Antelopes in The Pleistocene of Southern Africa

The study area of 2 786 ha contained over 200 springbok. The data were gathered during 78 separate day visits over four years. The most important social groups were (1) nursery herds of females and young; (2) harem herds similar to (1) but containing one adult male; (3) bachelor herds of males; and (4) solitary males. Other groupings, e.g. mixed adults of both sexes, were very uncommon. About twice as many adult females were to be found in harem herds as in nursery herds. The mean size of female herds (1 and 2 above) was between seven and nine animals (range 2-40) and of bachelor herds about five animals (range 2-14). Rutting and lambing tended to be seasonal. The lambing peak appeared to be about mid-September, though lambs were seen in every month September-April. It is suggested that lambing is correlated with the onset of Spring rains. Courtship activity seemed to be most intense during February-April. The adult sex ratio was about 85 males : 100 females.     

Geographic segregation and evidence of density‐dependent changes in sex ratios in an abundant colonial waterbird

Demographic information, such as geographic segregation of sexes and sex ratio data, is needed to develop, model and evaluate conservation and management strategies for wildlife. A variety of physiological, behavioral and environmental factors can influence segregation of sexes and sex ratios, many of which originate with density‐dependent processes. Departure from 50:50 sex ratios of double‐crested cormorants (Phalacrocorax auritus) collected during control efforts in breeding and wintering areas across their eastern range of the USA were evaluated using using a Z‐test as well as Stouffer's weighted Z‐tests. In addition, a specifically‐designed randomization test was used to evaluate density‐dependent effects on primary sex ratios in cormorants from egg collections and colony nest count data over a 21‐year period. Cormorants collected from breeding colonies were strongly male‐biased, whereas cormorants collected from feeding flocks were slightly biased toward females. Cormorants were partly segregated by sex on the wintering grounds, with significantly more males found in areas with intensive channel catfish aquaculture. The null hypothesis that females produced a balanced sex ratio independent of number of nesting cormorants was rejected: more male embryos were produced during rapid population growth, whereas at maximum nesting number more female embryos were produced. Once populations stabilized, the sex ratio was more equal. This examination of sex ratios indicates that different management methods and locations result in sex‐biased culling of cormorants. Sex‐biased culling in cormorants could make population reduction efforts more efficient and reduce overall take. We suggest further research to examine density‐dependent effects on primary sex ratios documented here.     

The Ecology of South African Estuaries Part X. St. Lucia: A Second Report

The active–inactive model predicts temporal variation in the operational sex ratio (OSR) throughout a breeding season, as a function of each male’s optimal strategy for finding mates. I tested the model using data for the raucous toad, Bufo rangeri, collected nightly over three breeding seasons. The numbers of active males and fertilizable females were correlated in two of the three breeding seasons. The OSR, defined as the average ratio of sexually active males to fertilizable females, decreased throughout each season, except for the first, when it rose to a peak before decreasing. The OSR fluctuated towards the end of the season in two of the three seasons, and rose again at the end in only one. Although the equal-performance assumption was violated, the temporal pattern of the OSR in this species complied largely with that predicted by the active–inactive model. Reasons for deviations from the model’s predictions are discussed. Despite the lack of data on mortality rates, this study represents the most comprehensive test of the model yet, as tests on other species have been based on data collected intermittently, as opposed to nightly, over only two breeding seasons.     

Breeding versus survival: proximate causes of abrupt population decline under environmental change in a desert rodent,the midday gerbil (Meriones meridianus)

