Friday, March 31, 2017

How do Bats find Water?

A large part of an animal’s capacity to survive is its ability find resources. Each species of animal develops unique strategies for finding resources that permit them to survive and reproduce. For bats, the identification of water bodies is crucial to their survival and navigation. Ponds, lakes, and rivers provide an ideal habitat for bats as mating, breeding, and drinking grounds. Two researchers: Stefan Greif & Bj√∂rn M. Siemers hypothesized the main strategy that echolocating bats used to find bodies of water is their echolocation. Because bodies of water generally have large smooth horizontal surfaces the researchers predicted that water acts as acoustic mirror; reflecting most of the energy in the echolocating calls back to the bats.

The bats collected for the experiment were presented two plates, smooth or textured made of the same material. The three types of material used were, metal, wood, and plastic. After each trial the bats were also presented water to determine their motivation for drinking. 15 different species of bats were tested in total. 

To determine how much dominance water like echoacoustic cues took dominance over behavior, a sooth metal was put under a table. The bats still tried to drink from the metal plate under the table. Based on the rationale bats use to find water this meant they were drinking water under another body of water. It seems the water like echoacoustic cues of the metal plate took dominance even with conflicting information. 
Echo signatures of natural and experimental surfaces.

A few variations of the experiment were conducted to confirm to different things about echolocating bats. The initial experiment was conducted on Juvenile bats who had never experienced a pond or rivers before. The juvenile bats showed identical drinking behavior for smooth plates as they did with water. To test conflicting sensory stimuli the experiment was also conducted in the dark. In the dark the bats had more drinking attempts for the metal plate than with the lights on. 

At the end of the experiment the hypothesis initially proposed by the researchers were confirmed. The echoacoustic cues of smooth plats were mistaken by bats as bodies of water. This was displayed through the bats’ attempts to drink the metal, wooden, and plastic plates. In each variation of the experiment the bats were consistent in their choice of the smooth plats over the textured plates. The smooth plates did in fact give of echoacoustic signals identical to water because they had smooth uniform surfaces which returned echoes identical to water. The results suggest information received through echolocation takes dominance over other sensory information. Even when the bats could see the plates weren’t water they still tried to drink them. The juvenile bats tested with no experience locating water still demonstrated preferential drinking behavior for smooth plates opposed to textured plats. This finding suggested the strategy for detecting bodies of water by echolocating bats is an innate ability. The juvenile bats never had the opportunity to learn this water locating strategy but they still used it.  

The foresight and efficiency Greif & Siemers conducted their experiment with is astonishing. They were able to validate two hypotheses with high certainty. These findings contextualize some bizarre behaviors of bats; like their affinity for car hoods and attics. The smooth surfaces of car hoods and rooftops could be attracting bats who perceive these inanimate objects as bodies of water. Based on the findings presented by the experimenters, efforts can be made to divert bats away from residential areas by incorporating more textured suffices into urban/residential design. 


Posted by: Michael Aflakpui group A

Thursday, March 30, 2017

Biodiversity in Hawaii

The islands of Hawaii emerged from the ocean over a period of 6 million years. The formation began with Kauai 6 million years ago, with the Big Island (1.3 million years ago) currently the only island still growing. As each new island was formed, it was colonized by plants and animals from the older islands and as they spread out to fill each island’s ecological niches, a wealth of new species emerged.