Demography, life history, and social structure in Propithecus diadema edwardsi from 1986–2000 in Ranomafana National Park, Madagascar / Sharon T. Pochron  

Public ISBD Titre : Demography, life history, and social structure in Propithecus diadema edwardsi from 1986–2000 in Ranomafana National Park, Madagascar Type de document : texte imprimé Auteurs : Sharon T. Pochron, Auteur ; W. Troy Tucker, Auteur ; Patricia C. Wright, Auteur Année de publication : 2004 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : LEMURS  LIFE TABLE  MORTALITY  FERTILITY  POPULATION GROWTH  GROUP STRUCTURE Résumé : Prosimian lemurs differ fundamentally from anthropoid primates in many traits related to social structure. By exploring the demography of Milne-Edwards' sifakas (Propithecus diadema edwardsi), and comparing it to other well-studied primates, we explore the effect of demographic and life-history factors on social structure. Specifically, we compare lemur survivorship and fertility patterns to two published composite models: one created for New World and another created for Old World monkeys. Using longitudinal data collected on individual Propithecus diadema edwardsi from four study groups from 1986–2000 in Ranomafana National Park, Madagascar, we quantify 1) group composition, 2) birth seasonality, 3) interbirth interval, 4) life-table values, and 5) population growth estimates. The mortality, survivorship, and life-expectancy schedules indicate high infant and juvenile mortality. Fertility remains high until death. The intrinsic rate of increase and net reproductive rate indicate a shrinking population. We suggest that high mortality rather than low fertility causes the observed population decline. While sifaka survivorship closely resembles New World patterns, fertility resembles Old World patterns, i.e., like New World monkeys, few sifakas survive to reproductive age, and those that do, reproduce at a slow rate resembling the Old World pattern. This necessarily impacts social structure. An adult sifaka at the end of her lifespan will have one only daughter who survives to reproductive age, compared to 3.4 for New World or 2.7 for Old World monkeys. Demography limits the formation of large kin-based groups for sifakas, and survivorship and fertility patterns do not easily permit sifakas to form large same-sex family groups Titre du périodique : American Journal of Physical Anthropology Volume : 125: 61-72 En ligne : DOI: 10.1002/ajpa.10266 Demography, life history, and social structure in Propithecus diadema edwardsi from 1986–2000 in Ranomafana National Park, Madagascar [texte imprimé] / Sharon T. Pochron, Auteur ; W. Troy Tucker, Auteur ; Patricia C. Wright, Auteur . - 2004. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : LEMURS  LIFE TABLE  MORTALITY  FERTILITY  POPULATION GROWTH  GROUP STRUCTURE Résumé : Prosimian lemurs differ fundamentally from anthropoid primates in many traits related to social structure. By exploring the demography of Milne-Edwards' sifakas (Propithecus diadema edwardsi), and comparing it to other well-studied primates, we explore the effect of demographic and life-history factors on social structure. Specifically, we compare lemur survivorship and fertility patterns to two published composite models: one created for New World and another created for Old World monkeys. Using longitudinal data collected on individual Propithecus diadema edwardsi from four study groups from 1986–2000 in Ranomafana National Park, Madagascar, we quantify 1) group composition, 2) birth seasonality, 3) interbirth interval, 4) life-table values, and 5) population growth estimates. The mortality, survivorship, and life-expectancy schedules indicate high infant and juvenile mortality. Fertility remains high until death. The intrinsic rate of increase and net reproductive rate indicate a shrinking population. We suggest that high mortality rather than low fertility causes the observed population decline. While sifaka survivorship closely resembles New World patterns, fertility resembles Old World patterns, i.e., like New World monkeys, few sifakas survive to reproductive age, and those that do, reproduce at a slow rate resembling the Old World pattern. This necessarily impacts social structure. An adult sifaka at the end of her lifespan will have one only daughter who survives to reproductive age, compared to 3.4 for New World or 2.7 for Old World monkeys. Demography limits the formation of large kin-based groups for sifakas, and survivorship and fertility patterns do not easily permit sifakas to form large same-sex family groups Titre du périodique : American Journal of Physical Anthropology Volume : 125: 61-72 En ligne : DOI: 10.1002/ajpa.10266

