Population dynamics of the sea snake Emydocephalus annulatus (Elapidae, Hydrophiinae)

Richard Shine,Gregory P. Brown,Claire Goiran

doi:10.1038/s41598-021-00245-2

Richard Shine, Gregory P. Brown + Show 1 more

Open Access

https://doi.org/10.1038/s41598-021-00245-2

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Abstract

For sea snakes as for many types of animals, long-term studies on population biology are rare and hence, we do not understand the degree to which annual variation in population sizes is driven by density-dependent regulation versus by stochastic abiotic factors. We monitored three populations of turtle-headed sea snakes (Emydocephalus annulatus) in New Caledonia over an 18-year period. Annual recruitment (% change in numbers) showed negative density-dependence: that is, recruitment increased when population densities were low, and decreased when densities were high. Windy weather during winter increased survival of neonates, perhaps by shielding them from predation; but those same weather conditions reduced body condition and the reproductive output of adult snakes. The role for density-dependence in annual dynamics of these populations is consistent with the slow, K-selected life-history attributes of the species; and the influence of weather conditions on reproductive output suggests that females adjust their allocation to reproduction based on food availability during vitellogenesis.

Highlights

All populations change in numbers through time, and an understanding of the mechanisms that drive those fluctuations can contribute to management and c onservation[1]
Using a mixed-model multiple regression approach, annual changes in abundance showed significant density-dependence; that is, a low population density was generally followed by an increase the following year, whereas a high population density was followed by a decrease (“pop. density” effect in Table 1; see Fig. 2 for univariate plot of these data)
At each of the three sites that we studied, the population densities of turtle-headed sea snakes varied among years

Summary

Introduction

All populations change in numbers through time, and an understanding of the mechanisms that drive those fluctuations can contribute to management and c onservation[1]. Several studies have documented a link between annual variation in population densities and stochastic environmental factors, often mediated by abiotically-driven shifts in prey a vailability[4,9,10,11,12]. Density-dependence has been detected in reptile populations, most powerfully through experimental manipulations of abundance[17,18] Few data on this topic are available for marine snakes, due to logistical obstacles. We analyse information on numbers and recruitment-relevant traits (age structure, body condition, reproductive rate) to examine the roles of density-dependence and stochastic weather-induced factors in driving year-to-year variation in abundance in sea snake populations in small bays beside the city of Noumea

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