Zoological institutions often use immersive, naturalistic exhibits to create an inclusive atmosphere that is inviting for visitors while providing for the welfare of animals in their collections. In this study, we investigated physiological changes in salivary cortisol and blood pressure, as well as psychological changes among visitors before and after a walk through the River’s Edge, an immersive, naturalistic exhibit at the Saint Louis Zoo. Study participants had a significant reduction in salivary cortisol and blood pressure after walking through the exhibit. Psychological assessments of mood found that most visitors felt happier, more energized, and less tense after the visit. Additionally, participants who spent more time in River’s Edge, had visited River’s Edge prior to the study, and had seen more exhibits at the Zoo prior to entering River’s Edge experienced greater psychological and/or physiological benefits. We conclude that immersive, naturalistic exhibits in zoos can elicit positive changes in physiological and psychological measures of health and well-being and argue for a greater scientific focus on the role of zoos and other green spaces in human health.

After giving informed consent, each participant completed a pre-visit questionnaire form. The included the following questions: first visit to River’s Edge (Yes or No), age, parking experience rating (scale from 1 to 10, where 1 is “poor” and 10 is “excellent”), number of exhibits seen prior to River’s Edge, and time of arrival at the Zoo. Each participant then answered the pre-UMACL, which included 24 mood adjectives, with eight corresponding adjectives to each of the three dimensions. Regarding the UMACL, participants marked how each adjective reflected his or her current mood using a four-point scale (1 = “definitely not,” 2 = “slightly not,” 3 = “slightly,” 4 = “definitely”). Within each set of eight adjectives, four represented the positive end of each dimension and four the negative end (Table 1). Responses for adjectives negatively related to each dimension were reversed, and sub scores for each dimension were obtained by summing the responses for each adjective. After completing all forms, we then collected physiological data. Prior to saliva collection, each participant rinsed their mouth with water (supplied by the researcher) and placed a SalivaBio Oral Swab (Item # 5001.02, Salimetrics, State College, PA) under their tongue for two minutes (as specified by the manufacturer), while sitting quietly. After two minutes, the swab was inserted into a Saliva Storage Tube (Item # 5001.05, Salimetrics, State College, PA), either directly by the participant or by the researcher without direct contact. After collection, saliva samples were placed in a cooler on ice packs for no longer than two hours, and then brought to the lab for processing. Next, a trained researcher took the participant’s blood pressure using an OMRON M6 AC (HEM-7322-E) upper arm blood pressure monitor in accordance with the IRB-approved protocol. The American Heart Association recommends a five-minute rest period prior to blood pressure collection to normalize pressure. By having participants fill out forms and complete cortisol collection prior to taking their blood pressure, we ensured that participants fulfilled their five-minute rest period. Additionally, we asked participants to sit quietly without their cell phones for two minutes after cortisol collection, averaging a total of seven minutes resting time. Per manufacturer directions, blood pressure was recorded using the participant’s left arm placed flat on a table with both feet flat on the ground. Prior to the study, all researchers were given formal training by Zoo medics on using the OMRON M6 AC (HEM-7322-E). Finally, we asked participants to wear a colorful lanyard to identify themselves to the researchers at the end of the exhibit trail. Participants were also instructed not to consume any food or drinks (other than the boxed water provided) and refrain from chewing gum during their walk through the exhibit. We invited participants to enjoy their time in River’s Edge at their normal pace without any time restrictions. Once the participant finished walking through River’s Edge, they performed a similar suite of tests, including measurement of blood pressure and collection of saliva samples, and a post-visit questionnaire. This had the following questions: gender (as identified by the participant), party size, number of kids in party under 14 years old, incidence of having a staff interaction, animal that they found most engaging (if any), whether they had a close up encounter with that animal, and looked into the animal’s eyes. Each participant then answered the post-UMACL. The same version of the UMACL was used pre- and post-River’s Edge experience. A researcher timed and recorded each step in the data collection process. The total number of minutes spent in River’s Edge was calculated, total number of minutes spent in the Zoo prior to entering River’s Edge and outside air temperature during River’s Edge was recorded for each participant. Daily Zoo attendance was included as an additional variable. This study was approved by Heartland Institutional Review Board (IRB) and all principal investigators completed the Collaborative Institutional Training Initiative (CITI) IRB training. The study was deemed expedited with written consent.

Inferential statistical analyses were performed in SAS® Studio 3.7 (SAS Institute Inc., Cary, NC, USA). Prior to analysis, study participants were assigned to two blocks based on the time of day they entered River’s Edge (prior to 12:30 PM vs. after 12:30 PM), controlling for effect of time of day on the response variables measured. The effects of possibly associated factors on systolic and diastolic blood pressure, salivary cortisol concentrations, TA, EA, and HT were all evaluated using a generalized linear mixed model within the MIXED procedure. Fixed categorical factors included time (pre or post River’s Edge experience), gender (male or female), first visit to River’s Edge (yes or no), found the elephants the most engaging (yes or no), had a staff interaction (yes or no), had a close up encounter with the animal found to be most engaging (yes or no), and looked into this animal’s eyes (yes or no). Quantitative variables included air temperature, age, daily Zoo attendance, party size, number of kids in party under 14 years old, parking experience score, total number of exhibits seen prior to River’s Edge, total number of minutes spent at the Zoo prior to River’s Edge, and total number of minutes spent in River’s Edge. Individual ID and block (described above) were included as random factors, as well as the interaction terms between time, and the fixed and quantitative factors. Non-significant interaction terms between time and quantitative factors were removed to generate a single slope term for the final models.  All other variables, regardless of statistical significance, were included in the final models. Though the design of the study is repeated measures in nature, there were only two measurements made within each subject, therefore a simple variance component (VC) covariance structure was used.