May 7, 2002

BI 441

Abstract

The shyness-boldness continuum is an essential element of behavioral variation that is researched in both humans and other species. The differences in shyness and boldness of individuals may be due to the tendency to take risks. I measured the context specificity of shyness and boldness in Guppies, Poecilia reticulata, by exposing the fish to a potentially threatening stimulus (a red-tipped metrestick extended towards the individual) and a non-threatening stimulus (a novel food source). The results showed that guppies responded more boldly to a novel food source over a potentially threatening object. My results suggest that individual differences in shyness and boldness in guppies are context-dependent.

Keywords: Guppies-Poecilia reticulata, minnow, red-metrestick, shyness, boldness, exploring, predator.

Introduction

Is there a difference between shyness and boldness in a natural population of guppies (Poecilia reticulata) in response to a potentially threatening stimulus (a red-tipped metrestick) and a non-threatening stimulus (a novel minnow (Phoxinus phoxinus) lure)? The terms ‘shy’ and ‘bold’ refer to personality traits and the willingness of an individual to take risks (Coleman & Wilson, 1998). Researchers can measure shyness and boldness in guppies by noting their response to a novel object. Child psychologists have used this technique to measure shyness and boldness in children (Wilson et al. 1994). This same criterion was exercised to measure the behavior in juvenile pumpkinseed sunfish (Lepomis gibbosus) by conducting novel object tests in experimental ponds. Researchers focused on: (1) if a shy-bold continuum exists, (2) how it correlates with age, sex, and size, (3) the ecological consequences and (4) if individual differences are similar in how they appear (Wilson et al. 1993). The main purpose of this experiment was to examine context-specific shyness and boldness in guppies. To examine context specificity, I repeatedly measured behavior in two relevant contexts: reaction to a potentially threatening object and reaction to a novel food source. I hypothesized that guppies will display a bold behavior towards a novel food source as compared to threatening object.

The shy-bold continuum has not been identified in many species. Research has been completed on pumpkinseed sunfish and on marmots (Marmota flaviventris). The researchers use terms such as ‘approach’, ‘avoidance’, and ‘sociability’ that correlated with this type of behavior. These same researchers suggested that the shy-bold continuum is just one important aspect of behavioral variation in animals (Wilson et al. 1994). Fish that encounter different levels of predation have been shown to differ in their behavioral response to predators in ways that could be interpreted as shy and bold. The inclination to take risks might explain these individual differences in shyness and boldness (Coleman and Wilson,1998). Predator inspection can also be viewed as an exploring type of behavior. For example, when minnows detect a persecuting pike (Esox lucius), one of their first responses is to approach the predator in an inspection type of behavior. They have a tendency to stop foraging, form a shoal, and display a ‘predator inspection behavior’, which is defined as approaching the pike within 20 cm (Magurran, 1986). The concept of ‘inspection behavior’ is an interesting correlation to the behavior of boldness in the guppy.

Methods

The study was conducted in the home of the researcher.

Materials

12 guppies

2 fish tanks

1 small fish bowl

A 90 cm red metrestick

A 6 cm fake minnow

A small fish net

A clock with a second hand

Tanks and models

The experiment was carried out in two 10 gallon identical tanks, each of which measured 51 cm x 28 cm x 24 cm. The tank floors were covered with aquarium gravel. A small artificial weed bed was placed in one corner of each tank. The water in each tank was treated with Start Right prior to carrying out the experiment. A small filter was attached to the back corner of each tank. A small bowl was used to place the fish once the individual trials of the experiment were completed. Once all twelve were studied they were placed back into the 10- gallon tank from which they originally started. Experimental protocol I used a context –specific measure of shyness and boldness by the following categories of response for analysis:

M (metrestick)-BOLD-approached or allowed the metrestick to be extended within 5 cm.

M-SHY-retreated immediately upon introduction of the stimulus.

L (lure)-BOLD-approached the lure within 5 cm.

L-SHY –retreated immediately upon introduction of the stimulus or approached but did not come within 5 cm of the lure.

The experiment was carried out over 14 days 7:00 PM and 8:00PM. My assistant began by placing two guppies in the extra tank. We gave them approximately 3 minutes to adapt to the new tank. To create a potentially threatening situation, the red-tipped metrestick was slowly extended towards an individual fish and then remained in the tank for one minute. The response of the fish varied from approaching the stick to immediately fleeing. Some fish even fled to the weed bed until the stick was removed. We noted and recorded the initial reaction of the fish whether they fled immediately or came within 5 cm of the stick. Next, we measured shyness and boldness by introducing the novel food source (fake minnow). We observed and recorded the type of behavior using the same criteria as the red-metrestick. The response of the fish also varied from immediately fleeing to approaching or exploring. The fake minnow was also allowed to remain in the tank for one minute. Once the two types of situations were tested with these 2 fish we placed them in the small bowl. We carried out the same method with the next two fish until all 12 were tested and observed. When the two weeks of testing was completed the data was recorded and analyzed.