Studying abrupt ecological shifts under gradual environmental change caused, in particular, by human activity is important for understanding the fundamental aspects and underlying mechanisms of ecological resilience. One of the rare well‐documented examples of an abrupt ecological shift is the delayed step transition of the population of a desert rodent, the midday gerbil (Meriones meridianus), from high‐abundance (1994–2002) to low‐abundance (2003–2017) regimes. This was in response to landscape transformation from desert to steppe caused by the drastic reduction of livestock in the rangelands of southern Russia after the collapse of the USSR in the early 1990s. In this study, we tested whether demographic parameters were correlated with the observed abrupt downward population shift. We found that reproductive activity (the percentage of breeding females, the number of litters, fecundity and the number of young recruited per female) showed no trend over time and did not differ between periods of high and low abundance. In contrast, the adult sex ratio (SR = males: females) decreased significantly with time and was as much as twice more female‐biased for the low‐abundance population regime. However, SR was not related to any reproductive parameter, including the percentage of breeding females. We conclude that proximate reasons for an abrupt population decline in M. meridianus are not associated with the changes in breeding patterns or mate limitation caused by the Allee effect but relate to the increased mortality as a result of the desert landscape being fragmented by steppezation. The mortality is expected to be higher for males as the mobile and dispersing sex.     

Narrow versus broad: sexual dimorphism in the wing form of western European species of the subgenus Avaritia (Culicoides,Ceratopogonidae)

While wing form is known to differ between males and females of the genus Culicoides, detailed studies of sexual dimorphism are lacking. In this study, we analyze sex-specific differences in the wing form of 5 species of the subgenus Avaritia, using geometric morphometrics and comparative phylogenetic methods. Our results confirm the existence of marked sexual dimorphism in the wing form of the studied species and reveal for the first time that while there is a shared general pattern of sexual shape dimorphism within the subgenus, sexual size dimorphism, and particular features of sexual shape dimorphism differ among species. Sexual shape dimorphism was found to be poorly associated to size and the evolutionary history of the species. The tight association of sexual shape dimorphism with aspect ratio suggests that the shape of the wing is optimized for the type of flight of each sex, that is, dispersal flight in females versus aerobatic flight in males. Moreover, the fact that interspecific shape differences are greater and more strongly associated to aspect ratio in males than in females might be indicating that in males the selective pressures affecting flight performance characteristics are more heterogeneous and/or stronger than in females among the studied species.     

Field evidence for colony size and aseasonality of breeding and in Ansell’s mole-rat,Fukomys anselli (Rodentia: Bathyergidae)

Ansell’s mole-rat, Fukomys anselli, is a cooperatively breeding bathyergid endemic to the Lusaka Province of Zambia. During a 12-month field study involving the capture of 33 colonies of mole-rats, the number of occupants, breeding females and sex ratio within colonies were recorded. While thirty of these social groups contained a single breeding queen, three were found to exhibit plural breeding among females, having two queens present simultaneously. Mean±S.E.M. colony size was 8.7±2.2 (range 6–16,n=33). The occurrence of plural breeding and small group size is consistent with the predictions of the aridity food distribution hypothesis for social species inhabiting mesic habitats. The sex ratio of the population was skewed towards females at 1.2:1. The mean mass of adult males was 63.0 ± 18.3 g (range 36.7–110.3, n=87) while that for adult females was 52.9±11.8 g (range 35.1–77.8, n=86). Pregnant and lactating females were found throughout the study period from February 2009 to February 2010, indicating an aseasonal pattern of breeding in this species. Autopsy of individuals (n=288) from the 33 colonies revealed a total of 19 pregnant females. Nine of these were in the latter stages of pregnancy and mean litter size was determined as 2.7 pups (range 1–4). Collectively, these new data reveal that Fukomys anselli share many similarities in life history and reproductive traits with the phylogentically closely related giant Zambian mole-rat, Fukomys mechowii.     

Effects of social and climatic factors on birth sex ratio in Macaca mulatta in Mount Taihangshan area

Sex allocation theory predicts the optimal investment to male and female offspring. However, a biased sex ratio requires explanations as to why the deviation occurs. Rhesus macaque (Macaca mulatta) is the most widely distributed nonhuman primate species and the Taihangshan macaque (Macaca mulatta tcheliensis) occupies the northern limit of all rhesus macaque natural populations worldwide. We observed one macaque troop (Wangwu‐1 [WW‐1]) inhabiting Taihangshan Macaque National Nature Reserve and recorded all birth events and the sex of newborn macaques from 2004 to 2013. Our aim was to apply the Trivers–Willard hypothesis to this free‐ranging rhesus macaque troop, and to understand the relationship between climatic parameters (precipitation and temperature) and birth sex ratio. We found that the total newborn macaques showed a female‐biased sex ratio at birth in the WW‐1 troop, but there were no significant biased birth sex ratios in all matriarchs and in high‐ranking and middle‐ranking matrilineal units. However, the low‐ranking macaque matrilineal unit was significantly female‐biased. Moreover, we found that the annual precipitation of the previous year was positively associated with the birth sex ratio, and there was an interactive effect of troop size and current winter temperature on the birth sex ratio. The underlying mechanisms for the effects of social and climatic factors on birth sex ratio could be complex, and we discuss several plausible explanations.     

