Lovers, friends, and foes
Cetaceans are a diverse group of animals and as a whole, the toothed whales are both very social, and very intelligent. That socialisation can be seen in the way many of them travel in pods, and sometimes care for their young in collective ways, like the sperm whale babysitters we learned about earlier.
But that social nature can even transcend species boundaries in surprising ways. Unsurprisingly, it is the gregarious dolphins that lead this charge (and as we will see later, this even extends to humans), but the examples below tell a fascinating story of interspecies interaction.
It’s not all peace and love though, the animal kingdom can be cruel to our eyes and cetaceans are no exception. Battles for dominance, reproduction, and the hunt can all brutally turn on their own.
Wholphins?
We’ve touched on the naming confusion around dolphins and whales – both that all dolphins are a subset of whales, and that several species that bear the common name of ‘whale’ (like killer whales and pilot whales), fall within the dolphin subset.
But this distinction becomes even more fuzzy when taking into account that some of these confusingly named species have actually been known to breed across species lines, and produce living hybrids. While these hybrid offspring have been colloquially referred to as ‘wholphins’, this is a misnomer, as in all known cases, both parents taxonomically fall within the oceanic dolphin family within the broader order of whales (cetaceans).
A captive family
These hybrids are extremely rare, and most easily found in captivity, where mating partner choices are limited. The first such hybrid was reported at Tokyo SeaWorld in 1981 but died shortly after. In 1985, at Sea Life Park in Hawai’i, a male 900kg (2000lb), 4.3m (14ft) false killer whale called I’anui Kahei and a female 180kg (400lb), 1.8m (6ft) bottlenose dolphin named Punahele, unexpectedly produced a female offspring – Kekaimalu.
(Left) False killer whale at Churaumi Aquarium, Okinawa, Japan, by William Warby on Flickr. CC BY 2.0 (Right) Bottlenose dolphin, by Vince Smith from London, United Kingdom via Wikimedia Commons. CC BY 2.0
Kekaimalu, Sea Life Park, O’ahu, by Kelly via Flickr. CC-BY-NC-ND 2.0
Kekaimalu grew to be a near-exact blend of her parents in size, colour, and length. She has 66 teeth (to her father’s 88 and her mother’s 44), and a short, round beak – a mix of the rounded snout of the false killer whale, and the distinctive pointed beak of the bottlenose dolphin. The two species are known to associate closely in mixed pods in the wild, so there are likely other hybrids of the two in existence.
Unlike many hybrids, Kekaimalu proved fertile, and has reproduced three times with the bottlenose dolphin males in her enclosure. One calf died days after birth, the second was hand-reared and survived for nine years and the last, Kawili kai, was born in 2004, raised by her mother, and remains with her today. Kawili kai is ¾ bottlenose dolphin, and ¼ false killer whale. At one month old she was already the size of a one-year old bottlenose dolphin.
Kawili kai aged 9 months, the daughter of Kekaimalu the ‘wholphin’ and a male bottlenose dolphin, by Mark Interrante, via Flickr. CC BY SA 2.0
Click to expand
Family tree of the ‘wholphins’ at Sea Life Park, Hawai’i, Wikipedia. CC BY SA 4.0
It should be noted that while captivity has provided the opportunity to study these hybrids up close, there are significant ethical and animal welfare concerns associated with keeping whales and dolphins in captivity, and there is a growing movement to outlaw the practice.
In the wild
An odd melon
Melon-headed dolphin, by Cyril di Bisceglie via Wikimedia Commons. CC BY SA 4.0
In 2018, a hybrid of two different dolphin species was observed for the first time in the wild, when scientists spotted two melon-headed whales (again, actually members of the oceanic dolphin family) swimming with a pod of rough-toothed dolphins in the wild near Hawaii. They soon realised that one of the melon-headed whales was not what it seemed, with the eponymous slightly bulging forehead and snout accompanied by an unexpected beak.
Tissue samples confirmed the individual was indeed a hybrid of the two, and researchers speculated the mother – the melon-headed whale – had become separated from her pod and integrated with that of the rough-toothed dolphins, finding a mate in the process.
Narluga
Skeletal evidence has also been found of a narwhal/beluga whale hybrid (or ‘narluga’) in the Arctic. The skull, obtained by an Inuk hunter, was confirmed by genome analysis to be a hybrid, and its tooth morphology was a distinct mix of both species, with teeth bearing the forward direction and spiral of the narwhals horn (actually a single tooth), but arranged in the more regular rows of beluga teeth.
