The latest weapon in Chicago’s war against rats is plant-based, naturally flavored and nutritious.

It’s a birth control pellet made with corn and peanuts, and a team of researchers and volunteers will be serving it to discerning rats in a four-block area of Lincoln Park for a year.

The aim is to reduce the rat population without harming urban wildlife, including owls and hawks, which can die after eating poisoned rodents.

The study was sparked by the high-profile deaths of three beloved Lincoln Park owls — mom, dad and owlet — who made their home near North Pond and died in rapid succession last April and May. The deaths were all linked to rat poison, which causes internal bleeding.

“We just realized we had to do something,” said Judy Pollock, former president of the Chicago Bird Alliance, which raised $32,000 for the study and is working with partners including the Lincoln Park Zoo, the Chicago Department of Streets and Sanitation and 43rd Ward Ald. Timmy Knudsen.

The Chicago study comes at a time when the poisonings of high-profile birds of prey have helped launch rat contraception studies in New York and Boston.

New York lost Flaco the Eurasian eagle-owl, who famously flourished in the city after escaping the Central Park Zoo, to a 2024 building collision. But testing showed Flaco had been exposed to a level of rat poison that would have been “debilitating and ultimately fatal” even without the accident — and may have made the accident more likely, according to the Wildlife Conservation Society.

In 2023, a barred owl known as Owen was rescued near Boston’s Faneuil Hall after ingesting rat poison. Owen lost an eye but survived.

The Lincoln Park owls nested in an easily accessible park, and some fans would visit them on a daily basis.

Then all three owls died in the course of a single month.

“It was really sad and there were a lot of people that watched it and as a result, I think, a lot of people are very interested in our work,” Pollock said.

The contraceptive pellets, which are distributed in black feeding stations about the size of a traditional rat-bait box, look a lot like dry cat food and are sized for carrying (by a rat). The active ingredient is an extract of thunder god vine, an Asian plant that has been used for centuries in traditional Chinese medicine.

Thunder god vine, which is used to treat inflammatory diseases such as rheumatoid arthritis, has a notable side effect: It can decrease fertility, according to Alaina González-White, director of operations at Wisdom Good Works, the Arizona nonprofit that is supplying the contraceptive used in the Chicago study.

The Wisdom Good Works contraceptive targets both male and female rats, González-White said, interrupting ovulation in the females and inhibiting sperm development in the males.

While standard rat poisons accumulate in the animal’s body, the active ingredient in the Good Works contraceptive is rapidly metabolized in the rat’s liver. The rats need to continue to consume the pellets to maintain the contraceptive effect.

The contraceptive is formulated for rats and mice, so other animals would have to eat very large amounts to be rendered infertile, and even then, the effect would be reversible, according to Wisdom Good Works founder Loretta Mayer, who spoke at a recent webinar hosted by the Chicago Bird Alliance.

Mayer, the co-inventor of the contraceptive, which is called Good Bites, said that Wisdom Good Works hasn’t seen any negative effects on birds, dogs or squirrels.

During a study in the historic Jamaica Plain neighborhood in Boston that began in 2023, the rat population declined by 56% to 70% over the course of 16 months, Mayer said.

Asked if Chicago could expect similar results, Mayer quipped: “Well, if I knew that I’d be in Las Vegas, making my fortune. Our experience tells us that … a 50% reduction would be an expected reduction.”

She added, “If I were a betting woman, I’d probably bet somewhere around a 60-65% reduction level.”

Contraceptives address the great challenge of rat control: the animals’ rapid rate of reproduction, according to Maureen Murray, assistant director of the One Health initiative at Lincoln Park Zoo.

Murray, who is leading the Chicago rat contraception study, said rats can breed every three weeks, and they produce up to 12 pups in a litter.

Two rats can produce about 1,250 rats in the course of a year, according to the global pest control company Rentokil.

Killing a rat does, of course, end reproduction, but it’s incredibly difficult to kill enough rats to make a lasting dent in the population, Murray said. And when you kill rats, the remaining animals will multiply faster, because they have more access to resources such as food.

Rats in an alley in the 1900 block of North Halsted Street, Aug. 12, 2025, in Chicago. (Armando L. Sanchez/Chicago Tribune)

The Chicago rat contraception study will monitor the effects of the contraceptives using multiple measures. Researchers will look at how much of the contraceptive is consumed, how many rats are visiting the feeding stations, and how much rat activity is picked up at separate stations dubbed rat cams.

The rat cams — upside down buckets with wildlife cameras hanging from the “ceiling” and peanut butter inside — will be stationed in areas where rats travel, such as along fences. Small holes in the buckets will allow the rats to enter and exit.

