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Indo-Pacific bottlenose dolphins in Shark Bay Australia have been observed using sponges as tools for foraging. Learn more about dolphin tool use in this week’s episode.
In 1969, Neil Armstrong was the first human being to set foot on the moon, marking a major milestone in technological advancement. And, as we all know, he took a giant leap for mankind. This was an important and perhaps much needed victory for humanity; as just 9 years earlier, mankind suffered a major setback at the hands of David Greybeard. Greybeard wasn’t particularly interested in whether or not humanity was advancing forward. – he was a wild chimpanzee living in Tanzania. On a very special day in 1960, the celebrated biologist Jane Goodall became the first scientist to report that chimpanzees (Mr. Greybeard, in this case) used tools. She watched Greybeard as he shaped a termite catching device out of a blade of grass. Until that fateful day, mankind was convinced that no other animal species was capable of using tools. In response to this startling news, Jane Goodall’s supervisor, Dr. Louis Leakey famously stated: “Now we must redefine tool, redefine Man, or accept chimpanzees as humans.”
Many decades of fruitful animal research have passed since that day in 1960, and mankind has been obliged to admit that tool use is by no means exclusive to the human species. Chimpanzees, monkeys, crows, vultures, gorillas, owls, orangutans, finches, and even the naked mole rat have all used some form of tool for some function – with varying degrees of ingenuity.
It should come then as no surprise that researchers have observed dolphins using tools to manipulate their environment. As early as 1997, researchers at Shark Bay in western Australia began reporting some surprising behavior in the Indo-Pacific bottlenose dolphins that they were studying. Some of these wild dolphins were seen carrying sponges on the tips of their rostrums (that is, beaks). They had picked up these sponges from the sea floor. These dolphins apparently use these sponges a bit like a glove to protect the sensitive skin on their rostrums. As they poke around on the ocean floor looking for food, they use the sponge to protect themselves from objects that might hurt them, including animals with stingers like the stonefish. They may even use the sponges to stir up the bottom a bit, flushing out potential prey.
What is surprising about this study; however, is not how these dolphin spongers go about sponging (although it certainly is a rather ingenious use of a sponge), but rather who is doing the sponging. I’m sorry to say guys, but sponging is performed almost exclusively by the females! In an article about Shark Bay dolphin spongers in 2005, researchers reported that only 1 sponger was a male compared to 13 females. Hmph. It seems my gender is the perpetual late bloomer … Anyhow, what is quite shocking is the discovery that this sponging skill seems to be a result of cultural transmission, and not a product of ecology or genetics. The Shark Bay researchers suggest that the sponging ability is passed down from mother to daughter – that is, along a matriline. After an exhaustive and comprehensive analysis, researchers weren’t able to find any one gene that seemed to be shared by all of the spongers, ruling out a genetic component. And, since sponging dolphins and non-sponging dolphins live side-by-side, foraging for fish in the same environment, this sponging behavior simply can’t be attributed to their ecology. It is likely then that young dolphins learn the sponging skill from their mothers, and then pass it along to their offspring. DNA analysis suggests that this skill didn’t arise all that long ago and that there may have been a lone female dolphin who first came up with the idea of sponging – a ‘sponging eve’ of sorts. But, this doesn’t really explain why the young male dolphins never learn to sponge. The article suggests that “sponging is time-consuming solitary activity that may not be compatible with the requirement for males to associate at high levels with alliance partners.” In other words, maybe the male dolphins are just too busy hanging out with their friends to learn how to sponge.
Here is some more food for thought: much like the positively astonishing research that has been conducted on tool use by New Caledonian crows who are able to shape twigs as tools using only their beaks, what is intriguing about dolphin tool use is that it developed in a species that does not have any hands. It is easy enough to picture the evolution of tool use behavior in chimpanzees and monkeys – they possess nimble fingers capable of manipulating a variety of materials. But, for a streamlined species like the dolphin, with appendages badly designed for grabbing onto things, tool use seems just that much more remarkable. Just think of what dolphins would do if they ever evolved fingers! This scenario has been beautifully outlined in an Onion article titled ‘Dolphins Evolve Opposable Thumbs” – I personally highly recommend reading it – it is fake science of the highest caliber. But, there is nothing fake about our sponging dolphins – these ladies are the real deal. I guess you could say this looks like a case of ‘Sponge Mom Wears Plants’!
Haha! Get it – sponge bob square pants – sponge mom wears plants? No? Was that … no? Yeah, I know sponges are animals. Did I go too far? Should I, should I stop recording now?