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Monica B. Martella - One of the best experts on this subject based on the ideXlab platform.
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Yolk immunoreactive corticosterone does not relate with maternal fecal glucocorticoids in a captive population of Greater Rheas (Rhea Americana)
Journal of Ornithology, 2020Co-Authors: Natalia S. Della Costa, Joaquin L. Navarro, Raúl H. Marin, Monica B. MartellaAbstract:Der Dottergehalt an immunreaktivem Corticosteron steht bei einer Gehegepopulation von Nandus (Rhea Americana) nicht in Relation zum Glucocorticoidgehalt im mütterlichen Kot. Mütterliches Corticosteron im Dotter von Vogeleiern kann die herrschenden Umweltbedingungen widerspiegeln und die Vogelküken auf diese vorbereiten. Eine solche Anpassung erfordert allerdings flexible Regulationsmechanismen, welche zu einer Entkopplung der Hormonspiegel im Mutterleib beziehungsweise im Eidotter führen. In dieser Arbeit untersuchten wir, ob beim Nandu ( Rhea Americana ), einer Laufvogelart mit Gemeinschaftsnestern, ein Zusammenhang zwischen dem Dottergehalt an immunreaktivem Corticosteron und dem mütterlichen Glucocorticoidspiegel besteht. Während der mittleren Legeperiode einer Brutsaison führten wir tägliche Nestbeobachtungen durch, um Eier zu sammeln, bei denen das legende Weibchen bekannt war. Außerdem sammelten wir frische Kotproben der identifizierten legenden Weibchen, um deren Spiegel an Glucocorticoid-Metaboliten im Kot (FGM, fecal glucocorticoid metabolite) während der Dotterbildungsphase (sieben Tage vor der Eiablage) zu bestimmen. Der Dottergehalt an immunreaktivem Corticosteron sowie der FGM-Spiegel wurden mittels eines Immunoassay-Kits gemessen, welches zuvor als für die Art geeignet validiert wurde. Es fanden sich keine signifikanten Zusammenhänge zwischen dem FGM-Wert der Weibchen und dem Dottergehalt an immunreaktivem Corticosteron. Obwohl für die Aufklärung der zugrundeliegenden Mechanismen weiter Untersuchungen notwendig sind, legen unsere Befunde doch nahe, dass Nanduweibchen dazu fähig sein könnten, die Abgabe von Corticosteron ins Eidotter zu kontrollieren, was wiederum die Vermutung unterstützt, dass dieses Hormon einen adaptiven mütterlichen Einfluss vermittelt. Maternal corticosterone in avian egg yolks may signal and prepare offspring for the prevailing conditions. However, this adjustment requires flexible mechanisms of regulation that lead to the absence of a correlation between hormone levels in the mother and the yolk. In this study, we examined whether yolk immunoreactive corticosterone and maternal glucocorticoid levels are related in the Greater Rhea ( Rhea Americana ), a ratite species with a communal nesting system. During the intermediate laying period of the season, we carried out daily nest-observations to collect those eggs in which the laying female was identified. We also collected fresh fecal samples from the identified laying females to quantify their fecal glucocorticoid metabolite (FGM) levels during the yolk formation period (7 days before egg-laying). Yolk immunoreactive corticosterone and FGM levels were measured using a corticosterone^125 radioimmunoassay kit, previously validated for the species. No significant relationships were found between female FGM and yolk immunoreactive corticosterone. Although futures studies are needed to elucidate the underlying mechanisms, our results suggest that Greater Rhea female may be able to control the distribution of corticosterone into their yolks, supporting the idea that this hormone may be mediating an adaptive maternal effect.
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Genetic identification of the ciliates from greater Rheas (Rhea Americana) and lesser Rheas (Rhea pennata) as Balantioides coli
Parasitology Research, 2020Co-Authors: Juan José García-rodríguez, Joaquín Luis Navarro, Monica B. Martella, Rafael A. Martínez-díaz, Francisco Ponce-gordoAbstract:The ciliate species Balantioides coli can be cross-transmitted between humans and several animal species. Usually harmless, sometimes it can be pathogenic and cause the death of the host. In birds, B. coli has been confirmed in ostriches by genetic analysis, but the identification from South American greater Rheas ( Rhea Americana ) and lesser Rheas ( Rhea pennata pennata ) is tentative. Since these species are reared for commercial purposes and for reintroduction into the wild, it is necessary to elucidate whether the ciliate from Rheas is B. coli to minimize health risks for humans and for other domestic and wild animals. Individual parasite cells are collected from Argentinean isolates of reared greater Rheas and of wild and reared lesser Rheas, and their ITS region was PCR amplified; the cloning products were sequenced and compared with sequences available in public databases. The results have shown that several sequence types are expressed at the same time in the parasite cells, and all correspond to B. coli , confirming the possibility of cross-transmission of the parasite between wild and reared South American Rheas and several mammal species and humans.
