Not many Deer down-under, but there's lotsa Roo's on the roads!
I haven't bothered to track down the details, but a couple of the Universities here in Aust did some fairly comprehensive research & testing on all of the electronic "Hopper Stoppers" as they are called down here that were available at the time.... we don't have too many deer infested localities, but hey, we certainly do have many areas with kangaroo & wombat infestations, and even a few areas that have issues with the numbers of camels or cattle & sheep on the road! Since hitting any/all of those animals can do some pretty horrific damage to a vehicle, fatalities resulting from animal strikes aren't un-common! Anyhow, I'm pretty sure the Universities came to the same conclusion as the referenced investigations into the air driven jobbies - if they work at all it's purely co-incidental!
From my own experience after more than 40 years driving vehicles around this country, vehicles ranging from heavy transport trucks & Semi's thru to motorbikes large and small and everything in-between, racking up quite a few (million) miles of driving on roads with animal problems in the process, both with and without these devices (yeah, we've tried them all!

pps

that pretty much agrees with my experience! The only thing that really works in minimising the risk of animal strikes is slowing down and taking extra care when you are in areas where animals are prone to wander onto the roads.... and remember that here that pretty much includes
all of the country anything more than a couple of miles outside of the towns/cities - at times/places/seasons the animals on the roads have been known to reach concentrations of hundreds per mile!! :yikes: Besides, here in Oz someone hits a roo in the middle of one of our cities fairly often - you'd be surprised at how far these things can travel into a city, and there's literally millions of them around, but not one of them knows or obeys the road rules for safe crossings!! :shocked:
Still, I 'spose if it floats your boat to pay for & install devices like that and ride (or drive) under the misapprehension that it's somehow making things safer for you, then I'm OK with that, just so long as I'm not forced to install one too! :2thumbs: