Wild Animals/Bats: Human Biomedical uses
QUESTION: I'm competing in the Battle of the Brains group for Science City and were doing a project on bats (the mammal). Each of us got a sense to research, I got hearing and echolocation. I already know a lot about the subject, but I'm looking for further info for my group members.
What I'm looking for is more information on their coned ears and how they funnel the sound, echolocation, and anything else you can find on the topic of bat hearing.
Thanks so much!!
You have no idea
How helpful this
ANSWER: Dear Raven
Thank you for your question. I also wish to thank the authors of the websites I used. Please note that this information includes complicated material, involving physics and other sciences. I have tried to simplify the data, but I must admit that I wasn't particularly good at physics at school. I have used several websites that provide different aspects in the use of the ears. This means that some of the information is repeated and I apologise for this.
says that different species of bats vary in their hearing range. They use two types of calls: one type is constant frequency (CF) calls, while frequency modulated (FM) calls descend in pitch. They use CF calls to detect an object and FM calls assess its distance. The calls lead to FM and CM echoes that indicate the size and distance of the prey. The bat produces sound pulses lasting a few thousandths of a second; silences between the calls enable the bat to listen for the information returning as an echo. The bats use the change in pitch of sound produced via the Doppler effect to assess their flight speed in relation to objects around them. They use information regarding size, shape and texture to build up a picture of their surroundings and the location of prey. This helps them track changes in movements to hunt down their prey.
says that a bat can tell if an insect is to the right or left by comparing when the sound reaches its right ear to when it reaches its left ear. If the sound of the echo reaches the right ear before it reaches the left ear, the insect is to the right. The ears have a complex collection of folds that help it determine an insect's vertical position. Echoes coming from below hit the folds of the outer ear at a different point than sounds coming from above and will sound differently when they reach the inner ear.
Martin Obristi, M. Brock Fenton, Judith Eger and Peter Schlegel (http://jeb.biologists.org/content/180/1/119.full.pdf
) give details about the ears of different families of bats.
has additonal information about echolocation. It says that when bats use low duty cycle echolocation, they can separate their calls and returning echos by time. They time their short calls to end before the echoes return. They contract their middle ear muscles when they emit a call, so they can avoid deafening themselves. The time interval between call and echo lets them to relax these muscles, so they can hear the returning echo. The delay of the returning echoes helps the bat estimate where the prey is.
When bats use high duty cycle echolocation, they emit a continuous call and separate pulse and echo in frequency. Their ears are sharply tuned to a specific frequency range. They emit calls outside this range to avoid self-deafening. They receive echoes back at the finely tuned frequency range by using the Doppler shift of their motion in flight. The Doppler shift of the returning echos gives information linked to the motion and location of the prey. These bats deal with changes in the Doppler shift due to changes in their flight speed. They can change their pulse emission frequency in relation to their flight speed so echoes still return in the optimal hearing range.
Bat ears are sensitive to fluttering moth wings, insect sounds and the movement of ground-dwelling prey. Ridges on the inner surface of the ears help to sharply focus echolocation signals and passively listen for other sounds.
Alain Van Ryckegham (http://www.scientificamerican.com/article.cfm?id=how-do-bats-echolocate-an
) says the ears and brain cells in bats are especially tuned to the frequencies of the sounds they emit and the resulting echoes. Concentrated receptor cells in the inner ear make bats extremely sensitive to frequency changes. Bats can listen to the echoes of their calls without being temporarily deafened by the intensity of their calls. The middle ear muscle (the stapedius) contracts to separate the three bones and reduce the hearing sensitivity. This contraction occurs about 6 ms before the larynx muscles (crycothyroid) begin to contract. The middle ear muscle relaxes 2 to 8 ms later. At this point, the ear can receive the echo of an insect a metre away, which takes 6 ms. The ears of different bats vary in size, shape, folds and wrinkles, which probably help in the reception and funneling of echoes and sounds emitted from prey.
says that upright ears capture high-quality echoes from objects ahead, while ears bent downward and backward hear echoes from more directions but not as well. some scientists suggest that bats tune their hearing to specific tasks. They use bent ears to sweep an area for potential prey, such as moths, or for predators like owls, and use upright ears to zero in on prey when bats dive for an attack.
has a series of diagrams concerning echolocation and hearing, which may help explain some of the data.
says that the large, funnel-shaped ears of funnel-eared bats let the bats detect near silent sounds and return echoes through echolocation. Small papillae cover the ears and increase auditory sensitivity.
