The Dry Season Shuffle: Gorges Provide Refugia for Animal Communities in Tropical Savannah Ecosystems

In the wet-dry tropics, animal species face the major challenges of acquiring food, water or shelter during an extended dry season. Although large and conspicuous animals such as ungulates and waterfowl migrate to wetter areas during this time, little is known of how smaller and more cryptic animal...

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Published in:	PloS one Vol. 10; no. 7; p. e0131186
Main Authors:	Doody, J Sean, Clulow, Simon, Kay, Geoff, D'Amore, Domenic, Rhind, David, Wilson, Steve, Ellis, Ryan, Castellano, Christina, McHenry, Colin, Quayle, Michelle, Hands, Kim, Sawyer, Graeme, Bass, Michael
Format:	Journal Article
Language:	English
Published:	United States Public Library of Science 02-07-2015 Public Library of Science (PLoS)
Subjects:	Animal behavior Animal Migration - physiology Animal species Animals Anura - physiology Aquatic animals Aquatic fauna Australia Bias Buffer zones Canyons Chelodina burrungandjii Communities Developmental biology Droughts Dry season Ecology Ecosystems Endangered & extinct species Fauna Food chains Frogs Grassland Life sciences Lizards Lizards - physiology Mammals - physiology Migration Museums National parks Parks & recreation areas Rainy season Refugia Refugium Reptiles & amphibians Return migration Savannahs Seasons Shelters Snakes Snakes - physiology Species Terrestrial environments Toads Tropical Climate Tropical environments Turtles Turtles - physiology Ungulates Vertebrates Water - physiology Waterfowl Wetlands Woodlands Australia
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Summary:	In the wet-dry tropics, animal species face the major challenges of acquiring food, water or shelter during an extended dry season. Although large and conspicuous animals such as ungulates and waterfowl migrate to wetter areas during this time, little is known of how smaller and more cryptic animal species with less mobility meet these challenges. We fenced off the entire entrance of a gorge in the Australian tropical savanna, offering the unique opportunity to determine the composition and seasonal movement patterns of the small vertebrate community. The 1.7 km-long fence was converted to a trapline that was deployed for 18-21 days during the early dry season in each of two years, and paired traps on both sides of the fence allowed us to detect the direction of animal movements. We predicted that semi-aquatic species (e.g., frogs and turtles) would move upstream into the wetter gorge during the dry season, while more terrestrial species (e.g., lizards, snakes, mammals) would not. The trapline captured 1590 individual vertebrates comprising 60 species. There was a significant bias for captures on the outside of the fence compared to the inside for all species combined (outside/inside = 5.2, CI = 3.7-7.2), for all vertebrate classes, and for specific taxonomic groups. The opposite bias (inside/outside = 7.3, N= 25) for turtles during the early wet season suggested return migration heading into the wet season. Our study revealed that the small vertebrate community uses the gorge as a dry season refuge. The generality of this unreplicated finding could be tested by extending this type of survey to tropical savannahs worldwide. A better understanding of how small animals use the landscape is needed to reveal the size of buffer zones around wetlands required to protect both semi-aquatic and terrestrial fauna in gorges in tropical savannah woodland, and thus in ecosystems in general.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Conceived and designed the experiments: JSD CC DR GS KH MB. Performed the experiments: JSD DR SC GK CC GS KH DD SW RE. Analyzed the data: SC JSD. Contributed reagents/materials/analysis tools: MQ CM. Wrote the paper: JSD SC CM. Competing Interests: Christina Castellano is General Curator at Hogle Zoo, and Michael Bass was Wilderness Park Manager at El Questro Wilderness Park. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.
ISSN:	1932-6203 1932-6203
DOI:	10.1371/journal.pone.0131186