Polygamous Species Research Articles

Females increase reproductive investment when mated to less sexually attractive males in a serially monogamous fish

Reproductive investment decision is an integral part of life-history theory. Differential allocation hypothesis predicts that females should increase investment when mated to high-quality males, conversely, reproductive compensation hypothesis predicts that females should increase investment when mated to low-quality males. Empirical research dominantly focuses on polygamous species and rarely on serially monogamous species. So, the question remains: which hypothesis does serially monogamous species fit? And if it fits reproductive compensation hypothesis, do females only compensate once or continuously for multiple times when mating to low-quality males? Here, we used a serially monogamous fish, the lined seahorse (Hippocampus erectus), to investigate the reproductive investment pattern of females in relation to male quality (measured by sexual attractiveness). We found that females allocated more resources into eggs when they mated to less-sexually-attractive males, indicating the investment pattern of lined seahorse falls in with the prediction of reproductive compensation hypothesis. This finding may imply that the sex role of seahorses is reversed, and female is the side imposed on a greater sexual selection pressure. On this basis, we compared the investment difference of females in two consecutive breeding events when mated to less-sexually-attractive males. We found that females allocated less resources into eggs in the second breeding than in the first one. Females reduced their reproductive compensation in the second breeding, which may be attributed to the improvement in the quality (e.g., paternal care ability) of their mates after the first breeding, thus eliminating the need for them to invest more in the second breeding.

The use of anthropogenic areas helps explain male brown bear movement rates and distance travelled during the mating season

AbstractDuring the reproductive period, mating strategies are a significant driver of adaptations in animal behaviour. For instance, for polygamous species, greater movement rates during the mating season may be advantageous due to the increased probability of encountering several potential mates. The brown bear Ursus arctos is a solitary carnivore that lives at low densities, with a polygamous mating system and an extended mating season of nearly 3 months. Here, we hypothesized that male brown bears may show changes in movement patterns and space‐use behaviour during their mating season. Using long‐term (2002–2013) telemetry data from the Finnish Karelia male population (n = 24 individuals; n = 10 688 GPS locations), we first analysed daily movement metrics, that is, speed, net and total distance with respect to the period (mating vs. post‐mating) and several environmental predictors. Then, we conducted a step‐selection analysis for each of these periods. Throughout the year, male bears selected forested/shrub habitats and increased movement rates near main roads. During the mating season, reproductive needs seem to trigger roaming behaviour in adult males to maximize encounter rates with potential receptive females. However, all movement metrics increased within areas of high human activity, suggesting a bear response to a higher risk perception while using those areas. During the post‐mating period, overlapping with the bear hyperphagia and the hunting season, males selected anthropogenic areas farther from main roads and trails, suggesting a trade‐off between foraging opportunities and risk avoidance.

Egg characteristics vary longitudinally in Arctic shorebirds

Arctic environments are changing rapidly and if we are to understand the resilience of species to future changes, we need to investigate alterations in their life histories. Egg size and egg shape are key life-history traits, reflecting parental investment as well as influencing future reproductive success. Here we focus on egg characteristics in two Arctic shorebirds, the Dunlin (Calidris alpina) and the Temminck's stint (Calidris temminckii). Using egg photos that encompass their full breeding ranges, we show that egg characteristics exhibit significant longitudinal variations, and the variation in the monogamous species (Dunlin) is significantly greater than the polygamous species (Temminck's stint). Our finding is consistent with the recent "disperse-to-mate" hypothesis which asserts that polygamous species disperse further to find mates than monogamous species, and by doing so they create panmictic populations. Taken together, Arctic shorebirds offer excellent opportunities to understand evolutionary patterns in life history traits.

