Unique Form of Mammal Communication Found in Madagascar
I was actually watching a documentary on Animal Planet the other day about Madagascar, and the tenrec struck me as a great animal to blog about. Tenrecs are small mammals, sometimes described as appearing to be a cross between a shrew and a hedgehog. They are covered with protective quills, and are endemic to Madagascar, where there are about 30 known species. I was particularly intrigued by the Lowland Streaked (or Striped) Tenrec, (Hemicentetes semispinosus), a largely nocturnal insectivore that lives in family groups of up to 20 individuals, usually living together in the same burrow. What is unique about these tenrecs is their ability to use a strange form of communication known as stridulating in a number of different scenarios (such as foraging), although much about this is still not understood.
Stridulation is accomplished by vibrating specialized quills on their back, making a unique high-frequency grinding sound that they can easily differentiate from the sounds of other animals foraging at night, likely so they can keep track of their family group. This behavior is also said to be more commonly observed between mother and offspring, likely so they can communicate information about their location to each other without attracting the attention of potential predators. What is particularly interesting about this is that the streaked tenrec is the only known mammal to communicate using stridulation, something that is most commonly seen in insects, fish, snakes, and arachnids.
Something else that struck me while I was doing background research was the general lack of information on these curious mammals. Many of the sources I came across had conflicting information about their foraging habits (some said they were entirely nocturnal, others said they forage during the day as well), as well as basic information about when they breed, when young mature, etc. This was really surprising to me because I think an understanding of a species’ life history traits is essential for understanding possible reasons for various adaptations. Also, I think there is a lot to be learned from these tenrecs, such as how long ago did they develop these specialized quills? Did something happen during this time period that may have caused them to develop this adaptation (such as the introduction of a new predator)? Do any of their close relatives have similar adaptations? Or, when comparing their stridulations with those of insects, are there any similarities between them that may suggest context or meaning? I think there is a lot to be learned from the Lowland Streaked Tenrec, especially on the communication front, so I was surprised when I had so much difficulty finding reliable information.
In conclusion, while little is known for sure about the Lowland Streaked (or Striped) Tenrec, it is undoubtedly a great example of how Madagascar's geographic isolation has promoted the divergence of many unique animal adaptations not found anywhere else on Earth.
http://www.youtube.com/watch?v=W9kJKu4cpXM
Posted by Brianna Eddy (1)
(additional sources of background info: http://www.arkive.org/lowland-streaked-tenrec/hemicentetes-semispinosus/ & http://www.tsaracamp-madagascar.com/mammals.html)
I find it very interesting that the tenrec would evolve such a form of communication when most mammals have not. I wonder if there are any other purposes for the high frequency sound besides communication between mothers and their offspring. Perhaps there should be research done on the type of food these tenrecs eat – maybe they use the high frequency to attract insects?
ReplyDeletePosted by James Lin
Cool post! The video of them communicating using their quills is bizarre! Especially since they are the only mammals that are known to do that. You mentioned that some insects do it, as well as fish. Do you know what species of fish do this? Seems like it could definitely be a case of convergent evolution in many different species, I wonder what the evolutionary pressure to develop such a trait could be?
ReplyDeletePosted by Janelle Hayes
This seems like a very effective form of communication. It's high pitched enough to cut through background noise, distinct enough that the young will be able to easily identify it, and strange enough that predators will likely not be attracted to is as they won't associate it with food. It's so strange that this mechanism evolved in a mammal when it is usually used by insects and fish.
ReplyDeletePosted by Rhys Ursuliak
This is so interesting! I wonder if every family of tenrecs has a different vibration pattern or range of frequency specialized to their own relatives? Since they are considered by some researchers to be nocturnal, I also wonder how strong their senses are. Their hearing would obviously be geared toward receiving the quill frequencies, and having developed such a form of communication, they must not rely as much on their eyesight. It may be a stretch, but I wonder if rubbing those quills together gives off any sort of chemical, as well. It could not only be a way of finding each other, but also a warning to the other's that danger is near. This is a great species to conduct further research on!
ReplyDeletePosted by Chelsea Van Thof
I too watched the Animal Planet documentary and highly suggest it! It was incredible footage on some amazing creatures. These tenrecs are pretty cool and they are a great example of the mechanical way that animals can produce sound. I would be interested in knowing how well these animals hear and how far the range of their sound is if it is meant to keep mom and baby together. This makes me wonder what other kind of mammals use mechanics to produce sound
ReplyDeletePosted by Suzanne Sullivan
James- That's actually a really good point, I hadn't thought of that. When I learned that the sounds of the stridulation had to be recorded with a bat detector, (something that is normally used to study echolocation in bats), I thought they may use the sound as a form of echolocation to make up for poor eyesight, something that is common in animals that burrow underground.
ReplyDeleteJanelle- It turns out fish stridulate by grinding their jaws/teeth together, which is then amplified or modified by their swim bladder. This is seen in sea catfish, grunts, and seahorses, and it is suggested that they use this primarily for territorial disputes. I don't know much about fish, but it would be interesting to compare the strengths/weaknesses of these species to those of the tenrecs; I wonder if they all have poor eyesight, relying on auditory & tactile cues?
While I couldn't find any evidence of our theories, a number of sources mentioned another form of communication the tenrecs use, tongue-clicking. These sources also suggested that the tenrecs use tongue-clicking for echolocation, and stridulation as a way to warn predators that they are aware of their presence, so pursuit is futile; something I hadn't considered.
Either way, there definitely seems to be a lack of research in this area, (and I looked into a number of different scientific databases to see if there were any studies published, too!) so I think there is potential for truth in all our theories; only time will tell.
Posted By Brianna Eddy
(Additional Sources: http://www.britannica.com/blogs/2011/02/the-lowland-streaked-tenrec-and-its-quills-of-communication/ ; http://animaldiversity.ummz.umich.edu/site/accounts/information/Hemicentetes_semispinosus.html ; http://afrotheria.net/tenrecs/ )