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distribution and concentration of maternal progesterone in the yolk of greater Rhea eggs Rhea Americana
Journal of Experimental Zoology, 2017Co-Authors: Natalia S. Della Costa, Joaquín Luis Navarro, Juan Manuel Busso, R H Marin, Monica B. MartellaAbstract:Progesterone is the most concentrated maternal yolk steroid characterized to date in birds; however, no information about it is available in ratite eggs. We collected freshly laid eggs from zoo-housed Greater Rhea females (Rhea Americana) bred under similar rearing conditions during two breeding seasons to characterize concentration and distribution of maternal yolk progesterone. After high-performance liquid chromatography analysis, yolk hormone was measured using a commercial electrochemiluminescence immunoassay. Progesterone concentrations were found to vary significantly among the yolk layers, supporting a follicular origin for this steroid in Greater Rhea eggs. Additionally, highly similar mean absolute yolk progesterone concentrations were detected between 2013 and 2015 breeding seasons (1,332.98 ± 82.59 and 1,313.59 ± 85.19 ng/g, respectively). These values are also comparable to those found in some domestic carinate species. Findings suggest that at population level, when rearing conditions are similar, mean absolute yolk maternal progesterone concentrations also appear bounded. Future research on the factors and mechanisms that regulate progesterone deposition in Greater Rhea eggs is needed to better understand whether its levels depend on different rearing conditions.
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Stress in wild Greater Rhea populations Rhea Americana: effects of agricultural activities on seasonal excreted glucocorticoid metabolite levels
Journal of Ornithology, 2014Co-Authors: A. Lèche, G. Bazzano, R H Marin, C. Hansen, J. L. Navarro, Monica B. MartellaAbstract:Stress in freilebenden Nandupopulationen Rhea Americana: Effekte landwirtschaftlicher Aktivitäten auf saisonale Glukokortikoidmetabolitspiegel im Kot In den letzten Jahren haben freilebende Populationen des Nandus ( Rhea Americana ) drastisch abgenommen, hauptsächlich wegen der Umwandlung von Grünland in Ackerland infolge intensiver, spezialisierter landwirtschaftlicher Methoden. In dieser Studie testen wir mögliche Stresseffekte landwirtschaftlicher Aktivitäten auf diesen Laufvogel, indem wir seine adrenokortikale Antwort abschätzen. Wir haben die Spiegel von Glukokortikoidmetaboliten (FGM) im Kot von Nandus verglichen, die in zwei Gebieten mit sehr unterschiedlicher Landnutzung leben: Grünland, auf dem hauptsächlich Rinder grasen, und Agrarökosysteme, die intensiv für den Pflanzenbau genutzt werden. Die Nandugruppen wurden 45-50 min lang aus einer Entfernung von etwa 1 km beobachtet, um jegliche potenzielle Störung zu vermeiden. Daher war es nicht möglich, Kotproben einem bestimmten Geschlecht oder Individuum innerhalb der Gruppe zuzuordnen. Radioimmunassays der Kotproben von 269 Individuen zeigten keine signifikanten Unterschiede in der mittleren FGM-Konzentration zwischen den beiden untersuchten Habitaten. Im Agrarökosystem fanden wir keinen Gesamteffekt landwirtschaftlicher Methoden auf die FGM-Spiegel der Vögel. Während der Trockenzeit waren die FGM-Konzentrationen jedoch signifikant höher, was eine Stressantwort auf die geringe Nahrungsverfügbarkeit in der Zeit nach der Ernte widerspiegeln könnte. Im Gegensatz dazu wurde im Grünland, wo Nahrung das ganze Jahr über verfügbar war, kein Anstieg der FGM-Spiegel festgestellt. Hier fiel der stärkste Anstieg der FGM-Spiegel mit der Fortpflanzungsperiode zusammen, wahrscheinlich weil es zu dieser Zeit häufig zu aggressiven Begegnungen zwischen Männchen kommt. Unsere Befunde deuten daher darauf hin, dass landwirtschaftliche Methoden als chronische Umweltstressfaktoren für Nandupopulationen, die unter solchen Bedingungen leben, betrachtet werden müssen. Die vorliegenden Ergebnisse stützen frühere Forschungsergebnisse, die schädliche Auswirkungen landwirtschaftlicher Aktivitäten auf diese Vogelart zeigten, welche die produktivsten Regionen Südamerikas bewohnt. In recent years, wild populations of Greater Rhea ( Rhea Americana ) have declined drastically, due mainly to the conversion of grassland into cropland as a result of intensive, specialized agricultural practices. In this study we