Structure of a population of the lizard Podarcis bocagei in northwest Spain: variations in age distribution, size distribution and sex ratio

2004 ◽  
Vol 54 (1) ◽  
pp. 57-75 ◽  
Author(s):  
Pedro Galán
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Size Distribution ◽  
Age Distribution ◽  
Lizard Species ◽  
Pregnant Females ◽  
Lacertid Lizard ◽  
High Maximum ◽  
Males And Females ◽  
Podarcis Bocagei

AbstractMark-recapture techniques were used to investigate population size, age distribution, size distribution and sex ratio in a population of the lacertid lizard Podarcis bocagei in an abandoned gravel pit in northwest Spain. The study was carried out over a 2-year period. Despite relatively high maximum longevity, the population age distribution was characteristic of small, short-lived lizard species (i.e., there was a relatively high proportion of immature individuals). Population size declined over the study period, largely because of a drop in the number of immature animals: this may be partially attributable to density-dependent factors, but was probably due largely to a decline in habitat favourability as a result of colonisation of the study site by vegetation. The sex ratio was significantly female-biased in all cohorts studied, not only among adults but also among juveniles and sub-adults. However, sex ratio at hatching (as investigated by laboratory hatching of clutches laid by captured pregnant females) did not differ significantly from one-to-one. There was no difference found in survival probabilities between males and females. The observed bias in sex ratio must therefore be attributed to between-sex differences in net emigration.

Brachioteuthis beanii Verrill, 1881 (Cephalopoda: Brachioteuthidae) in the northwest Atlantic

2020 ◽  
Vol 96 (2) ◽  
pp. 309-322
Author(s):  
Elizabeth K Shea ◽  
Judy Stadler ◽  
Annie Lindgren
Keyword(s):  
Nova Scotia ◽  
Food Web ◽  
Population Size ◽  
Size Distribution ◽  
Protected Area ◽  
Marine Protected Area ◽  
Measurement Data ◽  
Spawning Aggregation ◽  
Males And Females ◽  
External Ornamentation

Four research cruises to the Gully Marine Protected Area (known as "the Gully") off Nova Scotia, Canada (2007–2010) collected 1454 specimens of the oegopsid squid family Brachioteuthidae. All specimens were identified as Brachioteuthis beanii, and the 842 individuals collected in 2007 were used to describe the morphology and ecology of the species. A subset of 565 specimens were measured for population size distribution, and over 200 of these individuals (21–117 mm ML) were fixed, vouchered, measured, dissected, and sexed to examine the internal and external characters of juveniles, males, and females. Specimens <40 mm ML were almost entirely juveniles. Specimens 40–49 mm ML were a mix of juveniles, males, and females. The smallest specimens, where the spermatophoric complex and nidamental glands could be identified, were approximately 39 mm ML in both males and females, suggesting that maturation begins at roughly the same size in both sexes. Specimens >50 mm ML could be sexed based solely on the color and texture of the mantle. Male mantles were fusiform in shape with few small, widely spaced chromatophores and a reticulated net on the mantle that developed concurrent with the internal spermatophoric complex. Females had a flaccid mantle with larger and denser chromatophores on the mantle and head and no external ornamentation (i.e., ridges or nodules). Measurement data showed that males had slightly larger arms and wider fins than females. The high abundance of B. beanii at the Gully in August/September may be a spawning aggregation and suggests that this small squid is an important component of the canyon food web.

scholarly journals Effect of exposure time of pregnant females guppies, Poecilia reticulata Peters, in 17a-methyltestosterone solution on sex ratio of their offsprings

2007 ◽  
Vol 1 (1) ◽  
pp. 47
Author(s):  
M. Zairin Junior ◽  
A. Yunianti ◽  
R.R.S.P.S. Dewi ◽  
Kusman Sumawidjaja
Keyword(s):  
Sex Ratio ◽  
Exposure Time ◽  
Treatment Duration ◽  
Poecilia Reticulata ◽  
Female Offspring ◽  
Control Group ◽  
Time Interval ◽  
Water Flea ◽  
Pregnant Females ◽  
Males And Females

