Diademed Sifaka (Propithecus diadema) Ranging and Habitat Use in Continuous and Fragmented Forest: Higher Density but Lower Viability in Fragments? / M.T. Irwin  

Public ISBD Titre : Diademed Sifaka (Propithecus diadema) Ranging and Habitat Use in Continuous and Fragmented Forest: Higher Density but Lower Viability in Fragments? Type de document : texte imprimé Auteurs : M.T. Irwin, Auteur Année de publication : 2007 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Fragmentation, Habitat Mots-clés : CONSERVATION  DAILY PATH LENGTH  EDGE EFFECTS  HABITAT DISTURBANCE  HABITAT FRAGMENTATION  HOME RANGE  MADAGASCAR Résumé : The mechanisms through which forest fragmentation threatens the survival of mammal populations remain poorly known, yet knowledge of this process would greatly aid conservation efforts. I investigated ranging behaviors of diademed sifakas (Propithecus diadema) in continuous and fragmented forest at Tsinjoarivo, eastern Madagascar, using focal animal observations to examine home range size, daily path length (DPL), and habitat use relative to forest edges over 12 mo. Sifaka groups in forest fragments had home ranges that were 25–50 percent as large as continuous forest groups, and moderately reduced DPLs. Continuous forest groups foraged more than expected near forest edges while fragment groups avoided edges. Fragments have higher population density than continuous forest; however, several lines of evidence suggest that fragment groups' food resources may be denser, but lower quality. Continuous forest groups appear to be energy-maximizers, maintaining large ranges and preferentially feeding in rare fruiting trees found only in continuous forest interiors, while fragment groups appear to be time-minimizers, using small home ranges and primarily feeding on mistletoe (a fallback food in continuous forest). Therefore, the consequences of fragmentation on long-term viability remain unknown; it is possible that the advantage of increased density is outweighed by longer-term demographic challenges, or other threats (e.g., nutrition, health, social behavior, disease). When animals stranded in forest fragments exhibit complex and potentially unpredictable responses, simple ecological proxies (e.g., incidence patterns and density) are probably inadequate in assessing population health and viability. Ecological study and monitoring is essential in judging the viability of fragmented populations. Titre du périodique : Biotropica Volume : 40 (2) : 231-240 En ligne : https://onlinelibrary.wiley.com/doi/10.1111/j.1744-7429.2007.00368.x Diademed Sifaka (Propithecus diadema) Ranging and Habitat Use in Continuous and Fragmented Forest: Higher Density but Lower Viability in Fragments? [texte imprimé] / M.T. Irwin, Auteur . - 2007. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Fragmentation, Habitat Mots-clés : CONSERVATION  DAILY PATH LENGTH  EDGE EFFECTS  HABITAT DISTURBANCE  HABITAT FRAGMENTATION  HOME RANGE  MADAGASCAR Résumé : The mechanisms through which forest fragmentation threatens the survival of mammal populations remain poorly known, yet knowledge of this process would greatly aid conservation efforts. I investigated ranging behaviors of diademed sifakas (Propithecus diadema) in continuous and fragmented forest at Tsinjoarivo, eastern Madagascar, using focal animal observations to examine home range size, daily path length (DPL), and habitat use relative to forest edges over 12 mo. Sifaka groups in forest fragments had home ranges that were 25–50 percent as large as continuous forest groups, and moderately reduced DPLs. Continuous forest groups foraged more than expected near forest edges while fragment groups avoided edges. Fragments have higher population density than continuous forest; however, several lines of evidence suggest that fragment groups' food resources may be denser, but lower quality. Continuous forest groups appear to be energy-maximizers, maintaining large ranges and preferentially feeding in rare fruiting trees found only in continuous forest interiors, while fragment groups appear to be time-minimizers, using small home ranges and primarily feeding on mistletoe (a fallback food in continuous forest). Therefore, the consequences of fragmentation on long-term viability remain unknown; it is possible that the advantage of increased density is outweighed by longer-term demographic challenges, or other threats (e.g., nutrition, health, social behavior, disease). When animals stranded in forest fragments exhibit complex and potentially unpredictable responses, simple ecological proxies (e.g., incidence patterns and density) are probably inadequate in assessing population health and viability. Ecological study and monitoring is essential in judging the viability of fragmented populations. Titre du périodique : Biotropica Volume : 40 (2) : 231-240 En ligne : https://onlinelibrary.wiley.com/doi/10.1111/j.1744-7429.2007.00368.x