test the potential stressful effects of agricultural activities on this ratite by assessing their adrenocortical response. Specifically, we compared fecal glucocorticoid metabolite (FGM) levels of Rheas living in two areas under very different land use: grasslands mainly used for cattle grazing and agro-ecosystems intensively used for crop production. Groups of Rheas were observed during 45–50 min from a distance of approximately 1 km to avoid any potential disturbance. Therefore, no matching of each fecal sample with a particular sex or individual within the group was possible. Radioimmunoassay of fecal samples from 269 individuals indicated no significant differences in mean concentrations of FGM from the two habitats sampled. In the agro-ecosystem we found no overall effect of agricultural practices on the birds' FGM levels. However, during the dry season FGM concentrations were significantly higher, which may represent a stress response to the low availability of food in the post-harvesting season. In contrast, no increase in FGM levels was registered during the dry season in the grassland, where food was available throughout the year. In this environment the highest increases in FGM levels coincided with the reproductive period, likely due to the frequent agonist encounters between males at this time of the year. Our findings, therefore, suggest that the agricultural practices have to be viewed as chronic environmental stressors for Greater Rhea populations living under such conditions. The present results support earlier research showing detrimental impacts of agricultural activities on this species, which inhabits the most productive regions of South America.
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space use by wild greater Rhea Rhea Americana in a relict grassland of central argentina during the non breeding season
www.scielo.ar, 2013Co-Authors: Ernesto Ezequiel Juan, Joaquín Luis Navarro, Gisela Bazzano, Monica B. MartellaAbstract:To determine movement patterns and home range of wild Greater Rhea (Rhea Americana), two subadult males were radio-tracked during the non-breeding season in a relict grassland of San Luis Province, Argentina. The average home range was 452.8 ha, the average daily distance travelled was 1.08 km/day, and the maximum distance from the capture/release site was 13.66 km. Rheas showed differences in habitat types used throughout the day. Grasslands were more frequently used early in the morning and late in the afternoon, whereas cultivated pastures (Medicago sativa) were used at noon. Although data is considered preliminary due to the small sample size, the importance of this study is here emphasized because it provides the first records of the spatial ecology of wild individuals for this species.
Joaquín Luis Navarro - One of the best experts on this subject based on the ideXlab platform.
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Genetic identification of the ciliates from greater Rheas (Rhea Americana) and lesser Rheas (Rhea pennata) as Balantioides coli
Parasitology Research, 2020Co-Authors: Juan José García-rodríguez, Joaquín Luis Navarro, Monica B. Martella, Rafael A. Martínez-díaz, Francisco Ponce-gordoAbstract:The ciliate species Balantioides coli can be cross-transmitted between humans and several animal species. Usually harmless, sometimes it can be pathogenic and cause the death of the host. In birds, B. coli has been confirmed in ostriches by genetic analysis, but the identification from South American greater Rheas ( Rhea Americana ) and lesser Rheas ( Rhea pennata pennata ) is tentative. Since these species are reared for commercial purposes and for reintroduction into the wild, it is necessary to elucidate whether the ciliate from Rheas is B. coli to minimize health risks for humans and for other domestic and wild animals. Individual parasite cells are collected from Argentinean isolates of reared greater Rheas and of wild and reared lesser Rheas, and their ITS region was PCR amplified; the cloning products were sequenced and compared with sequences available in public databases. The results have shown that several sequence types are expressed at the same time in the parasite cells, and all correspond to B. coli , confirming the possibility of cross-transmission of the parasite between wild and reared South American Rheas and several mammal species and humans.