Polygamy and purifying selection in birds

Good genes theories of sexual selection predict that polygamy will be associated with more efficient removal of deleterious alleles (purifying selection), due to the alignment of sexual selection with natural selection. On the other hand, runaway selection theories expect no such alignment of natural and sexual selection, and may instead predict less efficient purifying selection in polygamous species due to higher reproductive variance. In an analysis of polymorphism data extracted from 150-bird genome assemblies, we show that polygamous species carry significantly fewer nonsynonymous polymorphisms, relative to synonymous polymorphisms, than monogamous bird species (p = .0005). We also show that this effect is independent of effective population size, consistent with the alignment of natural selection with sexual selection and "good genes" theories of sexual selection. Further analyses found no impact of polygamy on genetic diversity, while polygamy in females (polyandry) had a marginally significant impact (p = .045). We also recapitulate previous findings that smaller body mass and greater geographic range size are associated with more efficient purifying selection, more intense GC-biased gene conversion, and greater genetic diversity.

Relaxed territoriality amid female trickery in a solitary carnivore

Territoriality (the defence of exclusive home ranges) is a strategy utilized within mammal populations to maximize individual fitness by monopolizing available resources. There is a trade-off, however, between acquiring the resources necessary for survival and reproduction and the cost of defending their exclusive use. Clarifying the sociospatial organization of wildlife populations is vital for understanding intraspecific competition and reproductive behaviour and, ultimately, conserving vulnerable or endangered species. We evaluated territorial behaviour in a solitary carnivore, the African leopard, Panthera pardus, under high-density conditions. We also assessed the influence of resource availability, sex-specific mating tactics and kinship on space sharing within the observed sociospatial structure. Both male and female leopards exhibited relaxed territoriality, with considerable intrasexual overlap occurring among both sexes, indicative of a risk aversion strategy. The risk of serious injury or death due to frequent territorial altercations in such a high-density system negated the benefits of strict spatial boundaries. Space sharing occurred more frequently in resource-rich areas: males overlapped more commonly in areas with high female density, and males and females overlapped more commonly in areas of high prey density. Males competed for access to females rather than monopoly of their home ranges; we hypothesize that the extralimital mating excursions undertaken by female leopards probably reduce the benefit of female monopoly (and consequently, of female defence) in this polygamous species. Space sharing among females was primarily driven by kinship; related females exhibited greater overlap than unrelated females, suggesting kinship benefits to space sharing among mother–daughter pairs. The contributions of resource availability, sex-specific mating tactics and kinship towards creating conditions permitting relaxed territoriality illustrate the complexity of ecological, demographic and behavioural factors involved in the sociospatial organization of solitary carnivores. • Male and female leopards display relaxed territoriality indicative of risk aversion. • Considerable intrasexual overlap occurred among male and female leopards. • For males, space sharing occurred more often in areas with high female density. • Males competed for access to females rather than monopoly of their home ranges. • Space sharing among females was primarily driven by kinship.

Big competition for small spots? Conspecific density drives home range size in male and female leopards

AbstractVariation in home range size exists among and within wildlife populations. Home range size variation may be driven by both intrinsic and extrinsic factors, including sex, food and reproductive resources, density and competition. In this study, we investigated the sex‐specific impacts of prey and reproductive resources, conspecific density and competition on leopard Panthera pardus home range size at two spatio‐temporal scales in the Sabi Sand Game Reserve, South Africa. Male leopard home ranges were more than twice the size of those of females, in line with expectations for a solitary, polygamous species. Both male and female leopard space‐use were primarily driven by short‐term changes in intra‐sexual conspecific density. Females were influenced by both short and long‐term drivers, with long‐term prey availability (home range and core) and refugia (core) further impacting size. Males were almost exclusively influenced by short‐term drivers; home range size was further impacted by short‐term changes in female leopard and prey density, and age. Long‐term prey availability contributed to male leopard core size. The difference in impact of short‐ and long‐term drivers between the sexes likely relates to tenure expectations; males may be forced out of their territories at any time and should therefore optimize their space‐use based on present conditions. Female leopards, however, must secure a home range that maximizes their reproductive success in the short‐ and long‐term in order to raise cubs to independence. Our findings challenge expectations that space‐use is primarily resource‐driven and demonstrate the critical role of social factors in saturated populations of solitary species. Furthermore, we illustrate the importance of considering temporally variable factors across different timescales to fully understand their impact on mammalian spatial organization.

