In most species of deer, the males have antlers. These bony, branching structures atop the animal's head begin growing in the spring and continue developing throughout the summer and fall. Starting in late winter, the antlers drop off, and the cycle starts all over again in the spring. Why deer grow antlers has long been a source of speculation. Below are three theories about the function of deer antlers.
First, some biologists have proposed that the antlers’ main function is to help the animal dissipate excess body heat. It is thought that wind blowing through the antlers cools the blood circulating in them. Antlers contain many blood vessels while they are growing, and a large volume of blood can fill them. Consequently, the antlers allow a lot of blood to be cooled by breezes, keeping the animal from overheating.
A second theory is that antlers—hard, pointy structures—evolved for defense against predators. Animals that evolved horns, a bony structure similar to antlers, clearly use them in self-defense. Just as bulls and male goats use their horns to combat would-be attackers, deer may use their antlers to defend themselves against animals that try to harm them.
According to a third theory, antlers function as a signal used by male deer to communicate their dominance to each other. Specifically, large-size antlers are believed to signal superior strength. According to this theory, males with large antlers are perceived as dominant by males with smaller antlers. Signaling through antlers is supposed to prevent unnecessary fights: according to the theory, when two males confront each other, the one with the smaller antlers will walk away rather than engage in a physical fight against a stronger rival.
Summarize the points made in the lecture, being sure to explain how they challenge the specific theories made in the reading passage.
In the lecture, the professor casts doubt on the reading passage’s idea that deer antlers serve specific functional purposes. The professor asserts that while the theories seem plausible at first, closer examination reveals they are not supported by scientific evidence or real-world observations.
Firstly, the passage claims that the main function of antlers is to help the animal dissipate excess body heat. By contrast, the professor asserts that this theory doesn't hold up because deer keep their antlers even during winter when cooling isn’t necessary. In fact, some deer even grow antlers during colder months. Additionally, deer in hotter regions, where cooling would be most useful, tend to have smaller antlers than deer in cooler areas.
Secondly, the author of the passage points out that antlers may serve as a form of self-defense against predators. However, the lecture notes that this theory is unlikely because female deer, who are the primary protectors of the young, do not have antlers. Moreover, studies show that deer defend themselves mainly by kicking, not with their antlers.
Lastly, the reading states that antlers function as a signal of dominance among males. On the contrary, the professor contends that although male deer do engage in dominance displays, the outcome of these confrontations is not determined by antler size. In many cases, males with larger antlers back down, indicating antler size does not clearly communicate strength or dominance.
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