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Posts Tagged ‘mating’


Ornaments and Weapons

July 9th, 2014 by nyn1

 

In this post, I will discuss two tactics that animals use in order to gain access to mates as well as an example in each. You can also find both articles on Wikipedia. Find the weapons article at: https://en.wikipedia.org/wiki/Weapons and the ornaments article at https://en.wikipedia.org/wiki/Ornaments.

Weapons are traits that are used by males to fight one another off for access to mates. A mate is won in battle either by a male chasing off a fellow competitor or killing it off, usually leaving the victor as the only option for the female to reproduce with[1]. However, because stronger organisms, whether mentally or physically, are usually favored in combat, this also leads to the evolution of stronger organisms in species that use combat as a way to secure mates[2]. Examples of weapons include the antlers bucks use to fight one another off when competing for females.

Ornaments are traits that are used to attract mates based on physical attractiveness. These traits may help show good genes that potential mates may find desirable[1]. Although these ornaments are usually the main strategy in order to procure a mate, they come with the large cost of making the individuals more susceptible to being tracked by predators as well[2]. The most notable form of ornaments comes in the ornate plumage that the peacock has in order to attract peahens; the brighter and bigger the feathers, the better chance of finding a mate.

An Analysis of a Media Portrayal of Goat Pheromones

July 7th, 2014 by cer7

 

Scientists have long searched for a tangible molecule that produces an effect on females called the “male effect” (Murata et. al. 2014). The male effect is a physiological process that causes the reproductive cycle of females to change in the presence of the scent of males. Researchers at the University of Tokyo were looking for a primer pheromone that would cause this change in the ovulation cycle of female goats, and they may have finally found one (Murata et. al. 2014). The researchers collected the smell released from a male goat’s head (known to be a place that secretes the most smell on a goat) and analyzed the chemical components of the mixture. Then, they isolated components and looked at which components elicited the biggest response in the female goat brain. They analyzed the female goat brain by looking at how many times her “GnRH pulse generator” was firing. GnRH is the gonadotropin-releasing hormone that activates LH (luteinizing hormone), which in turn causes female mammals to ovulate by stimulating their eggs to grow. When the GnRH pulse generator fires, GnRH is stimulated, and the researchers reasoned that this process caused ovulation in the female goats. This research could lead to some exciting new knowledge about the reproductive system of female mammals (especially other ruminants) and how it is affected by male pheromones.

The press release from this study was published in Science Daily very soon after the study was published. I found it interesting that the writing in Science Daily puts a heavier emphasis on human implications than does the original paper about the experiment. Science Daily publishes the quote “there is reason to think the findings will apply to other livestock, and perhaps even to humans, too” (Science Daily, 2014).  After reading the original paper from the researchers, I only noticed one mention of human implications, and the authors were discussing how the research would help humans to better breed livestock. The press release also uses words that seem to dumb down the scientific terms that the original study uses. For example, the press release uses the phrase “central reproductive axis” instead of using the actual terms for the neurotransmitters and the parts of the brain. These changes are logical considering that press releases are for a broad audience, and the emphasis of the press release might make the information more accessible to other scientists or the general public. (more…)

How to Steal a Mate: Frog Edition

June 30th, 2014 by nyn1

 

When it comes to finding mates, that privilege is usually saved for the biggest, strongest, smartest, and whatever other positive adjective you might think of to describe the “perfect mate.” But that leaves you to wonder, what about those who aren’t necessarily the best at what they do, but still find a way to mate? The answer is simple: they’re the cheaters! The saying goes that “cheaters never win,” but in the case of this species of frog, that isn’t always necessarily the case.

A study was done on the European tree frog, Hyla arborea, to figure out why the males in this species choose to either seek out mates “traditionally” or “parasitically.” The traditional way would include actually going out and finding attracting or procuring a mate on their own, while parasitically involves using another competitors skills in order to procure a mate. They wanted to know if this behavior is caused by the size of the frog, or if it is caused by the energy cost that it would take to attract a mate. In order to test these two hypotheses, Brepson and his team set up an experiment in which they randomly caught 100 male frogs from a pond in France and emptied said frogs’ stomachs. The frogs were then split into two groups, one group was fed crickets and flies for seven days consecutively while the other group was starved for the same period of time. Then each frog was put into a container with two speakers, one in the center that played the “chorus” noise (mating calls at the average frequency of the male H. arborea’s croak), and one at the end of the container that played either “attractive” or “unattractive” mating calls for that species. A call was determined to be “attractive” or “unattractive” depending on how low or high the frequency of the call was as well as how often the call was played, with lower and more often was considered more “attractive.” The “satellite” zone was set at any point that was 10 cm or less from the speaker playing the mating calls as a standard for measuring levels of parasitism in this species. Males found in the satellite zone were identified to be acting more “parasitically” than “traditionally”. (more…)