The Experts below are selected from a list of 4029 Experts worldwide ranked by ideXlab platform
Hervé Fritz - One of the best experts on this subject based on the ideXlab platform.
-
Anti-predator behaviour of kudu and Impala in response to mimicked African wild dog presence: do age and sex matter?
Behaviour, 2015Co-Authors: Hervé Fritz, Esther Van Der Meer, Olivier PaysAbstract:Predators not only prey upon certain prey species, but also on certain age–sex classes within species. Predation risk and an individual’s response to this risk might therefore vary with an individual’s characteristics. We examined the proportion of time different age–sex classes of kudu ( Tragelaphus strepsiceros) and Impala ( Aepyceros melampus) spent high quality vigilant (costly vigilance that detracts from all other activities) in response to mimicked predation risk by African wild dogs ( Lycaon pictus). For both species predation risk was the main factor determining the investment in high quality vigilance behaviour. Age–sex class-specific responses were not related to age–sex class specific lethality risk presented by African wild dogs. For Impala, regardless of predation risk, age seemed to have some effect on the investment in high quality vigilance with sub-adult Impala spending more time high quality vigilant than adult Impala, which is possibly why African wild dogs predominantly preyed upon adult Impala.
-
On the Advantages of Mixed-Species Groups: Impalas Adjust Their Vigilance When Associated With Larger Prey Herbivores
Ethology, 2014Co-Authors: Olivier Pays, Alice Ekori, Hervé FritzAbstract:Prey can obtain valuable benefits from associating with other species if heterospecifics help to detect predators or locate good food patches. In mixed-species groups, how species respond to the presence of other species remains a poorly explored question although it might give crucial insights into mechanisms underlying the interspecific coexistence. We studied temporary mixed-species groups of large herbivores in Hwange National Park (Zimbabwe) between the common Impala (Aepyceros melampus), the focal species here, and bigger species including the plains zebra (Equus quagga), the greater kudu (Tragelaphus strepsiceros) or the blue wildebeest (Connochaetes taurinus). In the Hwange savanna, the focal and smaller species are exposed to a larger range of predators than the associated species. In this context, we investigated how Impalas adjusted their vigilance with group size comparing Impala-only and mixed-species groups and whether the identity of heterospecifics affected vigilance of Impalas. Our study showed that the time Impalas spent in vigilance significantly decreased with group size when they formed Impala-only groups, whereas it did not significantly vary with group size in mixed-species groups. Moreover, in mixed-species groups, Impalas did not adjust their time spent in vigilance with the proportion of conspecifics and the identity of the associated species. Thus, the mechanism underlying the difference of Impalas' behavioural adjustment of vigilance with group size between single- and mixed-species groups seemed to be related to the presence but not to the number and the identity of heteropecifics. Finally, we discuss the concept that larger and dominant heterospecifics were likely to increase competition for food access, thereby forcing higher vigilance of Impalas, outweighing any reduction from collective vigilance.
-
Bush selection along foraging pathways by sympatric Impala and greater kudu
Oecologia, 2004Co-Authors: Michel Garine-wichatitsky, Hervé Fritz, Iain J. Gordon, Andrew W. IlliusAbstract:In order to identify the selection mechanism of two sympatric African browsers, we analysed encounter rates and selection of bushes along foraging pathways. We monitored the tracks, left overnight, by kudu and Impala on an experimental plot of natural Acacia nilotica and Dichrostachys cinerea in the highveld of Zimbabwe, and recorded the number of bushes attacked in each category. Both ungulates were selective for the bush categories, but kudu were consistently more selective than Impala, and showed a higher preference for the larger A. nilotica and D. cinerea bushes, which had a significantly greater number of bites which were not reachable by Impala. For both kudu and Impala, the probability of attacking larger bushes increased significantly with the proportion of large bushes encountered along the foraging pathways, whereas the consumption of smaller bushes was apparently unpredictable. For the most abundant food item (medium D. cinerea ), the probability of attack by Impala along a pathway decreased with increasing proportions of larger bushes in the experimental area, but was also dependent on Impala group size and season. In addition, we found that encounter rates with larger bushes were significantly higher for kudu than for Impala. Experimentally reducing the availability of the larger bushes had little effect on both Impala and kudu during the following rainy season. However, during the following cool dry season, kudu showed an increased selectivity with a strong preference for the remaining large bushes (large A. nilotica ), followed by a sharp decrease in selectivity in the hot dry season when they also fed from significant numbers of medium trees. Impala had little reaction to the experimental changes in the availability of bush categories in either season. We suggest that both kudu and Impala selected bushes on the basis of the potential number of bites they can provide, and this resulted in different search strategies. Kudu focussed on the larger bushes which have a larger number of twigs which are out of reach of Impala and kudu also probably directed their path preferentially towards the few larger bushes to maximize encounter rates with this favoured bush category. These differences in bush selection process lead to a low overlap in resource use between the two browsers in this type of savanna.
