Lake Eyre Basin Rivers 56 The ecology of the Cooper has characteristic boom and bust periods (Kingsford et al. 1999 Bunn et al. 2006 see Chapter 1). Long dry periods of low productivity (‘busts’) dominate but are punctuated by widespread floods, usually driven by rainfall high in the catchment (‘boom’ periods) (Puckridge et al. 2000). For the freshwater turtles, the boom comes in two forms. First, when the river runs, the turtles take advantage of foods carried into their waterholes with the floodwaters they often concentrate around the inflows. These are ‘mini-booms’ (Bunn et al. 2006), occurring with greater frequency than major floods. Second, there are the major floods which dramatically expand available habitat and access to new food sources. The key message we convey here is how dependent these animals are on flows – on the timing and frequency of river runs, on the frequency, extent and duration of major floods, and on the pattern of floodplain inundation across the landscape, essential to the metapopulation dynamic that sustains the turtles. The hydrology of Cooper Creek has been little affected by water resource development, with the main driver of flow being natural climatic fluctuations that influence rainfall and runoff (Puckridge et al. 2000). Although Cooper Creek experiences low-level flows in most years, the discharge rates are extremely variable and episodic (Puckridge et al. 1998). One of the greatest threats to natural flow and flooding regimes is the diversion of flows. This water resource development in dryland rivers often decreases the frequency and duration of flow pulses, reducing floods and sometimes elevating base flows (Bunn et al. 2006). We argue that it is the alteration of these flow attributes through water resource development and deliberate or inadvertent water diversion in a landscape of very low relief that will be potentially catastrophic for turtle populations, and for other species with similar requirements and dispersal capabilities. We compare the biology of two turtles in the Lake Eyre Basin. Eastern long-necked turtle The eastern long-necked turtle (Chelodina longicollis Fig. 5.2) is a carnivore, feeding on slow-moving prey such as macroinvertebrates, tadpoles, terrestrial insects that fall upon the water, and carrion (Georges et al. 1986 Kennett et al. 2009). It survives dry periods by migrating overland between temporary and permanent water (Roe and Georges 2008 Roe et al. 2010). Individuals have adaptations for surviving extended periods on land without access to food and water (Roe et al. 2008). During short dry periods, they move onto land and become semi-dormant (aestivate) in the leaf litter and other damp areas or waterholes, emerging when the rains come. They know the landscape well and navigate using the sun and an internal clock (Graham et al. 1996). They can maintain their body condition and water balance for up to a year, without access to freestanding water (Roe et al. 2008). During more extended dry periods, the turtles migrate from ephemeral swamps and wetlands to permanent water where their densities can reach 400 turtles/ha (Parmenter 1976). When there is insufficient food, the turtles stop growing and reproducing (Kennett and Georges 1990). Large populations in waterholes can enter a form of collective dormancy, waiting out the drought, like some fish and other reptiles. This contrasts with mammals whose populations crash and rebound when the good times return, or birds who move out and return during boom periods.
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