Estimates of sex ratio require the incorporation of unequal catchability between sexes

Evan J. Pickett; Michelle P. Stockwell; Carla J. Pollard; James I. Garnham; John Clulow; Michael J. Mahony

doi:10.1071/wr11193

Estimates of sex ratio require the incorporation of unequal catchability between sexes

Wildlife Research ◽

10.1071/wr11193 ◽

2012 ◽

Vol 39 (4) ◽

pp. 350 ◽

Cited By ~ 10

Author(s):

Evan J. Pickett ◽

Michelle P. Stockwell ◽

Carla J. Pollard ◽

James I. Garnham ◽

John Clulow ◽

...

Keyword(s):

Sex Ratio ◽

Population Size ◽

Population Studies ◽

Capture Probability ◽

Ecological Studies ◽

Mark Recapture ◽

Closed Population ◽

Litoria Aurea ◽

Biased Sex Ratio ◽

Probability Methods

Context Estimates of the sex ratio of a population are a common summary statistic used for ecological studies and conservation planning. However, methods to determine the sex ratio often ignore capture probability, which can lead to a perceived bias in the sex ratio when the sexes are detected at different rates. Aims To illustrate the bias from conventional count-based analysis methods for determining sex ratio by comparison with analytical methods that include capture probability. Methods Closed-population mark–recapture analysis was used to determine the population size of each sex within a population of green and golden bell frogs (Litoria aurea). This was then compared with the traditional count-based methods of estimating sex ratio to determine the effect of incorporating capture probability on the sex ratio estimate. Key results More males than females were detected during surveys, producing a male-biased sex ratio when there was no incorporation of capture probability. Mark–recapture results indicated a similar population size between the two sexes, suggesting that the sex ratio is closer to even. Conclusions Methods to estimate sex ratio that incorporate capture probability can significantly reduce the bias obtained from count data. Implications We suggest that population studies must incorporate capture probability to determine the sex ratio of a population.

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Population size of Aegla longirostri Bond-Buckup and Buckup, 1994 (Crustacea, Decapoda, Anomura): comparison of methods with the mark-recapture technique in closed population

Nauplius ◽

10.1590/2358-2936e2018016 ◽

2018 ◽

Vol 26 (0) ◽

Cited By ~ 1

Author(s):

Joele S. Baumart ◽

Gláucia B. Cogo ◽

Fidel E.C. Morales ◽

Sandro Santos

Keyword(s):

Population Size ◽

Comparison Of Methods ◽

Mark Recapture ◽

Closed Population

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Population Studies of the Polyandrous Spotted Sandpiper

The Auk ◽

10.1093/auk/100.2.272 ◽

1983 ◽

Vol 100 (2) ◽

pp. 272-285 ◽

Cited By ~ 38

Author(s):

Lewis W. Oring ◽

David B. Lank ◽

Stephen J. Maxson

Keyword(s):

Sex Ratio ◽

Population Size ◽

Population Studies ◽

Early Age ◽

Young Males ◽

Return Rates ◽

Fledging Success ◽

The Difference ◽

Short Time ◽

Older Males

Abstract A color-banded population of Spotted Sandpipers (Actitis macularia) was studied over a 10-yr period on Little Pelican Island, Leech Lake, Minnesota. A total of 75 females and 107 males bred for 144 ♀ ♀ yr and 200 ♂ ♂ yr. The observed skew in the population sex ratio was due primarily to behavioral exclusion of inexperienced females. Density appeared to limit population size and productivity. Locally hatched chicks accounted for 31% and 40% of the breeding females in the final 2 yr. Females laid eggs for 1.35-2.06 males per year. Experienced females had significantly more mates, eggs, chicks, and fledglings than did inexperienced females. Locally hatched chicks accounted for 21% and 19% of the breeding males in the final 2 yr. Males mated with 1.0-1.4 females per year. Experienced males had more mates and received more replacement eggs than did inexperienced males; in contrast to females, however, inexperienced males had no less hatching or fledging success than did experienced males. Thirty-eight marked females and 16 marked males tried unsuccessfully to enter the population, and 6 females and no males were observed to be nonbreeders all season long. Of 1,142 eggs, 442 hatched and 256 fledged. Experienced birds returned to breed more often in subsequent years than did inexperienced ones (61% vs. 50%). Return rates of successful birds were consistently higher than those of unsuccessful birds, the difference decreasing with age. Young males appeared to be less site-faithful than were females and older males. Successfully breeding females lived an average of 3.7 yr. Relative to other scolopacids with multipurpose territories, the Spotted Sandpiper is considered a pioneering species that quickly and frequently colonizes new sites, emigrates in response to reproductive failure, breeds first at an early age, lives a relatively short time, lays many eggs per female per year, and has relatively low nest success.

