Diet composition and foraging success in generalist predators: Are specialist individuals better foragers?

[EN]: Factors affecting individual diet specialization in generalist populations and the relationship between diet and foraging success remain poorly studied, particularly in terrestrial wide-ranging predators. We studied whether individual variations in diet in Montagu's harrier males (determined through a combination of direct foraging observations and pellet analysis) were associated with patterns of foraging habitat selection and foraging success of 12 radiotracked males during the breeding period. We found important differences in diet composition and breadth between individuals. Diet diversity was negatively related to hunting success: the most efficient individuals in terms of hunting success had the most specialized diet. This study also suggests an important role of individual foraging habitat selection in explaining individual diet, as the proportion of different prey types in the diet was associated with habitat composition within the home range, with higher proportion of those habitats that held higher abundances of their more frequent prey. This study thus provides evidence of individual diet specialization having a knock-on effect on foraging efficiency in a wide-ranging raptor and highlights the role of individual behaviour as a driving force of intra-population niche variation.The authors would like to thank the Centre Tecnològic Forestal de Catalunya for financial and logistic support. BA was supported by a Mobility Grant funded by the Spanish Ministry of Education and Culture (Salvador de Madariaga call, grant number PRX12/00181) while working on this paper in CEBC.Peer Reviewe

Influence de l’alimentation sur les performances des oies et la durabilité du système de production du foie gras : effets de la substitution du maïs par du sorgho et de la forme de présentation de l’aliment

Ce travail de thèse présente une synthèse de 5 expérimentations qui ont été réalisées afin d’évaluer les possibilités techniques (essais 1 et 4), l’intérêt zootechnique (essais 2, 3 et 5) et les conséquences sur la durabilité d’une substitution du maïs par du sorgho dans la ration alimentaire des oies en phase de croissance-finition et pendant le gavage. Le mode d’alimentation (entièrement granulée ou sous la forme d’un mélange de graines de céréales entières et de granulés riches en protéines) a également été étudié. Nous avons mesuré les performances des animaux (gain de poids, IC, consommation, développement corporel comportement alimentaire) ainsi que la qualité des produits (magret et foie gras) obtenus après gavage. Nous avons évalué in fine les conséquences de ces innovations sur la durabilité du système de production du foie gras à l’échelle de l’atelier de production (méthode S+Durable?) et sur le cycle de production d’un kilo de foie gras (méthode des ACV). Nos résultats montrent que la nature de la céréale (maïs vs. sorgho) utilisée pendant la phase de croissance-finition (6 à 14 semaines) n’a aucune influence sur les performances des animaux. Cependant, nous avons observé que la consommation d’aliments (+ 5% ; P \u3c 0,05), le poids vif (+ 4% ; P \u3c 0,05) et le développement des intestins (+ 9% ; P \u3c 0,05) en phase de croissance-finition étaient plus élevés lorsque le régime alimentaire contenait des graines entières. L’incorporation de sorgho pendant la phase de gavage, entraine une augmentation du poids des foies gras (+ 11% ; P \u3c 0,05) et une diminution de l’intensité de la couleur jaune du foie gras (- 25% ; P \u3c 0,05). Une substitution totale du maïs par du sorgho pendant les phases d’élevage et de gavage réduit les impacts environnementaux de la fabrication d’1 kg de foie gras et améliore les performances de durabilité économique et sociale de l’atelier de production. L’ensemble des résultats suggère que l’utilisation de sorgho dans l’alimentation des oies est techniquement possible pendant les phases de croissance-finition et de gavage, prometteuse zootechniquement et intéressante pour améliorer la durabilité du système de production. ABSTRACT : This thesis presents a summary of five experiments which were conducted to evaluate the technical feasibility (studies 1 and 4), zootechnical inetrest (studies 2, 3 and 5) and consequences on sustainability performance of the substitution of corn by sorghum in the diet of geese in growing-finishing period and during overfeeding. The form of diet presentation (totally pelleted or in form of a mixture of cereal whole seeds and protein rich pellets) was also studied. We measured animal performance (weight gain, FCR, feed intake, body characteristics, feeding behavior) and product quality (magret and foie gras) obtained after overfeeding period. We evaluated ultimately the consequences of these innovations on the sustainability of the foie gras production system at the level of rearing unit (S + Durable? method) and over the production cycle of 1 kg of foie gras (LCA method). Our results showed that the type of cereal (corn vs. sorghum) used during the growingfinishing period (6-14 weeks) has no effect on animal performance. However, we observed that feed intake (+ 5%; P \u3c 0.05), body weight (+ 4%; P \u3c 0.05) and the gut development (+9%; P \u3c 0.05) during the growing-finishing period were higher when the diet contained whole grains. The use of sorghum during the overfeeding resulted in an increased weight of fatty liver (+11%; P \u3c 0.05) and a decreased in the intensity of its yellow color (-25%; P \u3c 0.05). A total substitution of corn by sorghum during both growing and overfeeding periods reduced the environmental impacts of 1 kg of foie gras production and increased the economic and social performance of the rearing unit. These results suggest that the use of sorghum in the diet of geese is feasible both during the growing-finishing and overfeeding period, promising from a zootechnical point of view and interesting to improve the sustainability of production syste

