The reticulated giraffe (Giraffa reticulata) as an extreme form in its genus, and how our complacency may risk the extinction of the true species given the mislabelling of its hybrids

INTRODUCTION

The reticulated giraffe (Giraffa reticulata) is an extreme animal, beyond the extreme nature of giraffes generally.

As a distinct species, the reticulated giraffe is the largest-bodied terrestrial animal on Earth that possesses camouflage-colouration at the scale of the whole body.

This thoroughly camouflaging colouration is all the more remarkable, because the reticulated giraffe is the only member of its family that is not subject to the 'xeric pallor' typical of semi-arid environments (https://www.merriam-webster.com/dictionary/xeric and https://academic.oup.com/bioscience/article/55/2/125/221478?login=false and https://www.perplexity.ai/search/please-give-several-good-refer-lXsUKVZtSFG3dgUZ7Hue4Q).

AIMS

In this Post, I

• explain why the reticulated giraffe is categorically distinct from other giraffes,
• show that the most secure populations labelled as the reticulated giraffe are hybrids,
• point out a psychological principle whereby human resolve to conserve the real species might be diminished, and
• call for renewed efforts to secure the species in the heartland of its original distribution.

THE CATEGORICAL DISTINCTIVENESS OF THE RETICULATED GIRAFFE

The reticulated giraffe differs in colouration from other spp. of giraffes in at least three ways, viz. it

• is the only giraffe - and the only terrestrial mammal - that has camouflage-colouration in the form of a crisp, contiguous network of pale overlaying a dark ground-colour,
• is the only giraffe adapted to semi-desert that shows no 'xeric pallor',
• lacks most of the conspicuous patterns/features of colouration seen in other giraffes.

The important point is that the reticulated giraffe is not just another version of a palette of variations within a single theme, in the genus Giraffa. Instead, it is in 'a class of its own'.

OVERALL COLOURATION

There are three forms of giraffe that are adapted to semi-deserts, viz.

• Giraffa camelopardalis peralta, which formerly occurred in what is now the Sahara,
• Giraffa giraffa angolensis, which to this day occurs at the edge of the Namib Desert and in the most arid part of the Kalahari, and
• the reticulated giraffe.

The difference is that only the reticulated giraffe, of the three forms above, shows no 'xeric pallor'.

The 'xeric pallor' of the northern and southern forms of giraffes differs as follows.

In G. c. peralta, the 'xeric pallor' arises from a broadening of the matrix/ground-colour, at the expense of the blotches. The matrix/ground-colour is pale, whereas the blotches are dark.

The overall pallor seen in G. c. peralta and G. g. angolensis fits poorly into the concept of camouflage, despite the fact that 'xeric pallor' in small-bodied mammals, birds, and reptiles is well-known to enhance adaptive inconspicuousness. This is because

• there are too few trees in the Sahara/Sahel, the southwestern Kalahari, and the edge of the Namib for any giraffe to blend into a background of trees, and
• the animals tend to be so pallid that they stand out from treeless backgrounds.

In the case of the reticulated giraffe, the adaptive relationship is basically different. This is because

• there is no 'xeric pallor' of either of the two kinds described above, and
• the typical vegetation it inhabits remains wooded despite occurring in a climate with as little rainfall, on average, as 80 mm per year.

The vegetation with which the reticulated giraffe is associated (for example near Wajir and Garissa in Kenya) is 'acacia-Commiphora woodland'. This vegetation is remarkably tall and dense for a semi-arid (average annual rainfall about 250 mm per year) to arid (<100 mm per year) climate.

What is congruent with the anomalously tall and dense vegetation of its habitat is the adaptive colouration of the reticulated giraffe, in particular

• the unique pattern (reticulated and with an 'inversion' of the usual relationship between 'matrix/ground-colour' and overlaying markings), and
• the lack of most of the conspicuous features that are nested within the overall pattern in other giraffes.

LACK OF MOST OF THE FLAGS SEEN IN OTHER GIRAFFES

I have previously pointed out six flags in the adaptive colouration of giraffes (https://www.inaturalist.org/journal/milewski/48447-conspicuous-features-of-colouration-in-giraffes).

Of these, the reticulated giraffe possesses

• only two of the six, viz. the caudal flag (blackish) and the posterior auricular flag (whitish), and
• the sole pale flag (viz. the posterior auricular flag) is the smallest of all the flags possessed by giraffes.

The downplaying of flags in the colouration of the reticulated giraffe is consistent with its commitment to thorough camouflage.

Posted on July 21, 2024 02:20 PM by milewski