Hazing Ravens With Lasers: A Humane Way to Save Baby Tortoises? | KCET
Hazing Ravens With Lasers: A Humane Way to Save Baby Tortoises?
The laser rifle is heavier than it looks. The wind off the Mojave River is strong, kicking sand into our faces as we sit in this little foxhole, and that wind catches the rifle's boxy body. My target is a good thousand feet to the east. At this distance, even a minor arm wobble can make the difference between a hit and a miss, but I steady myself, get my quarry in the sights, and pull the trigger.
The raven doesn't move.
"Try again," says biologist Tim Shields. I pull the trigger again, see a momentary green flash across the raven's breast as I hit it, almost by accident. The bird flaps its wings but doesn't leave its roost in the cottonwood. "One more should do it," says Shields. I try again and at last the raven takes flight, joining a dozen or so of its colleagues in the air.
"That was a stubborn one," says Shields. "They always give up eventually."
We're on a bluff overlooking a large composting facility west of the Mojave River in Oro Grande, where food waste and garden trimmings undergo the slow process of turning into soil amendments. It's exactly the kind of place you'd expect to find a huge number of ravens. But ravens are largely absent from the scene. There were more ravens in the strip-mall parking lots I passed in Victorville an hour ago than there are here, on several acres of land covered with delicious compost.
That's because Shields and his colleague, biologist Al Demartini, have been harassing the ravens away from the composting facility with that laser rifle. To be precise, it's a TALI TR3 Counter-Piracy laser, designed as a form of non-lethal defense for ships in the western Indian Ocean, With an output of three watts of green laser light, the TR3 is designed to dazzle would-be pirates, interfering with their ability to see where they're going, while not actually hurting them.
Shields and Demartini are using the TR3 to see whether they can change raven behavior, to chase them away from a massive, 24/7 free meal. Ravens are killing federally Threatened desert tortoises, and it's entirely possible they might drive them to extinction. "Ravens hate the laser," says Shields. "Their vision is better than ours, and even in daylight they can see the beam so well that it looks like a solid object to them. Imagine having a bright green baseball bat waved in your face. You'd get up and leave too."
Demartini takes a few more carefully targeted potshots with the TR3. What few ravens were still in the cottonwoods are now milling around in the air above the compost windrows. "It's time," Shields says; Demartini hands me the gun, raises his binoculars, and starts counting off the number of ravens he sees in the trees, in the air, and on the compost itself. That last number is zero.
"Al's amazing at this," says Shields. "I've never met anyone who can get counts as accurate as quickly as he can." That skill comes in handy: every twenty minutes, the two stop shooting and count, compiling the data to measure how effective a deterrent the TR3 actually is.
This is no free-for-all, wildlife biology version of Doom. Shields and Demartini have certain rules by which they have to abide. The compost facility is in full operation, and the two can't shoot while workers are anywhere in sight. They can't fire at ravens in flight, due to the infinitesimally small chance that their 3-watt beam will hit the eyes of a pilot in an unseen aircraft. There's a road between us and the ravens, and though there's no traffic on it, the shooting would have to stop if any drivers showed up.
Even with those restrictions, the test has been remarkably effective. Shields and Demartini have been working for a week. When they started, late-afternoon counts showed more than 100 ravens actually feeding on the compost. A week later, that number has dropped essentially to zero.
"There are still ravens here," says Shields, "but none of them are feeding. Instead, they're milling around, flying, using up energy. They aren't taking compost and turning it into baby ravens. In just a week of the two of us sitting here, we've denied the ravens this massive subsidy."
A desert drained of tortoises
Tim Shields -- who, by way of full disclosure, is a friend and former neighbor of mine in Joshua Tree -- has been tracking and observing desert tortoises for close to 40 years. In that time, he's watched the desert lose as much as 95 percent of its tortoise population.
