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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. [ABSTRACT FROM AUTHOR]

In dynamic fission-fusion societies, following specific individuals consistently would not be expected in the absence of benefits to followers. Followers in groups may benefit if leaders have greater knowledge about habitats that are available for foraging and how to access these areas efficiently. A small residential population of bottlenose dolphins (Tursiops truncatus) in the Lower Florida Keys (LFK) demonstrates such specific individual leadership, but why others choose to follow is unknown. To determine whether consistent leaders demonstrated greater knowledge of resources and habitat we (1) compared habitat use patterns across areas that varied in prey abundance for groups led by consistent leaders and groups led by individuals that did not consistently lead, (2) compared directness of travel along with number of lead animal switches when traveling for these same two group types and (3) compared home range size and home range complexity between animals that consistently led and those that did not. Foraging groups led by consistent leaders were sighted more frequently over habitat with higher fish biomass, while those led by non-consistent leaders were sighted most often over habitat with lower fish biomass. Groups with consistent leaders had less frequent lead animal switches and took more direct paths when traveling than groups led by those that did not consistently lead. Home ranges of consistent leaders did not differ in size from other individuals, but were more complex. Our results indicate that followers in LFK dolphin groups could potentially benefit from those that consistently lead due to use of profitable habitat, ability to navigate efficiently and potentially the number of areas consistent leaders are familiar with. [ABSTRACT FROM AUTHOR]

Both food abundance and predation risk may influence habitat use decisions. However, studies of habitat use by birds in marine environments have focused only on food abundance. I investigated the possible influences of food abundance and predation risk from tiger sharks ( Galeocerdo cuvier) on habitat use by pied cormorants ( Phalacrocorax varius) over two spatial scales and on cormorant group size. Cormorants were usually solitary, but group size was highest in shallow habitats during months when shark density was low. Regardless of season, cormorant density within shallow habitats was higher over seagrass than sand, and cormorants were distributed between these two microhabitats proportional to prey density. Therefore, cormorants appear to respond to prey abundance at a relatively narrow spatial scale (i.e., tens of meters). At the habitat-patch scale (~1 km), the density of cormorants and their prey (teleosts) was higher in shallow habitats than in deep ones, but the density of cormorants was influenced by an interaction between water temperature (i.e., season) and habitat. There was decreased use of shallow habitats as water temperature, and the density of tiger sharks, increased. When shark density was low, cormorants were distributed across habitats roughly in proportion to the abundance of fish, suggesting that cormorants respond to food abundance at the scale of habitat patches. However, as shark abundance increased, the relative density of cormorants dropped in the dangerous shallow habitats such that there was a greater density of cormorants relative to their food in deep habitats when sharks were abundant. This suggests that pied cormorants trade-off food and risk by accepting lower energetic returns to forage in safer habitats. This study provides the first evidence that marine habitat selection by birds may be influenced by such a trade-off, and provides further evidence that tiger sharks are important in determining habitat use of their prey and mediating indirect interactions within Shark Bay. [ABSTRACT FROM AUTHOR]