1. Samantha Lough
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Introduction
One of the main drives of a prey animal is to ensure that they avoid and escape predators.
Being captured by a predator reduces the animal’s chance at reproduction, thus lowering their
overall reproductive fitness. When approached by an advancing predator, prey animals have two
choices, to remain and continue their current activity or to flee from the predator, however both
exhibit costs. Fleeing too soon causes the animal to cease its current activity which could result
in loss of foraging time or mating opportunities, however remaining too long can increase the
risk of attack or capture by the predator. Ydenberg & Dill (1986) identified this and created an
economic optimality model that relates the costs of remaining to the costs of fleeing as a predator
increases its advance. According to this optimality model, animals should defer flight until the
costs of remaining are greater than the costs of fleeing. Flight initiation distance (FID) is the
distance between the prey and an approaching threat when the prey chooses to flee and is
commonly used when studying optimal escape theory and anti-predator behavior.
A variety of factors can influence FID, namely how prey perceive the risk of the
oncoming predator, although various prey and environmental factors can alter FID as well
(Stankowich & Blumstein 2005). These can be expanded to include the predator’s behavior, the
direction as well as speed of their approach (Stankowich & Coss 2005), their size (Stankowich &
Blumstein 2005), in addition to the number of predators that are approaching and their
orientation (Geist et al. 2005). They can also include the prey’s group size or experience with
that particular predator (Stankowich & Blumstein 2005), or within the environment, the distance
to refuge (Kramer & Bonenfant 1996).
An extensive amount of literature exists on FID primarily because various studies have
examined a number of these factors’ effects on a wide range of species. Two species of birds,
Platycerus elegans and Strepera graculina had longer flight distances when approached by two
predators compared to one predator, although the orientation of the predators had no effect on
their FID (Geist et al. 2005). Even urbanized mammals that are expected to be habituated to
humans, such as the eastern gray squirrel, Sciurus carolinensis, fled at greater distances when
approached by a predator that was directly focusing on them during the approach (Bateman &
Fleming 2014).
Flight initiation distances are frequently used as measurements to create buffer zones for
various species so they will not be disturbed by humans. These zones help reduce animal stress

2. Samantha Lough
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due to human-induced disturbances. Harbor seals, Phoca vitulina, fled at shorter distances from
advancing pedestrians or boats during their breeding season compared to other times during the
year (Andersen et al. 2012). It was initially believed to be the result of habituation, but currently
thought that it may be due to a tradeoff between fleeing and nursing. It has been suggested that
particularly in reserves, restrictions should be addressed intermittently in order to assure that the
buffer zones are maintained accordingly based on the patterns of these human disturbances.
Little to no literature could be found on FID within the Procyonidae family and zero
studies were found measuring the effect of predator number on various species. In this particular
study we conducted human approaches towards the white-nosed coati (Nasua narica) to
determine how perceived risk influenced alert distance (AD) and FID. Humans are often used in
these types of approaches because observers are readily available. Based on knowledge gathered
from other studies, it was predicted that when AD and FID were measured in response to a
varying number of approaching predators, N. narica will flee at greater distances when
approached by three predators compared to a single predator. Three predators were chosen in
comparison to a single predator because various predators tend to hunt in groups rather than
alone. A greater number of predators is expected to be viewed as a greater risk by the coatis and
thus result in longer FID.
Materials and Methods
All approaches were conducted at the Palo Verde Biological Station located in the
Guanacaste Province in northwestern Costa Rica. The study was performed at various times
throughout the day, from March 26 through March 30. The station is located within the Palo
Verde National Park which is home to a seasonally dry, deciduous forest. Approaches were
executed in the mango grove as well as near base camp. The approaches were performed on the
white-nosed coati, Nasua narica. N. narica is distributed throughout Costa Rica and abundant
within Palo Verde. All of the approaches were performed on solitary coatis, however there was
no way to mark or identify individual coatis based on size or coloration. Due to their abundance
there is confidence that it is unlikely that the same individual was approached multiple times.
Approaches were never performed back to back on the same individual. Almost all of the
approaches were done on individuals that were actively foraging, however trials were done on