Sex ratio bias in managed populations of hylobatids

A number of explanations have been proposed for the occurrence of sex ratio bias in primates, including the Trivers-Willard hypothesis on differential investment, local resource competition or enhancement as a result of sex-biased dispersal, dominance-related advantages conferred on one sex but not the other, and the fragile male hypothesis. However, none of these theories was thought to be applicable to monogamous primate species. Here, we examine data on zoo-housed populations of three hylobatid species to test the null hypothesis of equal sex ratio. We analyzed over 40 years of demographic data on Nomascus leucogenys, Hylobates lar and Symphalangus syndactylus. We identified a strong male-biased birth sex ratio in N. leucogenys. Male infant mortality was consistently higher than female infant mortality for N. leucogenys, but this difference was not significant. We found that prime-age N. leucogenys females (aged 13-20) produced significantly more male offspring than female offspring, and young S. syndactylus females (<13 years) produced significantly more female offspring. Recent field evidence of more flexible mating systems in H. lar and S. syndactylus may also be occurring in N. leucogenys. However, N. leucogenys has not been well studied in the wild. Ecological differences among species may further contribute to these observed patterns.     

Sex Steroid Levels in XY Males and Sex‐Reversed XX Males,of Rainbow Trout (Oncorhynchus mykiss), During the Reproductive Cycle

In this study, the annual cycle of the gonadal steroids testosterone (T), 11‐ketotestosterone (11‐KT), 17β‐oestradiol (E2) and 17α, 20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) was determined using radioimmunoassay and then compared, for XY males (n = 35) and sex‐reversed XX males (n = 27) rainbow trout, to establish possible endocrinology differences. Both in XY males and sex‐reversed XX males, significant correlation was shown between body weight and T (r = 0.5046 and 0.34078, respectively; p < 0.0001) or KT (r = 0.52494 and 0.43545, respectively; p < 0.0001) concentrations. Plasma androgen levels in XY and sex‐reversed XX males were similar and showed an intense seasonal variation. The highest levels for T and 11‐KT were detected from December to April with a peak in January (51.67 ± 5.11 and 61.95 ± 4.25 ng/ml, for XY males and 57.1 ± 5.82 and 59.27 ± 4.84 ng/ml, respectively, for XX males). In addition, there was a positive correlation (p < 0.0001) between T and 11‐KT levels for XY males (r = 0.7533) and sex‐reversed XX males (r = 0.6019). Concentrations of DHP in XY males also showed seasonal variation with a peak in February (25.18 ± 12.99 ng/ml). However, DHP levels in sex‐reversed XX males were undetectable (<0.1 ng/ml) over the year. Levels of E2 were undetectable through the year in both groups of trout. In conclusion, the androgenic and oestrogenic profiles of sex‐reversed XX males were similar to those observed in XY males. The only difference in the annual gonadal steroid cycle between XY and sex‐reversed XX males was in the DHP profile.     

