There is a reason why after listening to a focus group an unknown corporation somewhere coined the phrase “one-stop shopping” because having to visit more than a couple of stores in a day for the things you need can stress you out.  

You hear the plea from friends and relatives all the time: “I just want to go in, get what I need, and get out.” When did going to the store for cereal and coffee turn into an expedition on par with fighting your way into a jungle to retrieve the artifacts of a lost civilization? We have choices though and that’s what makes being a human so nice.

But you know who doesn’t have a choice when it comes to where they get their food? The endangered howler monkeys living in the fragmented forests of Mexico.

A new study published this week says the monkeys are stressed out because they are having to eat more leaves and less fruit because the forests where they normally obtain their food are being disturbed by humans.  The howler monkeys are now forced to spend more time foraging or as we call it “running around.”

Dr. Jacob Dunn from Cambridge's Department of Biological Anthropology visited the tropical rainforests in the state of Veracruz on the East Coast of Mexico that borders the Gulf.  He had to analyze the hormones in monkey feces to find out just how stressed they were because catching the monkeys would have been too stressful for them.

In Veracruz rainforests are being mostly cleared for cattle raising but some for logging.  A World Wildlife Fund report noted that only 20% of Veracruz’s original ecosystem remains and 64% has been altered by humans. That WWF report cited data from the 90’s so the Veracruz ecosystem could be worse off now- or better, one can always hope.

"As forests are fragmented, the howlers become cut off, isolated on forest 'islands' that increasingly lack the fruit which provide an important component of their natural diet. This has led to the monkeys expending ever more time and effort foraging for food, often increasing leaf consumption when their search is, quite literally, fruitless," said Dunn.

Leaves are a 'fallback' food when fruit is hard to find. This may not sound like a problem because leaves are found on trees and trees are what rainforests are made of, right? But some leaves are difficult for the monkeys to digest and mature leaves can be filled with toxins.

The stress hormones Dr. Dunn found in the monkey’s feces are also linked to diminished reproductive success and in turn lower survival rates.  The monkeys clearly aren’t turning to sex to relieve tension. So remember that the next time you are eating a cheeseburger: Endangered howler monkeys in Mexico aren’t eating and having sex and yet you can do both stress-free.