Regional Variation in the Berg Adder

The Berg Adder (Bitis atropos) is known for exhibiting significant variation in its color patterns across its disjunct populations in southern Africa. This variation is often linked to the specific regions it inhabits, likely serving as camouflage to blend into its local environment.

Berg Adders from the Western Cape

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Western Cape Berg Adders are often characterized by their clearly-defined pattern and darker overall grey coloration. This color-pattern serves as excellent camouflage against the dark, often lichen-covered rocky outcrops and fynbos vegetation typical of the Western Cape. They are found from the coast to the mountains, such as the Cederberg, Swartberg & Outeniqua ranges. Their patterning is usually bold and distinct, featuring a series of dark grey or dark brown half-circle (or sometimes more square-ish) blotches along their dorsum. Crucially, these darker markings are frequently outlined with a thin, contrasting white or pale border, which further helps to break up the snake’s outline against a varied background.

: Berg Adder from Betty’s Bay area, Western Cape © Rob Holst

: Berg Adder from Helderberg Nature Reserve, Cape Town, Western Cape © Louis van Wyk

: Berg Adder from Meulriver area, Eastern Outeniqua Mountains, Western Cape (1) © Joy Paton

: Berg Adder from Montagu Pass area, Western Cape © David Hoare

: Berg Adder from north of Balmoral, Outeniqua Mountains, Western Cape © Stuart Heath

: Berg Adder from north of George, Outeniqua Mountains, Western Cape © Joy Paton

: Berg Adder from north of Overstrand, Greater Hermanus area, Western Cape © Amy Taylor

: Berg Adder from Table Mountain National Park, Cape Town, Western Cape © philips_world

Berg Adders from the Eastern Cape

While sharing many similarities with their Western Cape counterparts, Eastern Cape Berg Adders tend to lean towards a slightly browner or more muted grey-brown base color. They are found from sea-level to high altitudes within the province. The distinctive dorsal markings are still present and typically bold, but the overall contrast might be less stark than in some Western Cape specimens. The white outlining of the blotches may also be less pronounced or even absent in some individuals, allowing them to blend more seamlessly into the varying shades of brown, grey, and green found in the Eastern Cape’s mountainous grasslands and shrublands.

: Berg Adder from Kareedouw area, Eastern Cape © teedle

: Berg Adder from near Cape St Francis © Brian du Preez

: Berg Adder from Barkley East area, Eastern Cape © Deon du Plessis

: Berg Adder from near Cape St Francis, Eastern Cape © Kevin Ulett

: Berg Adder from near Groendal Nature Reserve, Eastern Cape © Roadrunr

: Berg Adder from near south of Misgund, Garden Route National Park, Eastern Cape © Matthew Sephton

: Berg Adder from south of Joubertina, Eastern Cape © Matthew Sephton

: Berg Adder from Tele Falls (close to the Lesotho southern border) Eastern Cape © Deon du Plessis

Berg Adders from Mpumalanga and Limpopo Escarpment

Berg Adders from these regions can be quite variable, appearing plain or well-patterned. They range in color from red to grey/brown. Brick-red individuals are particularly common in the Mpumalanga mountains, often without strong patterning, giving rise to the informal name Bitis atropos unicolor (Although this is now considered an outdated taxonomic distinction, the color morph remains).

: Berg Adder from near Lydenburg, Mpumalanga © Adriaan Jordaan.jpeg

: Berg Adder from Pilgrim’s Rest area, Mpumalanga © Courtney Hundermark

: Berg Adder from Pilgrim’s Rest area, Mpumalanga © Joubert Heymans

: Berg Adder from Pilgrim’s Rest area, Mpumalanga © Courtney Hundermark

: Berg Adder from Pilgrim’s Rest area, Mpumalanga © Joubert Heymans

: Berg Adder from Barbeton area, Mpumalanga © Duncan McKenzie

: Berg Adder from Barbeton area, Mpumalanga © Dylan Leonard

: Berg Adder from south of Haenertsburg, Mpumalanga © Adriaan Jordaan

Berg Adders from the Eastern Highlands of Zimbabwe and adjacent Mozambique

The Zimbabwean and adjacent Mozambique populations in the Eastern Highlands are usually well-patterned and tends to be an orange/brown color.

Key Characteristics and General Variation in Berg Adders:

Regardless of the regional color variations, some general features apply to Bitis atropos:

They are small, thick-bodied snakes, averaging 30-40 cm, with a maximum length of around 60 cm.
The head is distinct from the body but more elongated than in some other adders.
Their overall patterning provides excellent camouflage in their rocky, mountainous habitats.
While not always immediately apparent, the distinct regional color morphs highlight the species’ adaptation to different geological and vegetative backdrops.

It’s worth noting that while these regional differences are observable, the taxonomic status of Bitis atropos and its various populations has been a subject of ongoing research. There have been proposals to split the Berg Adder into multiple separate species based on these isolated populations and genetic differences, further emphasizing the distinctiveness of these regional color patterns.

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