Sperm competition risk affects ejaculate strategy in terms of sperm number but not sperm size in squid.

In polygamous species, the mode of sperm storage in females influences evolution of sperm quantitative and qualitative traits because it provides the arena for sperm competition, cryptic female choice and fertilization processes. In this study, we compared ejaculate traits of two squid species, Heterololigo bleekeri and Loligo reynaudii. Both species show dimorphic sperm traits associated with alternative reproductive tactics where consort and sneaker males transfer sperm to different storage sites within a female (on the oviduct and near the mouth, respectively). Due to differences in reproductive behaviours and sperm placement, sperm competition risk is expected to be higher in sneakers than in consorts of both species and higher overall in L.reynaudii. Our results demonstrate that the instantaneous number of released sperm is adjusted to the expected sperm competition risk via an elaborate sperm package. Consort sperm are similar in size; however, sneaker sperm have a significantly longer flagellum in H.bleekeri than in L.reynaudii, most likely due to intra-tactic conflicts associated with sperm storage conditions.From consideration of the different mating tactics, we suggest that while levels of sperm competition determine quantitative traits, sperm quality traits are determined more by the mode of sperm storage and fertilization.

No evidence for female kin association, indications for extragroup paternity, and sex-biased dispersal patterns in wild western gorillas.

Characterizing animal dispersal patterns and the rational behind individuals’ transfer choices is a long‐standing question of interest in evolutionary biology. In wild western gorillas (Gorilla gorilla), a one‐male polygynous species, previous genetic findings suggested that, when dispersing, females might favor groups with female kin to promote cooperation, resulting in higher‐than‐expected within‐group female relatedness. The extent of male dispersal remains unclear with studies showing conflicting results. To investigate male and female dispersal patterns and extragroup paternity, we analyzed long‐term field observations, including female spatial proximity data, together with genetic data (10 autosomal microsatellites) on individuals from a unique set of four habituated western gorilla groups, and four additional extragroup males (49 individuals in total). The majority of offspring (25 of 27) were sired by the group male. For two offspring, evidence for extragroup paternity was found. Contrarily to previous findings, adult females were not significantly more related within groups than across groups. Consistently, adult female relatedness within groups did not correlate with their spatial proximity inferred from behavioral data. Adult females were similarly related to adult males from their group than from other groups. Using R ST statistics, we found significant genetic structure and a pattern of isolation by distance, indicating limited dispersal in this species. Comparing relatedness among females and among males revealed that males disperse farer than females, as expected in a polygamous species. Our study on habituated western gorillas shed light on the dispersal dynamics and reproductive behavior of this polygynous species and challenge some of the previous results based on unhabituated groups.

Spawning-related movements in a salmonid appear timed to reduce exposure to visually oriented predators

Animals often exhibit extensive flexibility in movement behaviours on a range of temporal and spatial scales in response to cues that reliably predict fitness outcomes. The annual timing of movements between distinct habitats can be crucial, particularly in seasonal environments with narrow ecological windows of opportunity. In polygamous species, sexual selection may further shape sex-specific phenology and movement behaviours. Here, we characterized seasonal, daily and diel movement patterns in adult brown trout, Salmo trutta, between a lake feeding habitat and two spawning streams in northwestern Ireland, using passive integrated transponder (PIT) telemetry. Antennae positioned at the inflow and outflow of the lake were used to monitor movements of 197 lake-tagged adults between lake and stream habitats. Across 2 years in both streams, movements were overwhelmingly nocturnal and exhibited distinct seasonality, with a peak in daily detections close to the winter solstice. In both streams, seasonal movement activity of males began and peaked before that of females (protandry). Daily detection probabilities for both sexes increased as the moon waned (decreasing lunar illumination) and as river depth increased, the latter being associated with reduced water clarity. These findings are consistent with fish favouring movement between fluvial and lacustrine habitats when light (both solar and lunar) or hydrological conditions decrease their exposure to visually oriented predators. The observed protandry also suggests a role for intrasexual male competition, whereby earlier male arrival could increase mating opportunities.

