7-minute read

One has to wonder whether the horror writer H.P. Lovecraft had the star-nosed mole in mind when he created the Cthulhu Mythos. Fortunately for us mortals, this little mammal is harmless—though it is not without some extraordinary powers of its own. I first came across the work of biologist Kenneth Catania in the recently reviewed Sentient and had to dig deeper. Great Adaptations is a personal and entertaining account of his almost-five decades career investigating the biological mysteries of the star-nosed mole and other creatures.

Why does the star-nosed mole have a crown of tentacles front-and-centre of its face? A young and enthusiastic Catania got the chance to delve into their world when the head curator of the National Zoo in Washington, DC told Catania’s father he was looking for a volunteer to care for them, and maybe do some research. Starting with the idea that it might be for electroreception (it is not), Catania takes you down the research rabbit hole. He examines noses under the electron microscope to reveal Eimer’s organs and other specialised touch sensors. He enlists the help of a neurobiologist to show how the neocortex contains a literal sensory map of the nose. Curiously, the smallest pair of the 22 tentacles takes up most neocortical real estate. Examining embryos reveals not only that this pair of tentacles develops first and is the most sensitive, but also that the crown forms quite unlike any other appendage. Not by extrusion of tissue, nor by trimming excess tissue via programmed cell death, but as backwards-facing tubes that detach and bend forward during development. But what is this curious organ for? The use of high-speed video cameras shows the mole to be extremely fast at detecting, recognizing, and consuming invertebrate prey, taking on average just 230 milliseconds to do so.

There are some nice biology lessons hidden in this whirlwind of observations and remarkable experiments. Why is so much of the neocortex devoted to the smallest pair of tentacles? Catania draws a comparison to our eyes where we focus the image on a small, well-innervated area of the retina called the fovea. The smallest pair of tentacles act as a touch fovea: “instead of making the sensor […] high-resolution throughout, requiring vast neocortical territory for all the sensory processing, a single small area is analyzed in detail, and moved around a bit like a sensory flashlight” (p. 40). Why does the mole’s nose develop in such an odd fashion? He reminds the reader that the process of evolution has to tinker with what is available and cannot start from scratch, a recurrent theme in evolutionary biology. There is good reason to think that the mole’s ancestor had a nose with a proto-star. And why such a sensitive nose? Catania draws on foraging theory to argue that the mole is exploiting an unlikely niche space: by minimising prey handling time it can eat small prey that would normally not be energetically profitable for a warm-blooded mammal of its size.

“Great Adaptations is a personal and entertaining account of [Catania’s] almost-five decades career investigating the biological mysteries of the star-nosed mole and other creatures.”

Catania brings in an interesting idea, the “rare enemy effect”, when discussing the next two animals he has studied: the tentacled snake and human worm grunters. The snake hunts fish underwater and sports two tentacles on its snout that, as Catania shows through careful observation, are motion sensors. By exploiting the fish’s hard-wired escape response, the snake tricks fish to swim into its gaping mouth. Worm grunting is an old practice that humans use to collect earthworms for fish bait. By sticking a wooden rod into the ground and rubbing it with a piece of metal, the grunter creates subterranean vibrations that cause earthworms to emerge on the surface. Charles Darwin already suggested that earthworms might be fleeing the vibrations caused by their usual nemesis: moles burrowing in the soil. With the help of an experienced grunter, Catania confirms this idea and mentions other observations on animals such as gulls that also exploit this trick to bring food to the surface. In both cases, the question is why the fish and worms have not evolved a response. He invokes what Richard Dawkins calls the rare enemy effect: “A rare predator may have such a small impact on the large prey population that no counteradaptation ever evolves” (p. 75). The predators are getting away with trickery.

Similarly fascinating is Catania’s work on electric eels and predatory wasps. The former have an important place in the history of scientific discovery of electricity, inspiring no less than Alessandro Volta when he designed his batteries. Using ingenious experimental setups, Catania figures out how eels stun their prey (somewhat like a taser) and what the function is of shorter double bursts of electric discharge (blowing the cover of any edible prey in hiding when they involuntarily twitch). Meanwhile, the story of predatory wasps that turn cockroaches into zombified hosts for their offspring makes for engaging popular science. Catania’s contribution is to figure out the exact sequence of events by which the wasp overcomes the cockroach’s defences and violently subdues it. Though, as he shows, a prepared cockroach can hold its own and deliver some mighty kicks with its barbed hindlegs.

“It is […] easy to communicate [this sort of research] to a general audience as it does not require prior knowledge. [This research], and by extension this book, is a gateway drug to biology.”

Next to entertaining science experiments, Catania wrote this book to tell the stories that never make it into the published literature. Of the friendships with the people whose permission you seek to collect moles on their land, or the worm grunter who happily helps you out gathering data. The book is peppered with some genuinely entertaining anecdotes and personal interest stories. Catania has furthermore included photos, still frames from video clips, and diagrams to illustrate his work. As many of his experiments involved filming behaviour with high-speed cameras, some figure legends cleverly include QR codes that will take you to short clips on YouTube*.

Above all, Catania wrote this book to convey the sense of wonder that accompanies scientific discovery. The main reason I thoroughly enjoyed Great Adaptations is that it spoke to me on a very personal level. This is the sort of research that attracted me to biology in the first place (and which I have had the fortune to do myself). It is also easy to communicate to a general audience as it does not require prior knowledge of, say, genetics or ecological theories. All it needs is for you to observe animal behaviour with a healthy dose of curiosity and start asking questions. This kind of research, and by extension this book, is a gateway drug to biology. If I could go back in time 20 years I would be that student sitting in the front row during Catania’s lectures, and beseeching him afterwards about doing a research project in his group. Lacking a time machine, this book is the next best thing.

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* For those readers without a smartphone, there is, unfortunately, no separate list of URLs but you can find the channel here.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Great Adaptations

Other recommended books mentioned in this review:

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