As many of us have learned over the course of our lives, a restful night’s sleep is restorative and promotes good mental, physical, and emotional well-being. Specifically, research on humans shows that good-quality sleep is associated with improved concentration, cognitive performance, emotion regulation, and physical health. On the other hand, sleep deprivation and fragmentation are linked to depression, obesity, cardiovascular disease, diabetes, negative mood, anxiety, increased aggression, and lack of attention.

As you might guess, sleep is also a vital component of the health and well-being of non-human animals. Understanding sleep patterns–both at the level of the species and the individual–can help us gain insight into an animal’s welfare status. In fact, some researchers argue that sleep may be a crucial welfare indicator, as this behavior can serve as an index of adaptation to the environment. As you can imagine, it can be challenging to monitor sleep in non-humans. After all, depending on the species, our residents may be found sleeping in dens, trees/tree stands, burrows, hay/straw beds, etc. As a result, researchers often rely on technology, such as video cameras, biologgers (devices that capture activity levels, movements, and positional behavior), and sound recordings. 

In recent years, there have been studies on the sleeping patterns of a wide variety of taxa, including rodents, farm animals, shelter dogs, elephants, and primates. Believe it or not, male lions snooze for approximately 20 hours per day! In studies of various lemur species, researchers found that lack of sleep altered social behavior and negatively impacted cognitive tasks that measured foraging efficiency and memory consolidation. In chimpanzees, a poor night’s sleep was associated with an increase in inactive and abnormal behaviors the following day. Similarly, in laboratory rats, disturbed sleep was linked to an increase in aggression, as well as a decrease in self-grooming and enrichment-directed behaviors (e.g. sniffing and chewing enrichment objects).
 
Fortunately, zoos can make modifications to the environment and husbandry routine to promote better sleep quality. For example, there is evidence that chimpanzee sleep patterns can be influenced by temperature, humidity, and disruptions (e.g. vocalizations, displays) from neighboring groups. To improve the sleep quality of professionally managed chimpanzees, animal care teams can do their best to: 1) make adjustments to the ambient environment, 2) offer choices in terms of where/with whom an individual can sleep, and 3) introduce sound-proofing measures.  Zoos may also be able to learn from studies on domestic animals. For instance, there is evidence that shelter dogs who spend more time socializing (with humans and other dogs) fall asleep more quickly and spend more time in quiet sleep than dogs who interact less. Therefore, for species and individuals that have been shown to benefit from interactions with caretakers (e.g. certain felids, primates), an increase in these encounters may be beneficial.
 
So, the next time you stroll through the zoo, keep an eye out for our residents catching those zzzzz’s!
 
 
Dr. Jessica Whitham
Animal Welfare Biologist
Published August 31, 2023