Abstract:
Giraffe are thought to have excellent vision.We measured eye size, orbit orientation and retina
surface area in 27 giraffes of both sexes ranging in age from neonates to mature adults
(>10 yrs), to assess how it changes with growth, whether their eye anatomy correlates with
their apparently excellent vision and lifestyle, and we have compared our findings with those
for other large mammals to assess whether giraffe eye anatomy is unique.We found that giraffe
eye volume increases from 33 cm3 at birth to approximately 65 cm3 in adults. The focal (axial)
length increases from c. 40 to 48 mm in adults and retina surface area from c. 3000 mm2 at
birth to 4320 mm2 in adults. The orbital axis angle at birth is c. 73° and the horizontal visual
field mainly monocular and panoramic.With age the axis angle becomes more acute to c. 50° in
adults and the visual field more binocular, changes that occur concurrently with increasing
neck length. These results show that the giraffe eye and retinal surface area are larger than in
all other ungulates, and their visual fields more binocular, attributes which are consistent with
the idea that they have excellent vision.