-
effects of annual rainfall and habitat types on the body mass of Impala aepyceros melampus in the zambezi valley zimbabwe
African Journal of Ecology, 2002Co-Authors: Mathieu Bourgarel, Hervé Fritz, Jm Gaillard, M De Garinewichatitsky, F MaudetAbstract:Body mass is often considered as a good indicator of body condition of individuals in ungulates, hence of their fitness, and thus, may be used as an index to monitor the status of populations subject to harvesting schemes. Here, we report the influence of annual rainfall (a proxy for primary production) and habitat on the body mass of Impala in a population cropped for meat in a communal area of Zimbabwe. We analyzed the data from 2 contrasted years for rainfall, in two different habitats. In the good year (i.e. high annual rainfall) Impala were heavier than in the poor year, and adult females seemed to be less affected than males by variation in primary production. We show that adult males were suffering from a seasonal decrease in body mass, supposedly linked to the rut, particularly in good habitat. Overall, the habitat effect appeared to be dominated by the rainfall effect, and this may be due to the very high animal densities in the good habitat, i.e. fast resource depletion. Our results also suggest that males (juvenile and adult) are more susceptible to changes in food resource abundance and quality than females, which supports previous studies on sexually dimorphic and polygynous species. Resume On considere souvent que la masse corporelle est un bon indicateur de la condition physique chez les ongules, et donc de leur bon etat general; on peut donc s'en servir comme index pour controler le statut des populations qui font l'objet d'un programme de prelevements. Nous rapportons ici l'influence des chutes de pluies annuelles (qui sont liees a la production primaire) et de l'habitat sur la masse corporelle des Impalas d'une population ou l'on preleve des animaux pour la viande, dans une aire communale au Zimbabwe. Nous avons analyse les donnees de deux annees contrastees pour les chutes de pluies, dans deux habitats differents. La bonne annee (c.-a-d. fortes chutes de pluies), les Impalas etaient plus gros que la mauvaise annee, et les femelles adultes semblaient moins affectees que les mâles par les variations de la production primaire. Nous montrons que les mâles adultes subissaient une reduction saisonniere de leur masse corporelle, sans doute liee au rut, et surtout dans les bons habitat. Partout, l'effet de l'habitat semble etre surpasse par l'effet des chutes de pluie, et ceci est peut-etre dua la tres forte densite des animaux dans le bon habitat, c.-a-d. un rapide epuisement des ressources. Nos resultats suggerent aussi que les mâles, juveniles et adultes, sont plus sensibles que les femelles aux changements dans l'abondance et la qualite des ressources alimentaires, ce qui confirme des etudes anterieures sur les especes dimorphiques et polygames.
-
habitat use by sympatric wild and domestic herbivores in an african savanna woodland the influence of cattle spatial behaviour
Journal of Applied Ecology, 1996Co-Authors: Hervé Fritz, M De Grainewichatitsky, G LetessierAbstract:The spatial distribution of two wild ungulates, Impala and kudu, and of domestic cattle, was monitored across seasons in a 9400 ha ranch of the 'highveld' of Zimbabwe. Habitat use, preference, selectivity and overlap were estimated. Predation was negligible and the study concentrated on interspecific competition. Cattle were contained in paddocks, and were moved regularly, while wild ungulates moved freely. Wild ungulate habitat use, preference and selectivity between paddocks with and without cattle were compared, as was the variation in broad diet, group size and densities. All herbivores were selective, with a marked preference for the nutrient-rich Acacia/ Dichrostachys vegetation type. Terminalia communities were almost completely avoided. Selectivity increased as the dry season progressed. Habitat overlap was always high. Interspecific competition occurred between cattle and Impala, especially during the wet season and the hot dry season. Impala showed a switch in habitat preference and an increase in selectivity and started to concentrate on 'refuge habitat'. Some also switched in their diet composition. During the hot dry season, when resources were at their lowest, most Impala stopped using paddocks with cattle. Kudu seemed relatively unaffected by the presence of cattle: the variations observed in kudu spatial behaviour may have been caused by competition with Impala.
