The reproductive cycle of male long-fingered bats, Miniopterus minor (Chiroptera: Vespertilionidae), in a seasonal environment of the African Tropics

A cave population of Miniopterus minor had a seasonally monoestrous reproductive cycle that corrsponded closely to the rainfall-induced seasonality of coastal Kenya (4 S). Males had pronounced cycles of body weight resulting from the deposition of fat during periods of relative food abundance in both rainy seasons, and its depletion during competitive mating and the dry seasons, when numbers of insects were lowest. The annual period of sexual regeneration clearly followed the increase in body weight which occurred during the 'long rains' (April-June). Testicular recrudescence was accompanied by hypertrophy of the accessory glands and all reproductive organs involuted after mating in July, remaining inactive until the following April. An annual moult corresponded with the improvement in body condition that occurred at the beginning of the 'long rains'. The growth of new pelage was completed in May, by which time ambient temperatures had dropped and adult males entered a diurnal torpor that lasted over much of the colder 'long dry season' (July-October). The secretion of a pungent substance in the urine of adult males coincided with peak testicular activity during the annually competitive occupancy of a mating site (May-July).     

Does Estradiol Modulate Sexual Solicitations in Female Rhinopithecus roxellana?

Studies of the relationship between sexual behavior and reproductive endocrinology in females offer critical insight into sexual selection, mate choice, and female reproductive strategies in primates. We examine the relationship between sexual solicitations and urinary estradiol in female Sichuan golden monkeys (Rhinopithecus roxellana) living under semiwild conditions at the Shanghai Wild Animal Park, China. We collected data on the frequency of sexual solicitations and urinary samples on 4 adult females during 2 mating seasons. We determined urinary estradiol levels via radioimmunoassay. Our results indicate that during the ovarian cycle, solicitation focused on the periovulatory period around the estradiol peak. The frequency of female solicitations rose to a peak after the peak of estradiol level, suggesting that ovarian steroids modulate sexual behavior during the fertile phase of the ovarian cycle. We also found that females frequently solicited matings during pregnancy, most of which the α male accepted and that resulted in copulations. During pregnancy, however, there was no obvious relationship between sexual solicitation and urinary estradiol. We conclude that in Rhinopithecus roxallana, sexual behavior and estradiol production do not strictly correlate during different parts of the reproductive cycle. We discuss additional relationships between social interactions, dominance, sexual behavior, and endocrine function.     

Reproductive synchronization in squirrel monkeys (Saimiri)

Groups of squirrel monkeys (Saimiri) that are exposed to certain seasonal environmental stimuli experience a yearly reproductive cycle with discrete mating and birth seasons. Seasonal rainfall or some rainfall induced seasonal changes (such as changes in vegetation or insect fauna) appear to be responsible for timing theSaimiri reproductive cycle. Animals of both sexes show significant physiological and behavioral changes during the yearly cycle. Whether the environmental timing factors affect both the males and the females equally, or affect only one sex directly and the other sex indirectly through social communication is not clear. Three mechanisms by which the reproductive activity of both males and females could be synchronized are presented, and data from a laboratory study and a field study relevant to each mechanism are presented. Several social interaction patterns frequently observed in the field study suggest that (1) male sexual activity may excite female sexual activity through male penile display and/or other stereotyped interactions and/or (2) female sexual activity may excite male sexual activity through pheromone and/or other communication channels.     

Postmating sexual selection: the effects of male body size and recovery period on paternity and egg production rate in a water strider

The role of male body size in postmating sexual selection wasexplored in a semiaquatic insect, the water strider Gerris lateralis.To separate effects of male size per se from those due to numericsperm competition, male recovery period (shown here to be proportionalto ejaculate size) was manipulated independently of body sizein a factorial experiment where virgin females were mated firstwith sterile males and then with focal males. Both relativemale fertilization success and female reproductive rate were measured.The number of sperm transferred increased with male recoveryperiod, an effect that was mediated by longer copulation duration,but there were no effects of body size on ejaculate size. Neithermale size nor recovery period had any significant direct effectson male fertilization success. However, copulation durationinfluenced relative fertilization success, suggesting that malesable to transfer more sperm also achieved higher fertilizationsuccess. Females exercised cryptic female choice by modulatingtheir reproductive rate in a manner favoring large males andmales that were successful in terms of achieving high relativefertilization success. Thus, successful males gained a twofoldadvantage in postmating sexual selection. This study has important implicationsfor previous estimates of sexual selection in this group of insectsbecause pre- and postmating sexual selection will be antagonisticdue to limitations in male sperm production: males mating frequently(high mating success) will on average transfer fewer sperm ineach mating and will hence tend to fertilize fewer eggs permating (low fertilization success).     