A life-history perspective on sexual selection in a polygamous species

BackgroundEver since Darwin, evolutionary biologists have studied sexual selection driving differences in appearance and behaviour between males and females. An unchallenged paradigm in such studies is that one sex (usually the male) signals its quality as a mate to the other sex (usually the female), who is choosy in accepting a partner. Here, we hypothesize that in polygamous species these roles change dynamically with the mating status of males and females, depending on direct reproductive costs and benefits of multiple matings, and on sperm competition. We test this hypothesis by assessing fitness costs and benefits of multiple matings in both males and females in a polygamous moth species, as in moths not males but females are the signalers and males are the responders.ResultsWe found that multiple matings confer fitness costs and benefits for both sexes. Specifically, the number of matings did not affect the longevity of males or females, but only 67% of the males and 14% of the females mated successfully in all five nights. In addition, the female’s reproductive output increased with multiple matings, although when paired with a new virgin male every night, more than 3 matings decreased her reproductive output, so that the Bateman gradient for females fit a quadratic model better than a linear model. The male’s reproductive success was positively affected by the number of matings and a linear regression line best fit the data. Simulations of the effect of sperm competition showed that increasing last-male paternity increases the steepness of the male Bateman gradient and thus the male’s relative fitness gain from additional mating. Irrespective of last-male paternity value, the female Bateman gradient is steeper than the male one for up to three matings.ConclusionOur results suggest that choosiness in moths may well change throughout the mating season, with males being more choosy early in the season and females being more choosy after having mated at least three times. This life-history perspective on the costs and benefits of multiple matings for both sexes sheds new light on sexual selection forces acting on sexual signals and responses.

Contributions to the natural history of Mormopterus kalinowskii (Chiroptera: Molossidae) in the southwest of Peru

Mormopterus kalinowskii, is an insectivorous species restricted to the Andean western slopes of Peru and Chile, it is rare and has very scarce available information. We evaluated sex ratio, roost use, and relationship between reproductive patterns and monthly seasonal variation throughout a 13-month period. In addition, we performed the first description and characterization of its echolocation calls. The study area was located in the Ite Valley, Tacna department (southwestern Peru) at the northernmost part of the Atacama Desert, one of the driest deserts in the world. Bats were caught using mist-nets. Sex ratio in the population was calculated from all individuals captured, and its difference with regard to a 1:1 ratio was assessed through a Binomial Coefficient Test. Roost use was assessed through observation and inspection of the study area. Pearson and Spearman correlation coefficients were calculated to establish the relationship between the number of captures and temperature and precipitation data. Echolocation calls were recorded using a Petterson D240x Ultrasound detector plugged to a digital recorder. Spectrogram displays of recorded calls allowed describing structural patterns within echolocation calls and to measure frequency and time parameters. 79 individuals of M. kalinowskii were captured; 30 males and 49 females. Sex ratio obtained, 1:1.63, evidenced more females in the study area. M. kalinowskii uses crevices as roosts and has a single reproductive cycle per year. Higher capture rates are correlated with temperature (r = 0.526), but not precipitation (r = 0.096). Calls in search phase exhibited long duration pulses and a descending quasi-constant frequency (QCF) component from 39 to 33 kHz, reducing length and increasing bandwidth when attempting to catch prey. The sex ratio, 1:1.63 (≈ 2), suggests that M. kalinowskii is a polygamous species, as occurs in the others molossids, whereas the single annual reproductive cycle shown by M. kalinowskii would indicate a seasonal monoestrous reproductive pattern. Echolocation calls share several traits observed in other molossids; however, the frequency values for M. kalinowskii search phase pulses could be the highest recorded among the molossid bats of the Pacific coastal desert, allowing them to detect smaller prey as a strategy to mitigate food competition among insectivorous bats in arid environments.

