While I was reading through the March 2013 issue of the newspaper Animal People I saw a review of a book called Experiencing Animals Minds. A sentence in the review written by Debra White caught my eye: "Mount Royal University psychology professor Alain Morin in a chapter entitled 'What Are Animal Conscious Of?' asserts that 'Wild animals have never been observed worrying and do not seem to experience sleeping difficulties as a result.'” In the actual essay Professor Morin begins this sentence with the caveat, "To the best of my knowledge wild animals ..." (page 249)
I was astounded to read this claim and in the book review it is correctly noted, "This contradicts at least 50 years worth of ethological observations, including some very famous findings by primatologists Jane Goodall, studying wild chimpanzees, and Robert Sapolsky, studying wild baboons. Morin acknowledges, however, that laboratory animals show evidence of anxiety 'when asked to perform extremely difficult discriminatory tasks.'”
Do animals worry and lose sleep when they're troubled? Of course they do. By any standard definition of the word "worry" it's clear we're not the only occupants of the worry arena. There's plenty of research that shows clearly that nonhuman animals (animals) worry about various events that are happening in their lives and that they lose sleep when they are uneasy, anxious, distressed, troubled, or on edge. People who live with dogs, cats, and other animals who suffer from separation anxiety or a fear of loud noises including thunder (and lightning), for example, know this, as do researchers who study animals in a wide variety of conditions in captivity and in the field. I've shared my home with a number of dogs who paced around nervously or hid under the bed or wrapped themselves in the sheets, and lost sleep when there were severe thunderstorms in the area, and I know many others who have also lived with dogs who did the same. Often, after a night of raucous weather, the dogs would walk around obviously groggy from a lack of sleep.
Patterns of antipredator vigilance show animals worry about what's happening around them
Two other examples suffice to show that animals worry about what's happening around them. Researchers who study antipredator vigilance or sentinel behavior have observed individuals of many different species changing their behavior when there are predators in the area. These alterations in behavior, that are often a function of group size, include changes in feeding and scanning patterns, and individuals have been described as being "nervous" or "worrying" about possible danger. Across many species there is a more or less direct and positive relationship between group size (up until around 6-8 individuals) and the amount of time individuals feed or scan for potential predators. Furthermore, individuals in a group often show patterns of coordination so that there are "enough eyes" looking around for trouble. The more eyes the better. It's also known that when there is more cover protecting them individuals are less vigilant than when they are more exposed.
In a long-term study my students and I conducted about antipredator vigilance in Western Evening grosbeaks, we discovered that along with group size, the geometry of a group also influenced patterns of feeding and scanning (the text of the essay can be seen here).
Birds in a linear array who had difficulty seeing one another, when compared with individuals organized in a circle who could easily see one another: were more vigilant, changed their head and body positions more often, reacted to changes in group size more slowly, showed less coordination in head movements, and showed more variability in all measures. The birds who couldn't see all of the other birds in the group were more fidgety and nervous and there seems no reason not to conclude that they worried more about what was happening around them than birds who could see all group members and whether they were feeding or scanning.
In a number of species, mothers with young animals also show differences in behavior when compared to females without young in that when there are youngsters around the females are more vigilant and rest less than other females.
While I know I am glossing some of the nitty-gritty details that have been discovered in studies of antipredator vigilance, the data clearly show that individuals worry about what is happening around them and while it's not clear if they lose sleep because of impending danger, they surely lose downtime and rest.
Status uncertainty can cause anxiety
Another situation during which animals are nervous and worry about what is happening or might happen in the future is when social relationships are unclear. Ethologists often call this situation "status uncertainty." While this topic hasn't been studied in as much depth as antipredator vigilance as far as I can determine, I've heard many researchers note that individuals who are closest in social rank are more nervous when they interact with one another or are close to one another than those who are more distant in rank. For example, the top ranking and lowest ranking members of a group seem to be more at ease when they interact than the fourth and fifth ranking animals. I've seen these patterns of behavior in captive and wild young and adult coyotes, namely, the closest ranked individuals actively avoiding and constantly monitoring one another (details about the formation of dominance relationships in captive coyotes litters can be seen here). I remember seeing some wild coyote pups lying awake and carefully watching specific littermates who were similar in rank, while others slept. It seems logical and parsimonious to conclude they are more worried about one another than they are about more distantly ranked coyotes who they know they can dominate or they know can dominate them. And, these patterns of behavior can have more significant consequences in terms of individual dispersal and survival.
We also know that captive and wild animals suffer from post-traumatic stress disorder (PTSD) and these individuals can be said to be worried and anxious about the situations in which they are living. It's not only captive animals who suffer from emotional and physical disorders because they are worried.
Other animals have to get over the worry and move on
Just as I was finishing this essay I came across a study of monkeys in Ecuador that showed, "Reacting to potential predators takes a toll on animals. For example, the prey animal might cut a meal short or become stressed." And, "the monkeys’ ability to distinguish dangerous from more benign people 'may allow them to conserve both time and energy when encountering humans which pose no threat.'”
It's clear that nonhuman animals can be worrywarts and stress out and be anxious about many different things. We are not alone in worrying about events in our lives although we may be unique in having the luxury of obsessively perseverating on what's causing us stress. In the wild at least, animals have to get on with what they have to do to survive. Excessive worrying and a lack of rest and sleep can be costly.