<p>ABSTRACT</p><p>This experiment was carried out to study the effect of female broodstocks immersion in 17amethyltestosterone (MT) solution on sex ratio of their offspring, Three-months old males and females were paired to mate in aquaria for four days.  Broodstocks were fed with frozen blood worm and water flea 2-3 tii-nes daily.  Twelve days after mating, female broodstock were treated by immersing in 2 mg/1 MT solution for 0. 6, 12, 24 and 48 hours.  Birthed guppy babies were collected and reared separately from their parents.  During the rearing period, the babies were fed with artemia nauplius and silkworm until identification for male and female.  Percentage of female offspring in control group were higher than those of male.  Exposure of pregnant females to MT solution for 0, 6, 12, 24, and 48 hours resulted in 42, 1'/o, 51%, 84,6%, 1 00%, dan 100% of males offspring, respectively.  The best result was obtained from 24 hours treatment.  Longer treatment duration tend to shorten time interval between treatment and birth. Key words :  Guppy, 17(x-methyltestosterone, exposure time, broodstock immersion, sex ratio   ABSTRAK Penefitian ini bertuiuan untuk mengetahui pengaruh lama waktu perendaman induk di dalam larutan hormon 17a-metiltestosteron (MT) terhadap nisbah kelamin ikan gapi.  Induk Ikan gapi berumur tiga bulan dikawinkan berpasangan di dalam akuarium selama empat hari Induk diberi pakan cuk merah beku dan kutu air dengan frekuensi 2-3 kali sehari.  Dua belas hari setelah masa perkawinan, induk betina diberi perlakuan berupa perendaman di dalam larutan MT 2 mg/1 selama 0 (kontrol), 6, 12, 24, dan 48 jam.  Anak-anak ikan gapi yang baru lahir dipelihara terpisah dari induknya.  Selama masa pemeliharaan, anak ikan gapi diberi pakan nauplius artemia dan cacing rambut.  Pemeliharaan berlangsung sampai jenis kelamin anak ikan gapi dapat diidentifikasi.  Persentase anak ikan gapi betina pada semua ulangan kontrol lebih tinggi daripada .iantan dengan perbandingan persentase rata-rata 57,9%: 42,1%.  Adapun pada lama waktu perendaman 0, 6, 12, 24, dan 48 jam, menghasilkan persentase anak ikan gapi berfenotip jantan berturut-turut sebesar 42,1%, 51%, 84,6%, 100%, dan 100%.  Lama waktu perendaman terbaik adalah 24 jam.  Selain itu terdapat kecenderungan bahwa semakin lama waktu perendaman semakin cepat kelahirannya. Kata kunci :  Ikan gapi, 17ot-metiltestosteron, lama perendaman, perendaman induk, nisbah kelamin</p>

scholarly journals Population parameter, size distribution and sex ratio of the blue shark (Prionace glauca Linnaeus, 1758) caught in the southern of Nusa Tenggara

2021 ◽  
Vol 890 (1) ◽  
pp. 012054
Author(s):  
U Chodrijah ◽  
R Faizah
Keyword(s):  
Sex Ratio ◽  
Size Distribution ◽  
Utilization Rate ◽  
Population Parameter ◽  
Fishing Mortality ◽  
Blue Shark ◽  
Prionace Glauca ◽  
Management Actions ◽  
Exploitation Rate ◽  
Males And Females

Abstract The blue shark (Prionace glauca Linnaeus, 1758) was a targeted shark caught in the artisanal fisheries in Tanjung Luar, West Nusa Tenggara. This species was caught by drifting longline. The study aims to obtain the parameter population, size distribution and sex ratio of the blue shark from these waters. The research was conducted in Tanjung Luar during 2019-2020, and a total of 1676 blue sharks were caught by drift longline. The data were analyzed by using ELEFAN II. The size blue sharks varied from 73 cm to 397 cm total length (TL), with mean length was 266 cm for males and 72-390 cm with mean length 255,61 cm TL for females. Male was dominated sex ratio. The equation growth for blue shark for male was Lt = 400 (1 – e−0.28 (t-0.2921)) and female was Lt = 390 (1 – e−0.25 (t-0.3307)) . The first captured (Lc ) length for males and females are 267.76 cm and 250.98 cm, respectively. Natural mortality (M) = 0.42/year, the fishing mortality (F ) = 0.50/year. The exploitation rate was > 0.55/year it means that utilization rate of blue sharks in Southern of Nusa Tenggara waters was susceptible to overfishing. This condition needs good management actions for this species.

