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Wilson Bull., 104(4), 1992, pp. 644-655 BODY COMPOSITION, FAT RESERVES, AND
 

Summary: Wilson Bull., 104(4), 1992, pp. 644-655
BODY COMPOSITION, FAT RESERVES, AND
FASTING CAPABILITY OF CAPE GANNET CHICKS
REM A. NAVARRO'
AnsTRAcr.-Age-related changes in lipid, water, and non-lipid content and energy density
of four major body parts (integument, viscera, leg and pectoral muscles, and carcass) of
Cape Gannet chicks, juveniles, and adults were studied. The proportion ofwater was typically
high for neonates and decreased during development to near adult levels at fledging. The
percentage of lean dry matter remained almost constant for muscles and carcassbut decreased
in viscera and integument due to fat deposited during growth. Energy density was linearly
related to age @J/g = 4.46 + 0.076 Age (days), y2 = 0.845, P < 0.001). Fasting capability
(FC) of chicks (survival time when using only their lipid reserves, calculated from lipid mass
and field metabolic rate) increased exponentially up to 70 days of age (FC = 0.6e0.05Age,r*
= 0.8 15, P < 0.00 1). Newly fledged birds have a fasting capability between 8-l 6 days and
adults only l-2 days. Time between consecutive feeds, from field observations at the nest,
for chicks 21-40, 41-60 and 61-80 days old were 11.9 ? 0.7 h, N = 74; 16 f 1.1 h, N =
50; and 20 + 0.6 h, N = 35, respectively. The results are contrary to the hypothesis that
fat deposits are an insurance against an unpredictable fast, although they may serve for this
purpose. Fat deposits may be the physiological consequence of the temporal pattern of
feeding by adults, or they may serve as energy sinks to increase energy requirements relative

  

Source: Altwegg, Res - Avian Demography Unit, Department of Statistical Sciences, University of Cape Town

 

Collections: Environmental Sciences and Ecology