Top predators induce habitat shifts in prey within marine protected areas.

Emerging conservation efforts for the world's large predators may, if successful, restore natural predator-prey interactions. Marine reserves, where large predators tend to be relatively common, offer an experimental manipulation to investigate interactions between large-bodied marine predators and their prey. We hypothesized that southern stingrays-large, long-lived and highly interactive mesopredators-would invest in anti-predator behavior in marine reserves where predatory large sharks, the primary predator of stingrays, are more abundant. Specifically, we predicted southern stingrays in marine reserves would reduce the use of deep forereef habitats in the favor of shallow flats where the risk of shark encounters is lower. Baited remote underwater video was used to survey stingrays and reef sharks in flats and forereef habitats of two reserves and two fished sites in Belize. The interaction between "protection status" and "habitat" was the most important factor determining stingray presence. As predicted, southern stingrays spent more time interacting with baited remote underwater videos in the safer flats habitats, were more likely to have predator-inflicted damage inside reserves, and were less abundant in marine reserves but only in the forereef habitat. These results are consistent with a predation-sensitive habitat shift rather than southern stingray populations being reduced by direct predation from reef sharks. Our study provides evidence that roving predators can induce pronounced habitat shifts in prey that rely on crypsis and refuging, rather than active escape, in high-visibility, heterogeneous marine habitats. Given documented impacts of stingrays on benthic communities it is possible restoration of reef shark populations with reserves could induce reef ecosystem changes through behavior-mediated trophic cascades.

Corticosteroid injection in rheumatoid arthritis does not increase rate of total joint arthroplasty.

OBJECTIVE: To determine the relationship between frequent intraarticular corticosteroid injection and subsequent joint replacement surgery. METHODS: A 1987 database of patients with rheumatic diseases was reviewed to find patients with rheumatoid arthritis (RA) who had received 4 or more intraarticular injections in an asymmetric pattern in a single year. RESULTS: A subset of 13 patients with an average of 7.4 years of followup was established as the cohort of a 5 year prospective study. In this highly selected cohort of patients with RA in a university practice who received 1622 injections, joint replacement surgery was not significantly more common in the heavily injected joints. CONCLUSIONS: A strategy of frequent intraarticular steroid injection does not greatly increase, through added risk of joint replacement, the risk inherent in continued disease activity for patients with established RA. Frequent corticosteroid injection may offer some chondroprotection when the alternative is continuous disease activity.