Effect of reproductive rest on the subsequent breeding in Iberian red deer hinds (Cervus elaphus hispanicus)

The objective of this study was to examine the effects of reproductive rest during the preceding year on subsequent breeding in captive Iberian hinds. To achieve this, influences were assessed on hind weight at mating, precalving and postcalving weight, hind body condition at mating, hind weight gain during gestation, hind weight loss at calving, total milk yield and calf birth weight during the following breeding season. Sex ratio was examined according to hind age class (sub-adults or adults), precise age, body condition and weight at mating, and reproductive rest. One hundred and twenty seven gestations and their subsequent lactations were analyzed in pluriparous Iberian red deer (Cervus elaphus hispanicus) kept in captivity for two years. Sixty four of these gestations (50.4%) took place after no gestation during the preceding year.Hinds that did not gestate the preceding year were heavier at mating and after calving, gained less weight during gestation, and their body condition at mating was better than those hinds that had gestated. Also, calves from hinds that had reproductive rest the preceding year were heavier at birth than the others. Nevertheless, the probability of bearing a male was greater with increasing age, but not with reproductive rest or any other variable. Total milk yield was positively affected by hind postcalving weight and hind age at mating, but not by reproductive rest.In conclusion, reproductive effort during the preceding breeding influenced the subsequent gestation, having an effect on the following variables: hind weight and body condition at mating, hind weight gain during gestation, postcalving weight, and calf birth weight.     

Precopulation Sexual Selection in Nysius huttoni White (Heteroptera: Lygaeidae) in Relation to Morphometric Traits

Nysius huttoni White is a polygamous bug, endemic to New Zealand, and an important pest of wheat and brassicas. This bug has a female-biased sexual size dimorphism but relative to body length, males have longer antennae, suggesting that the allometric scales of antennal–body relationships may be highly selective in sexual selection. Body weight and most morphometric traits measured have no effect on mating success of either sex. Males significantly preferred mating with females having thicker abdomens, more mature eggs, and longer ovipositors. This result suggests that males may select their mates on the basis of immediate reproductive benefit: fertilizing more eggs and ensuring better survival of these eggs. Males with large genital structures have mating advantages over those with small ones, suggesting that precopulation sexual selection in this species act on male genital traits rather than body weight and nonsexual traits. Finally, females significantly preferred males with greater slopes for the antennal-body relationship for mating. The allometry in the male antennal length may be an indicator of male reproductive fitness.     

Costs of reproduction in male lizards, Sceloporus virgatus

Models of life history evolution typically assume a balance between the benefits of current reproductive activity and the costs to future reproductive success or survivorship, but empirical studies often find positive correlations between such components of fitness in undisturbed animal populations. I examined possible survivorship costs of reproduction in free-ranging male lizards, Sceloporus virgatus , and found that males with low levels of mating success were less likely to survive to the following breeding season. I also investigated two possible indicators of reproductive effort, increase in ectoparasite load and decrease in body weight during the breeding season. Levels of parasitism with trombiculid mites at the end of the breeding season were not associated with any measure of fitness or body condition (mating success, survivorship to the following year, relative weight loss). Yearling males (which have low levels of mating success) usually gained weight during the breeding season, while older males generally lost weight during this period. This suggests that young males may have postponed reproduction in favor of body growth and that seasonal weight loss of older males might reflect reproductive effort. Within the group of older males, individuals with the highest levels of mating success did not have high levels of either weight loss or mortality. Mate guarding behavior, an alternative to the aggressive territorial behavior typical of many lizard species, may allow certain males to obtain mates without expending large amounts of energy or exposing themselves to great mortality risks.     

