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Introduction

Coral Reefs

Life History
 

Herbivory

Study Site

Methods

Data

Discussion

Acknowledgements

Works Cited

 



     

            After performing a chi square test using a Yeats correction to normalize the data, I determined that the number of grazes per minute was non-random (p=0.026). Thus it can be said that Scarus guacamaia is indeed employing a strategy in its foraging decisions. I then determined that the strategy for the number of grazes per minute was of a clumped distribution as the variance (5.95) is greater than the mean (4.05). This can be seen in Figure 1, as the number of grazes does not follow a random or regular distribution, but rather are clumped around certain values. The main clump in the data is around the value of six grazes per minute.

Figure 1: Frequency distribution of the number of grazes per minute in Rainbow Parrotfish at John Smith’s Bay, Bermuda. This is a clumped distribution around six grazes per minute, with a mean of 4.05 and a variance of 5.95

          I also examined the length of each graze in a minute to determine if that was a factor in the foraging behavior. The mean graze length was 2.3 seconds and the variance was 1.0. Figure 2 shows the frequency distribution of each graze length and a very clear pattern is exhibited: the highest frequency of bites lasts for only one second. The frequency of bites continually decreases with increasing length, so that the extreme bite length of six seconds was only observed once compared to the 30 observations of a bite length of one second.

                                                       

 

 

 

 

 

 

 

 

Figure 2: Frequency distribution of the grazing lengths of each grazing event in Rainbow Parrotfish at John Smith’s Bay, Bermuda. The mean graze length was 2.3 seconds and the variance was 1.0.

       Thus it can be said that Scarus guacamaia does employ a foraging strategy. This pattern is one in which the number of grazes per minute is clumped and non random, with a tendency towards a high frequency of shorter bites. This can be discerned by combining the information from Figures 1 and 2. In Figure 1, the distribution is clumped around the number of bites value of 6, and in Figure 2 the bite length frequency is highest at one second. Thus, the optimal foraging strategy is one in which the number of bites is around 6, and the length of each bite is small at one or two seconds each. The fish take shorter bites but at a higher frequency, as opposed to a strategy of long bites at a low frequency.