and body reserves during food shortage. Thus, patterns of variation in fat levels indicated that Natrix maura is a capital breeder since it acquires resources in advance and stores them until they are invested during the reproductive period. Nevertheless, the shortage in April forces Natrix maura to turn into a facultative income breeder to fuel vitellogenesis. Finally, fat reserves in body components were compared with an estimate of body condition calculated by the residuals from the regression of body mass on body length. In male viperine snakes, the estimate of body condition was correlated with fat levels, revealing that this index is useful to measure condition in living individuals. On the contrary, body condition in females was not correlated with fat levels, which suggests that it is not appropriate to infer condition in female viperine snakes since it depends on the reproductive status of the individuals.     

A eugenic effect of medical care

Abstract

When sophisticated medical attention substantially increases the life expectancy of individuals with a severe homozygous condition without significantly raising their reproductive success, an increase in parental investment should render a concomitant decrease in parental ability to reproductively compensate. This process will lower the expected number of heterozygous carriers produced by heterozygous parents and, in turn, will lower the equilibrium frequency of the gene.     

Compensatory Growth Limits Opportunities for Artificial Selection in Alpine Chamois

ABSTRACT In ungulates, big males with large weapons typically outcompete other males over access to estrous females. In many species, rapid early growth leads to large adult mass and weapon size. We compared males in one hunted and one protected population of Alpine chamois (Rupicapra rupicapra) to examine the relationship between horn length and body mass. We assessed whether early development and hunter selectivity affected age-specific patterns of body and horn size and whether sport hunting could be an artificial selection pressure favoring smaller horns. Adult horn length was mostly independent of body mass. For adult males, the coefficient of variation of horn length (0.06) was <50% of that for body mass (0.16), suggesting that horn length presents a lower potential for selection and may be less important for male mating success than is body mass. Surprisingly, early development did not affect adult mass because of apparent compensatory growth. We found few differences in body and horn size between hunted and protected populations, suggesting the absence of strong effects of hunting on male phenotype. If horn length has a limited role in male reproductive success, hunter selectivity for males with longer horns is unlikely to lead to an artificial selective pressure on horn size. These results imply that the potential evolutionary effects of selective hunting depend on how the characteristics selected by hunters affect individual reproductive success.