Using satellite telemetry and environmental niche modelling to inform conservation targets for a long-distance migratory raptor in its wintering grounds

Understanding the ecology of migratory birds during the non-breeding season is necessary for ensuring their conservation. Using satellite telemetry data we describe winter ranging behaviour and movements of pallid harriers Circus macrourus that bred in Kazakhstan. We developed an ecological niche model for the species in Africa, to identify the most suitable wintering areas for pallid harriers and the importance of habitat in determining the location of those areas. We also assessed how well represented suitable areas are in the network of protected areas. Individual harriers showed relatively high fidelity to wintering areas but with potential for interannual changes. The ecological niche model highlighted the importance of open habitats with natural vegetation. Most suitable areas for the species were located in eastern Africa. Suitable areas had a patchy distribution but were relatively well included in the network of protected areas. The preferential use of habitats with natural vegetation by wintering pallid harriers and the patchiness of the most suitable areas highlight the harrier's vulnerability to land-use changes and the associated loss of natural vegetation in Africa. Conservation of harriers could be enhanced by preserving natural grasslands within protected areas and improving habitat management in the human-influenced portions of the species' core wintering areas.We thank to the Natural Research Ltd for funding. R. Limiñana benefited from a postdoctoral grant (reference 10/12-C) co-funded by ‘Consejería de Educación y Ciencia’ and the European Social Fund.Peer Reviewe

Adaptation du canard en gavage - Diminuer l’impact des transitions alimentaires

publié dans Plume de L'Oie (ISSN : 0764-521X)Les palmipèdes élevés pour la production de foies gras sont soumis à plusieurs phases de transitions alimentaires correspondant à des changements de forme, de composition et de valeur alimentaire de l’aliment ainsi qu’à des changements de rythme de prise alimentaire. Ces changements ont pour objectifs d’adapter l’alimentation à l’évolution des besoins des animaux, de les préparer à la phase de gavage et enfin de les soumettre au gavage. Ils se traduisent fréquemment, comme dans les autres espèces, par une réduction transitoire de l’ingestion qui peut entraîner une hétérogénéité du poids et des performances des animaux. Cette réponse et sa variabilité s’expliquent par la nécessité d’un délai dans l’adaptation comportementale et digestive des animaux et une variabilité individuelle de leur capacité adaptative

Using satellite telemetry and environmental niche modelling to inform conservation targets for a long-distance migratory raptor in its wintering grounds

