over the years i have asked the same thing - just got back from Yellowstone last week saw Elk with a collar and tried with my AOR no joy
and during summer visits of the past 12 years i have seen Photographers using simlar radios, in WY MT ID
and on national geographic / wolfs shows; ranchers are seen using AOR radios to track wolf and the like ; THEY have the freq's why not the rest of us
I have found information that some of the collars are in the 150-154 Mhz range. That being said I have never found any. There are GPS collars out there that send the actual coordinates of the animal but they are expensive and few are in use from the article I read. My guess is that the short burst of data at a relatively low power level in mountainous terrain will make them tough to receive.
I have found beeping transmitters in the upper band ranges. They were between 900 and 930 MHz FM. I was travelling over SR20 (in north central Washington) when I picked up a beeper. It sounded just like the ones you hear on TV. I presume it was a Cougar or Bear collar, since those are the two most commonly tracked animals in Washington. Lots of nuisance bears are collared and relocated there.