scholarly journals Male density, a signal for population self-regulation in Alligator sinensis

2019 ◽  
Vol 286 (1900) ◽  
pp. 20190191
Author(s):  
Lan Zhao ◽  
Li-Ming Fang ◽  
Qiu-Hong Wan ◽  
Sheng-Guo Fang
Keyword(s):  
Gender Differences ◽  
Population Density ◽  
Time Lag ◽  
Self Regulation ◽  
Adult Males ◽  
Male Density ◽  
Lag Effect ◽  
Evolutionary Advantage ◽  
Reproduction Costs ◽  
Alligator Sinensis

The regulation of population density is suggested to be indirect and occurs with a time-lag effect, as well as being female centred. Herein, we present a quantitative analysis on the precise, timely and male-dominated self-regulation of Chinese alligator ( Alligator sinensis ) populations. Analysis of 31 years of data revealed gender differences in regulation patterns. Population dynamics were restricted by male density rather than population density, and population growth was halted (birth rate = 0) when male density exceeded 83.14 individuals per hectare, until some males were removed, especially adult males. This rapid and accurate response supports the notions of intrinsic mechanisms and population-wide regulation response. Furthermore, density stress affected mating success rather than parental care to juveniles, i.e. females avoided unnecessary reproduction costs, which may represent an evolutionary advantage. Our findings highlighted the importance of further studies on related physiological mechanisms that focus on four characteristics: quantity breeds quality, gender differences, male density thresholds and nonlinearity.

scholarly journals Juvenile Experience with Male Cues Triggers Cryptic Choice Mechanisms in Adult Female Redback Spiders

Insects ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 825
Author(s):  
Maydianne C. B. Andrade ◽  
Aiswarya Baskaran ◽  
Maria Daniela Biaggio ◽  
Maria Modanu
Keyword(s):  
Population Density ◽  
Strong Evidence ◽  
Chemical Cues ◽  
Mate Preferences ◽  
Social Cues ◽  
Adult Males ◽  
Volatile Chemicals ◽  
Male Density ◽  
The Social ◽  
Female Choosiness

Female choice may be linked to population density if the expected encounter rates with potential mates affects choosiness (the energy and risk engaged to express mate preferences). Choosiness should covary with male availability, which could be assessed using the social cues available during development. We tested whether the exposure of juvenile females to cues of male density affected the mechanisms of choosiness of adult Latrodectus hasselti spiders in two experiments simulating natural contexts. The juvenile females were exposed to (1) volatile chemicals from two densities of adult males (airborne cues), and (2) tactile, vibrational and chemical cues from adult males or other females (cohabitation cues). As adults, the females mated readily, regardless of the treatment, but there was strong evidence for post-copulatory mechanisms of choosiness in females exposed to cues of high male availability. These included abbreviated matings (in both experiments), cannibalism of the males before the mating was complete (cohabitation), and, remarkably, a reduction in the successful placement of internal sperm plugs (cohabitation). These shifts decrease the likelihood that the first mate would monopolize paternity if the female chose to mate again. We conclude that female choosiness may impose a strong selection on males despite the high mating rates, and these effects can hinge on the cues of male availability detected by juveniles.

Time-budget variations in relation to density-dependent social interactions in female and yearling male fallow deer during the rut

1997 ◽  
Vol 75 (6) ◽  
pp. 971-977 ◽  
Author(s):  
Christophe Pélabon ◽  
Petr E. Komers
Keyword(s):  
Population Density ◽  
Social Interactions ◽  
Time Budget ◽  
Resource Depletion ◽  
Fallow Deer ◽  
Operational Sex Ratio ◽  
Time Budgets ◽  
Adult Males ◽  
Density Dependent ◽  
Male Density

