1. Results
From the audio recordings, we found the root mean squared (RMS)
amplitude, a relative measure of loudness not dependent on the
human hearing range, of each audio file using Sox
(sox.sourceforge.net). The mean RMS amplitude of ToT nights (M
= 0.0239, SE 0.001) was significantly greater, and thus louder,
than baseline nights (M = 0.0154, SE 0.003), t(4) = -2.74, p =
0.026.
At night, the monkeys had access to both their exhibit yard and a
night-house. If the animals were inside, they were out of view of
the researchers. When controlling for visibility, there was no
significant difference between the percentages of scans the
monkeys were active when comparing baseline and ToT
(Wilcoxon signed-rank test, p = 0.983). However, the monkeys
were inside during 40.8% of scans in the baseline condition and
only 0.5% of scans during ToT (Wilcoxon signed-rank test, one-
tailed p = 0.034, Figure 2). Thus, the monkeys were outside far
more often during ToT.
Given the large difference in where the monkeys spent time (inside
or outside) during ToT, we also analyzed the data without
controlling for visibility. In these analyses, we retain the data
points where the monkeys were not visible. Thus, we compared
the proportion of scans in which we know the monkeys were
active to the total number of scans, rather than only the scans in
which the animals were visible. The proportion of scans in which
the animals were active was significantly higher during ToT
observations compared to baseline (Dependent Proportions Test,
Z = 3.9, p < 0.001, Figure 2). This indicates that activity levels, or
at least outside activity levels, were much higher during the ToT
event, suggesting the event interrupted their typical resting
pattern.
Florida Institute of Technology – 2016
The effect of a nighttime zoo event on spider
monkey (Ateles geoffroyi) behavior
D. Proctor, H. Gedde, B. Baldrica, E. Burch, J. Kramer, J. Swanson and C. Vergason
Florida Institute of Technology
Introduction
The relationship between zoo visitors and animals, particularly
primates, is a complicated one and there is little consensus in the
literature on whether visitors cause stress, provide enrichment or do
not affect the animals (Hosey, 2000), although this varies by species.
For example, spider monkeys have higher urinary cortisol levels
when more visitors are present (Davis, Schaffner, & Smith, 2005).
Yet, there are also reports of other primates seeking visitor
interactions (Vrancken, Van Elsacker, & Verheyen, 1990). To gain
more information about this relationship and to ensure animal
wellness, it is important to monitor animal behavior in zoos when
adding new visitor experiences.
This is particularly true in regards to late-night zoo events, as there
has been little research on how events outside of the typical
operating hours affect animal behavior. In October, 2015, Brevard
Zoo in Melbourne, FL, USA added a new late-night (8-12 pm),
Halloween-themed visitor experience. The “Trail of Terror” (ToT;
runforyourfreakinlife.com) was a haunted house style event where
visitors walk through the woods surrounding the zoo and actors
startled them at certain locations on the trail. One such startle point
was located approximately 20 yards from the spider monkey exhibit.
To determine what effect, if any, this event had on the behavior of
these diurnal monkeys, we monitored their behavior during the event
and on baseline nights with no visitors present.
Methods
We observed the spider monkeys (n=4) at the Brevard Zoo on
Thursday through Sunday nights during the ToT event in October,
2015. Thursday and Sunday were considered baseline observations,
as ToT only ran on Friday and Saturday nights.
All the lights were turned off in the zoo, making observations
challenging. We used entry-level night-vision goggles to see the
monkeys, but they did not provide sufficient detail for reliable
individual identification (Figure 1). During the first min of each 10 min
period we observed the monkeys and coded whether they were
active (any movement or eyes visible), resting (no visible movement)
or inside (in their night building and not visible to researchers). This
totaled 202 data points for each of the four monkeys (101 data points
per monkey per condition, 808 total data points).
Additionally, we audio recorded the hour from 9:30 to 10:30 pm each
night. This allowed us to get an objective measure of the relative
degree of loudness during baseline and ToT observations.
Conclusions
• Spider monkeys changed their typical nighttime behavioral
patterns during ToT.
• They were outside much more frequently during ToT and were
likely active more as well, although this is less apparent when
controlling for visibility.
• This was likely a somewhat stressful event for the monkeys, as
they often appeared startled (rapid head movements and scanning
behavior) after actors and visitors screamed.
• This will be systematically explored in 2016 with higher-
resolution night-vision goggles.
• However, to determine whether this event negatively effected their
welfare, we should explore how they would respond to naturally
occurring loud and startling events, such as thunderstorms.
Figure 1: Photograph of the spider monkeys through the night vision
goggles. Due to the relatively poor resolution, we were unable to take
detailed behavioral data.
References
Hosey, G. R. (2000). Zoo animals and their human audiences: What is the
visitor effect? Animal Welfare, 9, 343-357.
Davis, N., Schaffner, C. M., & Smith, T. E. (2005). Evidence that zoo visitors
influence HPA activity in spider monkeys (Ateles geoffroyii rufiventris).
Applied Animal Behaviour Science, 90(2), 131-141.
Vrancken, A., Verheyen, R. F., & Elsacker, L. V. (1990). Preliminary study
on the influence of the visiting public on the spatial distribution in captive
eastern lowland gorillas (Gorilla gorilla graueri). Acta Zoologica et
Pathologica Antverpiensia (Belgium).
Figure 2: Percentage of total scans (not controlling for visibility) the
monkeys spent inside and active on baseline nights compared to ToT
nights.
*p < 0.05
0%
10%
20%
30%
40%
50%
Inside Active
PercentageofScans
Behaviors by Condition
Baseline
ToT
* *