Understanding the ecology of migratory birds during the non-breeding season is necessary for ensuring their conservation. Using satellite telemetry data we describe winter ranging behaviour and movements of pallid harriers Circus macrourus that bred in Kazakhstan. We developed an ecological niche model for the species in Africa, to identify the most suitable wintering areas for pallid harriers and the importance of habitat in determining the location of those areas. We also assessed how well represented suitable areas are in the network of protected areas. Individual harriers showed relatively high fidelity to wintering areas but with potential for interannual changes. The ecological niche model highlighted the importance of open habitats with natural vegetation. Most suitable areas for the species were located in eastern Africa. Suitable areas had a patchy distribution but were relatively well included in the network of protected areas. The preferential use of habitats with natural vegetation by wintering pallid harriers and the patchiness of the most suitable areas highlight the harrier's vulnerability to land-use changes and the associated loss of natural vegetation in Africa. Conservation of harriers could be enhanced by preserving natural grasslands within protected areas and improving habitat management in the human-influenced portions of the species’ core wintering areas.R. Limiñana benefited from a postdoctoral grant (reference 10/12-C) co-funded by ‘Consejería de Educación y Ciencia’ and the European Social Fund

Extending Drawings of Graphs to Arrangements of Pseudolines

International audienceIn the recent study of crossing numbers, drawings of graphs that can be extended to an arrangement of pseudolines (pseudolinear drawings) have played an important role as they are a natural combinatorial extension of rectilinear (or straight-line) drawings. A characterization of the pseudolinear drawings of Kn was found recently. We extend this characterization to all graphs, by describing the set of minimal forbidden subdrawings for pseudolinear drawings. Our characterization also leads to a polynomial-time algorithm to recognize pseudolinear drawings and construct the pseudolines when it is possible

Extending Drawings of Graphs to Arrangements of Pseudolines

International audienceIn the recent study of crossing numbers, drawings of graphs that can be extended to an arrangement of pseudolines (pseudolinear drawings) have played an important role as they are a natural combinatorial extension of rectilinear (or straight-line) drawings. A characterization of the pseudolinear drawings of Kn was found recently. We extend this characterization to all graphs, by describing the set of minimal forbidden subdrawings for pseudolinear drawings. Our characterization also leads to a polynomial-time algorithm to recognize pseudolinear drawings and construct the pseudolines when it is possible

Influence de l'alimentation sur les performances des oies et la durabilité du système de production du foie gras (effets de la substitution du maïs par du sorgho et de la forme de présentation de l'aliment)

