GPS Tracking of Foraging Albatrosses

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175

Concentrations of biodiversity, or hotspots, represent conservation priorities in terrestrial ecosystems but remain largely unexplored in marine habitats. In the open ocean, many large predators such as tunas, sharks, billfishes, and sea turtles are of current conservation concern because of their vulnerability to overfishing and ecosystem role. Here we use scientific-observer records from pelagic longline fisheries in the Atlantic and Pacific Oceans to show that oceanic predators concentrate in distinct diversity hotspots. Predator diversity consistently peaks at intermediate latitudes (20 -30°N and S), where tropical and temperate species ranges overlap. Individual hotspots are found close to prominent habitat features such as reefs, shelf breaks, or seamounts and often coincide with zooplankton and coral reef hotspots. Closed-area models in the northwest Atlantic predict that protection of hotspots outperforms other area closures in safeguarding threatened pelagic predators from ecological extinction. We conclude that the seemingly monotonous landscape of the open ocean shows rich structure in species diversity and that these features should be used to focus future conservation efforts.

Section: Resultsmentioning

confidence: 99%

Predator diversity hotspots in the blue ocean

Worm

Lotze

Myers

2003

238

175

“…High-temporal resolution GPS transmitters (19) that report an accurate geographical position approximately every 1 or 10 s were used to track the foraging movements of 27 Diomedea exulans and 61 Thalassarche melanophrys in the southern Indian Ocean during incubating or chick brooding periods (SI Appendix, SI Materials and Methods). The general pattern of foraging movements of the two species was different, with T. melanophrys concentrating searches closer to the shelf edge ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Foraging success of biological Lévy flights recorded in situ

Humphries

Weimerskirch

Queiroz

et al. 2012

Self Cite

314

357

It is an open question how animals find food in dynamic natural environments where they possess little or no knowledge of where resources are located. Foraging theory predicts that in environments with sparsely distributed target resources, where forager knowledge about resources' locations is incomplete, Lévy flight movements optimize the success of random searches. However, the putative success of Lévy foraging has been demonstrated only in model simulations. Here, we use high-temporal-resolution Global Positioning System (GPS) tracking of wandering (Diomedea exulans) and black-browed albatrosses (Thalassarche melanophrys) with simultaneous recording of prey captures, to show that both species exhibit Lévy and Brownian movement patterns. We find that total prey masses captured by wandering albatrosses during Lévy movements exceed daily energy requirements by nearly fourfold, and approached yields by Brownian movements in other habitats. These results, together with our reanalysis of previously published albatross data, overturn the notion that albatrosses do not exhibit Lévy patterns during foraging, and demonstrate that Lévy flights of predators in dynamic natural environments present a beneficial alternative strategy to simple, spatially intensive behaviors. Our findings add support to the possibility that biological Lévy flight may have naturally evolved as a search strategy in response to sparse resources and scant information.optimal foraging | organism | predator-prey | telemetry | evolution T heoretically, in situations where animals possess limited or no information on the whereabouts of resources, a specialized random walk known as a Lévy flight can yield encounters with sparsely and randomly distributed targets (e.g., prey) more efficiently than random walks such as Brownian motion (1, 2), which are efficient where prey is abundant (3) and probably more predictable (4, 5). Lévy flight, in which movement displacements (steps) are drawn from a probability distribution with a powerlaw tail (a Pareto-Lévy distribution), describes a search pattern composed of many small-step 'walk clusters' interspersed by longer relocations. This pattern is repeated across all scales, such that PðlÞ ∼ l −μ , with 1 < μ ≤ 3 where l is the flight length (move-steplength), and μ the power-law exponent. Simple model simulations of Lévy search generally describe a forager moving along consecutive step lengths drawn from a power law distribution, such that when randomly and sparsely distributed prey is detected within a "sensory" field, the current step length is terminated, the prey is consumed and then a new random direction and step length are selected (3). These Lévy search-model simulations indicate an optimal exponent of μ ≈ 2 for the power-law move-step frequency distribution, leading to searches that increase the probability of a forager encountering new prey patches (1-3). In recent years, Lévy flight or Lévy walk patterns approaching the theoretically optimal value of μ ≈ 2 have been identified in movements of divers...

“…S8). The lower ground speed values were interpreted as resting on ocean surface or on land, whereas higher ground speed values were interpreted as flight (40,41). Based upon the bimodal distribution in the histogram of ground speed, the resting phase was defined as a period when a bird moved less than 4 ms −1 for more than 10 s (Fig.…”

Section: Methodsmentioning

confidence: 99%

Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction

Yonehara

Goto

Yoda

et al. 2016

Self Cite

Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These birdbased wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps.biologging | dynamic soaring | satellite scatterometer | GPS | meteorology R ecently, remote-sensing systems used to record atmospheric circulation have been developed. Satellite-borne scatterometers estimate ocean surface wind velocities each day covering the majority of the global ocean. These wide-range wind data in combination with refined ocean models are used in numerical weather predictions and describe the oceanographic features more accurately (1-3). Buoys scattered over the ocean also measure fine-time resolution in situ surface winds and are used in validating remote-sensing measurements and are assimilated into model analyses (4, 5). However, because wind data are only acquired twice per day by each satellite and buoys have limited spatial coverage, finer-scale changes of hours to days in local wind conditions could be overlooked. In addition, in coastal areas, where high biological productivity is associated with ocean and atmosphere circulation patterns (6), wind data are lacking due to variations in wind and wave caused by complex topographic effects that satellites have difficulty measuring (5,7,8). Obtaining in situ high-resolution atmospheric and oceanographic data to fill these spatial and temporal observation gaps would deepen our understanding of physical processes relevant to interactions between the atmosphere and ocean, contribute to improved atmospheric and ocean model analyses (7,8), and reveal detailed structure that remains unresolved by using conventional methods (9).The recent development of miniaturized animal-borne data loggers presented a capability to use animals as indicators of environmental variables. The extensive movement range and locomotion ability of marine mammals and seabirds ena...