Sexually mature and immature yearling male European ground squirrels: a comparison of behavioral and physiological parameters

Early puberty may increase lifetime reproductive success, but may also entail diverse costs. In male European ground squirrels (Spermophilus citellus), age at sexual maturity varies among individuals. We compared sexually active and inactive yearling males under standardized conditions in outdoor enclosures. Non-reproductive yearling males hibernated significantly longer than mature males and emerged when the mating period had already started. Testosterone concentrations peaked in the precocious males during premating and mating, and were depressed in the non-reproductive individuals throughout the study period. Emergence body mass was similar in both groups, although sexually immature males were significantly heavier at the end of the active season. Additionally, non-reproductive yearlings grew faster than precocious individuals. Male–male aggression peaked during mating and the following 4 weeks. Intense aggressive interactions like chases and fights were mostly initiated by reproductive males and were directed towards mature competitors. Aggressive behavior in immature males was mainly expressed as spatial displacements. Non-agonistic interactions with females were only observed in sexually active males. Concentrations of fecal cortisol metabolites did not differ between the two male groups and were elevated in the second half of the active season. Leucocyte numbers were reduced during mating in mature males, whereas in immature animals, cell numbers did not change significantly. Our results indicate that early puberty in European ground squirrels involves lower growth rates, high intrasexual aggression, lower prehibernatory body mass, and probably worse immunological condition during mating.     

Body scarring as an indicator of social function of dugong (Dugong dugon) tusks

The fully aquatic lifestyle of dugongs means that direct observation of social tusk use is not usually possible. This study used body scarring as an indicator of tusk function by males. Tusk rake scars on 298 live wild dugongs, of both sexes and all sizes, were categorized and counted in over 1,000 photographs, and examined in relation to maturity and reproductive activity over seasons. All dugongs had tusk scars, but adults were the main recipients. Sexually active adults acquired the greatest number of fresh tusk wounds during the mating season. Subadults received fresh rakes at similar numbers year-round. Adult males had more scars on the mid and posterior dorsum, indicating that males direct combative force to these regions of the male body when competing for females. Adult females had heaviest scarring and more tusk puncture wounds on the anterior-mid dorsum and head, suggesting that male dugongs use tusks in sexual coercion. Heavy scarring sustained by solitary calves compared to dependent ones, suggests that mothers afford some protection. Body scarring caused by tusks may serve as an indicator of reproductive contribution of the recipients, providing that successful males are involved in more reproductive competitions, and successful females in more mating events.     

Consequences of breeding system for body condition and survival throughout the annual cycle of tidal marsh sparrows

An individual's body condition and probability of survival can change throughout the annual cycle, based on the combined effects of many factors, including reproductive investment during breeding, colder temperatures during winter, and elevated risks during migration. We evaluated body condition and survival during breeding and non‐breeding periods in two closely related species with notably different reproductive systems. Male and female saltmarsh sparrows Ammodramus caudacutus represent extremes in parental care: males perform none, leaving females to do everything from build nests to care for fledglings. In contrast, male and female seaside sparrows A. maritimus have bi‐parental care and similar levels of reproductive investment, intermediate between male and female saltmarsh sparrows. Our results are consistent with the idea that females experience non‐lethal effects of reproduction, and that differences between the breeding season and winter affect condition. In both species, females had lower scaled mass index (SMI) values than males during both breeding and non‐breeding seasons, and female saltmarsh sparrows had lower SMI values than female seaside sparrows. Females carried more fat than males during the breeding season, and female, but not male, fat and muscle scores decreased over time, which is consistent with the adaptive mass hypothesis. In winter, all groups carried more fat and had higher muscle scores than when breeding, despite having lower SMI scores. Although we observed variation in body condition, within‐season survival was uniformly high in both seasons, suggesting that sex, species, season, body size, and body condition have little impacts on within season survival. Comparisons with previously‐published estimates of annual adult survival suggest that most mortality occurs during migration, even in these short‐distance migrants. The importance of considering multiple aspects of body condition, multiple seasons, and difficult‐to‐monitor events, such as migration, should not be ignored when thinking about the events and processes that cumulatively determine population dynamics.     