The researchers will also be using the rat cams to monitor four neighboring blocks where contraceptive pellets won’t be distributed. That’s to help assure the researchers that any drop in the rat population in the area with pellets is due to contraception, rather than broader factors such as weather or sanitation.

A rat’s range varies, but the animals typically stay within an area smaller than a city block.

A 50% reduction in rats would be a great outcome for the study, said Gloria Pittman, Chicago deputy commissioner of the Department of Streets and Sanitation, at the Chicago Bird Alliance webinar.

Streets and Sanitation helped choose the areas where the contraceptive is being placed and is part of the team that is monitoring the results.

Knudsen, the 43rd Ward alderman, said in a news release that if all goes well with the study — and he believes it will — he wants to pitch a citywide rat contraception program.

“It would be great if contraception could be one of the tools in the tool kit for rats,” said Murray. “I’m not sure that any one single tool is going to be the best in all scenarios, but I think having another tool so that we are less reliant on rat poison will benefit everyone. It will benefit people, it will benefit pets and it will benefit wildlife.”

nschoenberg@chicagotribune.com

The latest weapon in Chicago’s war against rats is plant-based, naturally flavored and nutritious.

It’s a birth control pellet made with corn and peanuts, and a team of researchers and volunteers will be serving it to discerning rats in a four-block area of Lincoln Park for a year.

The aim is to reduce the rat population without harming urban wildlife, including owls and hawks, which can die after eating poisoned rodents.

The study was sparked by the high-profile deaths of three beloved Lincoln Park owls — mom, dad and owlet — who made their home near North Pond and died in rapid succession last April and May. The deaths were all linked to rat poison, which causes internal bleeding.

“We just realized we had to do something,” said Judy Pollock, former president of the Chicago Bird Alliance, which raised $32,000 for the study and is working with partners including the Lincoln Park Zoo, the Chicago Department of Streets and Sanitation and 43rd Ward Ald. Timmy Knudsen.

The Chicago study comes at a time when the poisonings of high-profile birds of prey have helped launch rat contraception studies in New York and Boston.

New York lost Flaco the Eurasian eagle-owl, who famously flourished in the city after escaping the Central Park Zoo, to a 2024 building collision. But testing showed Flaco had been exposed to a level of rat poison that would have been “debilitating and ultimately fatal” even without the accident — and may have made the accident more likely, according to the Wildlife Conservation Society.

In 2023, a barred owl known as Owen was rescued near Boston’s Faneuil Hall after ingesting rat poison. Owen lost an eye but survived.

The Lincoln Park owls nested in an easily accessible park, and some fans would visit them on a daily basis.

Then all three owls died in the course of a single month.

“It was really sad and there were a lot of people that watched it and as a result, I think, a lot of people are very interested in our work,” Pollock said.

The contraceptive pellets, which are distributed in black feeding stations about the size of a traditional rat-bait box, look a lot like dry cat food and are sized for carrying (by a rat). The active ingredient is an extract of thunder god vine, an Asian plant that has been used for centuries in traditional Chinese medicine.

Thunder god vine, which is used to treat inflammatory diseases such as rheumatoid arthritis, has a notable side effect: It can decrease fertility, according to Alaina González-White, director of operations at Wisdom Good Works, the Arizona nonprofit that is supplying the contraceptive used in the Chicago study.

The Wisdom Good Works contraceptive targets both male and female rats, González-White said, interrupting ovulation in the females and inhibiting sperm development in the males.

While standard rat poisons accumulate in the animal’s body, the active ingredient in the Good Works contraceptive is rapidly metabolized in the rat’s liver. The rats need to continue to consume the pellets to maintain the contraceptive effect.

The contraceptive is formulated for rats and mice, so other animals would have to eat very large amounts to be rendered infertile, and even then, the effect would be reversible, according to Wisdom Good Works founder Loretta Mayer, who spoke at a recent webinar hosted by the Chicago Bird Alliance.

Mayer, the co-inventor of the contraceptive, which is called Good Bites, said that Wisdom Good Works hasn’t seen any negative effects on birds, dogs or squirrels.

During a study in the historic Jamaica Plain neighborhood in Boston that began in 2023, the rat population declined by 56% to 70% over the course of 16 months, Mayer said.

Asked if Chicago could expect similar results, Mayer quipped: “Well, if I knew that I’d be in Las Vegas, making my fortune. Our experience tells us that … a 50% reduction would be an expected reduction.”

