Abstract:
We have measured rumen-complex (rumen, reticulum, omasum, abomasum) and intestine (small and large
combined) mass in 32 wild giraffes of both sexes with body masses ranging from 289 to 1441 kg, and parotid
gland mass, tongue length and mass, masseter and mandible mass in 9 other giraffes ranging in body mass
from 181 to 1396 kg. We have estimated metabolic and energy production rates, feed intake and home range
size. Interspecific analysis of mature ruminants show that components of the digestive system increase linearly
(Mb1) or positively allometric (MbN1)with bodymasswhile variables associatedwith feed intake scalewithmetabolic
rate (Mb.75). Conversely, in giraffes ontogenetic increases in rumen-complex masswere negatively allometric
(Mbb1), and increases in intestine mass, parotid gland mass, masseter mass, and mandible mass were
isometric (Mb1). The relative masseter muscle mass (0.14% of Mb) and the relative parotid mass (0.03% of Mb)
are smaller than in other ruminants. Increases in tongue length scale with head length0.72 andMb.32 and tongue
mass with Mb.69. Absolute mass of the gastrointestinal tract increased throughout growth but its relative mass
declined from 20% to 15% of Mb. Rumen-complex fermentation provides ca 43% of daily energy needs, large intestine
fermentation 24% and 33% by digestion of soluble carbohydrates, proteins, and lipids. Dry matter intake
(kg) was 2.4% of body mass in juveniles and 1.6% in adults. Energy requirements increased from 35 Mj/day to
190 Mj/day. Browse production rate sustains a core home range of 2.2–11.8 km2.