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Feeding Ecology of Propithecus diadema in Forest Fragments and Continuous Forest / M.T. Irwin  

Public ISBD Titre : Feeding Ecology of Propithecus diadema in Forest Fragments and Continuous Forest Type de document : texte imprimé Auteurs : M.T. Irwin, Auteur Année de publication : 2008 Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : CONSERVATION  DIADEMED SIFAKAS  DIET  FOREST FRAGMENTATION  MISTLETOE  PROPITHECYS DIADEMA Résumé : Forest fragmentation is viewed as a serious threat to primates, yet whether or not it can disrupt food resources and cause energetic stress remains largely untested. I present the results of a 12-mo study of the feeding ecology of Propithecus diadema in fragmented and continuous forest at Tsinjoarivo, eastern Madagascar. Two continuous forest groups had higher dietary diversity and ate more fleshy fruit, but during the dry season, diversity was reduced and they relied heavily on mistletoe (Bakerella clavata). In contrast, 2 groups in fragments employed the lean season strategy of eating mistletoe year-round; the fruiting tree species that sustain continuous forest groups through the rainy season were largely absent. As expected, intersite dietary overlap was highest in the dry season. The level of specialization was high: fragment groups devoted 30–40% of feeding time to Bakerella clavata, compared to 28–30% in continuous forest. The major characteristic of Bakerella clavata enabling it to be an important fallback or staple resource, or both, is its extended phenology. The difference in resource utilization between sites may have important implications for nutritional status, as well as ranging and social behavior, largely owing to the small size and high abundance of feeding patches of Bakerella. Understanding resource shifts in fragments can shed light on socioecological questions by providing comparisons between continuous forest and fragment populations with differing diets and resource distributions. In addition, understanding dietary shifts in fragments can aid in species-specific conservation efforts, while contributing to a better understanding of the considerable interspecific variability of primates in responses to fragmentation. Titre du périodique : International Journal of Primatology Volume : 29: 95-115 En ligne : https://doi.org/10.1007/s10764-007-9222-9 Feeding Ecology of Propithecus diadema in Forest Fragments and Continuous Forest [texte imprimé] / M.T. Irwin, Auteur . - 2008. Langues : Anglais (eng) Langues originales : Anglais (eng) Catégories : LEMURIENS LEMURIENS:Biologie, Ecologie, Densité Mots-clés : CONSERVATION  DIADEMED SIFAKAS  DIET  FOREST FRAGMENTATION  MISTLETOE  PROPITHECYS DIADEMA Résumé : Forest fragmentation is viewed as a serious threat to primates, yet whether or not it can disrupt food resources and cause energetic stress remains largely untested. I present the results of a 12-mo study of the feeding ecology of Propithecus diadema in fragmented and continuous forest at Tsinjoarivo, eastern Madagascar. Two continuous forest groups had higher dietary diversity and ate more fleshy fruit, but during the dry season, diversity was reduced and they relied heavily on mistletoe (Bakerella clavata). In contrast, 2 groups in fragments employed the lean season strategy of eating mistletoe year-round; the fruiting tree species that sustain continuous forest groups through the rainy season were largely absent. As expected, intersite dietary overlap was highest in the dry season. The level of specialization was high: fragment groups devoted 30–40% of feeding time to Bakerella clavata, compared to 28–30% in continuous forest. The major characteristic of Bakerella clavata enabling it to be an important fallback or staple resource, or both, is its extended phenology. The difference in resource utilization between sites may have important implications for nutritional status, as well as ranging and social behavior, largely owing to the small size and high abundance of feeding patches of Bakerella. Understanding resource shifts in fragments can shed light on socioecological questions by providing comparisons between continuous forest and fragment populations with differing diets and resource distributions. In addition, understanding dietary shifts in fragments can aid in species-specific conservation efforts, while contributing to a better understanding of the considerable interspecific variability of primates in responses to fragmentation. Titre du périodique : International Journal of Primatology Volume : 29: 95-115 En ligne : https://doi.org/10.1007/s10764-007-9222-9

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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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