Effects of scale and habitat distribution on the movement of the southern stingrayPublished on 22. May 2013
Effects of scale and habitat distribution on the movement of the southern stingray Dasyatis americana on a Caribbean atoll
Alexander Tilley, Juliana López-Angarita, John R. Turner
The structure of animal movement paths at varying spatial scales allows insight into the importance of habitat distribution and their response to scale in heterogeneous landscapes. Home-ranging animals typically exhibit constrained random movements at large spatial scales, with small-scale orientation reflecting responses to sensory stimuli. The southern stingray Dasyatis americana is an abundant demersal elasmobranch found in coastal systems throughout the Caribbean, yet very little is known of its movement ecology. Twelve southern stingrays were manually tracked at Glovers Reef (Belize) for up to 32 non-continuous hours to evaluate movement structure and activity space. Response to spatial scale was analysed using fractal analysis, and domains of scale were compared to habitat spatial characteristics. Mean stingray activity space was relatively small (<0.5 km2) with daytime activity space significantly larger than nighttime activity space. Movement paths showed significant straightening correlated with increasing size in females. Stingray movement structure exhibited 2 distinct domains: at scales of <100 m, paths were more dispersed than a correlated random walk (CRW), and at scales >100 m, paths were more constrained than CRW, indicating directed movement at scales up to 100 m. Nearest neighbour spatial analysis of lagoon patch reefs showed mean spacing of 100 m (±4.5), equivalent to orientation distance seen in rays. Random walk movements at large scales are consistent with a home-ranging animal; however, larger scale orientation than expected and patch reef spacing equalling 100 m suggests that patch reefs represent important spatial and ecological networks, strongly influencing stingray movement, habitat use, and dispersal.
Mar Ecol Prog Ser 482:169-179