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distribution and concentration of maternal progesterone in the yolk of greater Rhea eggs Rhea Americana
Journal of Experimental Zoology, 2017Co-Authors: Natalia S. Della Costa, Joaquín Luis Navarro, Juan Manuel Busso, R H Marin, Monica B. MartellaAbstract:Progesterone is the most concentrated maternal yolk steroid characterized to date in birds; however, no information about it is available in ratite eggs. We collected freshly laid eggs from zoo-housed Greater Rhea females (Rhea Americana) bred under similar rearing conditions during two breeding seasons to characterize concentration and distribution of maternal yolk progesterone. After high-performance liquid chromatography analysis, yolk hormone was measured using a commercial electrochemiluminescence immunoassay. Progesterone concentrations were found to vary significantly among the yolk layers, supporting a follicular origin for this steroid in Greater Rhea eggs. Additionally, highly similar mean absolute yolk progesterone concentrations were detected between 2013 and 2015 breeding seasons (1,332.98 ± 82.59 and 1,313.59 ± 85.19 ng/g, respectively). These values are also comparable to those found in some domestic carinate species. Findings suggest that at population level, when rearing conditions are similar, mean absolute yolk maternal progesterone concentrations also appear bounded. Future research on the factors and mechanisms that regulate progesterone deposition in Greater Rhea eggs is needed to better understand whether its levels depend on different rearing conditions.
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space use by wild greater Rhea Rhea Americana in a relict grassland of central argentina during the non breeding season
www.scielo.ar, 2013Co-Authors: Ernesto Ezequiel Juan, Joaquín Luis Navarro, Gisela Bazzano, Monica B. MartellaAbstract:To determine movement patterns and home range of wild Greater Rhea (Rhea Americana), two subadult males were radio-tracked during the non-breeding season in a relict grassland of San Luis Province, Argentina. The average home range was 452.8 ha, the average daily distance travelled was 1.08 km/day, and the maximum distance from the capture/release site was 13.66 km. Rheas showed differences in habitat types used throughout the day. Grasslands were more frequently used early in the morning and late in the afternoon, whereas cultivated pastures (Medicago sativa) were used at noon. Although data is considered preliminary due to the small sample size, the importance of this study is here emphasized because it provides the first records of the spatial ecology of wild individuals for this species.
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Gastrointestinal parasites in greater Rheas (Rhea Americana) and lesser Rheas (Rhea pennata) from Argentina
Veterinary Parasitology, 2012Co-Authors: Rafael A. Martínez-díaz, Joaquín Luis Navarro, Monica B. Martella, Francisco Ponce-gordoAbstract:Abstract Few data exist on the parasites of ratites, especially from regions within their natural range. It is only recently that extensive studies on the parasites of ostriches ( Struthio camelus ) have been published, mainly from European countries where commercial farming has expanded. Two species of ratites are native in South America: the lesser Rhea also known as Darwin's Rhea ( Rhea pennata ) and the greater Rhea ( Rhea Americana ). Both species are considered near threatened by the IUCN and are included in the CITES’ Appendices I and II, respectively. Parasitological studies have conservation implications, as they allow us to assess the risk of transmission of pathogens from farmed ratites to wild populations. In this study 92 faecal samples from greater Rheas and 55 faecal samples from lesser Rheas from different localities in Argentine were analyzed to determine their gastrointestinal parasites. In greater Rheas the protozoa ( Balantidium coli -like and Entamoeba spp.) and helminths ( Fasciola hepatica and Deletrocephalus spp.). The protozoa had not previously been cited as parasites of greater Rheas in South America. Cysts and/or trophozoites of B. coli -like were found in 16.3% of the samples, while the prevalence of the remaining parasites was below 10%. Lesser Rheas harbored the protozoa B. coli -like, Entamoeba spp. and Chilomastix spp. as well as F. hepatica and nematode eggs and larvae. B. coli -like cysts were found in 20.0% of the samples, while the prevalence of the other parasites remained below 5%. Some of them had not been cited as infecting lesser Rheas yet.