Male heterogametic sex determination in Rana dybowskii based on sex-linked molecular markers

Identifying the mechanism for sex determination in amphibians is challenging. Very little is known about sex determination mechanisms of Rana dybowskii, a species of importance to evolutionary and conservation biology. We screened for sex-linked molecular markers in R. dybowskii in China using target region amplification polymorphism with 2 fixed primers against the sequences of Dmrt1. We found 2 male-linked molecular markers in R. dybowskii, which were 222 bp and 261 bp long. The detection rates of 222 bp marker in males form Xinglong, Huadian, and Dandong were 93.79%, 69.64%, and 13.64%, respectively, while the rate in females from Huadian was 27.50%. Besides, the detection rates of 261 bp marker in the above 3 regions were only observed in males at the rate of 93.79%, 87.50%, and 32.73%, respectively. The inheritance patterns of sex-linked molecular markers showed that the 2 sex-linked molecular markers were heterozygous. Compared to the XY-male parent, progeny from XX-pseudo-male parent possessed lower sex reversal ratio at the same rearing temperature, and the proportion of female froglets from an XX-pseudo-male parent was more than 95% at low rearing temperature (15°C). Our findings suggest that R. dybowskii displays male heterogamety, and the 2 sex-linked molecular markers may have a guiding significance for the protection and utilization of R. dybowskii.     

Sheep grazing causes shift in sex ratio and cohort structure of Brandt's vole: Implication of their adaptation to food shortage

Livestock grazing has been demonstrated to affect the population abundance of small rodents in grasslands, but the causative mechanism of grazing on demographic parameters, particularly the age structure and sex ratio, is rarely investigated. In this study, we examined the effects of sheep grazing on the cohort structure and sex ratio of Brandt's vole (Lasiopodomys brandtii) in Inner Mongolia of China by using large manipulative experimental enclosures during 2010–2013. Our results indicated that sheep grazing significantly decreased the proportion of the spring‐born cohort, but increased the proportion of the summer‐born cohort. Grazing increased the proportion of males in both spring and summer cohorts. In addition, we found a negative relation between population density and the proportion of the overwinter cohort. Our results suggest that a shift in the cohort structure and the sex ratio may be an important strategy for small rodents to adapt to changes in food resources resulting from livestock grazing.     

Parasites of South African wildlife. XVI. Helminths of some antelope species from the Eastern and Western Cape Provinces

The numbers and species of helminths recovered from one black wildebeest, Connochaetes gnou, three eland, Taurotragus oryx, 18 mountain reedbuck, Redunca fulvorufula, one red hartebeest, AIcelaphus buselaphus and two springbok, Antidorcas marsupialis, in the Mountain Zebra National Park, Eastern Cape Province; two black wildebeest, two grey rhebuck, Pelea capreolus, two mountain reedbuck and four springbok in the Karoo National Park, Western Cape Province; two bontebok, Damaliscus pygargus dorcas, two eland, two gemsbok, Oryx gazella and two springbok in the West Coast National Park, Western Cape Province; and a single springbok on a farm near Bredasdorp, Western Cape Province, are recorded. Nematodes belonging to a total of 12 genera and 20 species were identified. A single cestode was also recovered. Sixteen new host associations are recorded for the nematodes and one for the cestode Moniezia benedeni. Nematodirus spathiger had the widest host spectrum and with the exception of black wildebeest, was collected from all the host species examined.     

The role of weather and density dependence on population dynamics of Alpine‐dwelling red deer

The dynamics of red deer Cervus elaphus populations has been investigated across different environmental conditions, with the notable exception of the European Alps. Although the population dynamics of mountain‐dwelling ungulates is typically influenced by the interaction between winter severity and density, the increase of temperatures and the reduction of snowpack occurring on the Alps since the 1980s may be expected to alter this pattern, especially in populations dwelling at medium ‐ low elevations. Taking advantage of a 29‐year time series of spring count data, we explored the role of weather stochasticity and density dependence on growth rate and vital rates (mortality and weaning success), and the density‐dependent variation in body mass in a red deer population of the Italian Alps. The interaction between increasing values of density and snow depth exerted negative and positive effects on growth and mortality rates, respectively, while weaning success was negatively affected by increasing values of density, female‐biased sex ratio and snow depth. Body mass of males and females of different age classes declined as population size increased. Our data support the role of winter severity and density dependence as key components of red deer population dynamics, and provide insight into the species' ecology on the European Alps. Despite the recent decline of snowpack on the Alpine Region, the negative impacts of winter severity and population abundance on growth rrate (possibly mediated by the density‐dependent decline in body mass) confirms the importance of overwinter mortality in affecting the population dynamics of Alpine‐dwelling red deer.     