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Evaluating effects of deforestation, hunting, and El Niño events on a threatened lemur / Amy E. Dunham ; Elizabeth M. Erhart ; Deborah J. Overdorff ; Patricia C. Wright  

Public ISBD Titre : Evaluating effects of deforestation, hunting, and El Niño events on a threatened lemur Type de document : texte imprimé Auteurs : Amy E. Dunham, Auteur ; Elizabeth M. Erhart, Auteur ; Deborah J. Overdorff, Auteur ; Patricia C. Wright, Auteur Année de publication : 2008 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Menaces et Pressions Mots-clés : DEMOGRAPHY  EL NINO  ENDANGERED SPECIES  EXTINCTION RISKS  MANAGEMENT  POPULATION MODELS  POPULATION VIABILITY ANALYSIS  PROPITHECUS ADWARDSI  LEMURS  MADAGASCAR Résumé : Madagascar ranks as one of the world’s top extinction hotspots because of its high endemism and high rate of habitat degradation. Global climate phenomena such as El Niño Southern Oscillations may have confounding impacts on the island’s threatened biota but these effects are less well known. We performed a demographic study of Propithecus edwardsi, a lemur inhabiting the eastern rainforest of Madagascar, to evaluate the impact of deforestation, hunting, and El Niño on its population and to re-evaluate present endangerment categorization under the IUCN. Over 18 years of demographic data, including survival and fecundity rates were used to parameterize a stochastic population model structured with three stage classes (yearlings, juveniles, and adults). Results demonstrate that hunting and deforestation are the most significant threats to the population. Analysis of several plausible scenarios and combinations of threat revealed that a 50% population decline within three generations was very likely, supporting current IUCN classification. However, the analysis also suggested that changing global cycles may pose further threat. The average fecundity of lemurs was over 65% lower during El Niño years. While not as severe as deforestation or hunting, if El Niño events remain at the current high frequency there may be negative consequences for the population. We suggest that it is most critical for this species continued survival to create more protected areas, not only to thwart hunting and deforestation, but also to give this endangered lemur a better chance to recover from and adapt to altered climate cycles in the future. Titre du périodique : Biological Conservation Volume : 14(1): 287-297 En ligne : https://doi.org/10.1016/j.biocon.2007.10.006 Evaluating effects of deforestation, hunting, and El Niño events on a threatened lemur [texte imprimé] / Amy E. Dunham, Auteur ; Elizabeth M. Erhart, Auteur ; Deborah J. Overdorff, Auteur ; Patricia C. Wright, Auteur . - 2008. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Menaces et Pressions Mots-clés : DEMOGRAPHY  EL NINO  ENDANGERED SPECIES  EXTINCTION RISKS  MANAGEMENT  POPULATION MODELS  POPULATION VIABILITY ANALYSIS  PROPITHECUS ADWARDSI  LEMURS  MADAGASCAR Résumé : Madagascar ranks as one of the world’s top extinction hotspots because of its high endemism and high rate of habitat degradation. Global climate phenomena such as El Niño Southern Oscillations may have confounding impacts on the island’s threatened biota but these effects are less well known. We performed a demographic study of Propithecus edwardsi, a lemur inhabiting the eastern rainforest of Madagascar, to evaluate the impact of deforestation, hunting, and El Niño on its population and to re-evaluate present endangerment categorization under the IUCN. Over 18 years of demographic data, including survival and fecundity rates were used to parameterize a stochastic population model structured with three stage classes (yearlings, juveniles, and adults). Results demonstrate that hunting and deforestation are the most significant threats to the population. Analysis of several plausible scenarios and combinations of threat revealed that a 50% population decline within three generations was very likely, supporting current IUCN classification. However, the analysis also suggested that changing global cycles may pose further threat. The average fecundity of lemurs was over 65% lower during El Niño years. While not as severe as deforestation or hunting, if El Niño events remain at the current high frequency there may be negative consequences for the population. We suggest that it is most critical for this species continued survival to create more protected areas, not only to thwart hunting and deforestation, but also to give this endangered lemur a better chance to recover from and adapt to altered climate cycles in the future. Titre du périodique : Biological Conservation Volume : 14(1): 287-297 En ligne : https://doi.org/10.1016/j.biocon.2007.10.006

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Lemur traits and Madagascar ecology: Coping with an island environment / Patricia C. Wright  

