Poisoning rats kill hawks and owls that results in rising rat populations

Somerville residents are encountering rats with increasing frequency.  Some for the first time; some for too many times.  A retired Somerville police officer of 40 active years says in the last 5 years the rat problem has reached “biblical proportions.”  Here are some other comments submitted to the Mayor’s Office:

  • I hate rats sauntering through my back yard, across my street and on one memorable occasion, up my front steps to see what I was reading.
  • We got a new can from the city and now, on our other trash can, we can see they have almost eaten/clawed the tiniest hole through the top. I don’t know if they are getting in through the tiny hole, but they have been pulling out dirty diapers from the cans and sort of burrowing in them behind the trashcans. It’s insanely disgusting.
  • On a normal morning I could see one, maybe two, which is bad enough in my world, but this morning there were about six or seven.  This is just totally out of hand.
  • We have also lost the enjoyment of our backyard and deck and have had to cut down our beautiful gardens to cut out rat We used to appreciate that quality of life element in our Somerville house, but not as much as we do now that it is gone.  More often than not, now when we we’re outside and talk with neighbors, it’s no longer about gardening or what’s going on in the neighborhood, but about rat sightings.

How can this be?  The days of spilling trash cans of all shapes and sizes have been replaced by extra-tough city containers.  Building and health inspectors are on the lookout for rat dwellings.  Residents have been invited to have their properties inspected for rats at no cost. The population of feral cats in Somerville is rising along with diligent efforts to spay and neuter all cats. With so much knowledge, because humanity and rats have cohabited spaces for some time, you’d think we’d be better at managing rats.  And yet, despite it all, there are today so many more rats that it’s “just totally out of hand.”

Part of the rat problem is their impressive capacity to generate more rats. A bit of rat arithmetic calculates how quickly one pair of rats can go to “biblical proportions.”  A female rat typically gives birth to six litters a year.  After 3 months a pair of rats produce about 10 offspring.  After 6 months, 50 rats are produced by the two rats.  Young rats mature in four or five weeks to commence having more generations of more rats.

In one year, two rats assisted by their offspring can produce 1,250 rats.  At the end of three years, an exponential explosion of rats to  a total of 482,508,800 rats are born of two rats. As long as there is sufficient food and burrows for rats, there will be plenty more than one pair of rats to begin with, and soon many more rats all over town.

Enough rats! Somerville residents are declaring war.  Kill the rats.  The arsenal includes snap traps, bait traps, carbon monoxide, dry ice, even sticky paper, and of course, feral cats.

For the battlegrounds, residents point to new developments as the source of the scourge.  Yet, developments are not new to Somerville. Developers are more diligent today than a decade ago about the rat problem, either by choice or regulation.  They could do more.  But why is there the sensation that a rat-hydrant has burst and hairless-tail rodents are flooding the city?

The howitzer of choice for rat control is the bait trap.  Rat eats the bait, an anticoagulant drug used by humans. Rat then goes somewhere discrete to bleed-out and die.  People like this rodenticide because they don’t see dead rodents and feel better at the sight of lots of bait boxes.

Until the dead rat becomes known.  A Somerville resident writes about a big, stinking drawback to the use of bait traps: “Rats who are poisoned hide while dying.  Rats hide in places that are hard to get to – e.g., deep in weeds, in holes, in garden, OR worse, and hardest to get to, DRAINS.  Dead, decomposing, rats (that die in place and can’t be found due to the above) smell awful – like can’t go out in the backyard awful.”

Red-tailed hawks no longer perch on The Charles Hotel outside my office window.  For years, when the weather cooled a pair of hawks sat atop the letter “H” in the “THE” posted high on the building above “CHARLES”.  I think it’s been about five years since they left.

Ruby and Buzz were a pair of red-tailed hawks that nested high in a pine tree by Fresh Pond near the Cambridge Belmont line.  The pair were very popular with a plethora of bird-watchers that walked around Fresh Pond.  Updates on the big birds of prey were often the start of conversations when people passed each other on the mile-long lake trail.

