Male sexual display and attractiveness in the great bustard Otis tarda: the role of body condition

Individual display rates and attractiveness of 17 radio-tagged, free-living great bustard males in north-western Spain were studied in relation to the degree of development of secondary sex traits, body condition, and age. Variance in display rate was significantly explained by body condition and length of moustache feathers, and neck development and display rate significantly accounted for the variance in male attractiveness. Age did not present any clear association with display rate or attractiveness, and it was significantly correlated only with neck development. These results suggest a total viability scenario of female mate choice in which the advertisement of global fitness is based on condition-dependent phenotypic and behavioural traits. Electronic Publication     

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

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

白洋淀流域大鸨越冬栖息地的适宜性评价

基于大鸨越冬期生境选择的相关研究成果,结合专家意见和近年来白洋淀流域大鸨的分布点记录,选择3项一级指标和13项二级指标,用以表征影响大鸨越冬生境选择的关键因子,并通过构建适宜性评价模型,对白洋淀流域大鸨越冬生境的质量进行了评价.结果表明:2005年,白洋淀流域内大鸨越冬适宜栖息地面积11907.25 km2,占流域总面积的34.1%;其中,最适宜生境面积4596.25 km2,仅占流域总面积的13.2%.研究区最适宜生境的空间分布相对集中,主要位于流域东部的白洋淀自然保护区及其周边(I区)和流域西南部的行唐、曲阳2县(II区).I区和II区中最适宜生境面积之和达2803.55 km2,占流域内最适宜生境面积的61.0%.为保护流域内大鸨的越冬生境,须重点针对上述2个区域的特点,分别采取适当措施加以保护.     

Factors causing long-term dynamics in the abundance of the Trans-Volga Great bustard (Otis tarda L.) population

The results of our survey of bustards in the southern part of the Saratov Trans-Volga region over an area of 12000 sq. km in 1990–2010 are presented; analysis of the abundance dynamics is performed; and the factors causing it are revealed. Data on the distribution of bustards over their biotopes in the period of premigration roaming are studied, and the demographic and spatial structure of the population is analyzed.     

Field determination of age in male great bustards (Otis tarda) in spring

During a long-term study of individually marked, free-living male great bustards captured as chicks and radio-tracked through several years in Spain, we studied the development with age of two secondary sex traits, the moustachial feathers and the neck plumage pattern. Juvenile males acquired full adult plumage between their fourth and seventh years. The main changes occurred at the neck, coinciding with the onset of sexual maturity. The grey colour typical of immature males turned to ivory white around the fourth to fifth spring, and a gradual increase was appreciated in adults in the brightness of the white colour of the upper neck and in the contrast between this and a progressively more intense chestnut brown at the neck base. Based on these changes, we proposed four neck plumage patterns that can be used to differentiate male age classes during the mating period. The development of moustachial feathers showed more interindividual variability and was not as useful as the neck plumage to estimate male age.     

Satellite telemetry reveals long‐distance migration in the Asian great bustard Otis tarda dybowskii

The range of the great bustard stretches 10 000 km across Eurasia, one of the largest ranges of any threatened species. While movement patterns of the western subspecies of great bustard are relatively well‐understood, this is the first research to monitor the movements of the more endangered Asian subspecies of great bustard through telemetry and to link a breeding population of Asian great bustards to their wintering grounds. Using Argos/GPS platform transmitter terminals, we identified the annual movement patterns of three female great bustards captured at their breeding sites in northern Mongolia. The 4000 km round‐trip migration we have recorded terminated at wintering grounds in Shaanxi, China. This route is twice as long as has previously been reported for great bustards, which are among the heaviest flying birds. The journey was accomplished in approximately two months each way, at ground velocities of 48–98 km h^?1, and incorporated multiple and variable stopover sites. On their wintering grounds these birds moved itinerantly across relatively large home ranges. Our findings confirm that migratory behavior in this species varies longitudinally. This variation may be attributable to longitudinal gradients in seasonality and severity of winter across Eurasia. The distance and duration of the migratory route taken by great bustards breeding in Mongolia, the crossing of an international border, the incorporation of many stopovers, and the use of a large wintering territory present challenges to the conservation of the Asian subspecies of great bustard in this rapidly changing part of the world.     