"In the late 1970s and early 1980s, I could often find ten or more tortoises a day," Shields said in a 2014 TEDX talk. "Now, on the same plots, I can go days without seeing a single one... my job has mostly been to take careful notes on a quiet catastrophe."
After 38 years of taking notes, Shields is ready to take action. His startup, Hardshell Labs, is looking at different ways to use emerging technology to find ways to save tortoises and other animals from the peril they face. One Hardshell Labs project involves using replica juvenile tortoises crafted on a 3-D printer to watch how ravens treat their potential prey. The firm is also examining the use of drones both to document ravens and to haze them away from potentially vulnerable areas.
And then there's the TR3, lent to Hardshell by manufacturer Xtreme Alternative Defense Systems' CEO Pete Bitar, who had been investigating whether the rifle could be used to haze geese nonviolently away from airport runways. "We got together and talked and Pete was very enthusiastic about our idea," says Shields.
There are a whole lot of reasons for the decline in the desert tortoise, also known as Gopherus agassizii. There's Upper Respiratory Tract Disease, or URTD, a highly communicable infection that was discovered in desert tortoises in the 1980s and is often fatal. We've converted desert tortoise habitat into desert cities, landfills, mines, and other developments. Tortoises have fallen prey to vehicles of both the street-legal and off-road varieties.
But one of the biggest threats to tortoises -- perhaps the biggest -- is a staggering increase in the number of ravens in the desert in the last 50 years.
Ravens seem like they've always been part of the California desert ecosystem, and they have indeed been there for a very long time. But they used to be really rare. In the early 20th Century, one biologist trying to collect a west Mojave raven for a natural history museum spent two years looking for one.
The desert ecosystem has changed. As modern American society has colonized the desert, we've brought with us things that help ravens survive and thrive in a place that once severely tested their survival skills. We've brought food in the form of garbage, orchard trees, and landscape plantings. We've brought sprinkler systems, artificial lakes, and swimming pools to provide ravens with a regular supply of year-round drinking water.
We've even changed the structure of the desert, stringing transmission lines across hundreds of miles of open plain, providing ravens with thousands of nesting trees and perches in areas that never used to have them.
And while advocates of desert renewable energy used to ask semi-seriously if desert tortoises might not benefit from the shade solar panels provide, it's a fact that ravens do benefit from the shade our artificial structures provide, which makes it more likely that ravens will survive hot spells and go on to make new baby ravens.
As a result of those subsidies from human beings, raven numbers in the deserts of the Southwest have jumped dramatically. In 1995, biologists Kristin Berry and William Boarman estimated that raven numbers in the west Mojave had climbed by 1,500 percent or so since the 1960s. That's a 15-fold growth in the raven population in three decades, and that 1960s raven numbers baseline was already much higher than had been the case a generation earlier.
That increase has been catastrophic for desert tortoises, juveniles in particular. Ravens don't pose much of a threat to adult tortoises, but torts under age five are vulnerable to ravens in two important ways: their shells aren't yet hard enough to withstand determined pecking, and they're small enough to be carried away.
Biologists have found macabre piles of tortoise shells beneath multi-year raven nests in the Mojave Desert, where adults have scoured the nearby desert for baby tortoises and brought them back to eat at home like so many take-out burritos. In 1989, Kristin Berry told the New York Times that biologists had found 250 baby tortoise shells beneath a nest occupied by a single pair of ravens.
Multiply that 250 baby tortoises by the immensely increased number of ravens in the desert, and the scope of the problem might make you want to pull your head into your shell. There would seem to be little way to save the desert tortoise without drastically reducing the number of ravens in the desert, and no one really likes the idea of killing ravens.
That's especially true since by any objective metric, ravens are really freaking awesome. The largest North American member of the crow family, a.k.a. corvids, ravens share the prodigious intelligence of their close kin. Among birds, only some parrots surpass corvids in sheer intellectual prowess.
