What is a wholphin, and does it really exist?

The word itself sounds as though it came out of a fantasy bestiary. Wholphin: a contraction of whale and dolphin. A whale-dolphin. Yet the wholphin really does exist. It is a documented hybrid, a cross between two cetacean species. But its biological reality conceals a complexity more interesting than mere zoological curiosity: what science has learned by studying it sheds light on evolution, on captivity and even on cetacean taxonomy.

A hybrid between two delphinids

The wholphin is the result of a cross between a common bottlenose dolphin (Tursiops truncatus), the familiar “Flipper”, and a false killer whale (Pseudorca crassidens). Despite its name of “false killer whale”, which suggests a kinship with killer whales, and despite the name “wholphin”, which suggests a mixture of whale and dolphin, the false killer whale is in fact itself a delphinid: a member of the large dolphin family. Biologically, then, this is a cross between two dolphin species, not between a whale and a dolphin.

This point matters. Natural hybrids between different species exist in several animal groups, but they are generally more likely between species that are phylogenetically close. The common bottlenose dolphin and the false killer whale, despite their morphological differences (size, shape of the melon, colour), share a recent common ancestor on the evolutionary timescale, which makes hybridisation genetically possible.

Kekaimalu, the best known wholphin

The best known and best documented case is that of Kekaimalu (meaning “from the peaceful ocean” in Hawaiian), born in 1985 at Sea Life Park on the island of Oahu in Hawaii. Her mother was a female common bottlenose dolphin named Punahele; her father, a male false killer whale named Iʻanui Kahei. The two shared the same tank, which made mating possible. The birth was unplanned and unexpected, taking the keepers by surprise.

Kekaimalu showed a fascinating mixture of characteristics from both parent species. Her size (about 3 metres as an adult) was intermediate between that of her common bottlenose dolphin mother (2.4 m) and that of her false killer whale father (4.5 m). Her number of teeth, 66, was also intermediate (the common bottlenose dolphin has 88, the false killer whale 44). Her grey colouring was darker than that of typical common bottlenose dolphins. Her dorsal fin had an intermediate shape.

Fertile, against all expectation

A remarkable feature of Kekaimalu was her fertility. In many interspecific hybrids (such as the mule, a cross between a donkey and a mare), sterility is the rule, the paternal and maternal chromosomes being too different to allow normal meiosis. Not so for Kekaimalu. She gave birth to three calves in succession, the first in 2004. Her firstborn, nicknamed Kawili Kai, is therefore “one quarter false killer whale” and lived in good health. Kekaimalu’s ability to produce viable offspring shows that common bottlenose dolphin and false killer whale chromosomes remain compatible enough to allow normal reproduction.

This fertility has revived an old taxonomic debate: if two “species” can interbreed and produce fertile offspring, are they really two distinct species in the strict biological sense? The modern answer is nuanced, the definition of the species resting on reproductive isolation in the wild, not in captivity. In the wild, common bottlenose dolphins and false killer whales virtually never interbreed, despite their partial genetic compatibility.

Another case, more tragic

Before Kekaimalu, another wholphin had been documented in Japan, in Tokyo in 1981. But this firstborn, also the product of forced cohabitation in captivity, had survived only about 200 days. Its early death illustrates the considerable risks associated with hybrid births, even when genetic viability appears sufficient.

Similar hybrids have been reported in other dolphinaria around the world, but documented with less precision. Kekaimalu remains the reference case, studied since her birth by marine biologists and still alive at present.

And in the wild?

In the wild, crosses between cetacean species are extremely rare but they do occur. Several natural hybrids have been identified genetically in cetaceans that were caught or stranded: crosses between blue whales and fin whales, between killer whales and pilot whales, between different dolphin species. But confirmed cases remain exceptional, and the viability and fertility of these natural hybrids are poorly known.

The wholphin therefore remains essentially an artefact of captivity, evidence both of the genetic flexibility of cetaceans and of the ethical limits of keeping them in dolphinaria. Kekaimalu continues to live peacefully in Hawaii, an unwitting ambassador for a grey area of marine biology.

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Further reading