Conservation Maven

Good intentions, terrible impact. Roadside feeding of black bears (Ursus americanus) in Yosemite has likely modified their foraging behavior leading to increased human-bear confilcts.Say you're a hungry black bear in Yosemite National Park. You have a whole campground of cars for the pickings. What do you go for? The luxary sedan, the SUV, a Prius?

Well, researchers with the National Park Service and the USDA were wondering that very question. So they conducted a study of black bear break-ins at Yosemite. As it turns out, in the world of black bears, the minivan is top choice.

The percentage of break-ins for SUV's (22.5%), small cars (17.1%), trucks (11.9%), vans (4.2%), sports cars (1.7%), coupes (1.7%), and station wagons (1.4%) were all on target based on their relative makeup in the park. But minivan break-ins, which clocked in at a whopping 29% of the total, were more than four times higher than predicted (7%). Meanwhile bears tended to avoid sedans - only 14% of the break-ins were sedans even though they made up 28% of the cars in the park. So what motivates black bears in choosing cars?

The researchers state:

Black bears forage selectively to balance energetic and nutritional gains with foraging costs. Selection of minivans by bears in Yosemite National Park was the likely consequence of efforts to maximize caloric gain and minimize costs by targeting vehicles with higher probabilities of payoff.

In other words, bears are smart. There's a risk to breaking into cars. Park employees patrol the campgrounds nightly. So bears quickly learn to target the types of cars that are most likely to give the biggest payoff with the least amount of difficulty.

So what makes minivans so attractive to bears? The researchers offer several possible explanations:

• It is possible that minivans are more likely to emit food odors regardless of whether they contained meaningful amounts of food available. Minivans are designed for families with children and small children in particular are notorious for spilling food and drink while riding in vehicles.

• Perhaps passengers of minivans are more prone to leave large caches of food (e.g., coolers or grocery bags) in vehicles parked overnight.

• It could be that minivans are structurally easier to break into than other vehicles. Observations indicate that bears entering minivans typically did so by popping open a rear side window and it seems that this was easier for minivans compared to other vehicle classes.

• Selection of minivans could reflect the foraging decisions of a few individuals that learned how to break into minivans. Anecdotal evidence indicates that most of the break-ins resulted from a maximum of 5 bears.

This research is particularly timely. Bear-human conflicts is not just a parks issue. As development pushes farther out into natural habitat, interactions between wildlife and humans are increasingly leading to negative consequences for both people and bears. Understanding how wildlife behaves in the face of human development helps us lessen these conflicts.

 --Reviewed by Rob Goldstein

Breck, S., Lance, N., & Seher, V. (2009). Selective Foraging for Anthropogenic Resources by Black Bears: Minivans in Yosemite National Park Journal of Mammalogy, 90 (5), 1041-1044 DOI: 10.1644/08-MAMM-A-056.1