How does that intelligence express itself? There are a few ways. Ravens play, both in solitary diversions and group games that resemble the roughest human team sports. The birds, for all their size, have that increased wariness over potential threats that so often accompanies acute awareness. One study of ravens in California's Marin County indicated that the birds spent many days observing nests of unfamiliar bird species before eating the eggs, as if concerned that the eggs might be dangerous.
And most importantly for our purposes, ravens seem to have a rudimentary form of culture. They learn from each other, either directly or by watching things happen to other ravens. That intelligence has earned the raven a place in a lot of Native pantheons as a wise elder figure, or a trickster similar to Coyote.
Tim Shields says the best capsule description he's heard of ravens' brainpower came from a game warden in another state, discussing raven predation on tortoises at a meeting of tortoise biologists. "He said 'these are sentient creatures,' Shields had told me a few weeks earlier. "I'd never heard it put that matter-of-factly before, but it's really true."
And that makes the prospect of reducing their numbers -- which, to be frank, generally means killing them -- all the more distasteful, especially to biologists who got into the business in the first place because they like wildlife. If it was a virus or a fungal organism causing the problem, such as the mycobacterium suspected of causing URTD, few biologists would have any compunctions about wiping out as many of the offending organisms as they could.
But a big, charismatic bird that reminds us of ourselves? That gets icky.
In 1989, the Bureau of Land Management started an experimental program that would have killed about 1,500 ravens near Twentynine Palms, as well as in the vicinity of the Desert Tortoise Natural Area near California City, in an effort to relieve some of the predation pressure on local tortoise populations. The Humane Society of the United States sued to keep the BLM from killing any ravens; a settlement drastically reduced the allowable take of the birds from 1,500 to fewer than 60.
Had the program continued the poison of choice would likely have been Starlicide, a substance often used to kill starlings on farm fields. It's used because it's theoretically less toxic to other birds such as hawks than it is to starlings. Ravens are not one of those other birds. Starlicide kills ravens effectively by way of causing fatal kidney damage.
For wildlife control purposes on public lands in the west, Starlicide would have been applied by the agency Wildlife Services, which claims the pesticide kills birds painlessly. That would likely depend on your definition of pain. While the uremia induced by Starlicide poisoning may not cause pain directly at the site of the kidneys, the impaired kidney function that results does cause symptoms such as headaches, cramps, nausea, weakness, muscle pain, pins-and-needles tingling, and other such symptoms of renal system failure.
In other words, even if Starlicide doesn't directly cause pain, it would certainly be a distressing way to die, especially for a smart bird like the raven.
Since 1989, raven control has been sporadic at best. Land management agencies can put in requests for Wildlife Services to come out and dispatch "problem" ravens, and Wildlife Services will come out and kill some ravens in the area suggested. Whether they get the ravens that actually cause the problem of the moment is questionable. It's not like Wildlife Services arrives on the scene and finds a raven eating a baby tortoise, cackling with glee atop a pile of carcasses. In fact, says Shields, no biologist has ever actually observed a raven eating a tortoise. And as further evidence of ravens' intelligence, birds that are blase enough to ignore a truck belonging to the BLM, a rockhounder, or a freelance tortoise biologist will recognize a Wildlife Services pickup from a far ways off and make themselves scarce.
Even if you manage to kill the precise ravens that have been eating the local baby tortoises, that leaves a bit of open territory that neighboring ravens can colonize. Once established, they will likely pick up the babykilling where the previous ravens left off. That's true whether you use poison or firearms to kill the birds.
That territoriality in an intelligent species is precisely what Shields hopes to leverage by using tools like the TR3. By dissuading ravens from an area rather than killing them, Shields hypothesizes, people might be able to declare an area "off-limits" to ravens without completely disrupting local raven territories, and allowing raven culture to "spread the word" that an area is unpleasant and to be avoided.