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Diet preference and breeding success in captive-bred Greater Rheas (Rhea Americana): a preliminary study
Turkish Journal of Veterinary & Animal Sciences, 2011Co-Authors: Gisela Bazzano, Joaquín Luis Navarro, Monica B. MartellaAbstract:We conducted 2 consecutive experiments to verify whether adult captive Greater Rheas (Rhea Americana) could select diets differing in nutritional and energetic content, and to evaluate the effect of those diets on egg production and hatchability. From August to January, animals were offered four diets: processed feed for Rheas (diet 1), diet 1 + soybean (diet 2), processed feed for chicken (diet 3), and diet 3 + soybean (diet 4). Rheas preferred the diets containing feed for chicken (diets 3 and 4, 179,67 ± 12.12 [S.E.] g/ind./day). Diet 2 was more consumed (95.67 ± 16.70 g/ind./day) than diet 1 (60.09 ± 11.31 g/ind./day), whereas preferences for feed for chicken did not vary with supplementation. Diet 1 and soybean-supplemented diets were consumed by males (113 ± 13.66 and 163.57 ± 13.33 g/ind./day, respectively) in a greater amount than by females (42.27 ± 8.61 and 96.72 ± 16.52 g/ind./day, respectively). Diet type did not affect egg production (43-63 eggs), but hatchability was 13% higher in eggs from females fed soybean-supplemented feed (diets 2 and 4), and those fed diet 2 produced more chicks. While diets 3 and 4 were apparently of lower nutrient quality, they provided more energy than those formulated with processed feed for Rheas. Conversely, diet 2 seemed to be the most favourable for females during the reproductive season. The quality of diets provided to females would largely influence breeding success in captive Greater Rheas.
Gustavo J. Fernández - One of the best experts on this subject based on the ideXlab platform.
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Sequential predictability of the scanning behaviour of greater Rheas, Rhea Americana
Ethology Ecology & Evolution, 2011Co-Authors: Mariana Emilia Carro, Gustavo J. Fernández, Juan C ReboredaAbstract:Some models that predict the scanning pattern to maximise the probability of predator detection by prey assume sequential randomness (i.e. lengths of inter-scan intervals are independent of each other and of the length of scan events). Sequential randomness would prevent stalking predators synchronising their attacks with long inter-scan intervals. We analysed the presence of sequential randomness in the scanning behaviour of the greater Rhea (Rhea Americana), a large flightless bird that forages solitarily or in groups. We analysed sequences of behaviour of 40 wild Rheas, foraging solitarily or in groups of 2 to 17 individuals, in two populations in eastern Argentina. We used parametric (auto and cross-correlations) and non-parametric (runs and Spearman rank correlation) tests to detect dependence among intervals. We detected the temporal dependence of inter-scan intervals in 30 of 40 behavioural series, but only 11 of 40 sequences showed consistent dependence when tested using parametric and non-paramet...
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scanning pattern of greater Rheas Rhea Americana collective vigilance would increase the probability of detecting a predator
Journal of Ethology, 2009Co-Authors: Mariana Emilia Carro, Gustavo J. FernándezAbstract:Many models using vigilance to predict the probability of detecting an approaching predator assumes that prey scanning events should be produced at random. Consequently, the length of intervals among successive scans must follow a negative exponential distribution. We analyzed the scanning behavior of the greater Rhea, Rhea Americana, which is a gregarious, flightless bird, in eastern Argentina. We investigated whether individual and/or collective scanning departed from random and whether this departure varied with group size. We used two simulation models based on observed scanning sequences to assess the effectiveness of vigilance on the individual and collective level when faced with an opportunistic or stalking predator. The analysis of 59 behavioral sequences of wild greater Rheas foraging solitary or in groups of two to six or more individuals revealed that the inter-scan length of individual sequences significantly departed from random. In contrast, inter-scan intervals for collective vigilance were shorter than individual ones, but only fit the random expectation for groups of two and five individuals. Models showed that collective vigilance could increase the probability of detecting a predator, thereby reducing their vulnerability, independent of whether the predator uses a stalking or opportunistic approaching strategy.