3. Samantha Lough
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individuals that were traveling or resting. If the individuals were traveling, the observers waited
until the individuals’ ceased movement before beginning the approach.
A total of twenty trials were completed (n=20), with ten trials using a single predator
approaching and the other ten trials using three predators approaching. In order to measure start
distance (SD), alert distance (AD) and flight initiation distance (FID) an observer identified a
solitary N. narica. Upon locating an individual the observer positioned themselves within a
direct line of approach, dropped a weighted flag on the ground, and began walking towards the
individual at a constant pace, roughly 1.0 m/s. Once the observer noticed the coati become alert
to the observer’s presence, a second weighted flag was dropped. Alert behavior was noted as the
coati holding its head up with its eyes pointed in the direction of the observer. The observer
continued approaching the coati, and a third weighted flag was dropped when the coati decided
to flee. A fourth and final flag was placed at the location from where the coati fled from. The
approaches varied in number of observers approaching, one and three. The same procedure
mentioned above was performed with three approaching observers walking side by side towards
the focal individual. SD, AD, and FID were recorded for each trial.
In order to obtain SD, AD, and FID a 30 meter transect tape was used to measure the
distance between the weighted flags. The distances were recorded to the nearest 0.01 meter. SD
was recorded as the distance between the first flag, where the observer began approaching, and
the fourth flag, where the coati fled from. AD was measured as the distance between the second
flag, where the observer was when the coati became alert, and the fourth flag, where the coati
fled from. FID was measured as the distance between the third flag, where the observer was
when the coati fled, and the fourth flag, where the coati fled from. Minitab was used for all
statistical analyses. An analysis of covariance (ANCOVA) was performed, comparing the
number of people approaching, SD, AD, and FID. A Pearson’s correlation was also used to
determine the relationship between SD, AD, and FID.

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Results
The coatis fled the approaching observer in every trial (n=20). The relationships between
start distance (SD), alert distance (AD), and flight initiation distance (FID) were all compared to
one another (Figure 1). SD and AD were strongly and positively correlated with each other
(Pearson’s r=0.873, p=0.000, n=20; Figure 1a). AD and FID were also strongly and positively
correlated to one another (Pearson’s r=0.837, p=0.000, n=20; Figure 1b) as were AD and FID
(Pearson’s r=0.842, p=0.000, n=20; Figure 1c). Essentially, the further a predator started its
approach, the coati become alert sooner as well as fled sooner. Similarly, coatis tended to flee at
greater distances when they were alerted to the predator’s presence at greater distances.
(c)
(b)(a)
Figure 1. Scatterplots showing the relationships
between flight initiation distance (FID), start distance
(SD), and alert distance (AD) of Nasua narica in
response to approaching humans. The solid dots
represent the data points and the solid black lines
represent the best-fitted line that explained the overall
relationship between the variables. In (a), SD and AD
showa strong,positive correlation (r=0.873, p=0.000),
in (b) AD and FID exhibit a strong,positive correlation
(r=0.837, p=0.000) and in (c) SD and FID also show a
strong and positive correlation (r=0.842, p=0.000).
0
2
4
6
8
10
12
14
16
AlertDistance(m)
SinglePredator Three Predators
Figure 2. Comparison of alert distances for N. narica between one predatorand
three predators.The average alert distance for one predator, 13.089 meters, was
slightly larger than the average alert distance for three predators, 11.59 meters.
The alert distances based on a total of 10 trials for each predatorgroup did not
prove to be significantly different (F1,19=3.43, p=0.081).

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An analysis of covariance, ANCOVA, was performed on the alert distance and flight
initiation data. The number of approaching predators had no effect on alert distance (F1,19=3.43,
R2=0.778, p=0.081; Figure 2). However, start distance was determined to be a significant
covariate (F1,19=67.64, R2=0.674, p=0.000). Similarly the number of approaching predators had
no effect on flight initiation distance (F1,19=0.50, p=0.490; Figure 3). During the analysis, alert
distance was determined to be a significant covariate (F1,19=41.43, p=0.000).
Discussion
No support was discovered for the current hypothesis. Neither alert distance nor flight
initiation distance was significantly affected by the presence of one predator versus three
predators. Although, the data did support Ydenberg & Dill (1986), in that prey animals do not
necessarily always flee they moment they detect a predator, instead they weigh the costs of
remaining versus those of fleeing. However, it was determined that SD, AD, and FID were
strongly and positively correlated with each other. When a predator began approaching a greater
distance, the coatis became alert and fled at greater distances. Likewise, when the predator
became alert at a greater distance, they had longer FIDs.
The coatis found in Palo Verde are habituated to human presence, seeing as both
consistently appear in most areas of the station. It is possible that the coatis are accustomed to the
presence of humans in the station, whether they are solitary or in small groups. In this respect, it
0
1
2
3
4
5
6
7
8
9
FlightInitiationDistance(m)
SinglePredator Three Predators
Figure 3. Comparison of flight initiation distances (FID) for N. narica between
one predatorand three predators.The average FID for one predator, 8.492 meters,
was slightly larger than the average alert distance for three predators, 8.487
meters. The FIDs based on a total of 10 trials for each predatorgroup did not
prove to be significantly different between the two (F1,19=0.50, p=0.490).

