Availability of fishes for feeding purposes | Homework Help

1. Head Jerk Rate

Initially, under normal circumstances, the head jerk rate of fishes while looking for worms was very low. They jerked their heads only about 10 times per minute. As the time passed and they sensed no danger the rate increased to 20 times. This is clear evidence that during the first minute of the initiation of feeding the fishes were trying to adjust their vigilance under the prevailing conditions. As Osprey appeared there was a suIDen surge and the fishes started increasing the rate of head jerks. They only saw 2-3 Ospreys passing by and this resulted in losing their focus from feeding to protecting themselves.

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It was also observed that the rate of head jerk and intensity of vigilance is higher during the daytime as compared to the night. It seems that the birds are not able to locate fishes as easily in the nighttime as they can during the daylight. (- how were head jerk rate measured? (How done?)

Need background literature on how ospreys were observed)

2. Duration of Head Jerk

At the start of the feeding process the mean duration of the scan done by the fishes was about 4.5 s but as the time progressed it reduced to only about 2 s. This relatively large difference was from the first minute to the second minute in to the feeding process. A steep rise was seen when the fishes noticed Ospreys wandering around. It rose to as high as 8.8 s and continued to remain same for a very long duration. (include what measurement, how long observation period was, etc.)

3. Jump Frequency in and out of water
For the purpose of catching worms that were being supplied the fishes jumped in and out of the water at a frequency of 12 times per minutes. After the assurance that there is no predator in the sight this frequency increased to about 22 times in a minute. As an Osprey caught one of the fishes, other fishes lost control and they abruptly took a pause for about 2 minutes before resuming their feeding activity. This shows that due to vigilance and fear there is a loss of feeding time and the energy is also spent on the same rather than on feeding.

Tabular Representation
Results (10 marks) 5/10
-Presentation of the results should be well organized. Tables and graphs should illustrate results, and appropriate statistical tests and interpretations should be used.
– how were the head jerk rate measured? (Operational definition included
– how did you observe the fish observing the osprey? Need background literature on this.
need tests of statistical significance
– Need to include what measurement, how long observation period etc. methods?
– “Mean duration” is a new variable therefore must include:
o Give a night time and day time they were observed. How were fish seen at night? Do ospreyfish at night ? (support w. literature)
– Worms were used? Again how were fish obserbed?

Through the experiment conducted it was analyzed that the presence of a predator has a real time effect on the prey. The prey becomes more vigilant and this leads to a negative effect on the other activites like feeding and movement (Breed, 2001). As predicted, the vigilance is a behavioral factor that affects the activities of the prey in an adverse manner.

The background study conducted suggests that there is a slight fluctuation in the jerks of the head and the duration for which they last. There is also seen an effect of the presence and absence of a predator in the vicinity. These effects have clearly been seen in the videos recorded and the experiment conducted. The experiment clearly indicates that the fear of presence of the predator in and around or a look at the predator causes the behavior of the prey to change by and large (KELLY B. ALTENDORF, 2001).

The problems that occurred during the conduction of this experiment were the variable temperature conditions, which affected the frequency of Ospreys and also the availability of fishes for feeding purposes. Another trouble was the adjustments of the video camera to be made and the videos that got blurred due to unforeseen circumstances. There were also some disturbances from the adjacent road that scared away the predator under study. As a result the other research questions that can be framed include the scenario under perfect conditions i.e. without any disturbances from either the traffic and people or the unpredictable weather.
Discussion (15 marks)8 /15
A good discussion should meet some or all of the following criteria:
Elaborate how to improve (other research questions?, etc.)
• Interprets results with regard to the predictions.
• Relates results to the background literature.
•Suggests problems with the design and potential solutions.


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