Meet the mammalogist: Kris Helgen

When Kris Helgen was a boy of seven, he discovered a magic portal to an alternate universe in his local library. The way through the portal was to open the cover of a thick tome called The Encyclopedia of Mammals and start reading.

He sensed right away that this book would contain the answers he’d been searching for as a kid who’d known from an uncannily young age that he wanted to be a zoologist. Or a farmer. But mostly a zoologist. His family lived then at the edge of a small town in Minnesota, a town named after the raccoons that were once hunted for their pelts, where the flat open prairies meet the boreal forests stretching up to Canada; forests filled with moose, lynx, wolves, bears. It was bracingly cold there in the long winters. The blizzards would sometimes arrive as early as Halloween so that trick-or-treaters would have to wade through deep snow, and the icy winds would race along the prairies where bison and buffalo had once roamed and coyotes still sometimes do.

The Encyclopedia was not allowed to be borrowed from the library. He visited it in the reference section as often as he could, devouring the detailed information it contained about every mammal family in the world. It struck him that mammals are strangely diverse (whales, bats, humans) and yet their classification is so pleasingly simple: they all feed milk to their young.

At the very back of the book was an appendix, a list in small print of every species of mammal. To Kris, this felt like another magical opening, an invitation: for if a list could be made of known and named mammals, another shadow list must exist of the mammals that might be unknown, unnamed.

This thought thrilled him.

Eventually the librarians took pity and let him take the book home on loan. He read it so many times that his parents took note and bought him his own copy. Its oracular spell did not dim, not even as the years passed, not as he turned eight, nine, ten. He handled the book so much that the dust cover (with its colour photographs of lionesses on the front; orcas on the back) began to fall off.

The Encyclopedia raised urgent questions for him: How many species of mammals are there? Like, is this book everything?

But he knew it couldn’t be, because there were sections in the book that told him there was disagreement about how many species of particular mammals existed in the world. Take raccoons, for instance – an animal he’d spent plenty of time observing; they were so populous in his town they were considered pests (especially when stuck in house attics). The book said that nobody was actually sure how many species of raccoons there were.

How could this be? He wondered. And what could I possibly want to do except be the kind of person who could go out there and solve that question for everybody, so that the next time a kid is reading this book, the answer is really clear?

There’s another origin story in Kris’s family about why he grew up to be a mammalogist.

In this story, the spark came in the form of a wooden Noah’s ark toy set that he was given when he was three or four. Out of the ark, two by two, came the animals. Kris pointed out to his parents that the two horses went together, as did the two zebras, but the horse and the zebra did not go together, though they looked kind of similar. There was a logic or pattern to how nature had designed these animals – and he liked noticing patterns.

His mom was so inspired by his childhood fascination with these matching animals – and the line she could draw over time between that boy’s interest and her adult son’s talent for discovering new mammal species – that she began to collect Noah’s arks. Today, his parents’ home in Minnesota is filled with woodworked arks of every variety, spilling out pairs of animals.

When Kris got into Harvard University at age 17, his parents were a little disappointed. As a Midwestern family with proud Norwegian heritage, they’d expected him to go (like everybody in his family) to St. Olaf College, a Norwegian Lutheran university in Minnesota.

But he’d made up his mind, in large part because he’d long dreamed of visiting the Museum of Comparative Zoology, which happened to be housed at Harvard. This museum was not, to be fair, a place most other undergraduates would ever visit. Yet to Kris, it was like being allowed into Mammal Heaven. He’d first heard of the museum at sixteen, while reading a book by the Harvard naturalist E.O. Wilson. As a child, Wilson had been obsessed with ants, which led to him becoming an expert on insects, “the little things that run the world” (he later discovered that ants communicate through chemical means).

On Kris’s first day on campus, he went straight to the museum and knocked on the door of the Mammal Division. The collections manager kindly offered to show him around, and asked if there was anything in particular he wanted to see. Yes, please, he said. The Ethiopian wolf. In the Encyclopedia, this was one of the animals that wasn’t sufficiently fleshed out. As Africa’s rarest and most threatened carnivore species, he needed to know more about it.

The collections manager pulled open a drawer, and there it was: an Ethiopian wolf.

Soon afterwards, Kris started working part-time at the Museum (and practically living there, too). In the narrow corridors of the collections rooms, going through drawer after drawer of specimens, he became attuned to the fine-scale differences between species. What is the nature of variation within each group of mammals? was now the question powering his curiosity. He became a student of species variety, of all the weird and wonderful ways of being a mammal.