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would not matter if a single individual was present or three individuals. In addition to the
habituation to humans, past experience with humans may play a role in affecting FID. Humans
are commonly used to play the role of predator in estimations of FIDs in numerous studies.
Nevertheless, if coatis deem that humans are non-threatening or at the very least, less threatening
than their natural predators, i.e, jaguars (Panthera onca), this may indicate why a significant
difference is not seen. In future studies, it would be beneficial to substitute a human predator for
that of a simulated known predator, such as P. onca, and run a similar analysis.
P. onca are known to hunt alone around dawn and dusk. The number of advancing
predators may not significantly affect FID because the coatis are not familiar with a predator that
hunts in groups, so more individuals may not be perceived as a greater threat than a single
individual. Coatis may not take the number of predators into account at all when perceiving risk,
other factors may take a higher priority. Eumeces laticeps, the broad-headed skink, fled at further
distances when approached directly and at a rapid pace compared to when approached indirectly
and at a slower pace (Cooper 1997). It is possible that the speed of the predator’s approach or
their direction of approach may rank as a higher threat when assessing risk for N. narica.
When approached at greater SDs, N. narica exhibited greater FIDs. This strongly and
positively correlated relationship between SD and FID is seen in other taxa as well. Sixty-four
out of sixty-eight varying bird species flushed at greater FID when approached at greater SD
(Blumstein 2003). Once becoming aware of a predator directly approaching from a greater
distance, N. narica may act similarly. After monitoring the predator they decide to flee while
their cost of fleeing remains low. The relationship between AD and FID was likewise correlated,
indicating a comparable explanation. Although the coatis did not flee immediately after detecting
the observer’s approach, greater AD resulted in greater FID. However, there is a possibility that
N. narica was previously alert to the observer’s presence, and the observer did not have
knowledge of this. It was assumed that the coatis were not alert to the observer’s presence until
they displayed what was defined as alert behavior in the form of a raised head and eyes focused
on the observer.
Time of day may have an interesting effect on AD and FID. In this study, all approaches
were conducted at various times throughout the day, whenever N. narica was spotted and could
be approached. However if the same analysis was performed on data that included time of day as
a factor, it may produce different results. Aforementioned, the coati’s natural predator, the jaguar

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(Panthera onca) hunts alone around dawn and dusk. Therefore it is possible that N. narica may
show increased vigilance and thus have greater AD and thus FID around the early morning and
early evenings because they are aware that predators hunt around this time. During the day since
their predators tend to be sleeping, they alter their vigilance patterns and thus their FID.
Ultimately, measuring FID provides humans with a useful tool in determining the
distances that this species will tolerate. With this information, wildlife managers can create
buffer zones that minimize human impact on the species and reduce animal distress. It was
established that FID is a species-specific trait in a study performed on eight species of shorebirds
(Blumstein et al. 2003). When developing these buffers wildlife managers need to consider the
preliminary research regarding a particular species’ FID and not necessarily site specific data.
This may hold true for many, if not all species of wildlife. Further study is necessary to verify
what specific factors influence the FIDs of N. narica. More research is required from the
Procyonidae family as a whole in order to understand if this trend due to predator number is
exclusive to N. narica or to other species within the family as well. Since there are a multitude of
factors that can be explored with their effects on FID, future studies can compare these effects on
FID as well as their interactions to create the optimal wildlife buffer catered to this particular
species and recognize what behaviors it identifies as threatening. It is equally important to
continuously maintain this research to allow the most up to date data to be included in the
wildlife buffer zones. Human disturbances are constantly changing which will provoke a new
response from various wildlife species.

8. Samantha Lough
#010228554
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