Black bears in Boulder are expanding eastward
In 2014, a Bear Protection Ordinance in the city of Boulder required residents in the western part of the city to bear-proof their trash and compost at all times. Data on bear sightings show that bears in Boulder are expanding eastward and trash remains a huge attractant.
American black bear (Ursus americanus). Photo Marc-Olivier Jodoin / Unsplash
The American black bear (Ursus americanus) is North America’s smallest and most widely distributed bear species. American black bears are omnivores, with their diets varying greatly depending on season and location. Black bears typically live in forested areas but will leave forests in search of food. They are often attracted to human communities because of the immediate availability of food (Armstrong et al., 2010).
A series of events shook Boulder back in 2013. A sharp rise in bear encounters in the area led to four incidences where bears were ultimately killed by state wildlife officers. This number was unprecedented for Boulder (where previously, an average of 0.5 bears was lost annually to human-wildlife related conflict). The community set a plan into motion to address the dynamics that factored into the death of these four bears.
Boulder’s bear protection ordinance
The bear protection ordinance in the city of Boulder (Ordinance 8161) created an obligation for residents to secure trash and curbside compost in bear-resistant containers in certain parts of the city (west of Broadway and south of Sumac). The ordinance was put in place to protect bears, improve human-wildlife co-existence and increase sanitation and cleanliness of the city.
According to Valerie Matheson, Senior Wildlife Conservation Coordinator for the city of Boulder, the impetus for the ordinance was the observation that bears that spend time eating human-generated food sources, including trash, get used to being around people, lose their natural fear of people and spend more time in town. These habituated bears have a higher mortality rate than bears that live in natural areas. Though black bears tend to avoid humans, the potential for interaction with community members is a threat to human safety. The most effective way to prevent bears from learning to live off trash is to secure it.
Boulder bear sightings
When the bear ordinance was being considered, community and city council members wondered about the possible unintended consequence of pushing the bears east of Broadway because trash is secured and thus harder to get west of Broadway. Bear sighting data for the city of Boulder collected from 2009-2019 by Matheson show that bears appear to expanding eastward (Figure 1). While not presented here, other bear observations indicate that bears have been spotted as far east as Longmont, Louisville, and Lafayette.
Although bears do appear to be moving eastward in the city of Boulder, it is not clear that the ordinance is driving this eastward expansion. Observations throughout the Front Range indicate that bears have been sighted further east than usual in recent years, even in areas without trash ordinances. So, these observations suggest that this bear ordinance is not the sole driving force for the eastward expansion of black bears.
Instead, the increasing availability of food (a consequence of a rapidly growing population) may be driving the eastward expansion and the increase in bear sightings throughout Boulder. Data show that trash and compost are still the primary attractants of black bears, along with bird feeders, domestic animals, and planted items, such as fruit trees (Figure 2). When Matheson conducted a survey with residents east of Broadway, she found residents were often surprised to learn that bears could be on their property.
explore the data
Number and location of bear sightings, from 2009-2019.
Figure 1. These maps of the city of Boulder show bear sightings reported from 2009-2019. Police report data on bear sightings were added to this data set starting in 2015. The left-most border of the maps is the western city boundary, where city streets meet the foothills. The polygon in the upper right corner of the maps is Gunbarrel. The maps show an overall increase in individual bear sightings (gold circles) since the 2014 Bear Protection ordinance, and an increase in bear sightings in the eastern part of the city from 2015-2019. There are likely more bear sightings than reported to the city. Data provided by Valerie Matheson, Senior Wildlife Conservation Coordinator, City of Boulder Planning and Development Services Department.
Bear attractants in Boulder
Figure 2. The chart below shows the items that bears were attracted to when they were sighted in the city of Boulder from 2009 - 2019. We can see that trash and compost (a combined category in black) are the items most frequently associated with black bear sightings - nearly 80% of all sightings involved trash or compost. Data provided by Valerie Matheson, Senior Wildlife Conservation Coordinator, City of Boulder Planning and Development Services Department.
Attractant categories
Individual attractants include:
Domestic animals
Beehives
Chickens
Goats
Pets
Fish
Planted items
Fruit
Fruit trees
Flowers
Peppers
Gardens
Break ins
Sheds
Cars
Houses
Outside freezers
Garages
recommendations
Reduce attractants in your yard, report all bear sightings, and learn more about bears in Boulder.
To reduce attractants at your home, keep your trash and compost secured, keep domestic animals (including chickens and goats!) protected, and collect the fruit in your yard, especially in good fruit years. Alternatively, find fruit gatherers that will come collect the fruit for you, such as the Community Fruit Rescue. Registering your pets will also help the city identify pet-bear interactions more accurately.
Several local organizations provide excellent resources for learning more about bears, as well as specific guidance for improving human-wildlife coexistence:
The Boulder Bear Coalition hosts meetings and events and provides resources for understanding bear-human interactions. Wild Boulder engages in outreach and education campaigns, community science engagement, and collaborations with diverse stakeholders to promote wildlife protection. The Bears and People project by Melanie Hill provides “a visual case story of Boulder’s efforts to coexist with urban black bears.”
Call to report a bear sighting:
City of Boulder: 303-441-3004
Animal Protection, non-emergency: 303-441-1874
City Dispatch, non-emergency: 303-441-3333
If you want to share information about a bear sighting, you can file a report on the city of Boulder website here.
resources:
Armstrong, D.A., J.P. Fitzgerald, and C.A. Meaney. 2010. Mammals of Colorado, 2nd edition. University Press of Colorado, Boulder, CO.