On April 11, 2014, Ruby was found dead on the ground beneath her nest.  Susan Moses brought Ruby to the Tufts Wildlife Clinic in Groton.  She paid out-of-pocket for additional blood testing to identify what chemical led to Ruby’s death.  Death was found to be due to the ingestion of the anticoagulant drug of rat bait traps.  George McLean, a photographer who had observed Ruby for many years put it succinctly. “There are restaurants, grocery stores, [and] bread factories all over the area. The town is getting overwhelmed with rodents, but the creatures who eat the rats die just as easily.”

Unfortunately, predators instinctively go after the least healthy prey animals.  This helps to cull the unhealthy and saves those most fit for breeding to breed, if only to feed the predator later on.  It’s a mutual relationship.

Dr. Maureen Murray, assistant director of Tufts Wildlife Clinic at Cummings Veterinary Medical Center, has overseen research into the effects of rat poisons on birds of prey.  Specifically studied have been the red-tailed hawk, barred owl, great horned owl and Eastern screech owl.  When the birds are brought in alive, clinic doctors work to save the bird. It depends on how much poison was consumed and how much it takes to kill. The fate of each animal brought in was unique.

Postmortem studies on 161 birds brought in from 2006 to 2010 found that 86% had been exposed to anticoagulant rodenticide.  A second study from 2012 to 2016 with 94 birds found 96% exposed to anticoagulant rodenticide.  Dr. Murray noted that the food chain is extensively contaminated, meaning that an animal eating a poisoned rat could go on to poison the predator eating it.  Whether the bird ate a poisoned rat or ate the poison in the trap could not be determined.

“The exposure rates are so high, it’s almost all the birds.  Those birds are coming from a fair representation of the state, too, not extreme western or southeastern. By no means is the exposure restricted to cities.”

This is only the tip of a horrible iceberg. “We don’t have a lot of great ways to document how many animals are dying out there because it’s a very hard thing to study in the wild,” said Dr. Murray. “It’s hard to locate animals that have died in the wild. You will find papers on coyote exposure, out of Colorado, around Denver. There’s a lot of work in California on bobcats, where they find high exposure. There is plenty of other research out there showing exposure in other species.”

Ruby’s champion, Susan Moses, identified the problem. “Old-fashioned traps are more labor-intensive because somebody has to empty them, but these chemicals are extremely harmful, not just for wildlife, but people’s pets and children. Hawks die all the time, but there’s a difference when we feel it was caused by human action and could have been prevented.”

The problem of more rats than ever before is due to linear thinking and having no respect for nature.  Linear thinking is see rat, kill rat, problem solved.  Systems thinking is stepping back to get the bigger picture where it becomes obvious that to kill-a-rat like the game whack-a-mole is not going to address, let alone solve, the rat problem.

Tony Juniper, author of “What Has Nature Ever Done for Us?”, tells how use of a new anti-inflammatory drug unwound and disconnected a natural ecosystem with terrible consequences for people.  The oriental white-rumped vulture of Southeast Asia went from being arguably the most numerous larger bird of prey in the world to one of the least numerous, most threatened. In India from 1993 to 2007, the vulture population, three species of vultures combined, crashed from about 40 million birds to no more than 10,000 birds. The long-billed vulture dropped by nearly 97%.  The oriental white-rumped vulture dropped 99.9%.  It had gone virtually extinct.

Diclofenac, a new anti-inflammatory drug developed for people, has been found to often help sick livestock recover.  However, if cattle or water buffalo were treated with the drug a few days before their death, traces of the drug remained in their bodies.  Vultures that fed on the tainted carcasses died.  Compounding the problem, when vultures flock together to feed, the entire committee of vultures dies. (Yes, a murder of crows, a mischief of rats, a committee of vultures.)

The messy, clean-up work that vultures had been performing for humans suddenly stopped. Cattle died; cattle were quickly skinned by people for the leather industry.  Without the skin, it was once easy work for the vultures to clean up to the bones. Then people could pick up the bones and sell as feedstock for the fertilizer industry. Without vultures, carcasses putrefied out in the sun to become a public health hazard.  To clean up, carcasses were burned or buried, labor formerly done by vultures.

