Nyala are a species of antelopes who reside in areas of high-density woodland primarily found in parts of southeastern Africa. Aside from their massive height, a distinguishing trait of the Nyala is the spiral horns located above the eyes. This trait specifically found on males, instigates curiosity of the possible reasons for this adaptation of the sexually dimorphic antelope. The horns spiral upwards and can reach lengths of up to 80 cm and are yellow-tipped. Additionally, the horns can have one or two spirals. These horns show significance in the behavior of the male antelope when mating. The males lower their horns which exposes their white dorsal crest when approaching a herd of female Nyala. Similarly, to many animals the males Nyala experience fierce competition among their group when mating and must employ defense mechanisms to portray dominance. In a study done by Craig Packer from the University of Chicago finds traits of sexual dimorphism across genera of African antelopes. He observed that horns of male antelope are better suited for physical combat against other antelope with horns, whereas the use of the female’s horns are reserved for defense of their offspring (Packer 1983). Packer’s research gives insight into the primary usages of the horns and encourages further observations into how these behaviors can be extended into the species mating abilities and reproductive success. The horns of the Tragelaphus angasii poses an impact on the livelihood of the species and allows one to question the nature of this adaptation. I hypothesize that the length of the male Nyala’s horn may affect its ability to mate and reproduce with female species.
For this experiment I will use quantitative measurements of the horn length to determine if there is a relationship with the number of mates and general mating ability of the male Nyala. For this experiment I will be travelling to southeastern Africa where the species are primarily found. Additionally, it will be important to observe species living in a common area to ensure that habitat and other differences in environmental conditions does not affect the observations. I will measure the horn length of various individuals of the population also across many herds, this measurement will be the independent variable. Through observation I will determine the relative mating behaviors of the males this will include conflict or competition with other males, tendency to approach females, and number of sexual partners. These behaviors will be the dependent variables. I will attempt to determine if there is a pattern between these mating behaviors and horn length over a time period of 6 months-1 year. This time period will also allow significant time for the horns to grow and observe of there are changes in behavior occurring alongside the change in horn length.
My hypothesis is the length of the male antelope’s horns will affect it’s mating behavior and rate of successful sexual interactions. The null hypothesis is the length of the horns of the Nyala have no effect on its mating behavior and rate of successful sexual interactions. The first prediction of the experiment states: f the chances of mating and in turn the number of sexual interactions of the individual increases with greater horn length the null hypothesis is rejected. The second result of the experiment states: if the length of the horns of the Nyala will neither benefit nor hinder the mating abilities of the individual then we fail to reject the null hypothesis.
The ability of the Nyala to reproduce plays a significant role in the livelihood of the species and ultimately encompasses the fitness of the individual in the environment. This leads us to wonder about such traits that will affect the fitness of the species and of which includes the horn length. Given there be no correlation between the horn length and mating it suggests other factors influence the mating behavior of the animal and further investigation can be done to determine what these traits may be. We may also determine other possibilities for a variance in horn length among the population. Additionally, if the null hypothesis is rejected it gives further incentive to determine how the horns developed as an adaptation. A possible reason for this trait is studied by Torsten Wonski who states that an oily secretion created by the horns is used in marking male and herd territories. These studies encourage us to continue to investigate how the horns of the Tragelaphus angasii are an adaptation.
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