And he was lucky to be there, because while the museum wasn’t among the biggest or best-known in the world, it had one of almost everything. One Ethiopian wolf. One giant panda. One specimen of an obscure extinct species of tiny kangaroo, Caloprymnus campestris, a creature hardly anyone knew much about, with very little published on it.

At the end of his first year at college, he travelled to Australia over the summer break on a student research grant. He turned up at the Australian Museum in Sydney, and went looking for the office of palaeontologist and mammalogist Tim Flannery. Growing up, Kris had read in National Geographic all about Tim and his fieldwork discoveries of new mammals in New Guinea, so he was a bit starstruck when Tim opened his office door. But Tim was welcoming, and said he’d be happy to give Kris a quick tour of the mammal collections.

In the collections basement, Tim pulled open a drawer and asked Kris if he knew what he was looking at.

Yes, Kris said. That’s Caloprymnus campestris. An extinct species of tiny kangaroo.

There was a moment of silence. And that was that, they were off; opening drawers, talking non-stop, and making plans to collaborate on research when Tim – by another coincidence – would arrive at Harvard in the autumn as visiting Chair of Australian Studies.

When it came time to develop his senior thesis project, Kris thought back to the Encyclopedia’s revelation that nobody knows how many types of raccoons there are in the world. This was a problem he wanted to solve.

He’d learned about the raccoons on various islands of the Caribbean, which for over a hundred years had been believed to be their own endemic species. They were recognised by the IUCN Red List, and many islands had national environmental plans to protect their raccoons.

Yet Kris believed it was highly unlikely that these raccoons had speciated on the islands. He suspected they were instead an invasive species.

He worked through the problem from three angles (anatomy, DNA and archival array searches) to prove that the islands had first received raccoons during the trans-Atlantic slave trade period, introduced mostly from eastern North America.

In the Bahamas, this news that raccoons were invaders was celebrated, as they were known to damage crops and prey on endangered seabirds. But in Guadeloupe, some people struggled to come to terms with ‘losing’ a beloved icon that was on postage stamps and flags and sold as soft toys in tourist gift shops. After a long time treasuring these raccoons, it was a cultural shift to begin to think of them instead as pests.

Kris was proud of his research, and also humbled by how much he learned from its real-world impact as he travelled to the islands to help wildlife officials understand what this change meant for local conservation efforts. Scientific facts never exist in a vacuum, he realised, but must be woven into the fabric of a place in order to have meaning.

He took these lessons with him into his post-college life as a mammalogist, aware he would always need to balance his research on specimens in museum collections with embedded fieldwork in communities, mixing two very different ways of knowing what any given animal is – or what it might mean to humans.

In the quiet, sterile space of a collections vault, it was possible to do focused work on an animal’s anatomy, taxonomic background and history, how it evolved. Out in the world, it was important to develop what he came to call an empathy for the animal, a sense of what it’s actually like in life, how it experiences its surroundings, and how the people who live alongside it see it in return.

Kris met his partner, Lauren, also a mammalogist, while he was doing his PhD in Adelaide. Tim had become his mentor and close friend, and had encouraged him to move to Australia and take up the mantle of some of his New Guinea mammals fieldwork. Kris had organised a major expedition to search for gigantic wild rats that live in the mountain jungles there, and had also become familiar with the extraordinary long-beaked echidnas of New Guinea. These once roamed Australia too but became locally extinct about a hundred years ago.

Yet it was on a trip back home to Minnesota to introduce Lauren to his family that Kris made the most important discovery of his career.

He wanted to show her the Field Museum in Chicago. It was Christmas time, and Chicago was blanketed in snow. The museum was shut down for the holidays, but he had research access to the collections. They spent days working all alone in there, studying the specimens stored in heavy metal drawers in old wall-to-wall cabinets.

One evening, Kris was struck by a set of animal skins labelled as olingos, a nocturnal carnivorous mammal related to raccoons that lives mostly in the rainforests of South America. The long, soft fur of the specimens was an unusual reddish-orange colour.

He knew instinctively that these were not olingos.

He and Lauren worked through the night, pulling out every single skin and skull labelled as olingo or kinkajou (a related mammal from the same region) in the collection. By the time the sun rose, he’d come to the conclusion that this was a separate species altogether, one that he’d never seen before.