Krystyna A Golabek - One of the best experts on this subject based on the ideXlab platform.
-
Biomechanics of predator–prey arms race in lion, zebra, cheetah and Impala
Nature, 2018Co-Authors: A M Wilson, Tatjana Y Hubel, Simon Wilshin, J C Lowe, Maja Lorenc, Oliver P Dewhirst, Rebecca Diack, Emily Bennitt, Hattie L. A. Bartlam-brooks, Krystyna A GolabekAbstract:Nature might be red in tooth and claw, but the race is not always won by the strong. A detailed study of how lions chase down zebras and cheetahs pursue Impalas shows that, although the predators in each pair had substantially more muscle power than their prey, as well as much greater capacity to accelerate and decelerate, the prey species could slip away at lower speeds, at which they are more manoeuvrable. Nevertheless, predators need to be more athletic than their prey to sustain a viable kill rate. The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator–prey pairs, lion–zebra and cheetah–Impala, in their natural savannah habitat in Botswana. We show that although cheetahs and Impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator–prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate. Analysis and modelling of locomotor characteristics of two pursuit predator–prey pairs show that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival.
-
biomechanics of predator prey arms race in lion zebra cheetah and Impala
Nature, 2018Co-Authors: A M Wilson, Tatjana Y Hubel, Simon Wilshin, J C Lowe, Maja Lorenc, Oliver P Dewhirst, Hattie L A Bartlambrooks, Rebecca Diack, Emily Bennitt, Krystyna A GolabekAbstract:The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator-prey pairs, lion-zebra and cheetah-Impala, in their natural savannah habitat in Botswana. We show that although cheetahs and Impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator-prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate.
-
biomechanics of predator prey arms race in lion zebra cheetah and Impala
Nature, 2018Co-Authors: A M Wilson, Tatjana Y Hubel, Simon Wilshin, J C Lowe, Maja Lorenc, Oliver P Dewhirst, Hattie L A Bartlambrooks, Rebecca Diack, Emily Bennitt, Krystyna A GolabekAbstract:The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator–prey pairs, lion–zebra and cheetah–Impala, in their natural savannah habitat in Botswana. We show that although cheetahs and Impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator–prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate. Analysis and modelling of locomotor characteristics of two pursuit predator–prey pairs show that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival. Nature might be red in tooth and claw, but the race is not always won by the strong. A detailed study of how lions chase down zebras and cheetahs pursue Impalas shows that, although the predators in each pair had substantially more muscle power than their prey, as well as much greater capacity to accelerate and decelerate, the prey species could slip away at lower speeds, at which they are more manoeuvrable. Nevertheless, predators need to be more athletic than their prey to sustain a viable kill rate.
Thierry Langin - One of the best experts on this subject based on the ideXlab platform.
-
Transposition of autonomous and engineered Impala transposons in Fusarium oxysporum and a related species.
Molecular and General Genetics MGG, 2001Co-Authors: Aurélie Hua-van, Thierry Langin, João Alencar Pamphile, Marie-josée DaboussiAbstract:The Impala transposon of Fusarium oxysporum is an active element. We demonstrated that the imp160 copy, transposed into the gene encoding nitrate reductase, is an autonomous element, since it excises from this gene and reinserts at a new genomic position in backgrounds free of active elements. An element in which the transposase gene was replaced by a hygromycin B resistance gene was used (1) to demonstrate the absence of endogenous transposase in several F. oxysporum strains and (2) to check the ability of different genomic copies of Impala to transactivate this defective element. This two-component system allowed the identification of autonomous elements in two Impala subfamilies and revealed that transactivation can occur between highly divergent elements. We also demonstrate that the autonomous copy transposes in a closely related species complex, F. moniliforme, in a fashion similar to that observed in F. oxysporium. The ability of Impala to function as a two-component system and to transpose in a heterologous host promises further advances in our understanding of the factors that modulate transposition efficiency and demonstrates the potential of Impala as a means of establishing a transposon tagging system for a wide range of fungal species.
