As we’re currently in butterfly season, this month we decided to concentrate on the Butterfly Rays!

Within the family Gymnuridae, there are two genera and 12 species of Butterfly Ray. These species are morphologically different to lots of other rays because of the width of the disc and pectoral fins – in contrast to many other species of Butterfly Ray, their bodies are much wider than they are long, especially considering their very short tail. This gives them the appearance of gliding or flying across the sand.

Gymnura altavela – Spiny Butterfly Ray

Gymnura australis – Australian Butterfly Ray

Gymnura crebripunctata – Longsnout Butterfly Ray

Gymnura japonica – Japanese Butterfly Ray

Gymnura lessae – Lessa’s Butterfly Ray

Gymnura marmorata – California Butterfly Ray

Gymnura micrura – Smooth Butterfly Ray

Gymnura natalensis – Backwater Butterfly Ray

Gymnura peocilura – Longtail Butterfly Ray

Gymnura sereti – Seret’s Butterfly Ray

Gymnura tentaculata – Tentacled Butterfly Ray

Gymnura zonura – Zonetail Butterfly Ray

Today we’re taking a look at Gymnura altavela, the Spiny Butterfly Ray. Like all Butterfly Rays, the Spiny Butterfly Ray is a demersal species, meaning it spends the majority of its time on the bottom of the seabed. Butterfly Rays are known for their burying behaviour in the sand, a technique they use to camouflage themselves when they are resting during the day. This protects them from predators, in some areas larger sharks. It also aids them in their ambush hunting technique – by hiding themselves under the sand they are able to easily snatch up their dinner - usually crustaceans, molluscs or other small fish – as they swim by unawares. This behaviour can leave tell-tale butterfly-ray shaped imprints in the bottom of the seabed.

Spiny Butterfly Rays can grow up to 260 cm (disc width (wingspan)), although average is around 200 cm. They give birth to live young, and each litter consists of 1-8 pups. This species has also been found to aggregate, likely for mating. One study found that aggregations of primarily females in the coastal regions off Gran Canaria may correlate with the shifting water temperature.

It is estimated that the species has undergone a population reduction of 50-79% over the last 33 years. This is primarily due to fishing pressure – the Spiny Butterfly Ray is targeted and bycaught in both industrial and artisanal fisheries types using a variety of gear types. The species is now Critically Endangered in the Mediterranean and Southwest Atlantic.

Scientific Name: Gymnura altavela

Family: Gymnuridae

Maximum Size: 260 cm (disc width)

Diet: crabs, shrimps, various invertebrates, fishes, small crustaceans, and molluscs.

Distribution: throughout the Atlantic and Mediterranean and Black Seas.

Habitat: muddy and sandy substrates down to 150m.

Conservation status: Critically Endangered in the Mediterranean and Europe, Endangered Globally.

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Banner Image: ©Tomas Willems. Main image: ©Andy Murch