It took him many years of hard work to prove this definitively, based on both anatomy and genetic studies. Before he published his results, he also needed to know if this animal might still exist out in the wild. The skins would have been sitting in those museum drawers for over fifty years, and had mostly come from the rainforests of Colombia – there was no guarantee that this newly discovered mammal species would still be alive in these now heavily deforested regions. With help from local colleagues, he set up a fieldwork expedition to nearby Ecuador, to an area with relatively untouched rainforests.

By the time he finally arrived in the Ecuadorian cloud forest in August of 2013, ten years had passed since his initial encounter with that red-furred specimen in the Chicago Field Museum. On the very first night of the expedition, through the hazy mist, they spotted an animal in one of the trees that resembled the museum specimen in appearance. It had big eyes, a long tail, a slightly upturned snout, and dark orange fur. It looked like a cross between a tabby cat and a teddy bear. It was not an olingo. It was not a kinkajou. And it was very much alive.

The olinguito, as this new species was later named by Kris and his team, turns out to be fairly widespread in the cloud forests. It shares habitat and appearance with olingos and kinkajous, which is why it had fallen between the cracks both in terms of local knowledge and scientific classification. The news of its discovery – not only in a museum drawer but living in the cloud forests – spread quickly around the world, and ignited a passion for olinguito citizen science in Ecuador. August 15 was declared World Olinguito Day and is still enthusiastically celebrated each year.

It’s not often, in these times, that we become reacquainted with an animal that we’d assumed would be long gone, and discover that it’s not only still alive but thriving in its natural home. It feels like a small miracle.

When the pandemic sent Sydney into lockdown in 2020, Kris had only just started in his new job as Chief Scientist at the Australian Museum. One of the things that kept him sane through those difficult months was long, rambling conversations with Tim, now a climate change author and advocate and Honorary Associate at the Australian Museum.

What they mostly talked about during lockdown was monotremes.

These are a special group of egg-laying mammals only found in Australia and New Guinea. Once, there would have been many diverse monotreme species, but today only the platypus and short-beaked echidna survive in Australia. In New Guinea, both short-beaked and long-beaked echidnas still live in the wild (but the long-beaked variety is endangered).

Thanks to their expeditions to New Guinea and around Australia, Kris and Tim both knew a fair bit about monotremes, and the long-beaked echidna had become Kris’s favourite mammal of all time. As a palaeontologist, Tim is also an expert in the fossil record of Australian mammals, including monotremes.

There’s a long-running joke between them that Tim’s real goal is to turn Kris into a palaeontologist – and now he’d finally found a way to do it. He convinced Kris to join him in hatching a slightly nutty and random plan to review every known monotreme fossil in the record and see what insights about monotreme evolution might emerge: gaps to fill, details that had gone unnoticed, connections overlooked.

They slowly gathered together a team of colleagues from other institutions to work on this review with them remotely. It was the kind of painstaking scientific detective work they’d never have time to do in the usual hurly burly of their busy lives.

When the team combed through the existing information about the oldest known monotreme fossil in the record, Teinolophos trusleri, it became clear that this small ancient monotreme – which Tim describes as weighing no more than a slice of bread – was significantly different from any of the monotreme fossils that came after it. So different, in fact, that it deserved a new taxonomic family (Teinolophidae). For scientists, it’s extremely rare to be able to name a new family (dogs, deer, bears, etc.) because it’s such a high-level distinction among biological life. The fossil’s secrets had been hiding in plain sight; it just took fresh eyes – and some spare time – to see them.

This common distant ancestor of the platypus and the echidna was a toothy creature – the fossil record shows monotremes going from very toothy to gradually losing the complexity in their teeth, down to no teeth at all (as they are today). It would have lived in the Cretaceous period, 130 million years ago, when Australia was still connected to Antarctica and was much further south. Teinolophos lived under polar night for long chunks of the year, snuffling around in the undergrowth of dark forests for food.

This helps to explain the earliest evolution of the electro-sensory apparatus that monotremes have – a kind of sixth sense that allows them to sense weak electric fields (such as that given off by insects) with their bills or snouts. They are the only mammals to have evolved this electroreception ability.

From their review of the fossil evidence, the team was also able to name a new genus of monotreme: the largest echidna ever known, Murrayglossus, a wombat-sized creature that lived in southwestern Australia in the Pleistocene epoch (also known as the Ice Age).