Sex-biased juvenile survival in a bird with extreme size dimorphism, the great bustard Otis tarda

We explored sex-biased mortality patterns in a species showing the most extreme sexual dimorphism among birds, the great bustard Otis tarda . Between 1991 and 2005 we studied juvenile and immature survival in a sample of 361 great bustards radio-tagged at two different populations in Spain, Villafáfila and Madrid. Mortality decreased with age, from high rates during the first year (0.70), to 0.10 in the second year. Using the known-fate model in program MARK we found that monthly survival increased throughout the first year. Offspring showing higher body mass at marking, i.e. those hatched earlier in the season and those with better body condition, survived in higher proportion. This was probably related to the earlier breeding dates of more experienced mothers, as well as to the observed decrease in food availability as the season progresses. Monthly survival estimates were higher in females than in males, which suggests that juvenile males are more vulnerable to reduced food availability and other factors due to their much faster growth rates. The proportion of non-natural deaths increased with age, and was higher in the Madrid population, where illegal hunting and collision with powerlines showed a high incidence. The male-biased mortality found in young birds in this study explains the female-biased population sex ratios observed in great bustard populations. The different degrees of incidence of human-induced causes of mortality found between both populations studied suggest that such differences may contribute to the variation observed in the adult sex ratio among populations.     

Abundance of the Transvolga Population of Great Bustard (Otis tarda L.)

We studied the abundance, spatial structure, and demographic parameters of the Transvolga population of the great bustard and the connections of this species to habitats during relocations preceding migration. The data were obtained by monitoring a test area of 1200000 hectares in 1998–2000. Time-related changes in the structure of great bustard habitats in the Saratov Transvolga Region in the 20th century are described, and the mechanisms underlying changes in the species connection to habitats under the influence of anthropogenic factors are proposed.     

Cultural transmission and flexibility of partial migration patterns in a long‐lived bird,the great bustard Otis tarda

Factors responsible for individual variation in partial migration patterns are poorly known, and identifying possible causes of these changes is essential for understanding the flexibility in migratory behavior. Analyzing 190 life histories of great bustards Otis tarda radio‐tagged in central Spain, we investigated the changes in migratory tendency across lifetime in this long‐lived bird, and how migratory flexibility is related to individual condition. In females migratory behavior was not fixed individually. For every age class there was a fraction of ca 15–30% of females that changed their migratory pattern between consecutive years. Migrant females tended to remain sedentary in years when they had dependent young to attend. These findings show that the female migratory tendency is a behaviorally flexible, condition‐dependent trait. Immature females usually acquired their migratory behavior by learning from the mother in their first winter or by social transmission from other migratory females in their second winter. As for immature males, their summer migratory behavior was not related to mother–offspring transmission, but learned from adult males. We found that their age‐related increase in migratory tendency was associated to a greater integration in flocks of migrant adult males. These results show that within the partial migration system, cultural transmission mechanisms, either mediated by kin or not, and individual condition, may contribute to shape the migratory tendency. Our study reinforces the view that the migratory behavior is an evolutionary complex trait conditioned by the interaction of individual, social and environmental factors. Particularly in long‐lived species with extended parental care, the inherited migration program may be shaped by mother–offspring and social transmission of migratory patterns.     

Characterization of male killer whale (Orcinus orca) sexual maturation and reproductive seasonality

Longitudinal serum testosterone concentrations (n=10 males) and semen production (n=2 males) in killer whales were evaluated to: (1) characterize fluctuations in serum testosterone concentrations with respect to reproductive maturity and season; (2) compare morphologic changes to estimated age of sexual maturity, based on changes in serum testosterone concentrations; and (3) evaluate seasonal changes in sperm production. Classification of reproductive status and age class was based on differences (P < 0.05) in serum testosterone concentrations according to age; juvenile males ranged from 1 to 7 years (mean+/-S.D. testosterone, 0.13+/-0.20 ng/mL), pubertal males from 8 to 12 years (2.88+/-3.20 ng/mL), and sexually mature animals were 13 years and older (5.57+/-2.90 ng/mL). For captive-born males, serum testosterone concentrations, total body length and height to width ratio of the dorsal fin were 0.7+/-0.7 ng/mL, 495.6+/-17.5 cm and 1.14+/-0.13c m, respectively, at puberty; at sexual maturity, these end points were 6.0+/-3.3 ng/mL, 548+/-20 cm and 1.36+/-0.1cm. Serum testosterone concentrations were higher (P<0.05) from March to June than from December to February in pubertal animals (4.2+/-3.4 ng/mL versus 1.4+/-2.6 ng/mL) and than from September to December in sexually mature animals (7.2+/-3.3 ng/mL versus 4.0+/-2.0 ng/mL). Ejaculates (n = 90) collected from two males had similar (P > 0.05) sperm concentrations across all months. These data represent the first comprehensive study on male testosterone concentrations during and after sexual maturation, and on reproductive seasonality in the killer whale.     