scholarly journals Population dynamics of Aegla manuinflata Bond-Buckup and Santos 2009 (Decapoda: Aeglidae), an threatened species

2014 ◽  
Vol 26 (2) ◽  
pp. 154-162 ◽  
Author(s):  
André Trevisan ◽  
Sandro Santos
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Threatened Species ◽  
Sampling Method ◽  
Age Distribution ◽  
Population Data ◽  
Reproductive Period ◽  
Males And Females ◽  
Digital Caliper ◽  
Recruitment Period

AIM: We evaluate the population density, median size of males and females, age distribution, sex-ratio, reproductive period and recruitment period of the threatened species Aegla manuinflata. METHODS: Monthly samplings were made from May 2006 to April 2007 in the Passo Taquara stream, Brazil. An extra sampling was performed at each season of the year in order to determine population density. Animals were captured with traps and handnets. All the captured specimens were sexed and had their cephalotoraccic length measured with a digital caliper (0.01 mm), and were then released back in the stream. RESULTS: A total of 888 individuals were analyzed, including 17 unsexed juveniles, 572 males, 274 females and 25 ovigerous females. A mean population density of 1.52 ind/m² was estimated. Males showed median sizes larger than females (p < 0.01). Age distribution was bimodal for both males and females. Females predominated in intermediary size-classes, while males were more abundant in the larger classes, with no differences for the lower classes. The sex-ratio, in general, followed the expected 1:1 proportion only in the months of May, October and November (p > 0.05). Males and females caught only with handnet follow the expected 1:1 proportion in all months of the year (p > 0.05), demonstrating that the sampling method clearly affects the results. Ovigerous females and juveniles were registered in all seasons of the year and there is no significant different in the proportion of these animals among the seasons (p > 0.05), indicating continuous reproduction. CONCLUSIONS: Population data of this study can be used as a basis for the creation of conservation measures of A. manuinflata, since the species is considered vulnerable.

Some Population Parameters and Seasonal Changes in the Weights of Internal Organs of Rabbits, Oryctolagus cuniculus (L.), at Macquarie

1980 ◽  
Vol 7 (2) ◽  
pp. 235 ◽  
Author(s):  
IJ Skira
Keyword(s):  
Sex Ratio ◽  
Age Distribution ◽  
Food Plants ◽  
Adult Males ◽  
Internal Organs ◽  
Significant Difference ◽  
Quality Of Food ◽  
Males And Females ◽  
The Mean

The sex ratio, age distribution and seasonal variations in body weight and weight of several internal organs of rabbits were studied, between December 1973 and February 1975 on subantarctic Macquarie Island. The sex ratio (male : female) was 1 : 0.84. Rabbits over 18 months old predominated in the population in summer 1973-74, but from April 1974 the population was composed equally of adults and rabbits less than 18 months old. The second half of the 1973-74 breeding season contained only 36% of the births of that season, but supplied 70% of the young rabbits that entered the population. Females weighed more than male rabbits in the summer but males were heavier in the winter. The mean weights of liver, kidneys and spleen in adult females were significantly heavier in the summer, when food plants were growing and the quality of food highest, than in winter. In adult males these mean weights were similar in summer and winter. Both males and females showed no significant difference in the mean weight of adrenal glands between seasons.