Post-conception mating in wild long-tailed macaques (Macaca fascicularis): characterization, endocrine correlates and functional significance

In many anthropoid primates, mating activity is not restricted to the ovarian cycle but also occurs during pregnancy. Although it has been suggested that the main function of this post-conception mating is to confuse paternity, studies showing whether or not male primates can distinguish between the fertile phase of the conception cycle (FPCC) and the period of peak post-conception mating (peak PCM) are almost non-existent. Here, we examine whether the pattern of female sexual traits (specific sexual behaviors, sexual swelling) and female attractiveness to males differ between FPCC and peak PCM in 6 wild female long-tailed macaques. We also use fecal hormone analysis to investigate whether female traits during peak PCM are related to changes in female sex hormones. All females exhibited a distinct period of heightened mating activity around days 45-60 of gestation. During peak PCM, swelling size and frequency of female solicitations (but not reaching back) were significantly correlated with changes in the estrogen to progestogen ratio. Swelling size, frequency of female sexual behaviors and copulations and proportion of male-initiated copulations and ejaculations were not significantly different between FPCC and peak PCM. Although males spent significantly less time consorting females during peak PCM, all (particularly low-ranking and non-resident males) invested heavily in terms of reproductive costs associated with mate-guarding and mating during pregnancy. We conclude that post-conception mating in wild long-tailed macaques is not merely a by-product of endocrine changes and devoid of adaptive function. Our results more strongly support the hypothesis that it may form part of a female reproductive strategy to confuse paternity, which appears to apply particularly to low-ranking and extra-group males.     

Concealed fertility and extended female sexuality in a non-human primate (Macaca assamensis)

In numerous primates living in mixed-sex groups, females display probabilistic cues of fertility to simultaneously concentrate paternity to dominant males while diluting it amongst others as a means to reduce the risk of infanticide and to increase male care for offspring. A few species, however, lack these cues and potentially conceal fertility from males; yet, to date, little is known about mating patterns and their underlying proximate mechanisms in such species. Here, we investigated mating activity and sexual consortships relative to female reproductive state in wild Assamese macaques (Macaca assamensis), a species where females lack prominent anogenital swellings and copulation calls. During two mating seasons (2837 contact hours) we recorded sexual and social behaviors, sexual consortships, and collected 1178 fecal samples (n = 15 females) which were analyzed for progestogen concentrations to assess female reproductive state and to determine the timing of ovulation and conception. Although mostly conceiving in their first ovarian cycle, females were sexually receptive throughout the entire 4-month mating season, and within-cycle mating frequencies were not increased during fertile phases. Dominant males did not monopolize fertile matings, and consortships by high-ranking males lasted for long periods, which were not exclusively linked to female fertile phases. Furthermore, females copulated promiscuously but not randomly, i.e. for almost every female, matings were concentrated to a certain male, irrespective of male rank. Collectively, we demonstrate that fertility is undisclosed to males. The extreme extended female sexuality facilitated by concealed fertility may allow females to create differentiated mating relationships within a promiscuous mating system. Our study provides important new insight into the plasticity of female sexuality in non-human primates.     

Vagabond males and sedentary females: spatial ecology and mating system of the speckled rattlesnake (Crotalus mitchellii)

We used radiotelemetric data and behavioural observations to characterize seasonal (mating versus post‐mating seasons) and sexual variation in movement patterns, as well as to examine some of the ecological factors contributing to the evolution of the mating system in a venomous predator from the Mojave Desert of North America, the speckled rattlesnake, Crotalus mitchellii. Mating occurs in spring from late April to early June, shortly after emergence from hibernation, when snakes are predictably aggregated around the dens. Males and females travelled further per unit time in the mating season compared to the post‐mating season. Males also travelled longer distances per unit time than females in the mating and post‐mating seasons, and males with larger home ranges during the mating season had more potential mating partners. The results obtained suggest that males actively locate females during the mating season, and that the drastic increase in distance travelled by males during the mating season may be caused by strong male–male competition for access to females, probably because of the limited availability of sexually receptive females. Furthermore, males fight for access to females, and males of larger size are more likely to acquire females. Therefore, sexual selection apparently acts on two different male phenotypic traits: investment in mate‐searching activities and male body size. The present study demonstrates that combining quantitative spatial analyses and behavioural observations in an explicit temporal context can significantly advance our understanding of the ecology and evolution of organismal mating systems. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 681–695.     

