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Re: The Effect of Traffic Noise on Tree Frogs

Subject: Re: The Effect of Traffic Noise on Tree Frogs
From: "Dan Dugan" dandugan_1999
Date: Sun Jul 30, 2006 10:49 am (PDT)
>  > Dawson found that the noise appears to mask the calls of neighboring
>>  frogs, and the lack of stimulation inhibits calling. The male frogs
>>  would ratchet their calling up to the normal level when she played
>>  back calls near them. The effect of this on breeding is unknown. The
>>  inverse experiment, playback of traffic noise to frogs in quiet
>>  areas, had no significant effect, probably because she was using a
>>  tiny speaker.
>My own experience is somewhat at odds with this. For many of the species
>here traffic starts calling, not inhibits it. A aircraft flying over can
>do the same thing.  It's actually one of the annoying things for
>recording frogs. Call when a car passes, but not in the quiet times in
>I've not really seen a lot of avoidance of freeways in the frogs here,
>pretty much the same mix calling. It's more dependent on the character
>of the wet area involved than the nearby freeway. And water near
>freeways is as likely to have a bunch of tadpoles as any other if it's
>the sort of water they like. Again, such sites are hard to record.

Interesting, when I'm able to contact her I'll pass your comment on. 
This is only about one species that she says behaves differently from 
others re traffic noise.

>I agree, the results would be heavily thrown off using small speakers.
>It's the low frequency content you need to play.

I would think so, if the frogs were alerting to danger by sensing the 
low frequencies. If the calling behavior change was due to masking, 
however, maybe not. Then again, maybe the frogs could recognize the 
point source of the little speaker and tune it out, but the same 
sound level of more diffuse traffic noise had a different effect. 
Lots of variables.

-Dan Dugan

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