Public ISBD Titre : Lemur traits and Madagascar ecology: Coping with an island environment Type de document : texte imprimé Auteurs : Patricia C. Wright, Auteur Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : LIFE HISTORY  WEANING SYNCHRONY  FEMALE DOMINANCE  CATHEMERALITY  ENERGY CONSERVATION  DISEQUILIBRIUM HYPOTHESIS Résumé : The last decade's lemur research includes successes in discovering new living and extinct species and learning about the distribution, biogeography, physiology, behavior, and ecology of previously little-studied species. In addition, in both the dry forest and rain forest, long-term studies of lemur demography, life history, and reproduction, have been completed in conjunction with data on tree productivity, phenology, and climate. Lemurs contrast with anthropoids in several behavioral features, including female dominance, targeted female-female aggression, lack of sexual dimorphism regardless of mating system, sperm competition coupled with male-male aggression, high infant mortality, cathemerality, and strict seasonal breeding. Hypotheses to explain these traits include the “energy conservation hypothesis” (ECH) suggesting that harsh and unpredictable climate factors on the island of Madagascar have affected the evolution of female dominance, and the “evolutionary disequilibrium hypotheses” (EVDH) suggesting that the recent megafauna extinctions have influenced lemurs to become diurnal. These hypotheses are compared and contrasted in light of recent empirical data on climate, subfossils, and lemur behavior. New data on life histories of the rain forest lemurs at Ranomafana National Park give further support to the ECH. Birth seasons are synchronized within each species, but there is a 6-month distribution of births among species. Gestation and lactation lengths vary among sympatric lemurs, but all lemur species in the rain forest wean in synchrony at the season most likely to have abundant resources. Across-species weaning synchrony seen in Ranomafana corroborates data from the dry forest that late lactation and weaning is the life history event that is the primary focus of the annual schedule. Lemur adaptations may assure maximum offspring survival in this environment with an unpredictable food supply and heavy predation. In conclusion, a more comprehensive energy frugality hypothesis (EFH) is proposed, which postulates that the majority of lemur traits are either adaptations to conserve energy (e.g., low basal metabolic rate (BMR), torpor, sperm competition, small group size, seasonal breeding) or to maximize use of scarce resources (e.g., cathemerality, territoriality, female dominance, fibrous diet, weaning synchrony). Among primates, the isolated adaptive radiation of lemurs on Madagascar may have been uniquely characterized by selection toward efficiency to cope with the harsh and unpredictable island environmen Titre du périodique : Yearbook of Physical Anthropology Volume : 42: 31-72 En ligne : ttps://doi.org/10.1002/(SICI)1096-8644(1999)110:29+<31::AID-AJPA3>3.0.CO;2-0 Lemur traits and Madagascar ecology: Coping with an island environment [texte imprimé] / Patricia C. Wright, Auteur . - [s.d.]. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : LIFE HISTORY  WEANING SYNCHRONY  FEMALE DOMINANCE  CATHEMERALITY  ENERGY CONSERVATION  DISEQUILIBRIUM HYPOTHESIS Résumé : The last decade's lemur research includes successes in discovering new living and extinct species and learning about the distribution, biogeography, physiology, behavior, and ecology of previously little-studied species. In addition, in both the dry forest and rain forest, long-term studies of lemur demography, life history, and reproduction, have been completed in conjunction with data on tree productivity, phenology, and climate. Lemurs contrast with anthropoids in several behavioral features, including female dominance, targeted female-female aggression, lack of sexual dimorphism regardless of mating system, sperm competition coupled with male-male aggression, high infant mortality, cathemerality, and strict seasonal breeding. Hypotheses to explain these traits include the “energy conservation hypothesis” (ECH) suggesting that harsh and unpredictable climate factors on the island of Madagascar have affected the evolution of female dominance, and the “evolutionary disequilibrium hypotheses” (EVDH) suggesting that the recent megafauna extinctions have influenced lemurs to become diurnal. These hypotheses are compared and contrasted in light of recent empirical data on climate, subfossils, and lemur behavior. New data on life histories of the rain forest lemurs at Ranomafana National Park give further support to the ECH. Birth seasons are synchronized within each species, but there is a 6-month distribution of births among species. Gestation and lactation lengths vary among sympatric lemurs, but all lemur species in the rain forest wean in synchrony at the season most likely to have abundant resources. Across-species weaning synchrony seen in Ranomafana corroborates data from the dry forest that late lactation and weaning is the life history event that is the primary focus of the annual schedule. Lemur adaptations may assure maximum offspring survival in this environment with an unpredictable food supply and heavy predation. In conclusion, a more comprehensive energy frugality hypothesis (EFH) is proposed, which postulates that the majority of lemur traits are either adaptations to conserve energy (e.g., low basal metabolic rate (BMR), torpor, sperm competition, small group size, seasonal breeding) or to maximize use of scarce resources (e.g., cathemerality, territoriality, female dominance, fibrous diet, weaning synchrony). Among primates, the isolated adaptive radiation of lemurs on Madagascar may have been uniquely characterized by selection toward efficiency to cope with the harsh and unpredictable island environmen Titre du périodique : Yearbook of Physical Anthropology Volume : 42: 31-72 En ligne : ttps://doi.org/10.1002/(SICI)1096-8644(1999)110:29+<31::AID-AJPA3>3.0.CO;2-0

