– Species: Gray’s spinner dolphin (Stenella longirostris longirostris) x Clymene dolphin (Stenella clymene)
– Parentage: probably dam x sire, possibly sire x dam too
– Status in the wild: confirmed | Status in captivity: X

Leaving the right whale dolphins behind, we continue to the elegant Stenella genus. Up first is a rather subtle hybrid, that probably wouldn’t stand out much if you were to see it in the wild. In 2000-2001, a female spinner dolphin in the Fernando de Noronha Marine National Park, Brazil was seen with an odd calf. Though the baby stayed close by her side it didn’t look much like her. Its body shape was good for a spinner, but its colouration resembled a different Stenella species: the Clymene dolphin. Differences between both species are small to begin with, so the hybrid presented a very subtle mix of features.

The calf’s beak was intermediate in length: longer than that of a Clymene, but not quite as long as a purebred spinner. Though its dorsal fin was spinner-like, its flippers were shaped more like a Clymene’s. Overall colouration was similar to Clymene, though the dip in the dorsal cape – below the dorsal fin – was less pronounced and more straight like in a spinner. Most notably though the baby had that tell-tale Clymene “moustache”: stripes feathering from the rostrum’s dark top, reaching to or joining the eye stripe that runs onto the beak.

The Brazilian calf was seen for three months, and then never again. It was not the only one though. In quite a different part of the Atlantic a pair of hybrids turned up, and quite a bit earlier too: they were part of a mass stranding of Clymene dolphins near Tarpon Springs, Florida, in June of 1995. When the dolphins were collected for studies no one noticed anything odd. It was only when DNA analysis was performed – almost 20 years later! – that something strange was found. Two of the ‘Clymenes’ actually clustered closer to spinner dolphins in the genetic analysis. They too, were hybrids. Because the researchers looked at mitochondrial DNA (which is usually inherited from the mother) it’s possible these two also had spinner dolphin mothers, even though they associated with Clymenes. Fathers may contribute to mitochondrial DNA as well though, so this is not certain.

With photos from all three individuals available, and the hybrid being so similar to its well-documented parent species, I feel this illustration is pretty accurate. However, the Floridian animals showed post-mortem discolouration, and the published photos of the Brazilian calf were not terribly clear. There was some lovely variation between all three too, so I’ll still rate this hybrid’s appearance as “known” rather than “well known.”

• REFERENCES •
– Silva, J. M., Silva, F. J., & Sazima, I. (2005). Two presumed interspecific hybrids in the genus Stenella (Delphinidae) in the Tropical West Atlantic. Aquatic Mammals, 31(4), 468.
– Amaral, A. R., Lovewell, G., Coelho, M. M., Amato, G., & Rosenbaum, H. C. (2014). Hybrid speciation in a marine mammal: the clymene dolphin (Stenella clymene). PloS one, 9(1), e83645.