Adult Sex Ratio in the Parnassius Mnemosyne Butterfly: Effects of Survival, Migration, And weather

2009 ◽  
Vol 55 (3) ◽  
pp. 233-252 ◽  
Author(s):  
Petr Vlasanek ◽  
David Hauck ◽  
Martin Konvicka
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Linear Models ◽  
Adult Emergence ◽  
Adult Males ◽  
Effective Population ◽  
Weather Variables ◽  
Animal Populations ◽  
Adult Sex Ratio ◽  
Males And Females

Sex ratio biases in animal populations influence the genetically effective population size, and thus are of interest in conservation. A butterfly group in which many authors report biases towards males is the genusParnassiusLatreille, 1804 (Papilionidae). Using a vulnerable woodland species,P. mnemosyne, we carried out a detailed marking campaign designed to eliminate biases towards individual sexes on marking. We then estimated the numbers of males and females using constrained linear models (CLMs) (Cormack-Jolly-Seber and Jolly-Seber in MARK); compared details of mobility between males and females using the Virtual Migration (VM) model; and built CLMs containing weather variables in order to directly assess weather effects on survival. The estimated population size was 4000 adults, with a male: female sex ratio of 1.5-1.6. Both daily and average catchability were higher for males, while the residence values (i.e., survival) were higher for females. Migration parameters were similar for the sexes, with slightly lower male survival within patches and slightly higher male emigration. CLMs with weather substituted for or added to marking days performed worse than models with mere marking days, and although weather affected the sexes differently, males still retained lower survival. The surplus of adult males in the studied population ofP. mnemosynewas real, not caused by increased male survival or a difference in mobility. Therefore, the bias toward males must appear prior to adult emergence, probably during the larval period.

scholarly journals Can we reestablish a self-sustaining population? A case study on reintroduced Crested Ibis with population viability analysis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yashuai Zhang ◽  
Fang Wang ◽  
Zhenxia Cui ◽  
Min Li ◽  
Xia Li ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Carrying Capacity ◽  
Wild Population ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Viability Analysis ◽  
Crested Ibis ◽  
Reintroduced Population

Abstract Background One of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability. The wild population of the Crested Ibis (Nipponia nippon) has recovered to approximately 4400, and several reintroduction programs have been carried out in China, Japan and Korea. Population viability analysis on this endangered species has been limited to the wild population, showing that the long-term population growth is restricted by the carrying capacity and inbreeding. However, gaps in knowledge of the viability of the reintroduced population and its drivers in the release environment impede the identification of the most effective population-level priorities for aiding in species recovery. Methods The field monitoring data were collected from a reintroduced Crested Ibis population in Ningshan, China from 2007 to 2018. An individual-based VORTEX model (Version 10.3.5.0) was used to predict the future viability of the reintroduced population by incorporating adaptive patterns of ibis movement in relation to catastrophe frequency, mortality and sex ratio. Results The reintroduced population in Ningshan County is unlikely to go extinct in the next 50 years. The population size was estimated to be 367, and the population genetic diversity was estimated to be 0.97. Sensitivity analysis showed that population size and extinction probability were dependent on the carrying capacity and sex ratio. The carrying capacity is the main factor accounting for the population size and genetic diversity, while the sex ratio is the primary factor responsible for the population growth trend. Conclusions A viable population of the Crested Ibis can be established according to population viability analysis. Based on our results, conservation management should prioritize a balanced sex ratio, high-quality habitat and low mortality.

scholarly journals Effect of Pheromone Blend Components, Sex Ratio, and Population Size on the Mating of Cadra cautella (Lepidoptera: Pyralidae)

2020 ◽  
Vol 20 (6) ◽  
Author(s):  
Abeysinghe Mudiyanselage Prabodha Sammani ◽  
Dissanayaka Mudiyanselage Saman Kumara Dissanayaka ◽  
Leanage Kanaka Wolly Wijayaratne ◽  
William Robert Morrison
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Management Practices ◽  
Mating Disruption ◽  
Current Knowledge ◽  
Mating Status ◽  
Cadra Cautella ◽  
Synthetic Chemicals ◽  
Population Sizes ◽  
Lepidoptera Pyralidae