Sperm size is negatively related to relative testis size in West African riverine cichlid fishes.

Fishes show a great diversity of mating systems and fertilization mechanisms. This diversity creates an enormous potential for sperm competition. Typically, monogamous species face a low risk of sperm competition and invest less into sperm, and thus show smaller relative testis mass compared to polygamous species with high sperm competition. In cichlids, sperm competition risk is very variable. In lacustrine East African cichlids, large sperm are interpreted as an adaptation to sperm competition, as in those species sperm length correlates with sperm swimming speed. The aim of the present study was to examine variation in sperm and testis traits of substrate breeding cichlids from West African river systems and its relationship to sperm competition. Therefore, sperm traits (total sperm size, flagellum-, midpiece-, and head size) and sperm number were related to the gonadosomatic index (GSI), an indicator of sperm competition, in eight species of two large informal tribes, the chromidotilapiines and the haplotilapiines. We found significant differences between species in all examined sperm traits, sperm number, and GSI with pronounced differences between chromidotilapiines and haplotilapiines. We used a generalized least-squares approach to control for non-independence of data. GSI was positively correlated with sperm number but negatively correlated with total sperm size (also negatively with the flagellum and head size but not significantly with midpiece size). Sperm number and sperm size were negatively correlated suggesting a trade-off between sperm size and quality. Our results suggest that large sperm can evolve in species with relatively low sperm expenditure and probably in absence of high sperm competition between males.

Reproductive Behavior of the Amazonian Nurse-Frog Allobates paleovarzensis (Dendrobatoidea, Aromobatidae)

Allobates paleovarzensis is a diurnal leaf-litter anuran of the Dendrobatoidea superfamily inhabiting Amazonian forests. Based on behavioral field observations, conducted between 2008–2017 at three localities, we describe the courtship, mating, parental care behavior and territoriality of the species. Vocal activity is more intense in the morning and during the rainy season. Resident males respond aggressively to other males that invade their territories, whereas females are not territorial. Females are attracted by the advertisement call of males and enter their territories to breed. The male courtship call has a lower frequency than the advertisement call, indicating that males can modulate the frequency characteristics of their vocalizations. Amplexus stimulates the release of oocytes by females. Males attend multiple egg clutches within their territories and transport tadpoles on their backs to aquatic habitats. Males carry up to 60 tadpoles on a single transport event—the largest number ever recorded for Allobates. We did not record male nor female cannibalism of tadpoles. In summary, we found that Allobates paleovarzensis is a polygamous species with uniparental care performed by the male, complex courtship behavior, high fecundity, and territoriality related to male competition for space and females.

Size dimorphism and sexual segregation in pheasants: tests of three competing hypotheses.

Fine scale sexual segregation outside of the mating season is common in sexually dimorphic and polygamous species, particularly in ungulates. A number of hypotheses predict sexual segregation but these are often contradictory with no agreement as to a common cause, perhaps because they are species specific. We explicitly tested three of these hypotheses which are commonly linked by a dependence on sexual dimorphism for animals which exhibit fine-scale sexual segregation; the Predation Risk Hypothesis, the Forage Selection Hypothesis, and the Activity Budget Hypothesis, in a single system the pheasant, Phasianus colchicus; a large, sedentary bird that is predominantly terrestrial and therefore analogous to ungulates rather than many avian species which sexually segregate. Over four years we reared 2,400 individually tagged pheasants from one day old and after a period of 8–10 weeks we released them into the wild. We then followed the birds for 7 months, during the period that they sexually segregate, determined their fate and collected behavioural and morphological measures pertinent to the hypotheses. Pheasants are sexually dimorphic during the entire period that they sexually segregate in the wild; males are larger than females in both body size and gut measurements. However, this did not influence predation risk and predation rates (as predicted by the Predation Risk Hypothesis), diet choice (as predicted by the Forage Selection Hypothesis), or the amount of time spent foraging, resting or walking (as predicted by the Activity Budget Hypothesis). We conclude that adult sexual size dimorphism is not responsible for sexual segregation in the pheasant in the wild. Instead, we consider that segregation may be mediated by other, perhaps social, factors. We highlight the importance of studies on a wide range of taxa to help further the knowledge of sexual segregation.

