Does female dominance facilitate feeding priority in black-and-white ruffed lemurs (Varecia variegata) in southeastern Madagascar? / Deborah J. Overdorff  

Public ISBD Titre : Does female dominance facilitate feeding priority in black-and-white ruffed lemurs (Varecia variegata) in southeastern Madagascar? Type de document : texte imprimé Auteurs : Deborah J. Overdorff, Auteur ; Elizabeth M. Erhart, Auteur ; Thomas Mutschler, Auteur Année de publication : 2005 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : FEMALE  FEEDING PRIORITY  FEMALE DOMINANCE,  LEADERSHIP  VARECIA, MADAGASCAR Résumé : Although many Malagasy lemurs are thought to be female dominant and to have female feeding priority, to date the relationship between these behaviors has been rigorously established only in Lemur catta, and other ways that females might achieve feeding priority have not been examined closely. Erhart and Overdorff [International Journal of Primatology 20:927-940, 1999] suggested that one way female primates achieve feeding priority is to initiate and lead groups to food, thereby gaining access to the food first and positively influencing their food intake compared to other group members. Here we describe female dominance patterns and potential measures of feeding priority in two groups of black-and-white ruffed lemurs (Varecia variegata) that were observed over a 15-month period in southeastern Madagascar. We predicted that the females would 1) be consistently dominant to males, 2) lead groups to food sources more often than males, and 3) have higher feeding rates compared to males when they arrived at food sources first. The results were dissimilar between the study groups. During the study, the oldest adult female in group 1 died. There was no evidence for female dominance in this group, and the remaining (likely natal) female did not lead the group more often, nor did she have a higher food intake than males. Group 1 dispersed shortly after the time frame reported here. In contrast, the resident female in group 2 was dominant to group males (based on agonistic interactions), led the group to food sources more often, and experienced a higher food intake when she arrived first at a food source. How these patterns vary over time and are influenced by the number of females in groups, group stability, food quality, and reproductive condition will be examined in future analyses. Titre du périodique : American Journal of Primatology Volume : 66:7-22 En ligne : https://doi.org/10.1002/ajp.20125 Does female dominance facilitate feeding priority in black-and-white ruffed lemurs (Varecia variegata) in southeastern Madagascar? [texte imprimé] / Deborah J. Overdorff, Auteur ; Elizabeth M. Erhart, Auteur ; Thomas Mutschler, Auteur . - 2005. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : FEMALE  FEEDING PRIORITY  FEMALE DOMINANCE,  LEADERSHIP  VARECIA, MADAGASCAR Résumé : Although many Malagasy lemurs are thought to be female dominant and to have female feeding priority, to date the relationship between these behaviors has been rigorously established only in Lemur catta, and other ways that females might achieve feeding priority have not been examined closely. Erhart and Overdorff [International Journal of Primatology 20:927-940, 1999] suggested that one way female primates achieve feeding priority is to initiate and lead groups to food, thereby gaining access to the food first and positively influencing their food intake compared to other group members. Here we describe female dominance patterns and potential measures of feeding priority in two groups of black-and-white ruffed lemurs (Varecia variegata) that were observed over a 15-month period in southeastern Madagascar. We predicted that the females would 1) be consistently dominant to males, 2) lead groups to food sources more often than males, and 3) have higher feeding rates compared to males when they arrived at food sources first. The results were dissimilar between the study groups. During the study, the oldest adult female in group 1 died. There was no evidence for female dominance in this group, and the remaining (likely natal) female did not lead the group more often, nor did she have a higher food intake than males. Group 1 dispersed shortly after the time frame reported here. In contrast, the resident female in group 2 was dominant to group males (based on agonistic interactions), led the group to food sources more often, and experienced a higher food intake when she arrived first at a food source. How these patterns vary over time and are influenced by the number of females in groups, group stability, food quality, and reproductive condition will be examined in future analyses. Titre du périodique : American Journal of Primatology Volume : 66:7-22 En ligne : https://doi.org/10.1002/ajp.20125

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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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Infanticide in Propithecus diadema edwardsi: An Evaluation of the Sexual Selection Hypothesis / Elizabeth M. Erhart  