She added, “If I were a betting woman, I’d probably bet somewhere around a 60-65% reduction level.”

Contraceptives address the great challenge of rat control: the animals’ rapid rate of reproduction, according to Maureen Murray, assistant director of the One Health initiative at Lincoln Park Zoo.

Murray, who is leading the Chicago rat contraception study, said rats can breed every three weeks, and they produce up to 12 pups in a litter.

Two rats can produce about 1,250 rats in the course of a year, according to the global pest control company Rentokil.

Killing a rat does, of course, end reproduction, but it’s incredibly difficult to kill enough rats to make a lasting dent in the population, Murray said. And when you kill rats, the remaining animals will multiply faster, because they have more access to resources such as food.

Rats in an alley in the 1900 block of North Halsted Street, Aug. 12, 2025, in Chicago. (Armando L. Sanchez/Chicago Tribune)

The Chicago rat contraception study will monitor the effects of the contraceptives using multiple measures. Researchers will look at how much of the contraceptive is consumed, how many rats are visiting the feeding stations, and how much rat activity is picked up at separate stations dubbed rat cams.

The rat cams — upside down buckets with wildlife cameras hanging from the “ceiling” and peanut butter inside — will be stationed in areas where rats travel, such as along fences. Small holes in the buckets will allow the rats to enter and exit.

The researchers will also be using the rat cams to monitor four neighboring blocks where contraceptive pellets won’t be distributed. That’s to help assure the researchers that any drop in the rat population in the area with pellets is due to contraception, rather than broader factors such as weather or sanitation.

A rat’s range varies, but the animals typically stay within an area smaller than a city block.

A 50% reduction in rats would be a great outcome for the study, said Gloria Pittman, Chicago deputy commissioner of the Department of Streets and Sanitation, at the Chicago Bird Alliance webinar.

Streets and Sanitation helped choose the areas where the contraceptive is being placed and is part of the team that is monitoring the results.

Knudsen, the 43rd Ward alderman, said in a news release that if all goes well with the study — and he believes it will — he wants to pitch a citywide rat contraception program.

“It would be great if contraception could be one of the tools in the tool kit for rats,” said Murray. “I’m not sure that any one single tool is going to be the best in all scenarios, but I think having another tool so that we are less reliant on rat poison will benefit everyone. It will benefit people, it will benefit pets and it will benefit wildlife.”

nschoenberg@chicagotribune.com

By JON GAMBRELL, Associated Press

DUBAI, United Arab Emirates (AP) — Construction work has intensified on a major new structure at a facility key to Israel’s long-suspected atomic weapons program, according to satellite images analyzed by experts. They say it could be a new reactor or a facility to assemble nuclear arms — but secrecy shrouding the program makes it difficult to know for sure.

The work at the Shimon Peres Negev Nuclear Research Center near the city of Dimona will renew questions about Israel’s widely believed status as the Mideast’s only nuclear-armed state.

FILE – This file image, made from footage aired on Jan. 7, 2005, by Israeli television station Channel 10, shows what the channel claims is Israel’s nuclear facility near Dimona, the first detailed video of the site ever shown to the public. (Channel 10 via AP, File)

It could also draw international criticism, especially since it comes after Israel and the United States bombed nuclear sites across Iran in June over their fears that the Islamic Republic could use its enrichment facilities to pursue an atomic weapon. Among the sites attacked was Iran’s heavy water reactor at Arak.

Seven experts who examined the images all said they believed the construction was related to Israel’s long-suspected nuclear weapons program, given its proximity to the reactor at Dimona, where no civilian power plant exists. However, they split on what the new construction could be.

Three said the location and size of the area under construction and the fact that it appeared to have multiple floors meant the most likely explanation for the work was the construction of a new heavy water reactor. Such reactors can produce plutonium and another material key to nuclear weapons.

The other four acknowledged it could be a heavy water reactor but also suggested the work could be related to a new facility for assembling nuclear weapons. They declined to be definitive given the construction was still in an early stage.

This satellite photo provided by Planet Labs PBC shows the Shimon Peres Negev Nuclear Research Center near the city of Dimona, Israel, July 5, 2025. (Planet Labs PBC via AP)

“It’s probably a reactor — that judgement is circumstantial but that’s the nature of these things,” said Jeffrey Lewis, an expert at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies, who based his assessment on the images and Dimona’s history. “It’s very hard to imagine it is anything else.”

Israel does not confirm or deny having atomic weapons, and its government did not respond to requests for comment. The White House, which is Israel’s staunchest ally, also did not respond to requests for comment.

