Search Foraging Strategies of Migratory Raptors Under Different Environmental Conditions

Several studies have shown in different organisms how their movements can be fitted to different patterns to optimize search of food resources. According to abundance and availability of resources, different strategies will be optimal, such as Lévy and Brownian random search. We analyze the movement patterns of four species of migratory raptors with different degrees of ecological specialization in diet during the breeding and wintering periods to evaluate the differences according to species and season: the Egyptian Vulture, the Short-toed Snake Eagle, the Booted Eagle, and the Red Kite. From GPS locations, we obtained a set of segments and lengths that were analyzed to verify their fitting to the functions of Lévy and Brownian strategies. Egyptian Vulture’s trajectories fitted to both patterns during the breeding period, whereas during the wintering period most trajectories fitted a Brownian pattern. In the case of the Short-toed Eagle, fit was greater to a Lévy strategy throughout the year, while Booted Eagles and Red Kites exhibited a combination of search patterns. These differences could be accounted for different feeding strategies and environmental context over the annual cycle. In species with a specialized diet (i.e., Short-toed Eagle) the Lévy pattern would maximize the encounters with scarce and unpredictable resources, whereas for species with a broad trophic niche (i.e., Booted Eagle and Red Kite), movements could be adapted to exploit different resources according to their abundance. Scavengers like the Egyptian Vulture shift also between search strategies according to the distribution of carrion. Therefore, the analysis of food search patterns can be used as an indirect indicator to track changes in food availability across a broad range of environmental conditions. This is particularly important under the current context of global change which is largely expected to affect migratory species that spend their vital cycle in distant areas.Tracking of Booted Eagles and Red Kites has been made within the “Migra” program (www.migraciondeaves.org/en/) developed by SEO/BirdLife and financed by Fundación Iberdrola España. The Basque Government and the Biodiversity Foundation financed the tagging of several Red Kites in Spain. Tracking of Italian individuals was funded by Gallipoli Cognato Piccole Dolomiti Lucane Regional Park (Italy). Servicio de Vida Silvestre (Generalitat Valenciana) and different local governments funded part of the tagging. JV-M was supported by a FPU grant of Spanish Ministry of Education (reference FPU014/04671)

Hydrology Affects Environmental and Spatial Structuring of Microalgal Metacommunities in Tropical Pacific Coast Wetlands

The alternating climate between wet and dry periods has important effects on the hydrology and therefore on niche-based processes of water bodies in tropical areas. Additionally, assemblages of microorganism can show spatial patterns, in the form of a distance decay relationship due to their size or life form. We aimed to test spatial and environmental effects, modulated by a seasonal flooding climatic pattern, on the distribution of microalgae in 30 wetlands of a tropical dry forest region: the Pacific coast of Costa Rica and Nicaragua. Three surveys were conducted corresponding to the beginning, the highest peak, and the end of the hydrological year during the wet season, and species abundance and composition of planktonic and benthic microalgae was determined. Variation partitioning analysis (as explained by spatial distance or environmental factors) was applied to each seasonal dataset by means of partial redundancy analysis. Our results show that microalgal assemblages were structured by spatial and environmental factors depending on the hydrological period of the year. At the onset of hydroperiod and during flooding, neutral effects dominated community dynamics, but niche-based local effects resulted in more structured algal communities at the final periods of desiccating water bodies. Results suggest that climatemediated effects on hydrology can influence the relative role of spatial and environmental factors on metacommunities of microalgae. Such variability needs to be accounted in order to describe accurately community dynamics in tropical coastal wetlands.Agencia Española de Cooperación y Desarrollo/[A1024073/09]/AECID/EspañaAgencia Española de Cooperación y Desarrollo/[A/031019/10]/AECID/EspañaAgencia Española de Cooperación y Desarrollo/[C/032994/10]/AECID/EspañaAgencia Española de Cooperación y Desarrollo/[A3/ 036594/11]/AECID/EspañaUniversidad de Costa Rica/[741-B1-517]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP)UCR::Vicerrectoría de Docencia::Salud::Facultad de Microbiologí

Efectos ambientales a largo plazo sobre el fitoplancton de la laguna de Las Madres (Madrid)

