Bleeze, flag and semet: necessary new words for describing adaptive colouration in ungulates

All of Biology depends on precise use of words. And much of what makes the thousands of photos of ungulates and other mammals on iNaturalist interesting is the patterns of colouration.

However, words to describe adaptive colouration have been so imprecise and inconsistent that it has been hard to write coherently on this topic. Both the anatomical parts and the features of colouration have been misnamed, or named by misleading analogy.

Describing the carpal joint - which is actually homologous with the human wrist - as the 'knee' is a gross example of this. Confusion between the withers and the shoulders is a subtler but equally important case. However, in anatomy at least the correct word already exists in most instances.

When it comes to important aspects of colouration, we may not progress in our thinking until we fill in the gaps in our lexicon. Here, I introduce three new terms: the bleeze, the flag and the semet.

Various ungulates feature a conspicuous pale patch, informally called a 'blaze'. A typical example is the blesbok (Damaliscus pygargus phillipsi), named after the Afrikaans translation of blaze.

The metaphor applies because flame can be eye-catchingly pale, lighting things up. However, should we not avoid ambiguity with combustion?

I suggest the new term 'bleeze', applicable only to the biological topic of colouration.

We would describe the face of the blesbok as featuring a bleeze, not a blaze. An additional advantage is that bleeze can be defined to include conspicuously dark features, such as that on the face of the eastern white-bearded wildebeest (Connochaetes albojubatus) - or the juvenile of the blesbok itself.

The bleeze is, by its nature, large and prominent enough to be conspicuous to scanning predators even when the animal stands still.

However, many large mammals feature pale/dark patterns which are easily overlooked until moved or raised. For these dynamic forms of advertisement, I suggest the term 'flag' instead.

The most obvious examples are the caudal flags of the many species of ungulates which raise dark/pale tails in alarm or flight.

However, in principle the term can also apply to the ears (e.g. impala, Aepyceros melampus), the feet (e.g. bush duiker, Sylvicapra grimmia), or the buttocks (e.g. steenbok, Raphicerus campestris).

The third word, 'semet', is newly derived from the Greek word for sign (think of semaphore or aposematic).

This refers to dark/pale features too small-scale to matter for detection by potential predators, but moved in certain ways for social communication within the species.

For example, many species of ungulates have subtle markings around the mouth, or at the base of the ears, which help companions to monitor each other's cud-chewing or listening - facilitating the spread of any alarm within seconds.

And then there are many social signals involving colouration, used in rivalry and courtship, which are candidates for also being called semets.

Posted on May 12, 2021 01:23 AM by milewski milewski


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