Gonadal development and associated changes in liver size and sexual steroids during the reproductive cycle of captive male and female Atlantic cod (Gadus morhua L.)

Gametogenesis in female and male Atlantic cod (Gadus morhua L.) was investigated by sampling blood plasma and gonadal tissue from 19 to 33-month-old fish. The reproductive cycles of both female and male Atlantic cod are characterized by distinct annual variations in gonadal size and developmental stage and these are associated with changes in sex steroids and liver size. I(H) did not change during early gonadal development, but both spent females and males had lower I(H) than late maturing females and spermiating males, respectively. In females I(G) was correlated to plasma E2 levels and they were highest in spawning females. The lowest levels during the reproductive cycle were observed in spent females. Plasma T levels were low throughout ovarian development, and were at a minimum in spent females. 11-ketotestosterone in plasma of males increased rapidly during spermiation, while T increased at earlier testicular stages and reached maximum during spermiation. High plasma levels of steroids in male and female cod during spawning serve to promote further development and growth of less advanced stages of germ cells.     

Faecal sexual steroids in sex typing and endocrine status of great bustards

Faecal sexual steroids have been used in field studies evaluating the relationships between gender and the multiple factors influencing endocrine status of individuals. The determination of faecal steroids has been also proposed as an alternative, non-invasive sexing method when other methods were deemed impractical or risky for the health of birds. In this study, we quantified sexual steroid hormones in faeces of the great bustard (Otis tarda), a large and sexually dimorphic polyginic bird species that it is threatened and subjected to intense wildlife management. We evaluated differences between captivity and wild conditions, flocks and sexes, and used faecal steroids to develop sex determination procedures. We found similar steroid levels in captive and wild bustards, no differences between unisexual wild flocks and clear between-sexes differences in testosterone but not estradiol. Faecal steroids accurately discriminated gender in both captive and wild known-sex great bustards. Total testosterone concentration was always higher than estradiol concentration in faecal samples from males, but estradiol was not always higher than testosterone in females. Faecal steroids failed to reveal the presence of young males in female flocks during winter, despite faecal testosterone levels increased with age in a small sample of captive males. Our results show that faecal steroid measurement for both sexing and characterizing the endocrine status of great bustards is feasible, and therefore it should be valuable in wildlife management, especially in combination with additional information obtained from faeces as diet.     

Effects of photoperiod on sexual maturation and somatic growth in male Atlantic halibut (Hippoglossus hippoglossus L.)

A major obstacle in modern, intensive aquaculture is the precocious maturation of male fish, leading to decreased somatic growth and reduced filet quality. Effects of photoperiod on sexual maturation and growth in male Atlantic halibut were therefore examined. In June 1996, 1300 1+ fish of both sexes were distributed in two indoor tanks supplied with continuous light (LL) or a simulated natural photoperiod (SNP). In December 1996 and June 1997, 200 individuals were exchanged between the tanks creating six experimental groups that were followed until June 1998. LL stimulated growth and accelerated timing of first maturation by approximately 3 months. LL also appeared to interrupt circannual rhythmicity in sexual maturation. Sexual maturation led to reduced growth from 3 months pre-spawning and throughout the spawning season. Males that did not mature during the experiment attained the highest final body weight. All males reared on LL from June 1997 reached sexual maturity the following season. In contrast, only 26% of the males matured in the group transferred from LL to SNP in June 1997, and this group also had the highest final body weight. The results indicate a possible route for reducing the problem of precocious maturation in male halibut.     

Serum testosterone (T) and 5-alpha-dihydrotestosterone (DHT) in male fallow deer (Dama dama L.): seasonality and age dependence

1. Seasonal levels of testosterone (T) and 5-alpha-DHT (DHT) were determined by RIA in serum of seven adult male fallow deer living under outdoor conditions (G?ttingen, FRG; 51.32 degrees NL). 2. The study, spread over six consecutive years, reveals the following seasonal T changes: Minimum concentrations in November or December, around antler casting and at early antler growing phase; increasing levels in the course of late antler development (mineralization) with relatively high values around velvet shedding; peak levels occurring during onset of rutting period followed by a sharp decrease after the rut; and distinct and oscillating T peaks during late winter and spring. 3. For the first time DHT levels were measured in male cervidae. Surprisingly, large values of DHT were found and occasionally levels were higher than T concentrations, but without a significant annual periodicity. 4. In some individuals maximum DHT values were found shortly before and during the rut. 5. During several months of the annual cycle individual T and DHT profiles showed opposite relationships, particularly during antler growing phase and shortly before antler casting. 6. Around rut the size of T peak levels depends on animal age.     