Sex ratio variation and sex determination in the mallee dragon Ctenophorus fordi

Recent evidence suggests that many Australian agamids show temperature‐dependent sex determination (TSD) with variation in sex determining mechanisms among closely related taxa. However, as shown in other vertebrates, sex ratios can also be influenced by genetic or phenotypic differences among females in their propensity to produce sons or daughters, and these influences might confound any thermal effects of incubation per se. To address these issues, we investigated the determinants of sex ratios in the mallee dragon Ctenophorus fordi, together with a detailed analysis of karyotypes. There was no detectable variation in sex ratios arising from variation among females, clutches or incubation temperatures, which might indicate genetic sex determination for this species. However, there was no evidence of cytologically distinct sex chromosomes using standard banding techniques. The sex ratio pattern in C. fordi strongly contrasts with the results for the congener Ctenophorus pictus, where sex ratios show variation among females. Thus, Australian agamids offer promising opportunities to address fundamental issues in sex ratio biology.     

Preference status does not indicate intrinsic quality differences in Drosophila pseudoobscura

The good genes hypothesis states that choosers prefer individuals of high intrinsic quality to individuals of lower intrinsic quality. Variation in longevity is thought to reflect, in part, intrinsic quality differences of individuals in addition to the costs of mating and reproduction. Here we report longevity variation of Drosophila pseudoobscura, a species in which previous experiments have demonstrated that individual mate preferences (pre-touching mate assessments) of females and males are associated with enhanced numbers of eclosed (adult) offspring and higher egg-to-adult survival (offspring viability). Using mate assessment arenas and protocols similar to those in a previous experiment that demonstrated fitness benefits to breeders and their offspring of mating with individuals they preferred, we tested the following predictions: (i) preferred discriminatees live longer than non-preferred discriminatees; (ii) males live longer than females; and (iii) virgins live longer than mated individuals. The experiment yielded 938 individuals for longevity analysis. Sex and mating status affected longevity: males lived longer than females, virgin females lived longer than mated females, but there were no differences in longevity for mated and virgin males. Non-preferred discriminatees of both sexes survived as long as preferred discriminatees, a result inconsistent with the prediction of the good genes hypothesis for mate preferences. To our knowledge, this is the first demonstration of the cost of reproduction for females in D. pseudoobscura and of longevity variation of preferred and non-preferred discriminatees.     

The Influence of the Size,Age and Sex on the Computed Tomographic Measured Size of the Pituitary Gland in Normal Horses

The objective of this study was to examine the influence of the size, age and sex of the horse on the size of the pituitary gland and determine the possibility of using the pituitary gland height‐to‐brain area ratio (P:B ratio) to allow comparison of different sized and aged horses. Thirty‐two horses without pituitary pars inter‐media dysfunction that underwent a contrast‐enhanced computed tomographic (CT) examination were included in a cross‐sectional study. On the CT images, the pituitary gland height was measured and the P:B ratio was calculated. These measurements were correlated to the size, age and sex of the horses. The pituitary gland height was significantly associated with the size (P < 0.001) and the age (P < 0.001), but not with the sex (P = 0.40), of the horses. No significant association was found between the P:B ratio and the size (P = 0.25), the age (P = 0.06) or the sex (P = 0.25) of the horses. In conclusion, the pituitary gland size varies between different sized and aged horses. The use of the P:B ratio is a valuable metric for making comparisons between the pituitary glands of these horses.     