Abstract The almond moth Cadra cautella (Walker), a key pest of storage facilities, is difficult to manage using synthetic chemicals. Pheromone-based management methods remain a high priority due to advantages over conventional management practices, which typically use insecticides. Cadra cautella females release a blend of pheromone including (Z, E)-9,12-tetradecadienyl acetate (ZETA) and (Z)-9-tetradecadien-1-yl acetate (ZTA). The effect of these components on mating of C. cautella and how response varies with the population density and sex ratio remain unknown. In this study, the mating status of C. cautella was studied inside mating cages under different ratios of ZETA and ZTA diluted in hexane and at different population sizes either with equal or unequal sex ratio. The lowest percentage of mated females (highest mating disruption [MD] effects), corresponding to roughly 12.5%, was produced by a 5:1 and 3.3:1 ratio of ZETA:ZTA. Populations with equal sex ratio showed the lowest percentage of mated females, at 20% and 12.5% under lower and higher density, respectively. The next lowest percentage of mated females was produced when the sex ratio was set to 1: 2 and 2:1 male:female, with just 25% and 22.5% of moths mated, respectively. This study shows that mating status of C. cautella is influenced by ZETA:ZTA ratio, sex ratio, and population size. This current knowledge would have useful implications for mating disruption programs.

Demography and Group Structure in Wedgecapped Capuchin Monkeys, Cebus Olivaceus

Behaviour ◽  
1988 ◽  
Vol 104 (3-4) ◽  
pp. 202-232 ◽  
Author(s):  
John G. Robinson
Keyword(s):  
Sex Ratio ◽  
Life Table ◽  
Group Structure ◽  
Age Distribution ◽  
Capuchin Monkeys ◽  
Demographic Parameters ◽  
Adult Size ◽  
Sex Composition ◽  
Cebus Olivaceus ◽  
Age And Sex

AbstractThe extent to which population demography determines the age and sex composition of primate groups was examined using data from a population of wedge-capped capuchin monkeys Cebus olivaceus in central Venezuela. Demographic parameters were derived from censuses of individually recognized, aged, and sexed individuals living in nine groups over a ten year period. Animals were aged by extrapolation from census data. Animals of both sexes were classed as infants during their first year, and juveniles until they reached six years of age. Females reach sexual maturity at this time, while males were classed as subadults until they reached full adult size at age 12. Adulthood lasts at least 30 years in females, at least 24 years in males. Age-sex class specific mortality and fecundity rates generated a life table which indicated that the population was increasing (r = 0.087) between 1977 and 1986. The age and sex composition of the nine groups was described annually. On average, non-adults made up 60% of a group, with this percentage increasing with group size. There were more females than males in all groups in all years. The strong female-biased adult sex ratio (1:4.4) was a consequence of a biased birth sex ratio (1:1.9), higher female than male survivorship especially between the ages of 3 and 7 when males were dispersing, and a pronounced sexual bimaturism. The stable age distribution derived from the life table successfully predicted the observed average distribution of age-sex categories in groups. This suggests that the group structure of Cebus olivaceus groups is not a consequence of intragroup social interactions, but results from demographic parameters.

Variation in Weight, Size, and Sex Ratio of Coccinellid Adults (Coleoptera: Coccinellidae)

1966 ◽  
Vol 98 (6) ◽  
pp. 639-644 ◽  
Author(s):  
B. C. Smith
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Water Content ◽  
Food Supply ◽  
Sexual Differences ◽  
Intraspecies Variation ◽  
Food Scarcity ◽  
Food Requirement ◽  
Males And Females

AbstractThe weight and size of coccinellid adults varied with species, sex, and feeding. Intraspecies variation in weight was generally similar in the eight species studied. Females were more variable than males in body size. Females of some species were heavier and larger than males, and species can be classified on a basis of difference in the weight and size of the sexes.An increase in the food supply after a period of food scarcity affected the sex ratio, as the minimum food requirement of females was greater than males. Females increased in weight more rapidly than males after feeding. The availability of food in the field affected the weight and size of some species. Adult water content was influenced by feeding but not by sex or the quantity of food given to the larva.Males were more abundant in species with small sexual differences in weight and size. The degree of difference in weight and size between males and females may be used as a criterion to select species that are best adapted to survive when food is scarce.

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