Uno de los aspectos más desconocidos de los ecosistemas son sus respuestas a los cambios ambientales a largo plazo, que incluyen los efectos del cambio climático. Sin embargo, su estudio suele resultar difícil debido a la variabilidad espacial y la diversidad de respuestas que se generan en todos los niveles de complejidad biológica. En el caso de los lagos de pequeñas dimensiones, la respuesta a los cambios a largo plazo resultaría, pues, más fácil de describir. Se han descrito numerosos casos de la misma en lagos del norte y centro de Europa, pero se desconocen en la cuenca mediterránea, donde el calentamiento climático y otros efectos antrópicos repercuten de forma intensa y diferente. En esta Tesis Doctoral, hemos intentado caracterizar dichos extremos durante el periodo 1992-2011 mediante el estudio de la laguna de Las Madres, una laguna de reciente creación en Arganda del Rey (Madrid). Sus objetivos principales son: (i) comprobar si el cambio climático puede explicar cambios en la climatología local del entorno lacustre; (ii) constatar si las propiedades físico-químicas han variado a lo largo del periodo de estudio y si ese cambio puede explicarse por variaciones del clima regional y/o local; (iii) describir la dinámica del fitoplancton de la laguna de Las Madres e identificar sus factores condicionantes, tanto abióticos como bióticos; y (iv) determinar si el fitoplancton de la laguna de Las Madres resulta un buen testimonio de los efectos del cambio a largo plazo. Para ello, se muestrearon mensualmente las propiedades físicas (clima luminoso, clima térmico) y químicas (nutrientes) de la laguna, así como también las biomasas de fitoplancton, zooplancton y bacterias. Una estación meteorológica cercana registró datos sobre la velocidad del viento, la temperatura del aire, la radiación y las precipitaciones. También se analizaron los datos de clima regional, en forma de teleconexiones (Oscilaciones del Atlántico Norte y del Atlántico Oriental, Oscilación del Ártico, Oscilación de la corriente meridional de El Niño y efectos de la corriente del Golfo). Como cada una de estas variables puede actuar a diferentes escalas temporales, se han identificado su tendencia y su periodicidad mediante las metodologías de Asymmetric Eigenvectors Maps y del análisis de ondas. La dinámica de cada una de las series temporales puede responder a múltiples factores que pueden interactuar entre sí a múltiples escala temporales, por lo cual se identificaron los factores condicionantes para cada una de ellas, aplicando análisis de redundancias, particiones de la varianza y análisis de codependencias. Durante los meses cálidos (marzo a octubre), cuando el fitoplancton presenta su mayor crecimiento, la temperatura del aire en el entorno de Las Madres ha aumentado 1,2 ºC como respuesta a la Oscilación de Atlántico Oriental. El periodo vegetativo (primavera-verano) ha ascendido 48 días desde 1992 a 2011, produciendo un adelanto de la explosión primaveral del fitoplancton. Los cambios descritos en la temperatura atmosférica han modificado la estructura térmica de columna de agua la laguna. La temperatura del epilimnion ha aumentado 3 ºC durante los meses de verano, aumentando el gradiente térmico respecto al hipolimnion y, con ello, la estratificación se ha intensificado. La mezcla de la columna de agua entre los meses de noviembre a febrero ha sido cada vez más incompleta. La disponibilidad de los nutrientes para el fitoplancton ha variado con estos cambios y también se ha visto afectada por algunos procesos de teleconexión climática. La biomasa del fitoplancton mostró una tendencia decreciente a largo plazo, que podría corresponder con una respuesta indirecta al cambio climático y/o un proceso de estabilización del ecosistema. Además, presenta una estacionalidad unimodal, cuya explosión primaveral se ha adelantado, lo que demostraría su sensibilidad al cambio climático. Ni la biomasa bacteriana ni la zooplanctónica ejercieron control alguno sobre la del fitoplancton. Las teleconexiones climáticas regionales mostraron influencias sobre la dinámica del fitoplancton durante algunas fases de este estudio a largo plazo

Scavengers on the move: behavioural changes in foraging search patterns during the annual cycle