Results

We tested the guppies a total of 168 times. It is important to note that even though 2 guppies were tested at the same time, we counted each fish as one type of behavior. The guppies were bolder towards the novel food object(lure) as compared to the threatening object (red-metrestrick). They also were more shy towards the metre stick as compared to the lure (See figure 1). The guppies responded bold to the lure a total of 107 times as compared to 45 times to the red-metre stick (See figure 2). When the T-Test was performed to compare these 2 groups the P-value was 3.58 x 10^-5. This is considered statistically significant. The guppies responded shy to the lure 61 times as compared to 129 times to the red-metre stick (See figure 3). When the T-Test was performed to compare these two groups the P-value was 3.24 x 10^-7. This is also considered to be statistically significant.

Figure 1. Displays the number of times the way the guppies responded towards the novel object.

Figure 2. Comparison of boldness between the lure and metre stick.

Figure 3. Comparison of shyness between the lure and metre stick.

Discussion

My results suggest that individual differences in shyness and boldness in guppies are context-dependent. There was a difference for both responses to a threatening object and the response to a novel food source. Fish that boldly approached the metrestick did not necessarily boldly approach the novel food source. I did not specifically test this concept of behavior. Perhaps if the fish were somehow tagged this type of measurement could be accomplished. The number of time the guppy spent exploring the minnow was much higher than the red-metrestick. The results of the data support my hypothesis that guppies will respond more boldly to the novel food source as compared to the threatening object. Fish that were quick to explore a novel food object were also more shy towards a novel threatening object.

Research studies can help discover shyness and boldness behaviors in a variety of species of animals. Researchers in animal behavior should attempt to measure shyness and boldness across a variety of domains. Guppies that are hungry can forage in a way that increases the chances to be exposed to predators. Small fish species that are vulnerable to predators differ in their innate patterns of boldness (Wilson et. al. 1994). Instead of guppies immediately escaping upon encountering a potential predator, they may actually approach and ‘inspect’ it. Perhaps these small species of fish can make the distinction only after a close-range inspection of their predator and their assessment of risk is directly correlated to this behavior. Boldness to take risks can control the interactions with predators, conspecifics, prey and their environment (Coleman and Wilson, 1998).

According to research, fish take greater risks to obtain food when they are hungry rather than when they are well fed (Wilson et. al. 1993). Our experiment was carried out on the evening hours. The usual feeding time was approximately late afternoon. The correlation between the time the guppies were fed and the time the testing was performed is a factor to be considered when analyzing the results of the data.

Studies have shown that individual differences along the shy-bold continuum can possible be influenced by a large number of factors (Wilson et al,1993). Guppies may adapt to act more boldly or seek risks in some situations and avoid it in others. The fish may have displayed a different type of response if they were tested in their own natural habitat or even if the novel object was introduced before the threatening object. The guppies may react to these objects for other reasons than shyness and boldness. Their decision could be to avoid predation, sensitivity to risk or other various needs. For example, were these guppies ‘foraging’ or ‘inspecting’ or ‘fleeing’ from a predator? The evidence in my data does suggest a very small significant role in the study of shyness and boldness in guppies. If this experiment were to be performed again I would test the fish individually to observe the behavior. I could then analyze my data by comparing each fish to see if they reacted the same towards the different novel objects. My study suggests that the shy-bold continuum is an important aspect of behavioral variation in animals.

Acknowledgements

I would like to than Morgan Strick for her assistance with this research. I would like to extend my gratitude to Ms. Judy Schelkun for allowing me to borrow her fish tank.

Literature Cited

Coleman, Kristine, and David Sloan Wilson. 1998. Shyness and boldness in pumpkinseed sunfish: individual differences are context-specific. Animal Behavior, 56: 927-936.

Magurran, A.E. 1986. Predator inspection behaviour in minnow shoals: differences between populations and individuals. Behavioral Ecology and Sociobiology, 19, 267-273.

Wilson, D. S., Coleman, K., Clark, A. B. & Biederman, L. 1993. The shy-bold continuum in pumpkinseed sunfish (Lepomis gibbosus): an ecological study of a psychological trait. Journal of Comparative Psychology, 107, 250-260.

Wilson, D. S., Clark, A.B., Coleman, K. & Dearstyne, T. 1994. Shyness and boldness in humans and other animals. Trends in Ecology and Evolution, 9, 442-446.