Spatial and Temporal Variation in Reproduction of a Generalist Crocodilian, Caiman crocodilus yacare, in a Seasonally Flooded Wetland.

Balbina M. A. Soriano,Guilherme Mourão,William E. Magnusson,Zilca Campos,Marcos Coutinho

doi:10.1371/journal.pone.0129368

Abstract

We monitored the number of caiman (Caiman crocodilus yacare) nests in two ranches in the Brazilian Pantanal that cover an area of about 50.000 ha for 28 years (1987–2014). The number of nests was related to combinations of rainfall, water level, and number of days with temperature below 20°C, depending on the area. Most of the variation in number of nests could not be predicted by the environmental variables, but could be represented mathematically by a sine wave. We were not able to identify any external driver and suspect that the regular fluctuations may have resulted from an intrinsic population process. Presently, ranches are used as management units under the legislation for ranching Pantanal caimans. However, although some breeding females were recaptured in the area after periods of up to 21 years, most were not recaptured near nests or in general surveys of the area, suggesting that females are not strongly philopatric and that ranches do not represent isolated demographic units.

Highlights

Reproductive traits of organisms are limited by species-specific morphological characteristics, and these lead to predictable relationships, such as between body and clutch size [1], but many species show phenotypic plasticity in reproductive strategies in response to resource availability [2,3]
We surveyed ~1000 ha around an intermittent river on Campo Dora Ranch (18°55`S and 56°39 ́W), which is adjacent to Nhumirim Ranch and drains to the Taquari River, Brazilian Pantanal (Fig 1)
The species, like all members of the family Alligatoridae, only make mound nests [36]. These are visible if constructed in open areas, and areas of forest are limited to small patches, generally less than 50 m wide, around lakes, so we believe that we found most, if not all nests, in most of these areas each year

Summary

Introduction

Reproductive traits of organisms are limited by species-specific morphological characteristics, and these lead to predictable relationships, such as between body and clutch size [1], but many species show phenotypic plasticity in reproductive strategies in response to resource availability [2,3]. Females that can respond phenotypically are expected to increase overall reproductive output in good years [4], but they may respond behaviorally, seeking different locations to breed as conditions change. This flexibility may make it difficult to predict reproductive output from environmental predictors, because females may use different areas in different years. Management of local demographic units, such as egg collection and maintaining

Methods

Results

Conclusion