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Finite mixture models of heterogeneous capture probabilities for mark-recapture estimation of closed population size

10.31274/rtd-180813-10973 ◽

2001 ◽

Author(s):

Michael John Wallendorf

Keyword(s):

Population Size ◽

Mixture Models ◽

Finite Mixture Models ◽

Finite Mixture ◽

Mark Recapture ◽

Closed Population

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

Avian Research ◽

10.1186/s40657-021-00250-z ◽

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.

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

Journal of Insect Science ◽

10.1093/jisesa/ieaa128 ◽

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.

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No room for males in caves: Female‐biased sex ratio in subterranean amphipods of the genus Niphargus

Journal of Evolutionary Biology ◽

10.1111/jeb.13917 ◽

2021 ◽

Author(s):

Ester Premate ◽

Špela Borko ◽

Simona Kralj‐Fišer ◽

Michael Jennions ◽

Žiga Fišer ◽

...

Keyword(s):

Sex Ratio ◽

Biased Sex Ratio

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Male-biased sex ratio in Argulus canadensis Wilson, 1916 (Crustacea: Branchiura) ectoparasitic on sticklebacks

Canadian Journal of Zoology ◽

10.1139/z89-296 ◽

1989 ◽

Vol 67 (8) ◽

pp. 2078-2080 ◽

Cited By ~ 3

Author(s):

Robert Poulin ◽

Gerard J. FitzGerald

Keyword(s):

Salt Marsh ◽

Sex Ratio ◽

Laboratory Experiments ◽

Fish Predation ◽

Reproductive Behaviour ◽

Egg Deposition ◽

Alternative Hypotheses ◽

Biased Sex Ratio ◽

The Difference ◽

Fish Hosts

Females of the ectoparasitic crustacean Argulus canadensis must leave their fish hosts at least temporarily to deposit their eggs on the substrate. To test the hypothesis that this difference in reproductive behaviour between the two sexes could result in male-biased sex ratios on their stickleback hosts, we sampled sticklebacks in tide pools of a Quebec salt marsh from early July to early September 1986. During this period, fish harboured significantly more male than female A. canadensis. Laboratory experiments were done to test two alternative hypotheses offered to explain this biased sex ratio. The first hypothesis was that male A. canadensis were more successful than females in attacking their stickleback hosts; however, we found no differences in attack success on their hosts between the two parasite sexes. The second hypothesis was that sticklebacks ate more female than male A. canadensis. Although males were less vulnerable to fish predation than females, the difference was not significant. We conclude that sexual differences in reproductive behaviour, i.e., egg deposition behaviour of females, can account for the male-biased sex ratio of A. canadensis on sticklebacks.

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The closed-subpopulation method and estimation of population size from mark-recapture and ancillary data

Canadian Journal of Zoology ◽

10.1139/z99-218 ◽

2000 ◽

Vol 78 (2) ◽

pp. 320-326 ◽

Cited By ~ 6

Author(s):

Frank AM Tuyttens

Keyword(s):

Population Size ◽

Ancillary Data ◽

Mark Recapture ◽

Animal Populations ◽

Accuracy And Precision ◽

Population Size Estimates ◽

Minimum Number ◽

Flexible Framework ◽

And Performance ◽

Better Than

The algebraic relationships, underlying assumptions, and performance of the recently proposed closed-subpopulation method are compared with those of other commonly used methods for estimating the size of animal populations from mark-recapture records. In its basic format the closed-subpopulation method is similar to the Manly-Parr method and less restrictive than the Jolly-Seber method. Computer simulations indicate that the accuracy and precision of the population estimators generated by the basic closed-subpopulation method are almost comparable to those generated by the Jolly-Seber method, and generally better than those of the minimum-number-alive method. The performance of all these methods depends on the capture probability, the number of previous and subsequent trapping occasions, and whether the population is demographically closed or open. Violation of the assumption of equal catchability causes a negative bias that is more pronounced for the closed-subpopulation and Jolly-Seber estimators than for the minimum-number-alive. The closed-subpopulation method provides a simple and flexible framework for illustrating that the precision and accuracy of population-size estimates can be improved by incorporating evidence, other than mark-recapture data, of the presence of recognisable individuals in the population (from radiotelemetry, mortality records, or sightings, for example) and by exploiting specific characteristics of the population concerned.

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