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Seasonal variation in social organisation and diurnal activity budget of the Greater Rhea (Rhea Americana) in the Argentinean pampas
Emu, 2008Co-Authors: Mariana Emilia Carro, Gustavo J. FernándezAbstract:We analysed seasonal variation in the size and composition of groups, and individual behaviour, of a wild population of Greater Rheas (Rhea Americana) in the Argentinean pampas. We performed seasonal censuses over 8 years, and made focal observations on 59 individuals from different groups to assess the proportion of time spent in vigilance, feeding, walking, preening or resting, and noted the number of courtship displays, copulations and aggressive interactions. Rheas were solitary or formed groups of 2-20 individuals. Mean typical group-size (TGS) over the year was 7.61 birds but varied significantly with season, TGS decreasing during the breeding season (spring), possibly owing to formation of harems. TGS of males decreased in spring whereas TGS of females did not vary seasonally. During spring, individuals spent more time vigilant and less time feeding, and were involved in many courtship interactions. Most aggression (72%) was between males and mainly occurred during winter and spring, suggesting strong intrasexual competition. Social organisation and group dynamics appear to be profoundly affected by the mating system of the Greater Rhea.
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Egg losses and nest desertion in Greater Rheas Rhea Americana
Ibis, 2008Co-Authors: Gustavo J. Fernández, Juan C ReboredaAbstract:Avian nest desertion should occur when the cost of attending the nest results in a reduction of parental fitness. In Greater Rheas Rhea Americana, the male incubates the eggs so that the decision to desert the nest is made exclusively by him. Because of constraints, the timing of desertion may affect the possibility of renesting. We estimated nest desertion rates through the breeding season and at different stages of the nesting cycle (laying and early, mid- and late incubation). We also analysed the effect of egg losses at different stages of the nesting cycle on the probability of deserting the nest. Nest desertion rates decline throughout the breeding season. The probability of deserting the nest was higher during the laying stage and decreased through incubation. For all stages, egg losses were higher in nests that were deserted than in nests that were still active at the end of the corresponding stage. Egg losses were less likely to elicit nest desertion as incubation advanced. Egg losses in experimental (unattended) nests were not random. We postulate that egg losses during the first stages of the nesting cycle would be a good predictor of future egg losses and risk of nest failure. As females remain associated with the male during egg-laying and because incebation in Rheas is an energetically costly activity that may affect renesting attempts, early nest desertion could increase a male's ability to remate and renest.
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costs of large communal clutches for male and female greater Rheas Rhea Americana
Ibis, 2007Co-Authors: Gustavo J. Fernández, Juan C ReboredaAbstract:The breeding system of the Greater Rhea Rhea Americana is almost unique among birds as it combines harem polygyny and sequential polyandry, with communal egg-laying and uniparental male care. In this species, large communal clutches (more than 30 eggs) are rare and have a lower hatching success than smaller clutches. Here we analyse the proximate causes of hatching failures and the costs of large communal clutches (and therefore the costs of extensive polygyny) for males and females. We evaluated if length of the nesting period, egg viability, egg losses during incubation and male parental activity at the nest were affected by clutch size. We also evaluated if chicks hatched from large clutches have a lower survival during the first 2 months after hatching. Large clutches had longer nesting period and lower hatching success, mainly as a result of bacterial contamination of the eggs and increased hatching asynchrony. In addition, large clutches tended to lose more eggs as a result of accidental breakage or predation. Male activity at the nest and chick survival were not related to clutch size. Low hatching success, nest predation risk and energetic costs associated with large clutches penalize females that join large harems and males that accept additional eggs into the nest.
Juan C Reboreda - One of the best experts on this subject based on the ideXlab platform.
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Sequential predictability of the scanning behaviour of greater Rheas, Rhea Americana
Ethology Ecology & Evolution, 2011Co-Authors: Mariana Emilia Carro, Gustavo J. Fernández, Juan C ReboredaAbstract:Some models that predict the scanning pattern to maximise the probability of predator detection by prey assume sequential randomness (i.e. lengths of inter-scan intervals are independent of each other and of the length of scan events). Sequential randomness would prevent stalking predators synchronising their attacks with long inter-scan intervals. We analysed the presence of sequential randomness in the scanning behaviour of the greater Rhea (Rhea Americana), a large flightless bird that forages solitarily or in groups. We analysed sequences of behaviour of 40 wild Rheas, foraging solitarily or in groups of 2 to 17 individuals, in two populations in eastern Argentina. We used parametric (auto and cross-correlations) and non-parametric (runs and Spearman rank correlation) tests to detect dependence among intervals. We detected the temporal dependence of inter-scan intervals in 30 of 40 behavioural series, but only 11 of 40 sequences showed consistent dependence when tested using parametric and non-paramet...
