The Tres Cantos City Council is already penalizing the first owners identified thanks to a canine genetic census that allows each piece of feces to be associated with a specific animal. The measure, in place since the end of 2025, makes this municipality in northern Madrid one of the first in the region to move from awareness campaigns to effective fines for not picking up feces.
The municipal ordinance of Tres Cantos requires dog owners to “immediately” pick up excrement in any public area and deposit it in a trash can or container. Failure to do so is considered an offense punishable by a fine of €300 for the first offense and up to €600 for repeat offenses, according to the Councilor for Public Health, Mario Arancón. In addition, it is mandatory to carry a bottle of water to clean up urine, another rule that officers can monitor and penalize.
The council insists that the measure is not intended to raise revenue, but rather to act as a “deterrent,” and that most dog owners are responsible; the aim is to take action against the minority who fail to comply and damage the cleanliness of sidewalks, parks, and children’s areas.
A “canine CSI”: how dog DNA works
Editorial credit: sergey kolesnikov | shutterstock.com
In order to be able to penalize with objective evidence, the City Council launched the canine DNA project more than a year ago, with the campaign “I’m from Tres Cantos, I carry it in my DNA.” Owners are required to take their pets to a participating veterinary clinic to have a saliva sample taken, which is recorded in a municipal genetic database; the procedure costs around 40 euros, and failure to do so may also result in a fine.
When uncollected excrement is found on public roads, a laboratory technician and a police officer collect samples on random days and send them to the laboratory to compare them with the canine DNA database. If there is a match, the City Council identifies the dog and its owner and opens disciplinary proceedings in accordance with the ordinance, also applying the corresponding surcharge if the animal was not registered. In this new phase of the service, “several owners” who have committed offenses have already been located and are being penalized.
A response to neighborhood complaints
Dog excrement is one of the main reasons for neighborhood complaints in many cities, and Tres Cantos is no exception: the municipality has more than 2,000 registered dogs and abundant green areas, which multiplies the points of friction when some owners do not comply.
Tres Cantos thus joins the list of more than 80 Spanish municipalities that have opted for genetic registration of dogs to combat street poop, but it goes a step further by decisively applying the first fines.