I have managed to get through almost the entire semester without blogging! Good thing I have some students who are willing to catch us up to spend on the latest and greatest in biological news…
Tweeting History by Bio 94 Student Ahmed Akkad
Twitter! What a magnificent web program that has grown, in only 6 years, to one of the most used (ranked by Alexa as the 9th website in the world) and known social media apps in our world today. We humans use tweets nowadays to communicate anything from jokes to rumors to news and everything in between. We humans are also pretty late to the tweeting business, about 200-145 million years late to be (somewhat) precise. And, yes, as you surely figured out by now, we’re not talking about Twitter tweets anymore. We’re actually talking about bird tweets, sparrow birds in particular.
White crowned sparrow (Zonotrichia leucophrys) Photo by: Mike Baird
Almost every species in the world communicates between themselves and other fellow species. Birds primarily sing and tweet to communicate, although they also have other means of communication. Contrary to popular belief, communications between animals can get very sophisticated and have many functions, tones, frequencies and even have “accents,” like the sparrows we will be talking about. As any kid knows, there are even some animals that (other than humans) can utilize human language for communicating with humans, “Polly wants a cracker?” And as with most other traits in animals, they are all subject to evolving over the centuries.
According to a recent study by David Luther, Elizabeth Derryberry in 2012, a recent example of this evolution is the evolution of sparrow tweets of white-crowned sparrows living in San Francisco. The study, which is named “Birdsongs Keep Pace with City Life: Changes in Song Over Time in an Urban Songbird Affects Communication,” juxtaposes the sparrow’s songs from 1969 to the songs they sing today. The authors attribute the reasons the sparrows changed their songs to the level of noise in San Francisco, which, according to a different study, has grown considerably nosier from 1974 to 2008. As Luther muses, “We’ve created this artificial world, although one could say it’s the real world now, with all this noise — traffic, leaf blowers, air conditioners. A lot of birds are living in these areas, and what, if anything, is this doing to their songs?” The amount the songs changed is quite astounding, if I may say so myself. Keep in mind the study only revolved around the male white-crowned sparrow, and male birds typically sing more than the females.
Luther explains it in common day to day interactions; “Just as we raise our voices to be heard when a car speeds past, birds making their homes near busy intersections have to tweet a little louder. But it’s more than just whistling the same tune and turning up the volume.” The birds had to omit whole songs from their playlist because the old songs couldn’t make it through all the noise. Songs are the main means of communication for birds in general. They use various noises to mate, organize and warn each other of a predators, and not hearing a specific tweet or tune from another bird could result in a mess, maybe even an injury to the sparrow. What’s really interesting though, in my opinion, is how these San Francisco sparrows now only have one shared “dialect,” as opposed to the three they had back in 1969.
Read more at Science Daily.
The Sexual Struggles of Pond Skaters by Bio 94 Student Brian Ngo
Pond skaters (Rheumatobates rileyi), aka water striders, are water skimming bugs found in a variety of freshwater habitats. As a group they are known to fight over sex like many other organisms such as the banana slug’s penis chewing and the hermaphoditic flatworm’s penis fencing. Professor Locke Rowe from the University of Toronto suggested that the male pond skater antennae evolved to match the female pond skaters in efforts to make reproducing easier as female pond skaters are very resistive to males that they deem unfit or unworthy as a mate. The antennae of the male is used to pin down a female and restrain them to prevent any resistance at all from the female and they proceed to mate this way.
The antennae of water striders (Rheumatobates rileyi) are more complex and specialized in males (left) than females (Photo Credit: BBC Nature News)
This is a perfect example of sexual dimorphism and sexual selection because in this case the males head form is drastically different than the females due to the evolution in males head to combat the resistance of female sexual selection. To understand this more in detail Professor Locke Rowe used high speed video recording to capture the mating process of the Pond Skaters. They flash froze the data and analyzed it under the electron microscope to gain a better understanding and at that level of detail researchers could perfectly view the process and see that the male’s antennae were made perfectly and solely to restrain the female heads allowing the male to avoid any resistance and come on top of the female. This evolution of a strong male head to counter the strong resistance of females was not a simple one as there were multiple parts that evolved in the male head allowing them to gain leverage in successful mating. This specialized male head was found to be controlled by a single gene which was then manipulated by scientists and they found that the simple manipulating of this single gene resulted in an increase of successful mating of the males who were modified.
Read more at BBC Earth News.