-
three highly divergent subfamilies of the Impala transposable element coexist in the genome of the fungus fusarium oxysporum
Molecular Genetics and Genomics, 1998Co-Authors: Aurelie Huavan, Marie-josée Daboussi, Pierre Capy, F Hericourt, Thierry LanginAbstract:The transposable element Impala is a member of the widespread superfamily of Tc1-mariner transposons, identified in the genome of the plant pathogenic fungus Fusarium oxysporum. This element is present in a low copy number and is actively transposed in the F.␣oxysporum strain F24 that is pathogenic for melons. The structure of the Impala family was investigated by cloning and sequencing all the genomic copies. The analysis revealed that this family is composed of full-length and truncated copies. Four copies contained a long open reading frame that could potentially encode a transposase of 340 amino acids. The presence of conserved functional domains (a nuclear localisation signal, a catalytic DDE domain and a DNA-binding domain) suggests that these four copies may be autonomous elements. Sequence comparisons and phylogenetic analysis of the Impala copies defined three subfamilies, which differ by a high level of nucleotide polymorphism (around 20%). The coexistence of these divergent subfamilies in the same genome may indicate that the Impala family is of ancient origin and/or that it arose by successive horizontal transmission events.
-
The transposable element Impala, a fungal member of the Tc1-mariner superfamily
Molecular and General Genetics MGG, 1995Co-Authors: Thierry Langin, Pierre Capy, Marie-josée DaboussiAbstract:A new transposable element has been isolated from an unstable niaD mutant of the fungus Fusarium oxysporum . This element, called Impala , is 1280 nucleotides long and has inverted repeats of 27 bp. Impala inserts into a TA site and leaves behind a “footprint” when it excises. The inserted element, Impala -160, is cis -active, but is probably trans -defective owing to several stop codons and frameshifts. Similarities exist between the inverted repeats of Impala and those of transposons belonging to the widely dispersed mariner and Tc1 families. Moreover, translation of the open reading frame revealed three regions showing high similarities with Tc1 from Caenorhabditis elegans and with the mariner element of Drosophila mauritiana . The overall comparison shows that Impala occupies an intermediate position between the mariner and Tcl -like elements, suggesting that all these elements belong to the same superfamily. The degree of relatedness observed between these elements, described in different kingdoms, raises the question of their origin and evolution.
A M Wilson - One of the best experts on this subject based on the ideXlab platform.
-
Biomechanics of predator–prey arms race in lion, zebra, cheetah and Impala
Nature, 2018Co-Authors: A M Wilson, Tatjana Y Hubel, Simon Wilshin, J C Lowe, Maja Lorenc, Oliver P Dewhirst, Rebecca Diack, Emily Bennitt, Hattie L. A. Bartlam-brooks, Krystyna A GolabekAbstract:Nature might be red in tooth and claw, but the race is not always won by the strong. A detailed study of how lions chase down zebras and cheetahs pursue Impalas shows that, although the predators in each pair had substantially more muscle power than their prey, as well as much greater capacity to accelerate and decelerate, the prey species could slip away at lower speeds, at which they are more manoeuvrable. Nevertheless, predators need to be more athletic than their prey to sustain a viable kill rate. The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator–prey pairs, lion–zebra and cheetah–Impala, in their natural savannah habitat in Botswana. We show that although cheetahs and Impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator–prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate. Analysis and modelling of locomotor characteristics of two pursuit predator–prey pairs show that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival.
-
biomechanics of predator prey arms race in lion zebra cheetah and Impala
Nature, 2018Co-Authors: A M Wilson, Tatjana Y Hubel, Simon Wilshin, J C Lowe, Maja Lorenc, Oliver P Dewhirst, Hattie L A Bartlambrooks, Rebecca Diack, Emily Bennitt, Krystyna A GolabekAbstract:The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator-prey pairs, lion-zebra and cheetah-Impala, in their natural savannah habitat in Botswana. We show that although cheetahs and Impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator-prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate.