To understand what had happened, Tony Juniper researched the ecological niche occupied by the oriental white-rumped vulture, how the ecosystem operated, and what happened to the economy when vulture committees were no longer big players in it. He found that the vulture population decline created space for other predators, more rats and feral dogs. For starters, it was estimated that when 40 million vultures were living in India during the early 1990’s, they would have consumed about 13 million tons of meat a year.  This was figured to be sufficient to sustain around 4 to 7 million more dogs.  Sure enough, dog population increased by about 7 million. But that increase could be due to many factors other than more food left by absent vultures. The dog population was found to have been stable between 1982 and 1987, a time when committees of vultures were tucking into carcasses. The subsequent increase in dogs was very likely related to the decrease in vultures.  The trouble is that these are feral dogs, no veterinary care including shots, so they carry diseases. India has the highest rate of rabies infection in the world and over 95% of fatal cases are from dog bites.

Researchers estimated that in the period 1992 to 2006, nearly 40 million additional dog bites occurred due to the increase in the feral dog population. These bites were estimated to lead to between 47,395 to 48,886 deaths from rabies, compared to when vultures were in abundance. The impact on India due to the loss of vultures was estimated to cost about $34 billion.  When there were 40 million vultures, each and every vulture cleaning up carcasses was saving the nation nearly $1,000.

The value of giving an anti-inflammatory drug to sick cattle is dwarfed most dramatically by the expense of eliminating vultures from the ecosystem. Viewed from afar, viewed economically, it makes no sense.  Likewise, the expense of using an anticoagulant drug for rat bait is the loss of birds of prey and a plague of rats on the people of Somerville.

The use of bait traps should be stopped before hospital reports of people being bitten by rats further escalates, and families must pay an even dearer price.  Stop poisoning red-tailed hawks and other birds of prey by not using bait traps.  Let red-tailed hawks patrol local rat populations. Let the predators catch their prey, and let Nature manage.

The problem is bigger than rats and hawks, bait traps or the use of less poisonous methods. It’s systemic. To solve the burgeoning rat population problem once and for all, our perspective of economics must change.  Our view of economics must be unblinkered to pull our wagon towards prosperity and healthy living.

Many economists, especially those who say it’s either the economy or the environment, are too narrow in their models. They cannot see the bigger system that we are a part of. Ecological economics recognizes the economy as an open system nested and entangled inside the whole.

An economic paradigm shift is required because traditional economics are diminishing our quality of life with more work in worse living conditions. With birds of prey absent, not only must Somerville residents pay more to manage rats, their capacity to do so at any expense is questionable.

When dragonfly nymphs devour fewer mosquito larvae, town mosquito management programs pay more.  When fewer squirrels and ground birds, including robins, are bitten by Ixodes deer tick carrying Lyme disease, there are fewer animals serving as reservoirs for the disease. More people are bit by more ticks and families must pay more in suffering and medical costs.

Should the natural areas around the Quabbin Reservoir be degraded, Boston would have to pay more for clean drinking water.  This is similar to the way Lowell and Lawrence must pay for clean water from the Merrimack River. The benefits to stewarding healthy ecosystems are vast. Nature’s benefits are never appreciated because for most they are inconceivable.  Like entitled children crying when pricked by a rose’s thorn, they are clueless to how the workings of a healthy ecosystem are enabling us all.

Traditional economists chalk-up such increases in expenditures as good for the economy with more final goods and services produced (greater GDP and GNP). They attack a problem like it is a carnival game of Whack-a-Mole and measure success by the number of moles whacked.  If a bird of prey, say a red-tailed hawk, was brought to the enterprise, there’d be no need for people to expend so much energy and expense whacking moles.

To save Somerville from being overrun by rats, think holistically and look to the welfare of birds of prey.  Remember that ecological economics is better for quality of life than the prevailing economics, unless you are a Carny hawking prizes.

2 thoughts on “Poisoning rats kill hawks and owls that results in rising rat populations

  1. Great article, I wish more people could see the connections. I have ‘ What Nature Does for Britain’ waiting to be read but it’s Tony Juniper, not Jupiter!

    • Susan, That is very funny. In Katowice Poland for the UN Conference on Climate Change i was handed a schedule of speakers for Scientists Warning Panel and told to prepare media advisory for Tony Jupiter. I thought that an odd name for a Brit, but then Brits have odd names so put out the media release to hundreds of outlets. Later i had lunch with Tony and he would have given a hearty laugh. He actually dictated to me what to say, read carefully those words and missed the most blatant typo of all.

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