Pollen development in male sterile mangosteen (Garcinia mangostana L.) and male fertile seashore mangosteen (Garcinia celebica L.)

Protoplasma - Mangosteen (Garcinia mangostana L.) is an economically important tropical fruit, yet the reproductive biology of this dioecious plant is complex. Male trees are not known, and female...     

Behavioural mechanisms that undermine species envelope models: the causes of patchiness in the distribution of great bustards Otis tarda in Spain

Despite the general success of species envelope models, capturing the fine-scale detail of patchiness in the distributions of some species is problematic. For great bustards in Spain, apparently suitable habitat patches remain unoccupied and cannot be distinguished from occupied patches in current distribution models. We consider philopatry and conspecific attraction as main behavioural mechanisms which could account for this patchiness, and then look for evidence of their influence on the distribution of great bustards across the whole of Spain. We compared the characteristics of habitat patches classed as suitable by a distribution model according to whether they were actually used or not. Occupied patches were larger than unoccupied patches and over-used in proportion to their size, suggesting aggregation and a metapopulation structure. Arguing that conspecific attraction may serve to transfer information about site history and environmental predictability (at least over a short time period), we compared the coefficients of variation in time-series of vegetation and climatic factors at occupied and unoccupied sites. Great bustards chose sites which were more environmentally stable at critical periods in the breeding cycle, "public information" that can only be gained from others rather than through sampling. There is thus evidence that both metapopulation dynamics and conspecific attraction influence the large scale distribution of great bustards in Spain. We discuss how alternative predictor variables and multi-stage analyses may help us to incorporate behavioural mechanisms into distribution models, but acknowledge that there are limits to the value of species envelope models for animal species making decisions.     

Effects of sex steroids on calling,locomotor activity,and sexual behavior in castrated male Japanese quail

Castrated male Japanese quail were implanted with Silastic capsules containing testosterone (T), estradiol-17β (E₂), 5β-dihydrotestosterone (5β-DHT), Δ₄-androstenedione (Δ₄) 5α-androstanedione (A), 5α-dihydrotestosterone (5α-DHT) or with empty capsules. Calling, monitored continuously and automatically, was induced significantly by T and Δ₄. Locomotor activity, also monitored continuously by floor deflection, was enhanced by T, Δ₄, and E₂. Additional data concerning heterosexual and homosexual behavior were obtained from castrated quails after implantation of T, Δ₄, E₂, or 5α-DHT. T and Δ₄ restored hetero- and homosexual behavior as did E₂ but to a lesser extent. 5α-DHT did not induce either sexual behavior. Growth of the cloacal protrusion was induced in birds implanted with T, Δ₄, A, and 5α-DHT but not with 5β-DHT and E₂. These results indicate that calling and locomotor activity enhancement (including sexual behavior) are two different components of reproductive behavior which require different androgens or their metabolites to be activated.     

Home range and activity patterns of male red deer (Cervus elaphus L.) in the alps

Summary From 1978 to 1981 in the Bavarian Alps (Southern West Germany) the home range and activity patterns of nine male red deer have been studied using radio-telemetry. The home range patterns definetely change with age. Younger stags first follow the patterns of their mothers, then often emigrate from these home ranges and establish new ones elsewhere. Except for the change in range at about 2^1/2 years of age, these patterns seem to be very constant in both spatial as well as seasonal position and the size of the home ranges. Winter and rutting ranges are relatively small, averaging 113 ha and 134 ha, respectively, whereas the mean size of the home ranges used from spring to autumn amounts to some 386 ha. Just as do the home range patterns, so also do activity patterns exhibit a marked annual cycle. The daily sum total of activity varies from about 9 h in winter to some 15 h in summer. The daily distribution of activity reveals a typical bimodal 24-h rhythm which in the course of the year also shows modifications according to the seasonally varying LD-ratio. In the discussion, earlier results on female red deer are compared to those of this study. Notable differences between sexes occur in the home range patterns and the annual cycle of daily activity.