Nutritional stress and body condition in the Great Gray Owl (Strix nebulosa) during winter irruptive migrations

TY - JOUR

T1 - Nutritional stress and body condition in the Great Gray Owl (Strix nebulosa) during winter irruptive migrations

AU - Graves, Gary R.

AU - Newsome, Seth D.

AU - Willard, David E.

AU - Grosshuesch, David A.

AU - Wurzel, William W.

AU - Fogel, Marilyn L.

PY - 2012/6

Y1 - 2012/6

N2 - The largest irruptive migration of the Great Gray Owl (Strix nebulosa Forster, 1772) recorded since 1831 occurred in Minnesota, USA, during the winter of 2004-2005. We tested the hypothesis that morphometric indicators of nutritional stress covary with stable isotope signatures in a sample of 265 owls killed by vehicle collisions. The ratio of carbon to nitrogen in muscle (C/Nmuscle) was shown to be a reliable proxy of nutritional stress. δ13C values for liver and muscle were significantly higher in owls in poor condition, reflecting the depletion of lipid reserves in fasting individuals. On the other hand, δ15N values for liver and muscle were marginally lower or unchanged in owls in poor condition. Stomachs of emaciated owls were less likely to contain prey, implying that many nutritionally stressed individuals were too weak to hunt and were near the tipping point of irreversible fasts. In a broader context, sexual differences in the correlative relationships between stable isotope signatures, C/N, and body condition suggest that the consequences of reversed sexual size dimorphism extend to physiological processes during the nonbreeding season.

AB - The largest irruptive migration of the Great Gray Owl (Strix nebulosa Forster, 1772) recorded since 1831 occurred in Minnesota, USA, during the winter of 2004-2005. We tested the hypothesis that morphometric indicators of nutritional stress covary with stable isotope signatures in a sample of 265 owls killed by vehicle collisions. The ratio of carbon to nitrogen in muscle (C/Nmuscle) was shown to be a reliable proxy of nutritional stress. δ13C values for liver and muscle were significantly higher in owls in poor condition, reflecting the depletion of lipid reserves in fasting individuals. On the other hand, δ15N values for liver and muscle were marginally lower or unchanged in owls in poor condition. Stomachs of emaciated owls were less likely to contain prey, implying that many nutritionally stressed individuals were too weak to hunt and were near the tipping point of irreversible fasts. In a broader context, sexual differences in the correlative relationships between stable isotope signatures, C/N, and body condition suggest that the consequences of reversed sexual size dimorphism extend to physiological processes during the nonbreeding season.

U2 - 10.1139/z2012-047

DO - 10.1139/z2012-047

M3 - Journal article

SN - 0008-4301

VL - 90

SP - 787

EP - 797

JO - Canadian Journal of Zoology

JF - Canadian Journal of Zoology

IS - 7

ER -