Construction underway for years

The Associated Press first reported on excavations at the facility, some 55 miles south of Jerusalem, in 2021. Then, satellite images only showed workers digging a hole some 165 yards long and 65 yards wide near the site’s original heavy water reactor.

Images taken July 5 by Planet Labs PBC show intensified construction at the site of the dig. Thick concrete retaining walls seem to be laid at the site, which appears to have multiple floors underground. Cranes loom overhead.

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There’s no containment dome or other features typically associated with a heavy water reactor now visible at the site. However, one could be added later or a reactor could be designed without one.

Dimona’s current heavy water reactor, which came online in the 1960s, has been operating far longer than most reactors of the same era. That suggests it will need to be replaced or retrofitted soon.

“It’s tall, which you would expect, because the reactor core is going to be pretty tall,” Lewis said. “Based on the location, size and general lack of construction there, it’s more likely a reactor than anything.”

Edwin Lyman, a nuclear expert at the Cambridge, Massachusetts-based Union of Concerned Scientists, also said the new construction could be a box-shaped reactor that doesn’t have a visible containment dome, though he acknowledged the lack of transparency made it difficult to be certain.

Israel “doesn’t allow any international inspections or verification of what it’s doing, which forces the public to speculate,” said Lyman.

While details about Dimona remain closely held secrets in Israel, a whistleblower in the 1980s released details and photos of the facility that led experts to conclude that Israel had produced dozens of nuclear warheads.

“If it’s a heavy water reactor, they’re seeking to maintain the capability to produce spent fuel that they then can process to separate plutonium for more nuclear weapons,” said Daryl G. Kimball, the executive director of the Washington-based Arms Control Association. “Or they are building a facility to maintain their arsenal or build additional warheads.”

Israel’s program is thought to rely on byproducts of a heavy water reactor

Israel, like India and Pakistan, is believed to rely on a heavy water reactor to make its nuclear weapons. The reactors can be used for scientific purposes, but plutonium — which causes the nuclear chain reaction needed in an atomic bomb — is a byproduct of the process. Tritium is another byproduct and can be used to boost the explosive yield of warheads.

Given the secrecy of Israel’s program, it remains difficult to estimate just how many nuclear weapons it possesses. The Bulletin of Atomic Scientists in 2022 put the number at around 90 warheads.

Obtaining more tritium to replace decaying material may be the reason for the construction at Dimona, as Lyman noted it decays 5% each year.

“If they’re building a new production reactor,” he said, “it doesn’t necessarily mean they’re looking to expand the plutonium they have, but to manufacture tritium.”

Israel has a policy of nuclear ambiguity

Israel is believed to have begun building the nuclear site in the desert in the late 1950s after facing several wars with its Arab neighbors surrounding its founding in 1948 in the wake of the Holocaust.

Its policy of nuclear ambiguity is thought to have helped deter its enemies.

It is among nine countries confirmed or believed to have atomic weapons and among just four that have never joined the Nuclear Nonproliferation Treaty, a landmark international accord meant to stop the spread of nuclear arms. That means the International Atomic Energy Agency, the United Nations’ nuclear watchdog, has no right to conduct inspections of Dimona.

Asked about the construction, the Vienna-based IAEA reiterated that Israel “is not obligated to provide information about other nuclear facilities in the country” outside of its Soreq research reactor.

The Associated Press receives support for nuclear security coverage from the Carnegie Corporation of New York and Outrider Foundation. The AP is solely responsible for all content.

By JON GAMBRELL, Associated Press

DUBAI, United Arab Emirates (AP) — Construction work has intensified on a major new structure at a facility key to Israel’s long-suspected atomic weapons program, according to satellite images analyzed by experts. They say it could be a new reactor or a facility to assemble nuclear arms — but secrecy shrouding the program makes it difficult to know for sure.

The work at the Shimon Peres Negev Nuclear Research Center near the city of Dimona will renew questions about Israel’s widely believed status as the Mideast’s only nuclear-armed state.

FILE – This file image, made from footage aired on Jan. 7, 2005, by Israeli television station Channel 10, shows what the channel claims is Israel’s nuclear facility near Dimona, the first detailed video of the site ever shown to the public. (Channel 10 via AP, File)

It could also draw international criticism, especially since it comes after Israel and the United States bombed nuclear sites across Iran in June over their fears that the Islamic Republic could use its enrichment facilities to pursue an atomic weapon. Among the sites attacked was Iran’s heavy water reactor at Arak.

Seven experts who examined the images all said they believed the construction was related to Israel’s long-suspected nuclear weapons program, given its proximity to the reactor at Dimona, where no civilian power plant exists. However, they split on what the new construction could be.

