title: Losing grip: Senescent decline in physical strength in a small-bodied primate in captivity and in the wild.
abstract: Muscle strength reflects physical functioning, declines at old age and predicts health and survival in humans and laboratory animals. Age-associated muscle deterioration causes loss of strength and may impair fitness of wild animals. However, the effects of age and life-history characteristics on muscle strength in wild animals are unknown. We investigated environment- and sex-specific patterns of physical functioning by measuring grip strength in wild and captive gray mouse lemurs. We expected more pronounced strength senescence in captivity due to condition-dependent, extrinsic mortality found in nature. Males were predicted to be stronger but potentially experience more severe senescence than females as predicted by life history theory. We found similar senescent declines in captive males and females as well as wild females, whereas wild males showed little decline, presumably due to their early mortality. Captive animals were generally weaker and showed earlier declines than wild animals. Unexpectedly, females tended to be stronger than males, especially in the reproductive season. Universal intrinsic mechanisms (e.g. sarcopenia) likely cause the similar patterns of strength loss across settings. The female advantage in muscle strength merits further study; it may follow higher reproductive investment by males, or be an adaptation associated with female social dominance.
authors.affiliation: Sociobiology/Anthropology Department, Georg-August University Göttingen, Göttingen, Germany; Behavioral Ecology and Sociobiology Unit, German Primate Center DPZ, Göttingen, Germany. Electronic address: anni.m.hamalainen@gmail.com.
authors.forename: Anni
authors.initials: A
authors.lastname: Hämäläinen
authors.affiliation: Behavioral Ecology and Sociobiology Unit, German Primate Center DPZ, Göttingen, Germany; Animal Ecology, University of Potsdam, Maulbeerallee 1, 14469 Potsdam, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Dammhahn
authors.affiliation: UMR 7179, CNRS & Muséum National d'Histoire Naturelle, Brunoy, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Aujard
authors.affiliation: Sociobiology/Anthropology Department, Georg-August University Göttingen, Göttingen, Germany; Behavioral Ecology and Sociobiology Unit, German Primate Center DPZ, Göttingen, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Kraus
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D016565:Cheirogaleidae / Q000502:physiology*; D005260:Female; D018737:Hand Strength; D008297:Male; D055948:Sarcopenia / Q000209:etiology; D012727:Sex Characteristics
keywords: Functional aging; Grip strength; Microcebus murinus; Natural population; Sarcopenia; Sex difference