A new idea for how colouration of giraffes (Giraffa) achieves camouflage

Here is a possible explanation for how the camouflage colouration of giraffes (Giraffa) works.
 
As readers know, giraffes are doubly remarkable/exceptional:

• firstly they are the only non-cervid ungulates that are extensively blotched/spotted, i.e. here we have ruminants with colouration unusually similar to that of blotched/spotted predators such as big cats (Felidae); and
• secondly, giraffes are by far the largest land mammals with camouflage colouration.

Camouflage of this kind only really makes sense, at least to the human eye, where

• there is much vegetation cover, and
• the animal has a habitual pattern of ‘freezing’ when alarmed.

Because giraffes do not conform to either of these standards, it is hard to accept that giraffes rely on camouflage.

After all, giraffes are generally typical of low, open savannas rather than dense woodlands; indeed they have always been absent from most of the savannas of central Africa, and instead penetrate arid areas such as

• the Namib Desert (https://www.alamy.com/running-giraffe-in-a-flat-and-desolate-stone-desert-namibia-africa-image333419879.html and https://giraffeconservation.org/2021/04/07/giraffe-movements/ and https://www.allposters.com/-sp/Desert-Giraffe-Giraffa-Camelopardalis-Capensis-with-Her-Young-Namibia-Africa-Posters_i10508022_.htm),
• the Sahara (https://es.123rf.com/photo_12657640_rock-engraving-of-a-giraffe-in-the-sahara-desert-libya.html), and
• the Horn of Africa (https://www.independent.co.uk/news/world/africa/kenya-drought-giraffes-dead-wajir-b1975043.html and https://www.theguardian.com/world/2021/dec/14/six-dead-giraffes-kenya-drought-horror-captured-picture).

The females typically forage in low stands of acacias, where their necks must be held horizonally to browse (https://www.gettyimages.com.au/detail/photo/reticulated-giraffe-eating-in-samburu-royalty-free-image/514252744?adppopup=true and https://www.istockphoto.com/photo/african-giraffe-feeding-on-acacia-whistling-thorn-full-of-stinging-ants-gm1084764668-291070764 and https://www.tripadvisor.co.uk/LocationPhotoDirectLink-g297913-d9608611-i255407074-Windfall_Safaris_Day_Tours-Arusha_Arusha_Region.html).

This means that the animals are not usually hidden by trees.

Furthermore, selective browsers with long legs are continually on the move. Therefore, the movement of locomotion usually ‘blows the cover’ of giraffes – in contrast with big cats which typically remain immobile for most of the diel cycle.

And who has ever seen clear behaviour of ‘freezing’ when a giraffe is alarmed?

This is ambivalent, because giraffes

• do sometimes stand still, and
• may perhaps cease to swish their tails against insects, when alarmed.

However, any ‘freezing behaviour’ in giraffes is a questionable phenomenon.
 
What recently dawned on me is an extension of my explanation w.r.t. the striping of zebras:
The camouflage works not so much as seen by the human eye (which is relatively insensitive to motion), but more as seen by the ungulate/carnivore eye (which is extremely sensitive to movement).
 
Please recall that I have not suggested that zebras use their stripes to avoid detection by predators. Instead, the argument, in the case of zebras, is that they are reconciled to being easily detected by predators.

However, they use their stripes to dazzle the motion-sensitive visual systems of predators by a kind of flicker effect (which frustrates the predators' attempts to detect lameness/illness/vulnerability).

This effect makes it hard to discern individual vulnerability such as sickness, age and pregnancy.

I suggest that the phenomenon of flicker-distraction may also work to some extent in giraffes. However, my argument in the case of giraffes is different.
 
What has dawned on me is that leaves and branches of trees are usually moving, even if the breeze is slight. What this means is that any carnivore surveying a wooded scene may see considerable distraction, which is overlooked in human eyes.

Imagine an individual of a giraffe under a tree, partly obscured by the branches, with the foliage and twigs moving slightly in the wind. The figure can be partly in the shade by day, but the idea applies also at night.

The figure may be hard to see, not so much because its outline is disrupted (which is the classic textbook explanation), but because the eye of the predator is somewhat distracted by the flicker-effect in the whole scene.

What this would mean is that giraffes are indeed camouflaged in a strict sense (unlike zebras, to which the word ‘camouflage’ does not really apply). However, the camouflage works far better in the eyes of Carnivora than in the eyes of humans.

To us, the camouflage is not really convincing. However, this is because we ‘see through it' with our failure to be flicker-dazzled by either the blotch-lines or the foliage movements. 
 
Giraffa tippelskirchi thornicrofti, Luangwa, Zambia:
http://luambe-lodge.info/images/Einklinker/giraffe_ek.jpg

Posted on 02 September, 2022 03:02 by milewski