One of the questions that Kris and Tim puzzled over throughout this work together was the long gap in the echidna fossil record in Australia. By around 40 million years ago, echidnas and platypuses had begun to walk along separate evolutionary paths – leaving their common monotreme ancestor (the little Teinolophos) behind.

There’s plenty of evidence of different kinds of platypuses in the fossil record from then until now. But where are the echidnas? they kept asking each other. Echidnas only start to turn up in the fossil record in Australia two million years ago, though they have more robust skeletons than platypuses because of their digging arms, and thus tend to fossilise well.

By hashing things out in a safe conversational space, where they both felt comfortable asking obvious (or dumb) questions and chipping away at this mystery at their own pace, Kris and Tim developed a new theory of echidna evolution.

It’s still speculative, but they think that echidnas were evolving during that time in New Guinea rather than in Australia. This might not at first seem like a revelation, since it’s common knowledge that in the last several hundreds of thousands of years, New Guinea has been periodically connected with Australia as one landmass.

But going back to the level of millions of years, it’s a much more complicated picture.

New Guinea was a series of very different geological identities over that time, with islands coming and going in a conveyor belt of volcanic motion moving across the northern part of the Australian continent, some of them connecting and hitting and becoming part of the northern margin of Australia, others sailing onwards and becoming some of the main islands of Indonesia. It was a complex, dynamic land and seascape. It’s already known that some animals – like particular kinds of distinctive lizards, or birds of paradise – were evolving amongst that island-scape, bubbling away and becoming really different kinds of animals. And echidnas could have been part of that evolutionary story too.

It still remains to find the echidna fossils in New Guinea to prove this theory – which in itself is difficult, because things don’t fossilise well there, due to the warm and wet climate. You’d have to get lucky. But it’s not impossible that someone might, one day.

Today, short-beaked echidnas in Australia are faring much better than their aquatic platypus relatives.

Echidnas are surprisingly adaptable (if elusive) and, thanks to their prickly quills, they’re not as much at risk of predation by foxes, cats and other introduced predators. They’ve been found to be thriving at urban fringes as well as across every kind of habitat (snowfields; deserts; forests). They’re now the most widespread Australian mammal. But the freshwater habitats that platypuses live in are under threat due to deforestation, pollution, overdevelopment, bushfires. Their numbers are declining rapidly.

For Kris, looking back into the deep past at the ancient shared ancestors of these two creatures is an exercise not only in science but in emotion and connection. Thinking about their origin stories, rather than only focusing on the threat of end times, has helped him feel more in tune with them in their present incarnations. They’ve been around for so long, in so many different shapes and forms: think of that tiny first platypus-like monotreme, rooting around in the seasonal dark in the freezing cold polar forests…what a strange and wonderful creature!

Tim and Kris and their team published these monotreme evolution findings recently. Their lives are sort of back to normal – the new normal, at least – and filled with duties and distractions. They’re aware that brief window of stolen time during lockdown was precious in giving them a chance to reconnect intellectually and talk and think through bodies of accepted knowledge together.

They’re grateful that scientific discovery so often emerges like this, in community, through conversation and collaboration. It’s driven as much by intuition as it is by data, by following leads and hunches along meandering paths, not knowing you where you’re going and stumbling upon clues as much as digging for facts. It’s abstract and speculative as well as concrete and practice-based. It takes place in relationship with others.

Kris still has his copy of the Encyclopedia of Mammals, though he’s not quite sure in which box he has it stored in his home in Hornsby, where he and Lauren live with their young son, Danny, and a woolly Lagotto Romagnolo dog called Lana.

There’s one more story to tell about the Encyclopedia.

While Kris was Chief Mammalogist at the Smithsonian Museum in Washington, DC, in his thirties, he took a flight from Kenya to Uganda. He was getting settled into his seat when the scientist who had created The Encyclopedia of Mammals walked along the aisle and sat down in the seat next to him.

His face and name were burned into Kris’s memory: Professor David Macdonald, Oxford zoologist. By then, he’d read all of Professor Macdonald’s published scientific papers, seen all his BBC wildlife films, closely followed his career trajectory.

Kris tried to remain calm. He was sitting next to Professor David Macdonald!!!!!!

At first, he made polite conversation. Professor Macdonald, he learned, was going to Uganda to study chimps (Kris was going to see gorillas).

After a while, he summoned the courage to say, I realise who you are. He tried not to go over the top. You were an important part of my upbringing, he said, and you are why I became a mammalogist.