We investigated time-budget variations among female and yearling (socially immature 1.5-year-old) male fallow deer (Dama dama) during the rutting season in six captive populations in central Sweden. The effects of population density, male density, and operational sex ratio on time budgets were analyzed. Although no differences were apparent before the rut, populations differed in the time budgets of females and yearling males during the rut. During this period, the time spent by females in feeding and resting activities of yearling males decreased with increasing population density, whereas feeding and resting activities of yearling males decreased with increasing male density. Behaviour of adult males during the rut and interactions of adult males with other animals appeared to be the principal factors affecting the time budgets of both females and yearling males. Our results show that density-dependent effects may occur through social interactions alone, regardless of the effects on resource depletion. The decrease in the proportion of time spent in restoring (lying and grazing) behaviours represents an energy cost for both females and young males. Given the timing of the rut just before the winter, this cost may negatively effect the condition of individuals.

scholarly journals Size-at-maturity shift in a male-only fishery: factors affecting molt-type outcomes in Newfoundland and Labrador snow crab (Chionoecetes opilio)

2020 ◽  
Author(s):  
Darrell R J Mullowney ◽  
Krista D Baker
Keyword(s):  
Population Density ◽  
Newfoundland And Labrador ◽  
Cold Water ◽  
Large Male ◽  
Snow Crab ◽  
Size At Maturity ◽  
Chionoecetes Opilio ◽  
Factors Affecting ◽  
Male Density ◽  
Process Factors

Abstract A sex-asymmetric downward shift in size-at-terminal-molt has recently occurred in males in some portions of the Newfoundland and Labrador (NL) snow crab stock range, a first known occurrence for such processes in snow crab (Chionoecetes opilio) stocks. This study examines plausible factors promoting the shift in size-at-terminal-molt [synonymous with size-at-maturity (SaM)] including individual size, temperature, population density, and sex ratio. Analyses highlight expanse of cold water and large male density as being significant predictors of molt-type outcomes. A confluence of cold conditions and low density of large males promoted the SaM shift. In turn, the low male density was associated with recently elevated fishery exploitation rates under quota-controlled management. It remains unknown the extent to which the reduction in terminal size reflects a phenotypic vs. genotypic process. Factors affecting skip-molting in male snow crab are investigated, and we find that skip-molting occurs most frequently under extreme cold and high population density conditions. Potential complications arising from altered growth dynamics are discussed. Overall, the results advance knowledge on intraspecific competition processes within snow crab populations and inform fisheries management systems that male-only harvest strategies do not provide full protection from biological harm to aquatic resources through fishing.

scholarly journals A Weighted-Time-Lag Method to Detect Lag Vegetation Response to Climate Variation: A Case Study in Loess Plateau, China, 1982–2013

2021 ◽  
Vol 13 (5) ◽  
pp. 923
Author(s):  
Qianqian Sun ◽  
Chao Liu ◽  
Tianyang Chen ◽  
Anbing Zhang
Keyword(s):  
Climate Change ◽  
Loess Plateau ◽  
Time Lag ◽  
New Method ◽  
Climate Factors ◽  
The Loess Plateau ◽  
Climate Conditions ◽  
Vegetation Growth ◽  
Lag Effect

Vegetation fluctuation is sensitive to climate change, and this response exhibits a time lag. Traditionally, scholars estimated this lag effect by considering the immediate prior lag (e.g., where vegetation in the current month is impacted by the climate in a certain prior month) or the lag accumulation (e.g., where vegetation in the current month is impacted by the last several months). The essence of these two methods is that vegetation growth is impacted by climate conditions in the prior period or several consecutive previous periods, which fails to consider the different impacts coming from each of those prior periods. Therefore, this study proposed a new approach, the weighted time-lag method, in detecting the lag effect of climate conditions coming from different prior periods. Essentially, the new method is a generalized extension of the lag-accumulation method. However, the new method detects how many prior periods need to be considered and, most importantly, the differentiated climate impact on vegetation growth in each of the determined prior periods. We tested the performance of the new method in the Loess Plateau by comparing various lag detection methods by using the linear model between the climate factors and the normalized difference vegetation index (NDVI). The case study confirmed four main findings: (1) the response of vegetation growth exhibits time lag to both precipitation and temperature; (2) there are apparent differences in the time lag effect detected by various methods, but the weighted time-lag method produced the highest determination coefficient (R2) in the linear model and provided the most specific lag pattern over the determined prior periods; (3) the vegetation growth is most sensitive to climate factors in the current month and the last month in the Loess Plateau but reflects a varied of responses to other prior months; and (4) the impact of temperature on vegetation growth is higher than that of precipitation. The new method provides a much more precise detection of the lag effect of climate change on vegetation growth and makes a smart decision about soil conservation and ecological restoration after severe climate events, such as long-lasting drought or flooding.