Ce travail de thèse présente une synthèse de 5 expérimentations qui ont été réalisées afin d évaluer les possibilités techniques (essais 1 et 4), l intérêt zootechnique (essais 2, 3 et 5) et les conséquences sur la durabilité d une substitution du maïs par du sorgho dans la ration alimentaire des oies en phase de croissance-finition et pendant le gavage. Le mode d alimentation (entièrement granulée ou sous la forme d un mélange de graines de céréales entières et de granulés riches en protéines) a également été étudié. Nous avons mesuré les performances des animaux (gain de poids, IC, consommation, développement corporel comportement alimentaire) ainsi que la qualité des produits (magret et foie gras) obtenus après gavage. Nous avons évalué in fine les conséquences de ces innovations sur la durabilité du système de production du foie gras à l échelle de l atelier de production (méthode S+Durable?) et sur le cycle de production d un kilo de foie gras (méthode des ACV). Nos résultats montrent que la nature de la céréale (maïs vs. sorgho) utilisée pendant la phase de croissance-finition (6 à 14 semaines) n a aucune influence sur les performances des animaux. Cependant, nous avons observé que la consommation d aliments (+ 5% ; P < 0,05), le poids vif (+ 4% ; P < 0,05) et le développement des intestins (+ 9% ; P < 0,05) en phase de croissance-finition étaient plus élevés lorsque le régime alimentaire contenait des graines entières. L incorporation de sorgho pendant la phase de gavage, entraine une augmentation du poids des foies gras (+ 11% ; P < 0,05) et une diminution de l intensité de la couleur jaune du foie gras (- 25% ; P < 0,05). Une substitution totale du maïs par du sorgho pendant les phases d élevage et de gavage réduit les impacts environnementaux de la fabrication d 1 kg de foie gras et améliore les performances de durabilité économique et sociale de l atelier de production. L ensemble des résultats suggère que l utilisation de sorgho dans l alimentation des oies est techniquement possible pendant les phases de croissance-finition et de gavage, prometteuse zootechniquement et intéressante pour améliorer la durabilité du système de production.This thesis presents a summary of five experiments which were conducted to evaluate the technical feasibility (studies 1 and 4), zootechnical inetrest (studies 2, 3 and 5) and consequences on sustainability performance of the substitution of corn by sorghum in the diet of geese in growing-finishing period and during overfeeding. The form of diet presentation (totally pelleted or in form of a mixture of cereal whole seeds and protein rich pellets) was also studied. We measured animal performance (weight gain, FCR, feed intake, body characteristics, feeding behavior) and product quality (magret and foie gras) obtained after overfeeding period. We evaluated ultimately the consequences of these innovations on the sustainability of the foie gras production system at the level of rearing unit (S + Durable? method) and over the production cycle of 1 kg of foie gras (LCA method). Our results showed that the type of cereal (corn vs. sorghum) used during the growingfinishing period (6-14 weeks) has no effect on animal performance. However, we observed that feed intake (+ 5%; P < 0.05), body weight (+ 4%; P < 0.05) and the gut development (+9%; P < 0.05) during the growing-finishing period were higher when the diet contained whole grains. The use of sorghum during the overfeeding resulted in an increased weight of fatty liver (+11%; P < 0.05) and a decreased in the intensity of its yellow color (-25%; P < 0.05). A total substitution of corn by sorghum during both growing and overfeeding periods reduced the environmental impacts of 1 kg of foie gras production and increased the economic and social performance of the rearing unit. These results suggest that the use of sorghum in the diet of geese is feasible both during the growing-finishing and overfeeding period, promising from a zootechnical point of view and interesting to improve the sustainability of production systemTOULOUSE-INP (315552154) / SudocSudocFranceF

Demographic history, genetic structure and gene flow in a steppe-associated raptor species

<p>Abstract</p> <p>Background</p> <p>Environmental preferences and past climatic changes may determine the length of time during which a species range has contracted or expanded from refugia, thereby influencing levels of genetic diversification. Connectivity among populations of steppe-associated taxa might have been maximal during the long glacial periods, and interrupted only during the shorter interglacial phases, potentially resulting in low levels of genetic differentiation among populations. We investigated this hypothesis by exploring patterns of genetic diversity, past demography and gene flow in a raptor species characteristic of steppes, the Montagu's harrier (<it>Circus pygargus</it>), using mitochondrial DNA data from 13 breeding populations and two wintering populations.</p> <p>Results</p> <p>Consistent with our hypothesis, Montagu's harrier has relatively low genetic variation at the mitochondrial DNA. The highest levels of genetic diversity were found in coastal Spain, France and central Asia. These areas, which were open landscapes during the Holocene, may have acted as refugia when most of the European continent was covered by forests. We found significant genetic differentiation between two population groups, at the SW and NE parts of the species' range. Two events of past population growth were detected, and occurred ca. 7500-5500 and ca. 3500-1000 years BP in the SW and NE part of the range respectively. These events were likely associated with vegetation shifts caused by climate and human-induced changes during the Holocene.</p> <p>Conclusions</p> <p>The relative genetic homogeneity observed across populations of this steppe raptor may be explained by a short isolation time, relatively recent population expansions and a relaxed philopatry. We highlight the importance of considering the consequence of isolation and colonization processes in order to better understand the evolutionary history of steppe species.</p