Because these two have teeth specifically adapted for very different feeding styles (suction feeding on squid for the narwhal, and grabbing of fish by the beluga), this mixed morphology would have been problematic. Carbon analysis found that this hybrid had survived to adulthood – against all odds – by adopting a feeding pattern of seabed foraging for clams and invertebrates more similar to that of a walrus, and totally different to that of either of its parents.
Narwhal hybridization. A. Narwhal skull, B. Narluga hybrid skull, C. Beluga skull. Photos: Mikkel Høegh Post. Published by Mikkel Skovrind, Jose Alfredo Samaniego Castruita, James Haile, Eve C. Treadaway, Shyam Gopalakrishnan, Michael V. Westbury, Mads Peter Heide-Jørgensen, Paul Szpak & Eline D. Lorenzen, via Wikimedia Commons. CC BY 4.0
According to the Washington Post:
A 2016 study found reports of nearly 20 such hybrids [between different cetacean species], only seven of which occurred in captivity.Dolphins seem particularly open-minded. There are published accounts of the common bottlenose dolphin reproducing with Guiana dolphins, rough-toothed dolphins, Risso’s dolphins, Pacific white-sided dolphins, long-beaked common dolphins, Atlantic spotted dolphins, and Indo-Pacific bottlenose dolphins, as well as short-finned pilot whales and false killer whales.Spinner dolphins and pan-tropical spotted dolphins; dusky dolphins and southern right whale dolphins, and even blue whales and fin whales have hooked up to produce offspring. And these are just the hybrids we know of.
Adoption
Though hybridisation is thought to be extremely rare, it is fairly common for certain species of whales and dolphins to spend time together, and it isn’t unusual to find pods of mixed species running together.
In 2019, a bottlenose dolphin mother was found to have done something that was not just unusual, but unheard of. She was just the second scientifically documented case ever of interspecies adoption among wild animals (the first being a family of capuchin monkeys raising a baby marmoset in 2006).
The cow was observed rearing a melon-headed whale calf over three years. Even more unusual was that she also had a biological calf of her own. Bottlenose dolphins typically only raise one calf at a time, making it very unlikely that she had kidnapped the adopted calf (an unusual but known behaviour that seldom leads to a lasting connection).
This is an additional video, hosted on YouTube.
Making friends
In 2013, a pod of the usually quite reticent sperm whale adults and calves was observed spending time, and sharing affection, with an adult bottlenose dolphin with a spinal deformity akin to scoliosis.
This is an additional video, hosted on YouTube.
You can read more about this interaction in this Science article.
Enemies
Interactions are not always so heartwarming however. More antagonistic interactions between and within cetacean species can be both more complex, and more threatening.
As mentioned above, bottlenose dolphins have been recorded trying to steal the calves of their fellows. They mean no harm to the calf, but young females may find their maternal instinct taking over, as in the short clip below, featuring new mother Puck and her son Samu in Western Australia.
This is an additional video, hosted on YouTube.
Kidnapping is not the only threat from within the family for baby dolphins. Though rare, infanticide by adult males has been documented in four species of dolphin, including the bottlenose dolphin and the orca. This behaviour, as in other mammals where it is observed, is a form of sexual selection. Since dolphin cows tend to a single calf for years, killing the infant returns her swiftly to the available breeding pool.
Similar sexual aggression can be seen in some dolphin species with coercive or forced breeding of a cow by one or more males. Male cetaceans also frequently fight each other for dominance or mates, and orcas and some dolphins do actively hunt and prey upon smaller cetaceans.
A world of their own
It can be difficult not to look at many of these interactions through a human lens and project our emotions or interpretations onto them. It is indisputable that these animals are generally intelligent, with complex social bonds and communication, but because their vast ocean world remains so inaccessible to us, there is still a huge amount we don’t know about them and their behaviours.
It is not hard to see however, why we are so curious about them and seemingly at times, vice versa. This week we’ve come to know these incredible creatures and their interactions with each other a little better but in the next few weeks we’ll learn more about the significance and impact of their encounters with humans in Aotearoa New Zealand and the wider South Pacific.
We’ve covered a huge amount this week. In the next step it’s time to wrap up our whirlwind biology lesson and reflect!
Further resources
Hybrids May Thrive Where Parents Fear to Tread, New York Times
First ever ‘wholphin’ hybrid spotted in wild, Sky News
The ‘narluga’ is a strange hybrid. But it’s far from alone. The Washington Post
Researchers Document First Known Case of Dolphin Mom Adopting Whale Calf, The Smithsonian Institute
Slideshow: Sperm Whales Adopt Deformed Dolphin
Do Whales Practise Infanticide?, Whales Online
First Case of Orca Infanticide Observed, National Geographic
The Significance of Whales to Aotearoa New Zealand
The Significance of Whales to Aotearoa New Zealand
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