Give me a few tufts of grizzly bear fur, and I can tell you how many bruins might be in a forest. Show me a few scoops of bat guano, and I can identify a cave’s night-flying occupants. And with the gut contents of a dung beetle, I can name the mammals roaming about the Swaziland savanna.
OK, maybe I can’t do these things, but scientists can.
The techniques are examples of what’s known as noninvasive sampling, tricks scientists use to study animals they’ve never set eyes or hands upon. Whether it’s something as simple as setting up candid cameras or as complicated as measuring real-time polymerase chain reactions, noninvasive sampling is becoming an enormously important tool for conservation. Here are just a few ways scientists-turned-sleuths are uncovering the secrets of the rarest of the rare.
You’re probably already familiar with the camera trap—basically, a trigger-activated camera that catches passing wildlife unawares. These devices have been around since 1877, and while they may be little more than glorified photo booths, the humble camera trap is worth its weight in data.
These sneaky snapshots allow scientists to observe a patch of woods day and night for months on end without having to hunker down behind a blind, waiting out monsoons or fighting off malaria. Not only do the devices make already thin conservation dollars go further, they avoid habituating wildlife to humans or modifying an animal’s behavior. (That said, many do seem somewhat perplexed by the contraptions.)
There’s also something powerful about the visuals provided by camera traps, says Asia Murphy, a graduate student at Pennsylvania State University who is known on Twitter for her candid pics of fossas, lemurs, and various other inhabitants of Madagascar.
This is not "charming", "beautiful", or "gorgeous".— Asia Murphy🔪 (@am_anatiala) August 25, 2016
It is creepy and disturbing. pic.twitter.com/aueI0OUiIf
The data from her cameras “are easily shareable with others,” Murphy says. “People understand a picture or a video of animals, but they might not understand a map of GPS coordinates” like the ones scientists compile from radio collars and tags attached to animals.
There’s also the issue of permits, Murphy says. Depending on the country you’re working in and the status of the species you want to study, getting government clearance to capture and collar certain animals can be a torturous process.
While scientists of yesteryear would hope and pray to stumble across rare or endangered species, today we can set up dozens of motion- or heat-sensitive traps across miles of terrain and see what stirs.
Similarly, any camera trap set up where people are nearby runs the risk of theft or other, shall we say, attention. “We’ve gotten people flashing the cameras,” Murphy says.
The Things We Leave Behind
Most sampling methods do require obtaining more than pixels of an animal. Thanks to genetic samples taken by “remote biopsy darts,” scientists recently realized they could split giraffes into four distinct species, each with its own unique conservation needs. The darts, fired from tranquilizer guns, nab a small tissue sample of an animal before bouncing off, hopefully with no more disturbance than a bee sting.
Not noninvasive enough for you? OK, how about this 2008 study in which scientists were able to prove definitively that a single dog—not a pack of wolves as charged—attacked two sheep in central Sweden. The researchers fingered the culprit by swabbing the saliva left on the sheep’s bite wounds.
And then there’s feces. Honestly, we could sit here all day talking just about feces.
“I've often said we’re trying to save the world one fecal pellet at a time,” remarks Faith Walker, a conservation geneticist and director of the Bat Ecology & Genetics Lab at Northern Arizona University. Walker published a study in PLOS ONE in September describing a new, noninvasive way to identify all the bat species that inhabit a cave just by analyzing the DNA found within a few scoops of poop. This replaces the need to net bats as they emerge from a colony, a technique that causes the tiny animals stress and ultimately yields less accurate results, since you can never catch more than a fraction of the little flitters. “Guano is a wonderful thing because, unlike bats, it just sits around,” Walker says.
If your study animal doesn’t like to hole up in one place, you could always hire a team of rescue dogs to sniff out that scat. They’re called the Conservation Canines, and their whole job is to find endangered species feces.
Poop does have its shortcomings, however. Those dogs still require humans to chase after them. Small animals leave behind itty-bitty bowel movements that can be tough to spot, and large animals distribute their dung far and wide. That’s why some scientists have zoomed in on a creature that dines on the doo-doo of just about everybody in its ecosystem: dung beetles!
A study published in September in the journal bioRxiv showed that one can come up with a good roster of the wildlife inhabiting an area simply by studying the gut contents of dung beetles. Examining just 10 dung beetle species, the researchers found evidence that blue wildebeest, zebras, cattle, goats, and even mice were nearby. Oh yeah, and humans. (Guess someone’s been leaving the toilet seat up.)
In addition to DNA, poop contains hormones that can hint to an animal’s sex, reproductive status, and stress level. Carnivore feces also contain hair, which is itself a handy scientific tool.
In particular, strands of hair with the follicle still attached can provide higher-quality DNA than that derived from feces. The only catch is that the best method of obtaining strands from wild animals, the hair snare, isn’t all that dependable, according to some grizzly bear research also presented in September in PLOS ONE.
“We can track individuals, assess relatedness between animals, measure their movement through landscapes,” says lead author Jason Fisher, a wildlife ecologist with the government of Alberta. “[But] all of this depends on reliable genetic samples, and for the most part we’ve been relying on faith and hope in this aspect.”
The baited hair snare is essentially a tasty morsel surrounded by barbed wire, which draws an animal to an area and snags a lock of fur for its trouble. Unfortunately, it can’t tell us how many times a single bear visits the lure or how many other bears are out there who didn’t investigate the treat—or get to it first.
Fortunately, stacking noninvasive strategies on top of each other―say, by aiming a camera trap or two at the area surrounding a hair snare―can help remedy this problem. “The old adage in carpentry, ‘Measure twice, cut once,’ is really advice for life, and it applies to science, too,” Fisher says.
Loach in a Haystack
The endangered loach minnow and spikedace are two tiny fish native to remote streams and pools in the Gila River Basin in New Mexico and Arizona. They’re smaller than the sardines that come in a can, and so nondescript they require an expert to identify them.
The question is, how do you save a fish you can barely find?
One way is electrofishing, a technique in which wildlife managers run low-voltage current through a stream and then scoop up whatever floats to the surface. This sounds kind of gruesome, but the electrocution usually doesn’t kill the animals—just stuns them for a bit. (I’ve seen this collection tool in action in the Great Smoky Mountains National Park, and I can attest to the survival of all the newts, trout, and frogs we encountered.)
Still, wouldn’t it be nice if you didn’t have to shock the spit out of a fish to figure out if it still exists?
Thankfully, a new technique can sniff out the presence of even the most cryptic aquatic species with just a sample of the water they swim in. It’s called environmental DNA, or eDNA. Using an existing genetic profile of loaches and spikedace, scientists can check a cup of water to detect traces (skin cells, etc.) of the species. A proof-of-concept study published in September in PLOS ONE even provided evidence of the method’s effectiveness.
And let’s not forget drones. The drones are coming!
These unmanned planes are already helping track deforestation and catch poachers, but they could one day help scientists save a lot of time traveling back and forth among study sites. “If one could remotely collect camera data from a proximal drone, then a camera could sit in a remote area undisturbed for months, or even longer,” says Fisher. “Imagine if a DNA trap could be remotely piloted from its housing into a researcher’s hands.”
Whatever the technique, this one goes out to all the endangered species out there:
Every move you make.
Every twig you break.
Every crap you take.
Every wolf and snake.
We'll be watching you.
(And saving you, too.)
onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.