Sexually mature and immature yearling male European ground squirrels: A comparison of behavioral and physiological parameters

Early puberty may increase lifetime reproductive success, but may also entail diverse costs. In male European ground squirrels (Spermophilus citellus), age at sexual maturity varies among individuals. We compared sexually active and inactive yearling males under standardized conditions in outdoor enclosures. Non-reproductive yearling males hibernated significantly longer than mature males and emerged when the mating period had already started. Testosterone concentrations peaked in the precocious males during premating and mating, and were depressed in the non-reproductive individuals throughout the study period. Emergence body mass was similar in both groups, although sexually immature males were significantly heavier at the end of the active season. Additionally, non-reproductive yearlings grew faster than precocious individuals. Male–male aggression peaked during mating and the following 4 weeks. Intense aggressive interactions like chases and fights were mostly initiated by reproductive males and were directed towards mature competitors. Aggressive behavior in immature males was mainly expressed as spatial displacements. Non-agonistic interactions with females were only observed in sexually active males. Concentrations of fecal cortisol metabolites did not differ between the two male groups and were elevated in the second half of the active season. Leucocyte numbers were reduced during mating in mature males, whereas in immature animals, cell numbers did not change significantly. Our results indicate that early puberty in European ground squirrels involves lower growth rates, high intrasexual aggression, lower prehibernatory body mass, and probably worse immunological condition during mating.     

The combined effects of pre‐ and post‐copulatory processes are masking sexual conflict over mating rate in Gerris buenoi

In polygynandrous animals, post‐copulatory processes likely interfere with precopulatory sexual selection. In water striders, sexual conflict over mating rate and post‐copulatory processes are well documented, but their combined effect on reproductive success has seldom been investigated. We combine genetic parentage analyses and behavioural observations conducted in a competitive reproductive environment to investigate how pre‐ and post‐copulatory processes influence reproductive success in Gerris buenoi Kirkaldy. Precopulatory struggles had antagonistic effects on male and female reproductive success: efficiently gaining copulations was beneficial for males, whereas efficiently avoiding copulations was profitable for females. Also, high mating rates and an intermediate optimal resistance level of females supported the hypothesis of convenience polyandry. Contrary to formal predictions, high mating rates (i.e. the number of copulations) did not increase reproductive success in males or decrease reproductive success in females. Instead, the reproductive success of both sexes was higher when offspring were produced with several partners and when there were few unnecessary matings. Thus, male and female G. buenoi displayed different interests in reproduction, but post‐copulatory processes were masking the effects of copulatory mating success on reproductive success. Given the high mating rates observed, sperm competition could easily counter the effect of mating rates, perhaps in interaction with cryptic female choice and/or fecundity selection. Our study presents a complex but realistic overview of sexual selection forces at work in a model organism for the study of sexual conflict, confirming that insights are gained from investigating all episodes in the reproduction cycle of polygynandrous animals.     

The mating system and male mating success of the Virginia opossum (Didelphis virginiana) in Florida

The mating system of the Virginia opossum, a solitary, nocturnal marsupial, was studied over a period of two years in north–central Florida. There were two mating seasons each year, both lasting about four weeks and starting in mid-January and late April, respectively. Radio-tracking males and females revealed that, independent of body size, males doubled their home ranges during these periods to include an average of 5.9 females within their new ranges. Females were visited regularly and, on the night of oestrus, males directly competed for access to the female. Dominance and hence mating success was strongly related to body mass but not age. Dominant males weighed on average 3.18 kg (N = 20) compared to 2.65 kg of unsuccessful males. The largest of the competing males was successful in 20 of 23 cases involving at least two competitors. Individual male mating success varied from zero to three matings during a breeding season, but the range was probably underestimated. Mate searching activities were costly, as most males lost weight during both mating seasons. Weight changes were a function of body mass, with males over 2.2 kg losing up to 23% in weight and smaller males gaining weight. There was also evidence that male breeding activities entailed a survival cost.     

