Hamster echolocation?

Question
QUESTION: Hi, I'm new to hamsters and I'm hamster-sitting for a couple of months. Once a day, I take her out of her cage to play. I pile the sofa with pillows and blankets so that she has lots of things to climb on and crawl through, and she also has a playpen with toys in it. I've noticed that when she's playing on the sofa she sometimes vibrates, like a cellphone. I can't hear it, exactly, but I can definitely feel it when she's crawling on me, and I can even feel it when she's not on me but nearby (like how you can feel a song with heavy bass in your chest, as distinct from hearing it). I haven't noticed her doing this in her playpen or in her cage.

My immediate impression was that it was an investigative technique that she was using to gather info about her surroundings, like bats and echolocation. Once she did it while perched in my hand, looking towards a pillow, and then she jumped from my hand to the pillow with perfect form (when, normally, if she jumps somewhere it's all face-plants and tumbling over -- generally she doesn't jump unless she's desperately trying to get somewhere and this was not desperation, it was calculated).

I did some online searching, and some people said it's fear/nervousness. Some said it's happiness/contentment. (Based on the rest of her behaviour, I wouldn't either of these are true in this case.) Some said it's diabetes or another illness. Some said it's poor diet: too much sugar and/or not enough protein. Everyone seemed very sure of themselves but no one pointed to any literature on the subject or any evidence. I read in "Grzimek's Animal Life" that hamsters can hear and make noises in ultrasonic frequencies, which they use to communicate with each other, but it didn't say anything about doing that to learn about their environment like bats do. Do you know anything about this?

Thanks!

ANSWER: Hi Nicole

Thanks for your question although I'm not sure I can give you an answer.

I've had many hamsters who have behaved like this and I've always assumed the trembling is down to fear or uncertainty. Most hamsters I foster have never been  handled and are often worried especially about walking on skin and the vibrating/trembling is very apparent.

I'm fascinated by your ideas about this and would be very interested to know if you discover any more about this theory. If I find out anything I will certainly let you know.

Regards
Sheila

---------- FOLLOW-UP ----------

QUESTION: Hi Sheila,
Thank you for your answer, even if you don't have the info I'm looking for :) Since you are interested I thought I would give you a bit more detail. I'll try to explain why I don't think the vibrating is fear-based.

I guess this is a very socialized hamster! While playing on the sofa she freely crawls on me, including into my bare hands, and often she sits calmly while I carry her to her playpen or a different spot on the sofa -- no vibrating or shaking, but not frozen in fear, either: just sitting there, looking around, waiting until I put her down. Also she allows me quite naturally to guide her when she's trying to get down from, say, a high pillow, and I can see she won't be able to do it without falling, so I just kind of put my hand at her feet and let her do a controlled fall -- she doesn't flinch or try to get away or anything. She does sometimes desperately squirm when I pick her up but, considering how often she doesn't do that, I think it's only because I'm taking her away from where she wants to go. (I think she's desperate to get off the sofa and on to the floor, but I can't let her because this is an old house with too many holes for her to escape through). So, I don't think she feels any nervousness toward me.

As for fear behaviour, I think I have seen it: The first week or so, she would growl and bite when I tried to touch her, but she doesn't do that at all anymore. Also, I think I've twice seen her afraid while playing. The first time she was in her playpen, which I had just picked up and moved while she was in it (which I don't normally do), and she ran back and forth like mad a few times and then into her hidey-box, where she stayed a long time. The second time we were on the sofa and I got up and went across the room -- again she ran back and forth like mad for a bit, so I went back and put my arms and chin on the sofa and spoke softly, and she immediately ran towards me, past my arms and right up to my face, and she stayed close like that for awhile and then started acting normal again. (Reading this over, it sounds nuts, but I swear it's true!) So, I think that's what she does when she's scared -- does that make sense to you, so far as hamsters go?

As for the vibrating, it isn't at all like trembling or shaking. It isn't ongoing like that but instead it's in pulses -- really like a cellphone, "bzzt bzzt," always in twos like that, and it may or may not be followed by more sets of two. Except for that one time I told you about, when she jumped from my hand to the pillow, she doesn't vibrate while in my hand -- she does it while crawling around, sometimes on my legs, sometimes on the sofa cushions. I think there very well could be feelings of uncertainty in it but nervousness/fear just doesn't seem to fit, it seems more like searching to me, exploration... but I can't be sure!!!

I've continued to search for more info about this but I've been unsuccessful. According to a few sources, shrews do echolocation, but they are the only land animal known to do it, and hamsters have not been observed to do it in clinical studies (http://en.wikipedia.org/wiki/Shrew#Echolocation; also The Hamster Handbook by Patricia Pope Bartlett, page 39). I found one website where a person writes that hamsters do echolocation, but no sources are provided and they haven't yet answered my request for some (http://whitney05.hubpages.com/hub/Hamsters-Communicate). I did some searches in periodical databases and came up empty-handed (I looked in PubMed and Academic Search Premier; there's various studies about hamsters and ultrasonic noises used for communication, but none for echolocation). According to the book "Echolocation in Bats and Dolphins" there is evidence that rats do echolocation but, again, the same studies using hamsters did not produce any evidence of echolocation (here's a link to this book in Google books, although I'm not sure it will work: http://books.google.ca/books?id=LQZkbe9ye4sC&pg=PA562&lpg=PA562&dq=hamster+echol).

What I find frustrating is that none of these studies mention the hamster vibrating. If I could find a different scientific reason for the vibrations I could accept it, but so far I can't!

Anyway, thanks again for your interest. Hopefully someday we will find an answer!
Nicole

Answer
Hi Nicole

Thanks for this - it is fascinating. I personally think that hamsters are far more intelligent than most people think. I have had some very strange experiences with them so it wouldn't surprise me if you are right about this.

I'm going to pass your theory onto a vet friend who carried out a lot of research into hamsters when we were writing our book on them and he has written articles on them so I'll see if he has come across this before and let you know.

Regards
Sheila