I've heard they cause problems
I used to live in deer country and heard a lot of theories on the "Whistles". One that made a bit of sense was that the sounds freaks-out the deer, many times into jumping out of the ditch and onto the roadway.
Secondly, you need positive airflow, front-to-back, for the device to function. In that location in the grille, air probably fills up the space and doesn't allow airflow through the device. They'd have to be mounted either on the hood or right under the front lip.
A lot of deer avoidance is pure reaction. If it becomes a last-minute measure, some reccommend to aim for the deer in the roadway, since reflexes at that speed tend to steer you into what would be perceived as a path away from the deer. If it's running to the left, you'd hit it, if you aim right (hard to do), you have a chance of missing it.
I've had one hit the side of my car as I drove. It just left a dent (got really lucky). A family member was driving a '79 Suburban 3/4-ton on the same road, hit a deer, and it nearly totalled that tank of a vehicle.
I guess you just have to be vigilant. When I lived in rural SE Ohio, I had a set of driving lights focused on the ditches (in addition to some super-bright high-beams -- "off-road use only" on the latter, so dimming them for other drivers was imperative). Not sure what to do otherwise...
RH77
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