Morphometric signals of population decline in diademed sifakas occupying degraded rainforest habitat in Madagascar.

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Irwin, Mitchell T
Samonds, Karen E
Raharison, Jean-Luc
Junge, Randall E
Mahefarisoa, Karine Lalaina
Rasambainarivo, Fidisoa
Godfrey, Laurie R
Glander, Kenneth E

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Anthropogenic habitat change can have varied impacts on primates, including both negative and positive outcomes. Even when behavioural shifts are seen, they may reflect decreased health, or simply behavioural flexibility; understanding this distinction is important for conservation efforts. This study examines habitat-related variation in adult and immature morphometrics among diademed sifakas (Propithecus diadema). We collected morphometric data from sifakas at Tsinjoarivo, Madagascar (19 years, 188 captures, 113 individuals). Captures spanned 12 groups, five within continuous forest ("CONT"), and seven in degraded fragments ("FRAG") where sifakas have lower nutritional intakes. Few consistent differences were found between CONT and FRAG groups. However, using home range quality as a covariate rather than a CONT/FRAG dichotomy revealed a threshold: the two FRAG groups in the lowest-quality habitat showed low adult mass and condition (wasting), and low immature mass and length (stunting). Though less-disturbed fragments apparently provide viable habitat, we suggest the sifakas in the most challenging habitats cannot evolve fast enough to keep up with such rapid habitat change. We suggest other long-lived organisms will show similar morphometric "warning signs" (wasting in adults, stunting in immatures); selected morphometric variables can thus be useful at gauging vulnerability of populations in the face of anthropogenic change.





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Irwin, Mitchell T, Karen E Samonds, Jean-Luc Raharison, Randall E Junge, Karine Lalaina Mahefarisoa, Fidisoa Rasambainarivo, Laurie R Godfrey, Kenneth E Glander, et al. (2019). Morphometric signals of population decline in diademed sifakas occupying degraded rainforest habitat in Madagascar. Scientific reports, 9(1). p. 8776. 10.1038/s41598-019-45426-2 Retrieved from

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Kenneth Earl Glander

Professor Emeritus of Evolutionary Anthropology

Primate ecology and social organization: the interaction between feeding patterns and social structure; evolutionary development of optimal group size and composition; factors affecting short and long-term demographic changes in stable groups; primate use of regenerating forests.

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