Effectiveness of SNPs for parentage and sibship assessment in polygamous yellowtail kingfish Seriola lalandi

Single nucleotide polymorphisms (SNPs) have been used for quantitative traits and evolutionary studies, but only recently have they been applied to identify family relationships and construct pedigrees. Pedigree assignments can be challenging for mass spawning, polygamous marine species due to the large number of half-sib families arising from mass spawning, and small size of larvae, so genetic markers are required in order to achieve a highly accurate pedigree assignment. In the present study, sibship and parentage in yellowtail kingfish (Seriola lalandi) were obtained from SNPs and the results were compared with those obtained from DNA microsatellite data. The accuracies of pedigrees formed using COLONY and a more recently developed program, Sequoia, the latter designed to optimize speed of processing large data sets, were compared. We also considered the impact of choosing SNPs with varying minor allele frequencies (MAF from 0.05 to 0.50), varying the actual numbers of SNPs used in a given analysis (from 50 to 1000+) and varying assigned SNP genotyping error rates (0% to 10%). Accuracy of assignment, relative to DNA microsatellites, tended to increase with increasing MAF, and increased, up to a point, with increasing SNP number, but did not change with assigned genotyping error rates up to 10%. Both COLONY and Sequoia analyses, with moderate number of SNPs (500 SNPs) and MAF values (0.20–0.30), were able to predict full-sib pairs of which >95% were also predicted by DNA microsatellites, i.e. the concordance between SNP and microsatellite pedigrees was high; processing speeds were faster with Sequoia albeit with some minor reductions in accuracy. When parental data were included in the analyses, 98% of the individuals assigned to parents using SNPs were also assigned to the same parents using DNA microsatellites. Overall, the present study provides guidance as to the parameters (minor allele frequencies, number of SNPs, SNP genotyping error rates) that optimize accuracy, and once optimized, SNPs can be used efficiently for sibship and parentage assignments for polygamous species such as yellowtail kingfish in comparison to pedigrees obtained from traditional microsatellite markers.

Female Japanese quail visually differentiate testosterone-dependent male attractiveness for mating preferences

Biased mating due to female preferences towards certain traits in males is a major mechanism driving sexual selection, and may constitute an important evolutionary force in organisms with sexual reproduction. In birds, although the role of male ornamentation, plumage coloration, genetic dissimilarity, and body size have on mate selection by females have been examined extensively, few studies have clarified exactly how these characteristics affect female mate preferences. Here, we show that testosterone (T)-dependent male attractiveness enhances female preference for males of a polygamous species, the Japanese quail. A significant positive correlation between female mating preference and circulating T in the male was observed. The cheek feathers of attractive males contained higher levels of melanin and were more brightly colored. The ability of females to distinguish attractive males from other males was negated when the light source was covered with a sharp cut filter (cutoff; < 640 nm). When females were maintained under short-day conditions, the expression of retinal red-sensitive opsin decreased dramatically and they became insensitive to male attractiveness. Our results showed that female preference in quail is strongly stimulated by male feather coloration in a T-dependent manner and that female birds develop a keen sense for this coloration due to upregulation of retinal red-sensitive opsin under breeding conditions.