He did not say that he had read the Encyclopedia thousands of times, cover to cover; that the book still held the same magnetism for him; that he would cherish his copy until the day he died.

Professor Macdonald didn’t say much in response – but that was just fine. It was more than enough for Kris to sit side by side with him all the way to Kampala, wondering why the universe sometimes plays these generous, loopy tricks on us.

In the words of Kris Helgen

I can only be the mammalogist that I am because of having what we sometimes call an empathy for the animal – which is an understanding of what they're actually like in life. This is hard to develop; it takes hundreds of hours of trying to study wild animals in the field to get that instinct for who they are and how they actually experience the world.

To some extent, you can begin to build this empathy from looking at museum specimens, like this one of a platypus. Because we can puzzle over the fact that its eyes are so small, and we can puzzle over the nerves in its beak, and we can start to understand that form and function come together, and that gives us lots of clues about how this animal must be. But when you see it in life, all of a sudden, you can know what the animal is on its own terms. You can get to know this animal inside out, but it has to come through all those different ways of knowing.

Let’s look at this platypus specimen, and try to figure out what it might be like to be a platypus. You can see by looking at it that this animal can see, but those eyes are small. So that visual sense is not as important as it is in a lot of creatures, and the size of its eyes are a good indication that maybe there’s some reasons why it’s less sight-oriented than other animals. This can be a clue that it’s a night mammal; it lives a nocturnal kind of life. In some animals, it can mean they live underground, and doesn’t need to be exposed to light as much so the eyes aren’t quite as important. But animals can go the other way – some animals that are out at night, their eyes become bigger. With the platypus, we already know that it is nocturnal – this is an animal that doesn't have a lot of light in its world. You can also see where its ears are. There are little slits of ears back behind the eyes, what we call an absent external ear. So it can hear, but that is not very important to its senses either.

Look at those front feet. You can see they’re a bit bigger, and they spread out to have a much fleshier surface area of the front foot than they do on the back foot. In other words, the front feet end up being much bigger, with larger surface area. It’s a front-wheel-drive animal. That's how it gets around. It’s mostly powering its way through forward motion with those big front feet, and also with muscular movements of its tail. The hind feet are tucked in and less important in motion.

The male platypus is the only creature I can think of that envenomates through what we call a venomous horn or spur on the hind foot. There are a couple of other venomous mammals in existence, but it’s still pretty rare. There are a few species of venomous shrews, and then there are solenodons, which have survived largely unchanged in appearance since the time of the dinosaurs on some Caribbean islands. They live in burrows and have a pretty daunting-looking set of front sharp teeth. The venom runs down a groove in the tooth and it can bite you. I've never seen a solenodon alive, but I've seen several in museums.

One of the things about a platypus is they don’t have any teeth in their mouth. They just have some kind of thick pads, which they can use to crush up things like crustaceans. They do have baby teeth, deciduous teeth, like we do as kids. But once those are lost, they don’t have permanent teeth. And they just have these kind of leftovers, this empty mouth with these crushing pads. Platypuses in the fossil record, we can see they gradually lose their teeth over evolutionary time - and now they have no teeth.

The platypus has a sixth sense that other mammals don’t have. Only echidnas also have it. The platypus has a large set of nerves that go past the front of the face into that leathery bill. Around the edge of that bill there is bone, and underneath it too. Otherwise, it’s fleshy and filled with soft tissue. A large nerve goes in there, and spreads out through the whole front of the platypus’s face. This creates a sensory and mechanical preceptory organ. This isn’t something that any other mammals can do. They can actually detect electrical fields.

It's hard to imagine what it’s like to see the world through weak differences in electrical fields. With a bat, say, that echolocates, you can sort of think that it’s co-opting that echolocation as a visual sort of function, and then you can kind of imagine being a bat and seeing the world through sound. But I can’t really imagine what it’s like to see the world through the mechanical and electro-receptive organ of a platypus. It’s such a different way of being a mammal.

The platypus is a water animal. They live in rivers and streams and creeks, where they like to hunt invertebrates that are hiding at the bottom of these waterways. As they’re using the big strong motions of the front feet to move themselves along, they’re disturbing the bottom of those waterways, and animals are starting to move around. Little prawns, or insects, or crabs and things. And as that happens, the platypus is able to detect the gradients and electric fields – the life force, essentially – of these animals that are hiding and would otherwise be invisible in this silt-covered, dark bottom of the creek.