That's a message ravens seem to get pretty readily when it comes to harassment with a laser beam. In the video below, Shields and Demartini chat as a few short bursts of laser fire by Demartini cause a whole lot of ravens to leave, even if the beam didn't come anywhere near them:
If this technique pans out not only could we deprive ravens of subsidies such as compost, but we might be able to change the way we rear baby tortoises in so-called "headstarting" facilities, says Shields. "Right now, headstarting facilities need to be screened from above to keep ravens from eating the juvenile tortoises," says Shields. "That means the tortoises have to be kept at close quarters in pens, and that can lead to problems, like ants attacking the tortoises.
"If we can keep ravens off a square mile of tortoise habitat with a few lasers, that could change the way we design those headstarting facilities," he adds. "Instead of pens, we could just have a stretch of desert that's protected for the young tortoises."
It's an appealing concept, but two obvious questions present themselves. Will Shields' promising preliminary results translate into real-world success? And is shooting ravens with a laser cruel to the birds themselves?
Taking a shot for the ravens
Firing the TR3 is an anticlimactic event for someone who grew up watching "Star Trek." Aside from the whirring of the onboard fan to cool the electronics, and the slight "click" as the trigger is depressed, there really isn't immediate tactile feedback: no recoil, no phaser sound effects or "pew, pew, pew."
But watch the TR3 fired at dusk, as I did outside my house in Joshua Tree when Shields had offered a demonstration of the gun itself a few weeks earlier, and the laser is nonetheless impressive. It creates a startlingly bright beam of collimated green light stretching at least a half mile, like a light saber that a Jedi might wield if he had personal inadequacy issues.
The power of the laser is impressive, and this is something that people intend to aim at living things with neurons that can sense pain. Will ravens feel pain, or even discomfort, when shot with this thing?
The math says "probably not." The TR3's manufacturer, Xtreme Alternative Defense Systems, rates the weapon as safe to use without causing human beings vision damage at 200 feet, five times closer than the ravens we've been laser-tagging here in Oro Grande. Eyes are far more sensitive to damage from strong light than is skin: sitting in full sun for twenty minutes might give you a mild sunburn, while staring at the sun for a twentieth that time can permanently blind you. If the manufacturer says shining the TR3 in the faces of oncoming pirates won't hurt them at 200 feet, the weapon almost certainly won't harm birds whose skin is protected by a thick layer of feathers at the much longer distances Shields' project would involve.
But that's at best informed speculation, I thought during that earlier visit. What I needed to write this piece with any confidence I wasn't inadvertently plugging a technology that would burn birds, which prospect I found potentially ironic, was first-hand empirical data.
On that earlier meeting in the dusk in Joshua Tree, I broached the idea to Shields. Explaining my concerns, I suggested to him that my journalistic ethics required that we find a careful yet experimentally rigorous setting in which he would shoot me with the laser. The experience would allow me to report first-hand on whether the laser might cause physical discomfort to its intended targets.
Shields' inner 12-year-old was thrilled with the idea, and he beamed almost as bright as the TR3. But it only took three or four seconds for his inner grownup to regain control. While allowing that it would be helpful to have a first-hand report on what the laser felt like, he couldn't bring himself to approve of the idea.
Nor, when I broached the topic to my editor at KCET, could he see his way clear to approve it, given the obvious potential liability issues should my math be way off.
In the foxhole up above the composting facility, Demartini and I are discussing raven behavior, the capabilities of the TR3, and various other topics, some of them related, as Shields is away for 20 minutes making a phone call. The wind has picked up, and we're eating grit again. I try not to think about the fact that the grit is blowing from the direction of the composting facility. I mention my conversation with Shields about shooting me with the laser in order to ground-truth its relative harm to living things.
Demartini asks "Did Tim clear it?"
Thinking quickly, I lie through my grit-covered teeth.
Five minutes later I'm 150 yards south, crouched behind a large concrete pillar, holding my right arm out so that Demartini, still in the foxhole, can have a clear shot at the unprotected back of my hand. I stare at my hand and do my best not to blink so as not to miss anything. Within 20 seconds half my hand is bathed in a green glow, wobbling there for most of a second. I feel nothing. If I hadn't been watching, I wouldn't have known I'd been hit.