Information technology investment and innovation performance: does investment paradox exist?

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Peinan Ji ◽  
Xiangbin Yan ◽  
Yan Shi
Keyword(s):  
Information Technology ◽  
Time Lag ◽  
Innovation Performance ◽  
Test Model ◽  
It Investment ◽  
Firm Innovation ◽  
Data Set ◽  
Content Type ◽  
Lag Effect ◽  
Enterprise Innovation

Purpose The purpose of this study is to deepen the understanding of the effects of information technology (IT) investment on firm innovation performance and examining the investment paradox effect in China. Design/methodology/approach Using a sample of China’ public firms IT investment data between 2010 and 2016, the authors establish a test model of IT investment and innovation performance. Findings The result indicates that IT investment in firms have no effect on innovation performance in the investment period. However, in the full sample and manufacturing sample, the IT investment has a significant positive effect on innovation performance in the post-investment years. In addition, this study finds that large companies and low-age companies may contribute more to innovation when firm investment in IT. Research limitations/implications There are several limitations in this research. First, the authors are failed to obtain a larger sample about the IT investment information data set in China, so this study was compelled to use limited sample data from China, hence, this could lead to errors of too early generalization. Second, the authors use the number of invention patent applications to represent the performance of enterprise innovation, which may not show enterprise innovation effectively. Third, the firms in the sample are all in China Listed Companies, so this may not accurately reflect the entire environment of firm innovation performance, and could possibly. Practical implications The research confirms that there is a paradox and time lag effect in IT investment, which enterprises should pay attention to. Originality/value Existing research confirms that corporate IT investments can bring new products or services. However, the authors still do not know whether IT investment has improved the company’s ability of innovation. This study will fill this gap and the industry effect and time lag effect of the influence of IT investment on innovative performance are also examined.

Numerical Investigations for the Effect of Slender Body on Dynamic Rolling Characteristics of a 80°/60° Double Delta Wing

2013 ◽  
Vol 444-445 ◽  
pp. 286-292
Author(s):  
Bing Han ◽  
Min Xu ◽  
Xi Pei ◽  
Xiao Min An
Keyword(s):  
Stokes Equations ◽  
Delta Wing ◽  
Time Lag ◽  
Slender Body ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Rolling Motion ◽  
Navier Stokes Equations ◽  
Lag Effect ◽  
Double Delta Wing

The effect of slender body on the rolling characteristics of a double delta wing is found by comparing the numerical simulation results of the double delta wing and wing-body configuration. The coupled computation system solving the Navier-Stokes equations and the rolling motion equation alternatively to obtain the unsteady vortical flow around the two configurations while rolling. The results conclusively showed the upwash effect of the slender body enhanced the energy of strake vortex and merged vortex.The aerodynamic lag of double delta wing is weak, contrarily, the time lag effect of the wing-body configuration is significant. The asymmetry vortices structure nearby the trailing edge are believed to be the main reason for the unsteady time lag effect.

Mating success of alternative male phenotypes and evidence for frequency-dependent selection in Chinook salmon, Oncorhynchus tshawytscha

2010 ◽  
Vol 67 (12) ◽  
pp. 1933-1941 ◽  
Author(s):  
Barry A. Berejikian ◽  
Donald M. Van Doornik ◽  
Rob C. Endicott ◽  
Timothy L. Hoffnagle ◽  
Eugene P. Tezak ◽  
...  
Keyword(s):  
Mating Success ◽  
Oncorhynchus Tshawytscha ◽  
Pacific Salmon ◽  
Adult Males ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Male Density ◽  
The Family ◽  
Breeding Groups ◽  
One Year

