The search for an understudied Sengi

MAYBE THIRTY FEET from the campsite something rattled in a trap.

It was nearest Galen Rathbun’s sleeping bag, and it wrecked the veteran ecologist’s sleep. “God, that animal has been keeping me up all night long,” the California Academy of Sciences’ Rathbun told Duke’s Steven Heritage a few hours later, when the scientists woke up early enough to beat the fierce Djiboutian sun. The two exchanged a meaningful look, and while they were discussing how to proceed, Rathbun picked up the trap and peeked in.

That was early February 2019 and Heritage’s second morning in Djibouti. The day before, the Duke Lemur Center researcher had touched down in the Horn of Africa jet-lagged and tired from a long flight. Djibouti City—the capital and only city—isn’t big, and the nation itself is about the size of North Carolina’s Triangle region. Heritage spent a night in a hotel, with its comfy bed and running water, and hit the grocery store the next morning to stock up on fruit and nuts and food that would keep for weeks at a time, in a Land Cruiser, in 110-degree heat.

And then Heritage, Rathbun, and Djiboutian colleagues Houssein Rayaleh and Djama Awaleh left Djibouti City for a rocky wilderness called Djalelo, all on the gamble of finding a minuscule creature researchers knew precious little about.

No specimens had been taken in five decades.

Though also known as a species of elephant shrew, the Somali sengi is neither. It’s about the size of a mouse, but only superficially similar (humans are more closely related to mice than sengis are, in fact). It’s insectivorous, with a long snout and gazelle-like hind legs. Sengis mate for life, and their offspring can sprint within an hour of birth.

The sengi itself is an ancient endemic African mammal, its lineage predating even the charismatic “big game” African mammals. Heritage sounds almost proud as he describes its roots, which he has studied extensively. Not only is Heritage a sengi specialist, but he works at the Division of Fossil Primates, a department of the Duke Lemur Center focused on the mammalian fossil record. If it happened after dinosaurs but before now, its remains are studied here, by Heritage, curator Matt Borths, and their colleagues. The division houses remains of entire extinct genera the layperson has no reason to have heard of, as well as the ancestors of modern creatures like lemurs and, yes, sengis.

Among sengis, Somali sengis were especially data- deficient, with fewer than forty specimens in collections, as of early 2019. Some of these were “pickles”—specimens preserved in formaldehyde— and many more dated from the late 1800s and early 1900s. “And they’re just scrappy,” says Heritage. “Here’s a skull and, like, part of the skin of the animal.”

Needless to say, there were no photos or DNA samples.

None of this indicated that the Somali sengi was rare, but understudied. Decades of instability in Somalia made biological expeditions to that country unsafe, leaving a possibly common animal off-limits to the wider scientific community—even if Somalians saw them regularly. And this brings up a question of perspective that was historically absent in Western scientific literature: “The first sengi that ever got brought back to Europe in the 1800s from Somalia, even that wasn’t a discovery,” says Heritage. “The people that lived in Somalia already knew that sengis were there before the Europeans showed up.”

Since Somalia borders Djibouti, Heritage had the idea of a collaborative American and Djiboutian expedition. A mutual friend at the Smithsonian National Museum of Natural History connected Heritage and Rayaleh in 2017, and soon the two were planning a small mammal survey.

Djibouti is a biodiverse region, Rayaleh says, and its terrestrial and marine biomes range from underexplored to unexplored. For one, there are few Djiboutians working in biology or conservation: The nation’s university, he says, is all of ten years old, and its faculty tend toward law and the humanities rather than science.

“It seems I am the only crazy man who runs the countryside to see birds, mammals, reptiles, plants, and so on,” Rayaleh says.

Educated in France and Djibouti, Rayaleh started his “nomad city boy in the countryside” career teaching elementary school in remote villages, eventually moving into school administration and biological research. By the end of the ‘90s, he was organizing and coordinating expeditions studying different taxa—birds, reptiles, mammals, insects—and birdwatching tours. Having spent decades in rural and wild Djibouti, Rayaleh knew what lived there.

“The only thing I did not know was the taxonomy of the sengi in Djibouti,” he says matter-of-factly. “As a long-lasting naturalist in Djibouti, I encountered it many times.”

Based on interviews with locals and his own experience, Rayaleh selected Djalelo as the first field site, confident the team would find sengis. He chuckles as he thinks back to his American colleagues’ impression that these creatures would be difficult to find. From the international scientific community’s perspective, however, there remained no guarantee that the sengi species in Djibouti was the Somali sengi.

“You can imagine that if the IUCN [International Union for Conservation of Nature] has no records of any of that taxonomic order from that country, it’s really kind of a risk to go there,” Heritage says. “There have been three or four previous small mammal expeditions to Djibouti, and none of them had produced any sengis.”

