Rodent Control Re-imaged: Forty Local Parks Adopt Bird-Friendly Method

Rats | Bernie Hawes | Canva

A 2021 pilot project between Birds Connect Seattle and Seattle Parks & Recreation has taken flight and is reducing harm to countless birds.  

by Carol Roll, Development Director

In cities across the world, and especially ratty ones like Seattle, rats are a persistent challenge. They scurry through parks; burrow elaborate tunnels and make their homes in urban spaces where food is plentiful. While rats are a nuisance and a health risk to humans, they also pose a significant risk to wildlife—particularly birds. For years, the use of poisons to control rodent populations has been commonplace in Seattle neighborhoods, inadvertently poisoning birds and other animals that prey on the rats or consume contaminated carcasses. But in 2021, a partnership between Birds Connect Seattle (BCS), the Capitol Hill EcoDistrict, and Seattle Parks and Recreation (SP&R) launched a groundbreaking initiative that is not only more effective in rat control but also saving birds. 

The Hidden Dangers of Traditional Rodent Control 

Traditional rodent control methods often rely on the use of second-generation anticoagulant rodenticides (SGARs), a class of poisons that disrupt blood clotting in rodents, causing them to die slowly from internal bleeding. These poisons are highly toxic, long-lasting, and, tragically, they don’t just kill rats. SGARs have been detected in the tissues of over 100 local species, including more than 70 bird species, as well as numerous mammals and even slugs. Because rats are a primary food source for many birds of prey—like hawks and owls—the toxins spread through the food chain, poisoning animals that eat the rodents or their remains. 

BCS and other wildlife conservation organizations have long pushed for safer alternatives to SGARs. Our advocacy laid the groundwork for this collaboration with SP&R. 

Bait boxes, like this one, often contain harmful SGARs.

The Birth of a Safer Solution: CO2 Rat Control 

In 2021, thanks to funding from BCS via our Capitol Hill Connections Project, SP&R began testing a novel rodent control method through one of the pest control contractors at Cal Anderson Park. This approach, which uses carbon dioxide (CO2) gas to suffocate rats in their burrows, was a game-changer. 

The process is simple but highly effective. The rat burrows are sealed, leaving only one entrance open. A canister of CO2 is then inserted into the hole, and the gas fills the burrow, leaving the rats without oxygen. This method is effective for reducing rat populations while ensuring that no poisoned carcasses are left behind to endanger scavenging wildlife, such as birds.  

Another key benefit of the CO2 method is its precision. Unlike poison bait stations, which are often indiscriminate and leave dangerous residues in the environment, CO2 treatment targets the rats directly within their burrows. 

Not only does the CO2 method offer a safer alternative for birds, it comes at a similar price tag as traditional methods. Rodent birth control and other high-tech solutions are an emerging market but can be expensive. CO2 treatment has proven to be a reliable, maintainable, and affordable way to manage rat populations. 

Expanding the CO2 Program Across Seattle Parks 

The success of the pilot program at Cal Anderson and subsequent other parks including Woodland, Denny, and Albert Davis Parks prompted Seattle Parks and Recreation to expand the use of CO2-based rat control throughout more of Seattle’s parks. By 2024, the method is now being utilized in over 40 parks across the city, reports Bridget Kelsh, IPM and Wildlife Coordinator at Seattle Parks and Recreation. 
These specific parks were selected for CO2 utilization because of their generally high rat populations and because human activity is most concentrated, resulting in more food sources for rats—food waste, and accessible garbage. While some additional parks meet this high food source = high rat population criteria, not all parks are good candidates for this method. If a park has a lot of buildings surrounding rat burrows this method of treatment remains difficult to use because rat burrows often continue below buildings. While the risk is low, CO2 can leak upwards from burrows and so it is important to avoid the gas seeping up into buildings, especially occupied ones.  

In areas like 12th Avenue Square the CO2 method has been combined with landscape changes such as reducing shrub beds and keeping park areas clear of debris like leaves and low tree limbs—measures that also reduce places for rats to hide. 

Redesigning their trash cans has also been an important way to reduce attracting rats in the first place. The new design with a metal base and sides, and straight side that can’t be climbed by rodents in combination with frequent garbage pick-up services has reduced rodent food sources in parks.  

Not all Seattle Parks are good candidates for this method. In the parks where this CO2 treatment isn’t a good option SP&R is using several other bird-friendly methods including: 

• • Opting for no treatment because rodent populations are in balance and/or not a concern. Usually these are less utilized parks where there are fewer food sources. 

• • Setting out small (non-poison) food sources so they can see where the rats are visiting and feeding first and then respond appropriately with strategically placed snap traps at feeding locations and along the edges of buildings where CO2 treatment is less practical. 

SP&R’s current policy prevents the use of SGARs, however, they admit they use many different subcontractors to support their operations over 6,400 acres of parkland. Their next phase of focus will be to ensure each of these contractors will be adhering to their current policies for pesticide and rodenticide usage. Either way, the expansion of the CO2 program and their work with their pest control contractors has greatly reduced the amount of SGARs and other wildlife-harming chemicals being used across the city.  

Cooper’s Hawk | Matthew Sabouri | Audubon Photography Awards

A Model for the Future 

This partnership between BCS and SP&R is a model for cities looking to balance effective rodent control with wildlife conservation. With more than 485 parks under the management of Seattle Parks and Recreation, the collaboration is helping to set new standards for urban wildlife protection. 

Importantly, this success story has caught the attention of other agencies and groups. The King County Public Health Department is working alongside SP&R and other city departments to improve rat management strategies through cross-education and collaboration. They are even developing a Rodent Work Group to bring together experts from various sectors—including housing, parks, and utilities—to develop more integrated solutions for managing rat populations and protecting wildlife. 

Saving Birds, One Park at a Time 

The partnership between Birds Connect Seattle and Seattle Parks and Recreation proves that it’s possible to control rat populations effectively without resorting to harmful poisons. By adopting the CO2 method, Seattle is setting a new precedent for bird-friendly, sustainable urban pest management. And as more parks continue to adopt this approach, more birds will be protected from the dangers of secondary poisoning. 

The success of this initiative demonstrates the power of collaboration between environmental organizations, city agencies, and local communities. Together, they are creating safer spaces for both people and wildlife, one park at a time.