Background: Optimal foraging theory predicts that animals will tend to maximize foraging success by optimizing search strategies. However, how organisms detect sparsely distributed food resources remains an open question. When targets are sparse and unpredictably distributed, a Lévy strategy should maximize foraging success. By contrast, when resources are abundant and regularly distributed, simple Brownian random movement should be sufficient. Although very different groups of organisms exhibit Lévy motion, the shift from a Lévy to a Brownian search strategy has been suggested to depend on internal and external factors such as sex, prey density, or environmental context. However, animal response at the individual level has received little attention. Methodology/Principal Findings: We used GPS satellite-telemetry data of Egyptian vultures Neophron percnopterus to examine movement patterns at the individual level during consecutive years, with particular interest in the variations in foraging search patterns during the different periods of the annual cycle (i.e. breeding vs. non-breeding). Our results show that vultures followed a Brownian search strategy in their wintering sojourn in Africa, whereas they exhibited a more complex foraging search pattern at breeding grounds in Europe, including Lévy motion. Interestingly, our results showed that individuals shifted between search strategies within the same period of the annual cycle in successive years. Conclusions/Significance: Results could be primarily explained by the different environmental conditions in which foraging activities occur. However, the high degree of behavioural flexibility exhibited during the breeding period in contrast to the non-breeding period is challenging, suggesting that not only environmental conditions explain individuals’ behaviour but also individuals’ cognitive abilities (e.g., memory effects) could play an important role. Our results support the growing awareness about the role of behavioural flexibility at the individual level, adding new empirical evidence about how animals in general, and particularly scavengers, solve the problem of efficiently finding food resources.Satellite tracking devices were supported by the Terra Natura Foundation (Spain) and two Spanish Regional Administrations (Generalitat Valenciana and Junta de Comunidades de Castilla-La Mancha). PLL is supported by a “Juan de la Cierva” postdoctoral grant of the Spanish Ministry of Economy and Competitiveness (reference JCI-2011-09588)

Comparison of Lévy and Brownian motion.

<p>Example of two tracks of two different Egyptian vultures (<i>Neophron percnopterus</i>) recorded by GPS satellite telemetry at two-hour intervals corresponding to a Lévy foraging search pattern (A) and Brownian random motion (B).</p

Occurrence of Lévy and Brownian behavior types of six Egyptian vultures tracked by GPS satellite telemetry during breeding (Europe) and non-breeding (Africa) periods.

<p>Differences within and between periods of the annual cycle were tested by means of a one-way contingency table with the Yates's chi-squared test and a two-way contingency table test, respectively. See text for more details.</p

Ranked move-step-lengths plots with the best fitting models during the breeding period (Europe).

<p>Two random foraging strategies were considered: Lévy and Brownian motion. Lévy strategy was tested by fitting observed data (black circles) to the probability density function of a truncated Pareto distribution (red continuous line) whereas Brownian strategy was tested using the probability density functions of a truncated exponential distribution (orange dotted line) and a hyper-exponential distribution (green dashed line).</p

Ranked move-step-lengths plots with the best fitting models during the non-breeding period (Africa).

<p>Black circles show observed data. Three distributions are shown: truncated Pareto (red continuous line), truncated exponential (orange dotted line) and a hyper-exponential distribution (green dashed line).</p

Map of the study area (Costa Rica and Nicaragua Pacific coasts) indicating sampled aquatic ecosystems.

<p>Water bodies numbered as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0149505#pone.0149505.s001" target="_blank">S1 Table</a>. Reprinted from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0149505#pone.0149505.ref031" target="_blank">31</a>] under a CC BY 4.0 license (<a href="http://creativecommons.org/licenses/by/4.0/us/" target="_blank">http://creativecommons.org/licenses/by/4.0/us/</a>), with permission from <i>Asociación Ibérica de Limnología</i> (Limnetica), original copyright 2014.</p

Variation in the site scores of each selected PCNM variable (D1, D3, D4 and D10) along north (y-axis) and east (x-axis) coordinates in the Pacific coast of Nicaragua and Costa Rica.

<p>An overlaid map of the region (as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0149505#pone.0149505.g001" target="_blank">Fig 1</a>) is included in the first graph. The larger black or red dots: the higher positive or negative absolute values for a site respectively.</p