It was late afternoon by the time the team reached Djalelo Wildlife Protected Area. Like much of Djibouti, Djalelo is made up of rocky basalt hillsides, many at fifteen to thirty-degree grades. Heritage tore holes in his boots trekking across rocks and acacia thorns, though his Djiboutian colleagues happily walked around the campsite barefoot.

The team scoped the Djalelo landscape, checking for scat and paying attention to how rodents like gerbils, mice, and gundis moved through the terrain. Elsewhere, in Namibia and South Africa, sengi species live in sparse woodlands or flat gravel plains— nothing like this. Finding sengis, then, held its own set of challenges on these rock-strewn hillsides. Traps get lost or—in one instance this expedition— smashed by baboons.

In Djibouti, all sengis are called wali sandheer: wali for “small scurrying mammal” and sandheer for “long nose.” Photos existed of some kind of sengi at Djalelo— including one that was sent to the team days before the expedition—but it could have been another known sengi species or even an undescribed one.

The team picked a spot on the horizon. Then the four walked ten paces in that direction, put down a trap, moved ten paces, and set another. It went like this: Lay the trap against a rock or under a bush. Bait the trap with a mix of oatmeal, peanut butter, and marmite. Tie yellow flagging tape around a nearby rock. Take GPS coordinates. Move on. When it’s time to turn back, walk ten paces to one side and return to the starting point, ten paces at a time. Working together, Rathbun, Rayaleh, Awaleh, and an already sunburned Heritage laid 100 traps each day.

At times, Rathbun was in pain, Rayaleh recalls, but insisted on pushing forward.

Late the first night at Djalelo or early, early that morning, Rathbun heard something trip the nearest trap. Again—he woke at dawn, groused to Heritage that it had kept him up all night, and picked up the offending trap.

“It’s a sengi,” he said.

“No way,” Heritage replied.

“See? I told you,” Rayaleh said. “They’re all over the place here.”

Rathbun noted its tufted tail at first glance, and Heritage checked its incisors. From these indicators, the team was all but certain it had a Somali sengi. Science is a patient discipline, and it would take further analysis to say for sure, but that didn’t stop a sense of excitement that now, finally, missing data could be gathered—things like the Somali sengi’s habitat and diet and distribution.

“I can’t believe it,” Rathbun said. “I’ve never seen one before.”

Not long after Rathbun and Heritage returned to the States, the first DNA analysis came in, which indicated at the very least that this sengi belonged in its own genus. Heritage and Rathbun put off saying with certainty that it was a Somali sengi until the data were more complete, and Rathbun’s sentiment was that he’d be happy to be surprised. Yet a few weeks after returning to California, he became ill with metastatic melanoma, and died in April 2019.

Rathbun was easy to work with, says Heritage, a scientist to whom fieldwork came naturally and who made expeditions fun, razzing colleagues and even “playing chicken” with a camel at one point during the Djibouti trip. Heritage is in contact with his widow, Lynn Dorsey Rathbun, who has told him that bringing this missing species back into the realm of science was the perfect end to Rathbun’s life’s work. Indeed, when the Somali sengi was reclassified into a new genus, it was named Galegeeska: Gale- for Galen; geeska for the Horn of Africa.

This expedition was a win for Djibouti, too, Rayaleh says. Djiboutians don’t tend to know the true taxonomy or conservation status of the species around them, for one, and as a result of his team’s fieldwork, one long-“missing” creature is returning to the scientific community. A former French colony, Djibouti has only been independent since 1977 (Rayaleh was seventeen), and historically it’s been negatively stereotyped or useful only to world powers as military barracks and bases, he says. Yet this discovery highlights biodiversity in Rayaleh’s homeland, where he hopes a new generation will answer the call of ecology and conservation. “Natural history research in Djibouti is an important step in my country’s renaissance,” Rayaleh says.

And then there’s widespread media coverage. The Somali sengi is a furball with big eyes, round ears, a tufted tail, and a funky little trunk. It’s cute. People tweet about it, Rayaleh says. They draw cartoons of it. It’s a positive, scientific story about Djibouti, which has been a long time coming.

Since the Djalelo expedition, he has traveled to Durham and met with Duke Lemur Center director Greg Dye, Division of Fossil Primates curator Borths, and—of course—Heritage. Rayaleh’s next step is discussing the future of Djiboutian fieldwork with the Duke Lemur Center, Smithsonian, and other American institutions.

“I am not young, and we need the young generation to continue the same thing I am doing now,” he says.

In that moment, in February 2019, Rathbun, Heritage, Rayaleh, and Awaleh had in their trap what would turn out to be the Somali sengi, which had not been documented in the wild in more than five decades. They could only celebrate for so long, because there were ninety-nine traps still out on the hillside, and these needed checking before the fierce Djalelo sun hit their aluminum frames. (“Then you’re baking animals. And that’s not cool,” says Heritage).

So, the team put the first trap in the shade of the Land Cruiser, found the preselected spot on the horizon, walked ten paces to the next trap, and peeked inside.