Public ISBD Titre : Infanticide in Propithecus diadema edwardsi: An Evaluation of the Sexual Selection Hypothesis Type de document : texte imprimé Auteurs : Elizabeth M. Erhart, Auteur ; Deborah J. Overdorff, Auteur Année de publication : 1998 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Menaces et Pressions Mots-clés : INFANTICIDE  PROSIMIAN  SEXUAL SELECTION  MADAGASCAR Résumé : Infanticide might be described as a reproductive strategy employed by anthropoid primate males when they immigrate into new groups. But infanticide has rarely been observed in wild prosimian primates. For the Malagasy lemurs this may reflect one or more of the following: strict breeding seasons; relative monomorphism in canine tooth and body size; small group sizes; male–female dominance relations; and male–female dyads within groups. We addressed the following questions: Do prosimian males commit infanticide in circumstances similar to those in which anthropoids do? and Is there any reproductive advantage for a highly seasonal breeder to commit infanticide? To help answer these questions, we describe the death of a 24-hr-old infant male Propithecus diadema edwardsi from wounds received during a fight between his mother, her adult daughter, and a newly immigrant male. Interbirth intervals between surviving offspring are 2 years for Propithecus diadema edwardsi; therefore, a male could dramatically shorten the time between reproductive windows by killing an infant. Whether this tactic would be favored by sexual selection cannot be addressed until more information has been collected on the length of interbirth interval due to infanticide relative to that of infant death by other causes; how social factors such as stability of breeding relationships affect long-term male reproductive success; how effective female counterstrategies are to prevent infanticide and/or whether they choose to mate with males that commit infanticide; and how often males that kill infants subsequently sire infants, particularly in groups that contain a resident male. Titre du périodique : International Journal of Primatology Volume : 19 (1): 73-81 En ligne : https://doi.org/10.1023/A:1020306910493 Infanticide in Propithecus diadema edwardsi: An Evaluation of the Sexual Selection Hypothesis [texte imprimé] / Elizabeth M. Erhart, Auteur ; Deborah J. Overdorff, Auteur . - 1998. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Menaces et Pressions Mots-clés : INFANTICIDE  PROSIMIAN  SEXUAL SELECTION  MADAGASCAR Résumé : Infanticide might be described as a reproductive strategy employed by anthropoid primate males when they immigrate into new groups. But infanticide has rarely been observed in wild prosimian primates. For the Malagasy lemurs this may reflect one or more of the following: strict breeding seasons; relative monomorphism in canine tooth and body size; small group sizes; male–female dominance relations; and male–female dyads within groups. We addressed the following questions: Do prosimian males commit infanticide in circumstances similar to those in which anthropoids do? and Is there any reproductive advantage for a highly seasonal breeder to commit infanticide? To help answer these questions, we describe the death of a 24-hr-old infant male Propithecus diadema edwardsi from wounds received during a fight between his mother, her adult daughter, and a newly immigrant male. Interbirth intervals between surviving offspring are 2 years for Propithecus diadema edwardsi; therefore, a male could dramatically shorten the time between reproductive windows by killing an infant. Whether this tactic would be favored by sexual selection cannot be addressed until more information has been collected on the length of interbirth interval due to infanticide relative to that of infant death by other causes; how social factors such as stability of breeding relationships affect long-term male reproductive success; how effective female counterstrategies are to prevent infanticide and/or whether they choose to mate with males that commit infanticide; and how often males that kill infants subsequently sire infants, particularly in groups that contain a resident male. Titre du périodique : International Journal of Primatology Volume : 19 (1): 73-81 En ligne : https://doi.org/10.1023/A:1020306910493

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Population demography and social structure changes in Eulemur fulvus rufus from 1988 to 2003 / Elizabeth M. Erhart  

Public ISBD Titre : Population demography and social structure changes in Eulemur fulvus rufus from 1988 to 2003 Type de document : texte imprimé Auteurs : Elizabeth M. Erhart, Auteur ; Deborah J. Overdorff, Auteur Année de publication : 2008 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : PROSIMIAN  MIGRATION  BIRTH RATE  SEX RATIO  GROUP FISSION Résumé : Eulemur fulvus rufus has been described as having stable multi-male/multi-female groups, a male-biased sex ratio, and female philopatry. However, in a 16-year study of this subspecies we documented a great deal of demographic change as several groups permanently fissioned, some groups disappeared, and new groups formed. We split the dataset into two periods, 1988 to 1993 and 1994 to 2003, which coincided with the first disappearance of a study group (in August 1994) and the first permanent group fission (in December 1994). The average group size decreased by nearly half between the study periods (10.5–5.6), while the frequency of group membership changes increased (2.0–8.3 times/year), and the birth rate decreased (0.56–0.38). Females, as well as males, immigrated into study groups and transferred between groups, something that has been rarely seen in this subspecies. We also found a significant decline in the amount of fruit from the earliest part of the study to the latter part of the study. Study groups did not switch to other types of foods during periods of fruit shortage, but traveled outside of their home range areas more often over the study period. Finally, the density E. f. rufus decreased in the study area while the densities of their main food competitors, Varecia variegata and Eulemur rubriventer, increased. Although few primate populations are numerically stable over time, we suggest that female behavioral responses to decreases in fruit availability may have influenced some of the demographic changes we witnessed in this study Titre du périodique : American Journal of Physical Anthropology Volume : 136 : 183-193 En ligne : https://onlinelibrary.wiley.com/doi/10.1002/ajpa.20793 Population demography and social structure changes in Eulemur fulvus rufus from 1988 to 2003 [texte imprimé] / Elizabeth M. Erhart, Auteur ; Deborah J. Overdorff, Auteur . - 2008. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : PROSIMIAN  MIGRATION  BIRTH RATE  SEX RATIO  GROUP FISSION Résumé : Eulemur fulvus rufus has been described as having stable multi-male/multi-female groups, a male-biased sex ratio, and female philopatry. However, in a 16-year study of this subspecies we documented a great deal of demographic change as several groups permanently fissioned, some groups disappeared, and new groups formed. We split the dataset into two periods, 1988 to 1993 and 1994 to 2003, which coincided with the first disappearance of a study group (in August 1994) and the first permanent group fission (in December 1994). The average group size decreased by nearly half between the study periods (10.5–5.6), while the frequency of group membership changes increased (2.0–8.3 times/year), and the birth rate decreased (0.56–0.38). Females, as well as males, immigrated into study groups and transferred between groups, something that has been rarely seen in this subspecies. We also found a significant decline in the amount of fruit from the earliest part of the study to the latter part of the study. Study groups did not switch to other types of foods during periods of fruit shortage, but traveled outside of their home range areas more often over the study period. Finally, the density E. f. rufus decreased in the study area while the densities of their main food competitors, Varecia variegata and Eulemur rubriventer, increased. Although few primate populations are numerically stable over time, we suggest that female behavioral responses to decreases in fruit availability may have influenced some of the demographic changes we witnessed in this study Titre du périodique : American Journal of Physical Anthropology Volume : 136 : 183-193 En ligne : https://onlinelibrary.wiley.com/doi/10.1002/ajpa.20793

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