Shields, when he returns to the foxhole, takes only a split second to regain his equanimity when I inform him of our unauthorized experiment. "That was kind of... cowboy," he says. A second passes and then he starts to chuckle.
If my unscathed skin is any indication, the TR3's effect on ravens should be painless, pure annoyance -- at least at the range at which Shields and Demartini have been working.
Will it really work?
"Tim's a very good scientist," says veteran tortoise biologist Kristin Berry a few weeks later. "I've worked with him for a long time. And the work he's doing is very creative."
But Berry, a USGS biologist who's widely accepted as the dean of desert tortoise science, isn't ready to declare Shields' work a solution to the vexing issue of ravens eating tortoises.
"Tim presented his work so far to biologists at the Desert Tortoise Council symposium, and he got a lot of very positive support, " says Berry. "But I have doubts whether these promising initial results will translate into long-term benefit for the tortoises."
Berry points out that any new technique used to deter ravens from a particular site has the possibility that it will become less effective if the birds get used to it. This possibility, usually called "habituation," is why you see pigeons happily perched atop plastic owls sold to deter pigeons.
"And once you stop using the lasers in a certain area," asks Berry, "how long does it take for the ravens to figure that out and return? We just need more information."
Berry also points out that tortoises aren't the only animals at risk of predation by ravens. "I'm not just concerned about tortoises," she says. "If you defend tortoises in an area against ravens and they go somewhere else, they're not going to stop eating. They may not eat any tortoises, but ravens also eat bird eggs and baby birds, and lizards. What happens to those animals when we drive ravens into their part of the desert?"
"The real problem is numbers," Berry adds. "Tim's work might help protect individual areas of the desert, but this is a problem that extends across the whole desert. There are just far more ravens in the desert than the desert can support, and we need to change that."
Shields concurs that the possibility of changing raven behavior through laser aversion conditioning needs more study. "We absolutely need more data. This work is all very preliminary. We don't have nearly enough numbers to even think about publishing anything." Near the top of the priority pile, says Shields, is raising funds to do follow-up work at the composting facility in Oro Grande. "One question we did not answer with this test, and which is frequently asked of me, is 'How long will the birds stay away after the laser firing stops?' This can only be answered by a longer test. I plan to do this test ASAP."
Shields has also made a date with the owner of a pistachio orchard to run tests similar to those at the composting facility in Oro Grande. Pistachios in an orchard will ripen more or less all at once, and ravens know exactly when that is; providing Hardshell Labs with a place to test aversion techniques might well save the orchard owner thousands of dollars in protected pistachios.
As Berry says, the raven overpopulation problem in the desert is a systemic one, and local fixes can only go so far. And it's not just tortoises that are at risk. Berry points out that the Nevada Legislature recently passed -- by unanimous votes in both the Assembly and the State Senate -- a resolution asking the U.S. Congress to remove the raven from the list of birds protected under the Migratory Bird Treaty Act. The resolution specifically mentions allowing state agencies to "control" ravens that are preying not only on juvenile tortoises, but sage grouse eggs as well. Powers-that-be in Nevada are bending heaven and earth to keep the grouse off the Endangered Species list, and it's obviously being seen as an opportune time to roll back protection on the raven.
As is the case with the tortoise, any damage ravens are doing to the sage grouse is really more of a symptom of our wholesale alteration of the Western landscape -- in the case of the grouse, primarily by livestock grazing. And it's true: hazing ravens with lasers won't ever be a solution to that greater issue.
But if Shields' work does pan out, such hazing might provide a tool that could actually make things better for the tortoise in some areas, while being more humane to the ravens than euthanizing them, and putting a damper on the birds' unchecked population growth by denying them free meals here and there.
And how often do we get even partial solutions that work out across the board like that?
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