Discussion
The current study aimed to address whether countershaded prey are better protected from visually hunting predators compared to non-countershaded prey. The study also aimed to resolve these major differences in results from these previous research (Edmunds & Dewhist, 1994; Speed et al., 2005) on the effectiveness of countershading. The results from the current study partly addressed the aims indicating that countershaded prey had a better survival rate than non-background matched prey. The hypothesis that countershaded prey would be eaten less frequently than dark, light, or reverse countershaded prey was not supported. However, aspects of the functions of countershading was supported via the results and are discussed separately …show more content…
This supports the finds of previous research (Edmunds & Dewhist, 1994; Speed et al., 2005; Rowland 2007) that also showed a significant difference in predation amounts between these two prey groups. This result indicates that the two functions of countershading are responsible for the increase in crypsis and therefore the decrease in predation. Firstly, as self-shadow concealment is present in the countershaded prey and not the uniformly white prey lower detection occurred. This is due to the perception of three-dimensional bodies appearing less solid through concealing shadows (Thayer, 1896). However, self shadow concealment is largely dependent on the direction, and to a lessor degree, the intensity of the illumination (Hailman, 1977). For example, the diurnal change in sunlight angle falling upon prey may result in ineffective self shadow concealment (Hailman 1977; Kiltie 1988; Ruxton et al 2004a). Secondly, as countershaded prey matched their background when viewed from above, less contrast between the prey and background would be present. This reduction of contrast between the two indicates an increase in crypsis and a lower predation …show more content…
This supports the findings of previous research (Edmunds & Dewhist, 1994; Speed et al., 2005; Rowland et al., 2007). However, it should be noted that the orientation of prey with reverse countershading may effect the predation rate. It should also be noted, that various animals with this reverse countershading have been observed in up-side down orientations (Tinbergen, 1957; Chapman et al., 1994). For example, in prey such as caterpillars that are frequently positioned upside down (ventral surface pressed against leaf’s ventral surface) reduced predation rates have been demonstrated (Rowland et al., 2009). However, in the context of the current study’s experiment design, where the reverse countershaded prey was not oriented up-side down, the expected result of a higher predation rate than countershaded was indicated. This result, can be explain by both of the functions of countershading. Firstly, as countershaded prey matched the background when viewed (by bird species) from above, there would have less contrast, and therefore an increase in crypsis. Secondly, self-shadow concealment would only be present in countershaded prey items, and therefore a reduction in consumption of these could be due to the associated increase in crypsis. However, the function that is having the largest effect of increased crypsis in this comparison can not be clearly
The current study aimed to address whether countershaded prey are better protected from visually hunting predators compared to non-countershaded prey. The study also aimed to resolve these major differences in results from these previous research (Edmunds & Dewhist, 1994; Speed et al., 2005) on the effectiveness of countershading. The results from the current study partly addressed the aims indicating that countershaded prey had a better survival rate than non-background matched prey. The hypothesis that countershaded prey would be eaten less frequently than dark, light, or reverse countershaded prey was not supported. However, aspects of the functions of countershading was supported via the results and are discussed separately …show more content…
This supports the finds of previous research (Edmunds & Dewhist, 1994; Speed et al., 2005; Rowland 2007) that also showed a significant difference in predation amounts between these two prey groups. This result indicates that the two functions of countershading are responsible for the increase in crypsis and therefore the decrease in predation. Firstly, as self-shadow concealment is present in the countershaded prey and not the uniformly white prey lower detection occurred. This is due to the perception of three-dimensional bodies appearing less solid through concealing shadows (Thayer, 1896). However, self shadow concealment is largely dependent on the direction, and to a lessor degree, the intensity of the illumination (Hailman, 1977). For example, the diurnal change in sunlight angle falling upon prey may result in ineffective self shadow concealment (Hailman 1977; Kiltie 1988; Ruxton et al 2004a). Secondly, as countershaded prey matched their background when viewed from above, less contrast between the prey and background would be present. This reduction of contrast between the two indicates an increase in crypsis and a lower predation …show more content…
This supports the findings of previous research (Edmunds & Dewhist, 1994; Speed et al., 2005; Rowland et al., 2007). However, it should be noted that the orientation of prey with reverse countershading may effect the predation rate. It should also be noted, that various animals with this reverse countershading have been observed in up-side down orientations (Tinbergen, 1957; Chapman et al., 1994). For example, in prey such as caterpillars that are frequently positioned upside down (ventral surface pressed against leaf’s ventral surface) reduced predation rates have been demonstrated (Rowland et al., 2009). However, in the context of the current study’s experiment design, where the reverse countershaded prey was not oriented up-side down, the expected result of a higher predation rate than countershaded was indicated. This result, can be explain by both of the functions of countershading. Firstly, as countershaded prey matched the background when viewed (by bird species) from above, there would have less contrast, and therefore an increase in crypsis. Secondly, self-shadow concealment would only be present in countershaded prey items, and therefore a reduction in consumption of these could be due to the associated increase in crypsis. However, the function that is having the largest effect of increased crypsis in this comparison can not be clearly