Abstract
Run-of-the-river hydroelectric dams cause changes in seasonal inundation of the floodplains, and this may cause displacement of semi-aquatic vertebrates present before dam construction. This study evaluated the movement of crocodilians before and after the filling of the Santo Antônio hydroelectric reservoir on the Madeira River in the Brazilian Amazon, which occurred in November 2011. We radio-tracked four adult male Paleosuchus palpebrosus and four adult male Paleosuchus trigonatus before and after the formation of the reservoir between 2011 and 2013. The home ranges of the P. palpebrosus varied from < 1 km2 to 91 km2 and the home ranges of the P. trigonatus varied from < 1km2 to 5 km2. The species responded differently to time since filling and water level in weekly movement and home range. However, overall the dam appears to have had little effect on the use of space by the individuals that were present before dam construction.
Highlights
Traditional hydroelectric dams with large reservoirs flooded extensive areas of terrestrial habitat and changed the conditions from lotic to lentic, which presumably led to the exclusion of many aquatic species present in the area before dam construction [1, 2]
Effects of phase 2 differed from the other phases (p < 0.001) and the P. trigonatus moved more than the P. palpebrosus during phase 3 (p = 0.022, “S1 Fig”)
P. palpebrosus (Fig 2A, 2B and 2C) tended to increase their distance moved between locations with the increase in water level during phase 1 (p = 0.008) and phase 2 (p > 0.001) and ceased to do so in phase 3 (p = 0.252)
Summary
Traditional hydroelectric dams with large reservoirs flooded extensive areas of terrestrial habitat and changed the conditions from lotic to lentic, which presumably led to the exclusion of many aquatic species present in the area before dam construction [1, 2]. There has been a tendency for the construction of run-of-the-river dams [3, 4], which inundate much smaller areas and maintain the lotic nature of most of the upstream sections. Run-of-the-river dams have less drastic effects on the aquatic and semi-aquatic fauna than traditional dams. Even if species assemblages similar to those present before dam construction eventually reestablish, it is not known what happens to the individuals present when the dam fills and inundates local wetlands. Crocodilians are long lived and many species are territorial [5], so dam construction could lead to severe disruption of home ranges, possibly resulting in individuals abandoning the area and dispersing into areas where they experience increased risk of mortality, such as areas near dam turbines [6] or areas with less nesting habitat [7, 8].
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