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Egg losses and nest desertion in Greater Rheas Rhea Americana
Ibis, 2008Co-Authors: Gustavo J. Fernández, Juan C ReboredaAbstract:Avian nest desertion should occur when the cost of attending the nest results in a reduction of parental fitness. In Greater Rheas Rhea Americana, the male incubates the eggs so that the decision to desert the nest is made exclusively by him. Because of constraints, the timing of desertion may affect the possibility of renesting. We estimated nest desertion rates through the breeding season and at different stages of the nesting cycle (laying and early, mid- and late incubation). We also analysed the effect of egg losses at different stages of the nesting cycle on the probability of deserting the nest. Nest desertion rates decline throughout the breeding season. The probability of deserting the nest was higher during the laying stage and decreased through incubation. For all stages, egg losses were higher in nests that were deserted than in nests that were still active at the end of the corresponding stage. Egg losses were less likely to elicit nest desertion as incubation advanced. Egg losses in experimental (unattended) nests were not random. We postulate that egg losses during the first stages of the nesting cycle would be a good predictor of future egg losses and risk of nest failure. As females remain associated with the male during egg-laying and because incebation in Rheas is an energetically costly activity that may affect renesting attempts, early nest desertion could increase a male's ability to remate and renest.
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costs of large communal clutches for male and female greater Rheas Rhea Americana
Ibis, 2007Co-Authors: Gustavo J. Fernández, Juan C ReboredaAbstract:The breeding system of the Greater Rhea Rhea Americana is almost unique among birds as it combines harem polygyny and sequential polyandry, with communal egg-laying and uniparental male care. In this species, large communal clutches (more than 30 eggs) are rare and have a lower hatching success than smaller clutches. Here we analyse the proximate causes of hatching failures and the costs of large communal clutches (and therefore the costs of extensive polygyny) for males and females. We evaluated if length of the nesting period, egg viability, egg losses during incubation and male parental activity at the nest were affected by clutch size. We also evaluated if chicks hatched from large clutches have a lower survival during the first 2 months after hatching. Large clutches had longer nesting period and lower hatching success, mainly as a result of bacterial contamination of the eggs and increased hatching asynchrony. In addition, large clutches tended to lose more eggs as a result of accidental breakage or predation. Male activity at the nest and chick survival were not related to clutch size. Low hatching success, nest predation risk and energetic costs associated with large clutches penalize females that join large harems and males that accept additional eggs into the nest.
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Male parental care in Greater Rheas (Rhea Americana) in Argentina
The Auk, 2003Co-Authors: Gustavo J. Fernández, Juan C ReboredaAbstract:Abstract Greater Rheas (Rhea Americana) are precocial birds that show uniparental male care. We evaluated the extent of nest attention by males and estimated its effect on viability and survival of eggs. We assessed whether male absences during incubation were constrained to avoid embryos reaching lethal temperatures or to minimize risk of egg predation. We estimated (1) effect of nest attention on viability of eggs by comparing egg temperature in nests with and without male attention; and (2) effect of male care on egg predation, by comparing survival of eggs in nests with and without male care. Rhea males attended the eggs for 42 days, but effective incubation started 5–7 days after laying of the first egg. The proportion of time that males spent at the nest increased from 64% during egg laying (days 1–10) up to 97.5% during mid and late incubation (days 20–40). Male absences occurred at the warmest hours of the day and their lengths were positively correlated with the temperature of the environment. Ma...
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Male Parental Care in Greater Rheas (Rhea Americana) in Argentina
The Auk, 2003Co-Authors: Gustavo J. Fernández, Juan C ReboredaAbstract:AbstractGreater Rheas (Rhea Americana) are precocial birds that show uniparental male care. We evaluated the extent of nest attention by males and estimated its effect on viability and survival of eggs. We assessed whether male absences during incubation were constrained to avoid embryos reaching lethal temperatures or to minimize risk of egg predation. We estimated (1) effect of nest attention on viability of eggs by comparing egg temperature in nests with and without male attention; and (2) effect of male care on egg predation, by comparing survival of eggs in nests with and without male care. Rhea males attended the eggs for 42 days, but effective incubation started 5–7 days after laying of the first egg. The proportion of time that males spent at the nest increased from 64% during egg laying (days 1–10) up to 97.5% during mid and late incubation (days 20–40). Male absences occurred at the warmest hours of the day and their lengths were positively correlated with the temperature of the environment. Male nest attention reduced the rate of egg losses and kept eggs above lower lethal temperatures for embryos during the night. We also estimated relative cost of parental care after hatching by comparing the time allocated to feeding and vigilance by males with chicks, males in nonreproductive groups, and nonreproductive solitary males. Males took care of the chicks for 4–6 months. They allocated less time to feeding and more time to vigilance than males in groups of adults or solitary males. Investment in vigilance decreased as chicks aged. Our results indicate that Greater Rhea males would require high levels of energetic reserves to start a breeding attempt. That high demand could explain why less than only 20% of the males attempt to nest during a breeding season.