-
biomechanics of predator prey arms race in lion zebra cheetah and Impala
Nature, 2018Co-Authors: A M Wilson, Tatjana Y Hubel, Simon Wilshin, J C Lowe, Maja Lorenc, Oliver P Dewhirst, Hattie L A Bartlambrooks, Rebecca Diack, Emily Bennitt, Krystyna A GolabekAbstract:The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator–prey pairs, lion–zebra and cheetah–Impala, in their natural savannah habitat in Botswana. We show that although cheetahs and Impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator–prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate. Analysis and modelling of locomotor characteristics of two pursuit predator–prey pairs show that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival. Nature might be red in tooth and claw, but the race is not always won by the strong. A detailed study of how lions chase down zebras and cheetahs pursue Impalas shows that, although the predators in each pair had substantially more muscle power than their prey, as well as much greater capacity to accelerate and decelerate, the prey species could slip away at lower speeds, at which they are more manoeuvrable. Nevertheless, predators need to be more athletic than their prey to sustain a viable kill rate.
Matthew Jacobs - One of the best experts on this subject based on the ideXlab platform.
-
Impala: Eine moderne, quellen-offene SQL Engine für Hadoop
Big Data, 2016Co-Authors: Marcel Kornacker, Alexander Behm, Victor Bittorf, Taras Bobrovytsky, Casey Ching, Alan Choi, Justin Erickson, Grund Martin, Daniel Hecht, Matthew JacobsAbstract:Impala von Cloudera ist ein modernes, massiv paralleles Datenbanksystem, welches von Grund auf fur die Bedurfnisse und Anforderungen einer Big Data Umgebung wie Hadoop entworfen wurde. Das Ziel von Impala ist es, klassische SQL-Abfragen mit geringer Latenz und Laufzeit auszufuhren, so wie man es von typischen BI/DW Losungen gewohnt ist. Gleichzeitig sollen dabei sehr grose Quelldaten in Hadoop gelesen werden, ohne dass ein weiterer Extraktionsprozess in zusatzliche Systemlandschaften notwendig ist. Dieses Kapitel soll einen Uberblick uber Impala aus der Benutzerperspektive geben und detaillierter auf die Hauptkomponenten und deren Entwurfsentscheidungen eingehen. Zusatzlich werden wir einen Geschwindigkeitsvergleich mit anderen bekannten SQL-auf-Hadoop Losungen vorstellen, der den besonderen Ansatz von Impala unterstreicht.
-
Impala a modern open source sql engine for hadoop
Conference on Innovative Data Systems Research, 2015Co-Authors: Marcel Kornacker, Alexander Behm, Victor Bittorf, Taras Bobrovytsky, Casey Ching, Alan Choi, Justin Erickson, Daniel Hecht, Martin Grund, Matthew JacobsAbstract:Cloudera Impala is a modern, open-source MPP SQL engine architected from the ground up for the Hadoop data processing environment. Impala provides low latency and high concurrency for BI/analytic read-mostly queries on Hadoop, not delivered by batch frameworks such as Apache Hive. This paper presents Impala from a user’s perspective, gives an overview of its architecture and main components and briefly demonstrates its superior performance compared against other popular SQL-on-Hadoop systems.
-
CIDR - Impala: A Modern, Open-Source SQL Engine for Hadoop.
2015Co-Authors: Marcel Kornacker, Alexander Behm, Victor Bittorf, Taras Bobrovytsky, Casey Ching, Alan Choi, Justin Erickson, Daniel Hecht, Martin Grund, Matthew JacobsAbstract:Cloudera Impala is a modern, open-source MPP SQL engine architected from the ground up for the Hadoop data processing environment. Impala provides low latency and high concurrency for BI/analytic read-mostly queries on Hadoop, not delivered by batch frameworks such as Apache Hive. This paper presents Impala from a user’s perspective, gives an overview of its architecture and main components and briefly demonstrates its superior performance compared against other popular SQL-on-Hadoop systems.