Three said the location and size of the area under construction and the fact that it appeared to have multiple floors meant the most likely explanation for the work was the construction of a new heavy water reactor. Such reactors can produce plutonium and another material key to nuclear weapons.

The other four acknowledged it could be a heavy water reactor but also suggested the work could be related to a new facility for assembling nuclear weapons. They declined to be definitive given the construction was still in an early stage.

This satellite photo provided by Planet Labs PBC shows the Shimon Peres Negev Nuclear Research Center near the city of Dimona, Israel, July 5, 2025. (Planet Labs PBC via AP)

“It’s probably a reactor — that judgement is circumstantial but that’s the nature of these things,” said Jeffrey Lewis, an expert at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies, who based his assessment on the images and Dimona’s history. “It’s very hard to imagine it is anything else.”

Israel does not confirm or deny having atomic weapons, and its government did not respond to requests for comment. The White House, which is Israel’s staunchest ally, also did not respond to requests for comment.

Construction underway for years

The Associated Press first reported on excavations at the facility, some 55 miles south of Jerusalem, in 2021. Then, satellite images only showed workers digging a hole some 165 yards long and 65 yards wide near the site’s original heavy water reactor.

Images taken July 5 by Planet Labs PBC show intensified construction at the site of the dig. Thick concrete retaining walls seem to be laid at the site, which appears to have multiple floors underground. Cranes loom overhead.

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Today in History: September 3, Treaty of Paris ends Revolutionary War

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There’s no containment dome or other features typically associated with a heavy water reactor now visible at the site. However, one could be added later or a reactor could be designed without one.

Dimona’s current heavy water reactor, which came online in the 1960s, has been operating far longer than most reactors of the same era. That suggests it will need to be replaced or retrofitted soon.

“It’s tall, which you would expect, because the reactor core is going to be pretty tall,” Lewis said. “Based on the location, size and general lack of construction there, it’s more likely a reactor than anything.”

Edwin Lyman, a nuclear expert at the Cambridge, Massachusetts-based Union of Concerned Scientists, also said the new construction could be a box-shaped reactor that doesn’t have a visible containment dome, though he acknowledged the lack of transparency made it difficult to be certain.

Israel “doesn’t allow any international inspections or verification of what it’s doing, which forces the public to speculate,” said Lyman.

While details about Dimona remain closely held secrets in Israel, a whistleblower in the 1980s released details and photos of the facility that led experts to conclude that Israel had produced dozens of nuclear warheads.

“If it’s a heavy water reactor, they’re seeking to maintain the capability to produce spent fuel that they then can process to separate plutonium for more nuclear weapons,” said Daryl G. Kimball, the executive director of the Washington-based Arms Control Association. “Or they are building a facility to maintain their arsenal or build additional warheads.”

Israel’s program is thought to rely on byproducts of a heavy water reactor

Israel, like India and Pakistan, is believed to rely on a heavy water reactor to make its nuclear weapons. The reactors can be used for scientific purposes, but plutonium — which causes the nuclear chain reaction needed in an atomic bomb — is a byproduct of the process. Tritium is another byproduct and can be used to boost the explosive yield of warheads.

Given the secrecy of Israel’s program, it remains difficult to estimate just how many nuclear weapons it possesses. The Bulletin of Atomic Scientists in 2022 put the number at around 90 warheads.

Obtaining more tritium to replace decaying material may be the reason for the construction at Dimona, as Lyman noted it decays 5% each year.

“If they’re building a new production reactor,” he said, “it doesn’t necessarily mean they’re looking to expand the plutonium they have, but to manufacture tritium.”

Israel has a policy of nuclear ambiguity

Israel is believed to have begun building the nuclear site in the desert in the late 1950s after facing several wars with its Arab neighbors surrounding its founding in 1948 in the wake of the Holocaust.

Its policy of nuclear ambiguity is thought to have helped deter its enemies.

It is among nine countries confirmed or believed to have atomic weapons and among just four that have never joined the Nuclear Nonproliferation Treaty, a landmark international accord meant to stop the spread of nuclear arms. That means the International Atomic Energy Agency, the United Nations’ nuclear watchdog, has no right to conduct inspections of Dimona.

Asked about the construction, the Vienna-based IAEA reiterated that Israel “is not obligated to provide information about other nuclear facilities in the country” outside of its Soreq research reactor.

The Associated Press receives support for nuclear security coverage from the Carnegie Corporation of New York and Outrider Foundation. The AP is solely responsible for all content.