Long-Term Variation in Survival of A Neotropical Freshwater Turtle: Habitat and Climatic Influences

Mario F Garcés-Restrepo,John L Carr,Alan Giraldo

doi:10.3390/d11060097

Mario F Garcés-Restrepo, John L Carr + Show 1 more

Open Access

https://doi.org/10.3390/d11060097

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Journal: Diversity	Publication Date: Jun 20, 2019
Citations: 5	License type: CC BY 4.0

Affiliation: University of Valle, University of Louisiana at Monroe

Abstract

Few long-term demographic studies have been conducted on freshwater turtles of South America, despite the need for this type of inquiry to investigate natural variation and strengthen conservation efforts for these species. In this study, we examined the variation in demography of the Chocoan River Turtle (Rhinoclemmys nasuta) based on a population from an island locality in the Colombian Pacific region between 2005 and 2017. We calculated survival, recapture, and transition probabilities, and the effects of stream substrate and El Niño–Southern Oscillation (ENSO) phases (El Niño, Neutral, La Niña) on these variables using a multi-state model. We found differences in survival probabilities between ENSO phases, likely as a consequence of an increase in flood events. In addition, we found support for survival being greater in muddy streams than rocky streams, possibly because it is easier to escape or hide in mud substrates. Recapture probabilities varied by life stages; differences in the probability of recapture between size classes were associated with the high fidelity to territories by adults. The present increases in frequency and severity of El Niño and La Niña may exacerbate the consequences of climatic regimes on natural populations of turtles by increasing the mortality caused by drastic phenomena such as floods.

Highlights

In recent decades, many turtle species have shown declines in population size [1,2]
Of the set of 18 candidate models used to assess the influence of year, life stage, stream type, and El Niño–Southern Oscillation (ENSO) phase on survival, recapture, and transition probabilities, the most supported models included ENSO affecting survival, and life stage determining recapture and constant transition probabilities (w = 0.47, Table 1)
Annual survival probabilities were lower for La Niña phase (μ = 0.64, ± CI 95% = 0.13) and Neutral phase (μ = 0.70, ± CI 95% = 0.10) than El Niño phase (μ = 0.80, ± CI 95% = 0.11; Figure 2a)

Summary

Introduction

Many turtle species have shown declines in population size [1,2]. The most recent overview estimates that 54% of all turtle species are threatened, exceeding the threat levels of other vertebrate groups such as parrots, primates, or frogs, which are considered as examples sensitive to extinction [3]. There are a variety of causes that affect population viability among chelonians, including habitat loss and degradation, introduction of invasive species, environmental pollution, disease, and human exploitation [4,5]. These threats are intensified by factors inherent to the biology of turtles, such as the slow recovery of populations after declines and delayed sexual maturity [6,7]. Variation in precipitation can change net primary productivity (NPP), thereby affecting the food supply, body condition, and reproductive output in populations of different species [15], including turtles and tortoises [16,17]. Precipitation, NPP, and sea level will modify habitats and are projected to alter the geographic ranges of a significant number of turtle species under various

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Conclusion