Veronica Schmidt - One of the best experts on this subject based on the ideXlab platform.
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deteccao de salmonella sp em emas Rhea Americana atraves de suabes cloacais
Acta Scientiae Veterinariae, 2018Co-Authors: R A Pereira, Claudio Wageck Canal, Veronica SchmidtAbstract:A ema ( Rhea Americana ) e uma ratita nativa da America do Sul que esta sendo criada comercialmente em fazendas no sul do Brasil pela sua carne e penas. Devido ao potencial que as aves tem de transmitir sorovares de Salmonella sp capazes de causar toxinfeccao alimentar, torna-se fundamental conhecer o estado sanitario das emas em relacao a este patogeno. Com este objetivo, procurou-se verificar a viabilidade da utilizacao do suabe cloacal para o isolamento de Salmonella sp. em emas. Visceras e suabes cloacais foram coletadas de 26 aves abatidas em um frigorifico no Rio Grande do Sul. Utilizando-se o isolamento em figado e/ou ceco como metodo diagnostico padrao, determinou-se alta especificidade (80%) e valor preditivo positivo (90,91%); porem, verificou-se baixa sensibilidade (47,62%) e valor preditivo negativo (26,7%). Das 11 cepas isoladas a partir de suabes, duas (18,2%) foram identificadas como S. enterica enterica rugosa, tres (27,3%) como S . Newport e seis (54,5%) como S . Typhimurium. Atraves desse estudo, verificou-se que a utilizacao de suabe cloacal para deteccao de Salmonella sp . em emas deve ser criteriosa, uma vez que o numero de falsos negativos e elevado.
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Detecção sorológica e microbiológica de Salmonella spp. em emas (Rhea Americana)
Arquivo Brasileiro de Medicina Veterinária e Zootecnia, 2012Co-Authors: R A Pereira, Claudio Wageck Canal, Marisa Macagnan, Veronica SchmidtAbstract:The fast agglutination screening test, using S. Typhimurium as the antigen, was compared with the standard bacterial method to identify Rheas (Rhea Americana) contaminated with Salmonella spp.at slaughter.Seventy birds were serologically tested for Salmonella enterica Pullorum using a commercial antigen.Of these, 66 were also submitted to a macroagglutination test, using a strain of Salmonella Typhimurium isolated from Rheas.All birds did not react with the commercial S. Pullorum antigen, but 37 were positive for the FAST-ST.The isolation of Salmonella spp. was verified in 66 (94.2%) birds. 85.7% were found in liver samples, 60% in feces and 42.3% in cloacal swabs.A total of 16.6% were identified as being S. enterica enterica rugosa, 35.9% as S. Typhimurium, 46.5% as S.Newport and 0.9% as S. Anatum. An insignificant concordance between the results of bacterial isolation and the serological response was observed (k=0.016).The detection of Salmonella spp. by bacteriological and serological methods in samples from Rheas must be deemed important, because birds without a clinical manifestation can be significant sources of salmonellas in food infections.
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deteccao de salmonella anatum em ema Rhea Americana
Ciencia Rural, 2008Co-Authors: R A Pereira, Claudio Wageck Canal, Veronica SchmidtAbstract:In aiming to investigate the Salmonella spp. presence in one slaughterhouse in Rio Grande do Sul – Brazil, liver and cecum samples from 70 Greater Rhea (Rhea Americana) were collected. One Salmonella-like colonie was serologically typed and identified as Salmonella Anatum. Considering the high zoonotical potential of this microorganism, an effective microbiological control of wild animal slaughterhouses and the final product is needed.