Preliminary observations on sexual behavior and the mating system in free-ranging lesser galagos. (Galago moholi)

Sexual and associated patterns of behavior of lesser galagos (Galago moholi) were recorded during an 18-month study conducted at the Nylsvley Nature Reserve in South Africa. Animals were trapped and fitted with radio transmitter belts in order to monitor nocturnal activities during twice-yearly mating seasons. Most copulations occurred during the last week in May, while a subsidiary (post-partum) mating season occurred in late September-early October. Females came into estrus sequentially during the May season. Adult males exhibited increase in body weight and testes volume during the mating season, changes which were most pronounced among the larger males (> 226 g). Larger males also had the greatest mating success, initiating 88% of observed copulations. Sixty-seven percent of matings involved more than one male copulating with the same female during her estrus, which lasted 1-3 days. Mounts were prolonged (range 2-53 min, mean 9.0 min) and males copulated repeatedly (2-5 times) with the same partner during a single night. These observations of sexual behavior and of large relative testes size in free-ranging lesser galagos are consistent with the occurrence of a dispersed mating system involving sperm competition in this nocturnal prosimian species.     

Antagonistic pre- and post-copulatory sexual selection on male body size in a water strider (Gerris lacustris)

A crucial question in sexual selection theory is whether post-copulatory sexual selection reinforces or counteracts conventional pre-copulatory sexual selection. Male body size is one of the traits most generally favoured by pre-copulatory sexual selection; and recent studies of sperm competition often suggest that large male size is also favoured by post-copulatory sexual selection. In contrast to this general pattern, this study shows that pre- and post-copulatory sexual selection act antagonistically on male body size in Gerris lacustris. One large and one small male were kept together with two females in this experiment. Large males had a significant mating advantage, but small males copulated longer and gained higher fertilization success from each mating. Large and small males, however, gained similar reproductive success, and there was no overall correlation between mating success and reproductive success. These results suggest that estimates of male fitness based solely on mating success should be viewed with caution, because of potentially counteracting post-copulatory selection.     

Sexual size dimorphism and reproductive ecology in relation to mating system in waders

The relationship between sexual size dimorphism, body-weight and different reproductive traits (e.g. clutch size, egg weight and incubation period) in relation to mating system and forms of parental care was studied in waders. Two hypotheses were examined. (1) Sexual size dimorphism is correlated with the intensity of sexual selection. (2) The degree of sexual size dimorphism is the result of an interrelationship between the reproductive strategy of the female and her body size. In the polygynous species the male was significantly larger than the female. This is consistent with the sexual selection hypothesis. However, among waders, a positive correlation exists between egg weight, clutch mass and body-weight. Selection for small eggs or a short incubation period may therefore have an influence on female body-weight. If the lack of paternal care reduces the female's possibility for producing large eggs or incubating a large clutch mass, we would expect a selection pressure for small female size among polygynous species. Thus, large sexual size dimorphism among polygynous waders may be a result of selection for small female size to lack of paternal care, or selection for large male size due to intramale competition or a female preference for large-sized males. In multiple-clutch species (viz. species in which the female regularly lays more than one clutch during the season) egg weight was low both for a given female and male body-weight. The low egg weight of multiple-clutch species is assumed to be a result of the constraints placed on the female from producing several clutches during a single breeding season.     

Metabolic variables and plasma leptin concentrations in dairy cows exhibiting reproductive cycle abnormalities identified through milk progesterone monitoring during the post partum period

We have used milk progesterone analysis to monitor reproductive function in lactating dairy cows and have then related this reproductive function to a variety of metabolic variables. Monitoring of cows (n = 41) during the period of onset of luteal function (first milk progesterone reading>5 ng/ml) revealed that delayed onset was associated with increased milk yield and greater loss of body weight and body condition but was not related to plasma metabolite or leptin concentrations. Further monitoring of reproductive function in these 41 cows and an additional 33 cows (total n = 74) during the mating period (from weeks 6 to 14 post partum) identified reproductive cycle abnormalities in 29 (39.2% of animals). The occurrence of cycle abnormalities was associated with increased milk yield (P < 0.05), elevated plasma beta hydroxybutyrate (P < 0.05) and reduced plasma leptin (P < 0.01) concentrations as well as a lower (P < 0.05) rate of gain of body weight and condition score but was not associated with plasma urea or glucose concentrations. Furthermore, cows exhibiting cycle abnormalities had a longer (P < 0.01) interval to first service and a smaller percentage had conceived by 100 days post partum (34.5% versus 66.7%; P < 0.01). These results provide further evidence that impaired reproductive function during the post partum period in dairy cows is caused by a poor energy status and not elevated urea concentrations. Reduced plasma leptin concentrations in animals suffering reproductive dysfunction further supports this view.