Age- and Sex-Related Modifications of Hematology in Spanish Purebred Horse

The purpose of this study was to test the hypothesis that age and sex significantly modulate the changes in hematological parameters of physiologically healthy Spanish Purebred horse, establishing the reference values. Blood samples were obtained on a total of 159 horses (n = 77 males and n = 82 females), classified in four age groups: group A (1–2 years; n = 39), group B (>2–3 years; n = 38), group C (>3–4 years; n = 41), and group D (>4–7 years; n = 41). By means ADVIA 2020i, red blood cell (RBC), hemoglobin concentration (HB), packed cell volume, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration, platelets (PLTs), as well as total and differential white blood cells (WBCs) were determined. Total plasma protein was determined by spectrophotometry. Results obtained showed that sex had a limited influence on these parameters, being the HB higher in males and WBC higher in females (P = .047). Age caused a reduction in RBC, with a compensatory increase of MCV and MCH, decrease in WBC, PLT, lymphocytes (LYMPs), as well as an increase of N/L ratio (P = .047). Interactions between age and sex showed higher RBC in males than in females of the group B, and higher HB and WBC in males than in females of the group D. According to hematological data, Spanish Purebred horse was classified as a warm- or cold-blooded horse. Decline of RBC, WBC, and PLT parameters is a natural condition of horse with the advance of age, indicating a decrease of the narrow bone response.     

大连森林动物园散放区草食动物混养现状及模式初探

通过2004～2009年大连森林动物园的数据调查,从食物的营养价值,环境的丰富度,种群密度三个角度入手,针对大连森林动物园散放区草食动物在半散放混养条件下饲养繁殖及动物群体管理进行浅析,分析其驯养繁殖管理方案的优势,并从可持续利用的自然小生境角度出发,对建立稳定的动物关系群体提出建议。通过分析显示非洲的斑马,澳洲的羊驼,我国西北的岩羊比较适合大连的气候及混养的这种模式,种群数量逐年递增,繁殖状况良好,死亡率也比较低,尤其是岩羊,由于其善攀援跳跃,活动范围广,种群发展最好。长颈鹿,黑斑羚和跳羚适应能力较差,尤其是黑斑羚和跳羚,性情机警,敏感,应激反应强烈,引进后种群数量逐年递减,不适应此混养模式。作为东北地区物种的马鹿和梅花鹿,其种群情况也堪忧。鉴于这种情况,应从饲料营养和引种两方面加以改进以达到增加其种群数量的目的。     

Winter pairs of ruddy shelducks at Lashihai Lake,southwest China

It has been suggested that pairing behavior during winter in migratory ducks represents a trade‐off between costs (defense of the female) and benefits (early access to females). To investigate the benefits and costs for both sexes in wintering pairs of ruddy shelducks (Tadorna ferruginea), we compared time budgets for paired males and females, and surveyed the sex ratio of the birds wintering at Lashihai Lake, southwest China. The behavior of the paired ruddy shelducks was monitored for 5 activity types: feeding, resting (including sleeping), preening, drinking and warning. Feeding was the most dominant activity. The feeding time of both sexes increased as the winter season progressed. However, the paired females always spent significantly more time feeding and less time warning than the paired males. Paired ruddy shelducks had access to better feeding grounds than unpaired individuals, resulting in a food benefit for paired individuals over single individuals. Because the sex ratio of the wintering population was strongly male biased (M:F = 1.44:1.00), the paired male also gained the benefit of accessing a female in advance of the breeding season.     

Life-history characteristics of an age-validated established invasive African sharptooth catfish,Clarias gariepinus,population in a warm–temperate African impoundment

It has been suggested that the invasive, omnivorous Clarias garipienus is capable of rapid invasions and long-term persistence in recently inhabited freshwater systems. To test this hypothesis, the life history of the established, extralimital Darlington Dam (33°10’31”S, 25°09’13”E) population was investigated. By counting post-fluorescent mark increments on otoliths from 21 chemically tagged wild fish recaptured 244–537 days later, the deposition of growth zones, comprising alternating opaque and translucent bands, was validated as annual. Examination of sectioned otoliths from 175 fish revealed that the oldest fish, two males of 840 and 1074 mm total length (TL), were 25 years old – 10 years older than previously described for any C. gariepinus population. The oldest female was 885 mm TL and 21 years old. Length-at-age was subsequently described using the von Bertalanffy growth model. Combined-sex growth was best described as L_t = 931.7(1– exp(–0.15(t+2.43))) mm TL. Total mortality (Z) was calculated using catch curve analysis and the Chapman & Robson estimator to be 0.35/yr. The presence of specimens 15 years and older indicates that these fish established quicklyand supports the finding that mortality rates are low, which, in turn, suggests likely long-term population persistence.