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The state of lemur conservation in south-eastern Madagascar: population and habitat assessments for diurnal and cathemeral lemurs using surveys, satellite imagery and GIS / M.T. Irwin  

Public ISBD Titre : The state of lemur conservation in south-eastern Madagascar: population and habitat assessments for diurnal and cathemeral lemurs using surveys, satellite imagery and GIS Type de document : texte imprimé Auteurs : M.T. Irwin, Auteur ; Steig E. Johnson, Auteur ; Patricia C. Wright, Auteur Année de publication : 2005 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Conservation , Education , Ecotourisme Mots-clés : CONSERVATION STATUS  GEOGRAPHIC RANGE  GIS  LEMURS  MADAGASCAR  POPULATION DENSITIES  PRIMATES Résumé : The unique primates of south-eastern Madagascar face threats from growing human populations. The country's extant primates already represent only a subset of the taxonomic and ecological diversity existing a few thousand years ago. To prevent further losses remaining taxa must be subjected to effective monitoring programmes that directly inform conservation efforts. We offer a necessary first step: revision of geographic ranges and quantification of habitat area and population size for diurnal and cathemeral (active during both day and night) lemurs. Recent satellite images are used to develop a forest cover geographical information system, and censuses are used to establish range boundaries and develop estimates of population density and size. These assessments are used to identify regions and taxa at risk, and will be a useful baseline for future monitoring of habitat and populations. Precise estimates are impossible for patchily-distributed taxa (especially Hapalemur aureus, H. simus and Varecia variegata variegata); these taxa require more sophisticated modelling. Titre du périodique : Oryx Volume : 39(2): 204-218 En ligne : https://doi.org/10.1017/S0030605305000451 The state of lemur conservation in south-eastern Madagascar: population and habitat assessments for diurnal and cathemeral lemurs using surveys, satellite imagery and GIS [texte imprimé] / M.T. Irwin, Auteur ; Steig E. Johnson, Auteur ; Patricia C. Wright, Auteur . - 2005. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Conservation , Education , Ecotourisme Mots-clés : CONSERVATION STATUS  GEOGRAPHIC RANGE  GIS  LEMURS  MADAGASCAR  POPULATION DENSITIES  PRIMATES Résumé : The unique primates of south-eastern Madagascar face threats from growing human populations. The country's extant primates already represent only a subset of the taxonomic and ecological diversity existing a few thousand years ago. To prevent further losses remaining taxa must be subjected to effective monitoring programmes that directly inform conservation efforts. We offer a necessary first step: revision of geographic ranges and quantification of habitat area and population size for diurnal and cathemeral (active during both day and night) lemurs. Recent satellite images are used to develop a forest cover geographical information system, and censuses are used to establish range boundaries and develop estimates of population density and size. These assessments are used to identify regions and taxa at risk, and will be a useful baseline for future monitoring of habitat and populations. Precise estimates are impossible for patchily-distributed taxa (especially Hapalemur aureus, H. simus and Varecia variegata variegata); these taxa require more sophisticated modelling. Titre du périodique : Oryx Volume : 39(2): 204-218 En ligne : https://doi.org/10.1017/S0030605305000451

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