Phil Richardson (http://www.nhm.ac.uk/nature-online/life/mammals/bats/session3/
) says that many bats have large ears to gather as much sound as possible. Generally, bats with bigger ears have quieter echolocation calls. Many insectivorous bats have an extra spike of cartilage (the tragus) sticking up from the base of each ear and this may help give better sound definition in a particular plane.
shows different types of bat ears. The tragus is a small piece of cartilage and flesh that sticks up near the entrance of the ear. It is part of the margin of the ear and is thought to help echolocating bats estimate the heights of objects. Not all species have a tragus. Some bats have an antitragus instead.
gives details about how the tragus helps a bat avoid obstacles.
I hope this makes sense and that this will help your group in the Battle of the Brains.
---------- FOLLOW-UP ----------
QUESTION: Now we have to tie it in to Human Biomedical, So it qualifies. But well i was wondering if i could get some info on how We can or already do use bats for medical reasons.
For example I would like to know more on how we are finding ways to use vampire bats for heart problems.
Thank you so much
for taking the time!!!
Thanks for your question. I also wish to thank the authors of the websites I used.
Bats are used in various forms of medical research.
gives details of research into bat-borne viruses, which could affect humans.
gives details about research into the Ebola virus in bats.
give details about how vampire saliva could help stroke victims.
Thomas G. Barnes (http://www2.ca.uky.edu/agc/pubs/for/for48/for48.htm
) says bats have contributed to medical research in birth control and artificial insemination techniques, navigational aids for the blind, vaccines and drugs and new low-temperature surgical techniques.
says that scientists want to analyse vampire saliva to help develop pharmaceuticals that may help patients suffering from blood flow deficiencies.
Below is an article I included in the last copy of Natterer's News, the newsletter of the London Bat Group:
"Hepatitis C and bats
Bats are the source of SARS, ebola and some other human viral infections. Some scientists think that bats are a large natural reservoir to groups of viruses similar to the hepatitis C virus (HCV), which probably originated in Africa and South Asia and threatens the lives of over 150 million people.
Dr Phenix-Lan Quan and colleagues from Columbia University analysed nucleic acids in blood from bats from South America, Africa and Asia. About 5% of the bats had novel genetic sequences similar to those in pegiviruses and hepaciviruses. HCV is a type of hepacivirus.
Dr Quan constructed phylogenetic trees to determine the genetic relationships between the viruses. In the pegivirus and hepacivirus tree, the many, long branches leading to clusters of bat virus sequences indicate that bats have been infected by a great variety of strains for far longer than humans have.
If bats are the source of the HCV virus, the HCV sequences should nestle amongst the branches of the bat hepaciviruses. At first sight they do.
A 2005 paper in Science showed that SARS passed from bats via civets to humans, and a 2010 Royal Society journal article reported that HIV arose after transmission from African primates. Initial studies suggested that the bat was responsible, but there are other suspects that have now entered the line-up. In trees of virus sequences derived from wild primates, HIV is embedded firmly on the branch of the tree containing chimpanzee viruses. Genetically, HIV is most closely related to its chimpanzee counterparts and they are the most likely source.
In the hepacivirus tree, research in Emerging Infections Diseases shows that HCV is more related to viruses in horses and dogs rather than those in bats, but the branch leading to HCV is very long -with lots of genetic change and a long evolutionary time frame. It is unlikely that a virus made the jump into humans long ago. Dr Quan said that all known hepaciviruses and pegiviruses, including primates, horses and dogs, fall within the phylogenetic diversity of the bat-derived viruses, suggesting a longer evolutionary history of these viruses in bats than in primates, horses or dogs.
Dr Quan believes that bats harbour the greatest array of these viruses, but says that the data does not prove that bats are the 'ultimate' reservoir of hepaciviruses and pegiviruses, nor that HCV came from bats. Professor Amit Kapoor, from Columbia University in New York, reported in a study published in the journal mBioby, that many species of rodents harbour hepacivirus and pegiviruses. The rodent viruses, like the bat viruses, show a large degree of genetic variability, hinting at an enduring history of infection. Rodents could be the confirmed source of the virus
None of the rodent sequences were more related to HCV than the horse hepaciviruses, but one of the co-authors, Prof Peter Simmonds from the University of Edinburgh, thinks the large variability in rodent viruses may be significant. He said it seems that different bats and rodents carry a diverse range of HCV-like viruses. While none are genetically very close to HCV, other variants in other species could match HCV more closely. Simmonds predicts that scientists will find various bat and/or rodent species infected with viruses representing the immediate source of human infections in the parts of Africa and South Asia where HCV probably originated.
Bats and rodents have existed for over 50 million years, so have picked up several viruses. Some viruses, driven by habitat encroachment and human activity, have passed into humans.
I hope this will help you with your research.
All the best