No evidence for parental age effects on offspring leukocyte telomere length in free-living Soay sheep

In humans, the effect of paternal age at conception (PAC) on offspring leukocyte telomere length (LTL) is well established, with older fathers thought to pass on longer telomeres to their offspring in their sperm. Few studies have looked for PAC effects in other species, but it has been hypothesised that the effect will be exacerbated in polygamous species with higher levels of sperm competition and production. We test for maternal (MAC) and paternal age at conception effects on offspring LTL in Soay sheep, a primitive breed experiencing strong sperm competition. We use qPCR to measure relative telomere length in 389 blood samples (n = 318 individuals) collected from an unmanaged population of sheep on St Kilda, where individual age and parentage are known. We find no evidence that either MAC or PAC are associated with LTL in offspring across the age range, or when considering only young lambs (n = 164). This is the first study to test for parental age effects on offspring LTL in a wild mammal population, and the results contrast with the findings of numerous human studies that find a PAC effect, as well as predictions of a stronger PAC effect in polygamous species.

Nototriche chaniensis (Malvaceae), una Nueva Especie Poligámica de los Andes de la Argentina

We describe and illustrate Nototriche chaniensis C. A. Zanotti & J. C. Ospina (Malvaceae), a new Andean polygamous species of Argentina. Nototriche chaniensis is morphologically related to N. agyna Krapov., from which it differs mainly by having the central lobe of the blade entire, and the stipular sheath and free portion of the leaf petiole considerably shorter. A description, illustration, photos of the new species, and a key to differentiate the polygamous species are provided.

Влияние соотношения полов на динамику численности двухвозрастной популяции

This article develops and investigates a simple mathematical model that simultaneously studies influence of age and sex structure formation and sex ratio on demographic and evolutionary processes. We assume fertility depends on the population sex ratio and is described by the modified harmonic mating function with switching. The population size is regulated by limiting the juvenile survival rate when immature individual survival decreases with growth of sex-age class sizes. We received the conditions for sustainable development of the population in the parametric space of the model. The relationships between the group sizes of newborns and mature females and males are analyzed. The growth of the harem size is shown to result in higher the newborn group size in case of female numerical dominance. The offspring number demonstrates the same tendency as the sex group with the smallest number in the cases of higher female survival rate and higher newborn female proportion, and lower male survival rate. Excessive asymmetry of the sexes is shown to lead to a decrease in reproduction of polygamous species. Complex scenarios of population dynamics are studied. Transitions between different dynamic modes are caused by changes in both population parameters determining birth, survival and self-regulation rates, and the formation process of the mating pairs. The model parametric space is shown to have multistability areas in which the initial condition variation can lead to the realization of one dynamic mode or the other. The multistability is the result of both the system nonlinearity and the complex bifurcation mechanisms, and the changing pair formation principle. Consequently, even a small variation of the current population size changing the sex ratio complicates the population behavior and can give significant change in the dynamic mode observed.

Seasonal variation in the sex and age composition of the woodcock bag in Denmark

The Eurasian woodcock is a highly valued game bird in Western Europe from which c. 2.7 million individuals are harvested annually from an estimated population of 20–26 million birds. The population size and status remains uncertain due to the cryptic behaviour and widespread and solitary occurrence of woodcock, on breeding and wintering areas, making reliable population surveys difficult. Hunting bag records provide age ratios amongst bagged birds, but sex ratios remain poorly known because of the sexually monomorphic nature of this species. We used DNA analysis to determine sex ratios amongst 327 shot woodcocks from two hunting seasons in Denmark (1 October–31 January, 2012/13 and 2013/14). Based on bag totals, age ratios and sex ratios, juvenile females constituted 37%, juvenile males 27%, adult females 16% and adult males 20% of the annual woodcock bag. The female bias was related to a significant deviation from parity in the sex ratio amongst juvenile birds in October, although no such deviation was found at other times or amongst adults. Compared to limited data from other European countries, our data suggest that autumn migration of woodcock involves an initial wave of juvenile females followed by juvenile males and adults, and perhaps that males stay further north in Europe than females during autumn and winter. This migratory pattern would suggest that postponing the opening of the hunting season could reduce the hunting bag on reproductively valuable females in this polygamous species.