Abstract
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.
Highlights
Density dependence is a general tendency and fundamental principle of population ecology [1]
Population cycles usually persist for years or even generations, and are subject to self-regulation with the death of offspring contributing the most to population dynamics [3]
A study on red squirrels (Sciurus vulgaris L.) suggested that reproduction rate decreased when female density was high [12], which suggests that females are at the core of population regulation
Summary
Density dependence is a general tendency and fundamental principle of population ecology [1]. Population cycles usually persist for years or even generations, and are subject to self-regulation with the death of offspring contributing the most to population dynamics [3]. This regulation represents fitness returns in which trade-offs exist between cost and benefit [4]. Wild populations are only distributed in the Anhui Province, and the natural population size has remained at approximately 150 individuals for 20 years. To protect this species from extinction, two captive populations were established in Anhui Nature Reserve and Changxing Nature Reserve.
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