As with other species, frequency-dependent selection during reproduction has long been proposed as an important mechanism in maintaining alternative male reproductive phenotypes in Pacific salmon ( Oncorhynchus spp.). Jack salmon mature one year earlier than the youngest females in a population and are much smaller than older “adult” males. We tested the hypothesis that mating success of both phenotypes is consistent with the frequency-dependent selection model. By holding male density constant and varying the frequency of adults and jacks in eight separate breeding groups, we found that adult male access to females, participation in spawning events, and adult-to-fry reproductive success increased with their decreasing frequency in a breeding group. Jacks exhibited the same pattern (increasing success with decreasing frequency), although the relationships were not as strong as for adults. Overall, jack and adult males mated with a similar number of females, but jacks sired only 20% of all offspring. Observational data suggested that adult males benefited from sperm precedence associated with their ability to court females and enter the nest first at the time of spawning. Our work provides the first experimental evidence of frequency-dependent selection during mating in the family Salmonidae.

scholarly journals An SEIR Model for Assessment of Current COVID-19 Pandemic Situation in the UK

2020 ◽  
Author(s):  
Peiliang Sun ◽  
Kang Li
Keyword(s):  
Seasonal Influenza ◽  
Time Lag ◽  
Seir Model ◽  
Infected People ◽  
Proposed Model ◽  
Lag Effect ◽  
Novel Coronavirus ◽  
The Uk ◽  
Specific Symptoms ◽  
Limited Testing

AbstractThe ongoing COVID-19 pandemic spread to the UK in early 2020 with the first few cases being identified in late January. A rapid increase in confirmed cases started in March, and the number of infected people is however unknown, largely due to the rather limited testing scale. A number of reports published so far reveal that the COVID-19 has long incubation period, high fatality ratio and non-specific symptoms, making this novel coronavirus far different from common seasonal influenza. In this note, we present a modified SEIR model which takes into account the time lag effect and probability distribution of model states. Based on the proposed model, it is estimated that the actual total number of infected people by 1 April in the UK might have already exceeded 610,000. Average fatality rates under different assumptions at the beginning of April 2020 are also estimated. Our model also reveals that the R0 value is between 7.5–9 which is much larger than most of the previously reported values. The proposed model has a potential to be used for assessing future epidemic situations under different intervention strategies.

Observations on Activity Patterns, Population and Den Characteristics of The Water Rat Hydromys chrysogaster Along Badger Creek, Victoria.

1995 ◽  
Vol 18 (1) ◽  
pp. 71
Author(s):  
J.L. Gardner ◽  
M. Serena
Keyword(s):  
Population Density ◽  
Activity Patterns ◽  
Home Ranges ◽  
Adult Males ◽  
Fish Farms ◽  
Age Classes ◽  
Irrigation Channels ◽  
In Captivity ◽  
In The Wild ◽  
Hydromys Chrysogaster

The Water Rat Hydromys chrysogaster is Australia's largest amphibious rodent, occupying freshwater rivers, lakes, and coastal and estuarine habitats throughout the continent (Watts and Aslin 1981). Little is known of the species' social organisation or use of space in the wild although Harris (1978) suggested that adults might be intrasexually aggressive. The home ranges of all sex and age classes overlap to some extent but home ranges of adults of the same sex appear to overlap less (Harris 1978). Adult males occupy the largest home ranges which overlap those of one or more females. In captivity individuals kept in groups form hierarchies in which only the dominant females usually breed successfully (Olsen 1982). Fighting occurs primarily among males, with the highest incidence of injuries observed at the beginning of the main September-March breeding season (Olsen 1980, 1982). The results of trapping studies indicate that population density may vary considerably, with the greatest numbers of animals typically occupying man-modified habitats such as irrigation channels or fish farms (McNally 1960, Watts and Aslin 1981, Smales 1984). Aggressive behaviour appears to be related to pelage colour (phenotype) and population density; the higher the density the greater the number of injured individuals (Olsen 1980).

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