During my dive into EVs I wondered about this question. There are no real studies that I could find, but some individuals have done some ad hoc tests. Nothing conclusive with hard data. They have done things like having someone pick them up from a stand using a gas UTV on some nights and and EV UTV on others. In all cases, the deer left the field when the vehicle approached. They had game cameras on the field that recorded the time when the deer reentered the field after the pickup. They were convinced the deer came back quicker with the EV pickup.
That was about all I could find that was even close to a study.
However, my thought is something different than "spooking". It is along the lines of patterning. We pattern deer, but they also pattern us. We tend to drive and park at similar locations, and even walk the same trails, when we hunt particular stands. ATV noise can be heard from quite a distance even when puttering along. Does this help deer pattern us? Does it affect their movements? Will less noise from an EV make it harder to pattern us?
I don't know the answers, but I tend to think a quiet UTV is an advantage for deer as it at least draws less attention from a given distance. If the LI technology and electrical becomes solid, maintenance becomes much less than gas. No air filters, oil changes, and such to deal with. I also like the quiet transport simply for creating less disturbance. It is much easier to sneak up on trespassers. And, it is not only what the game hears, but what I can hear. I will never hear a turkey gobble when driving a gas powered UTV. I may be able to hear that in an EV. Even other. less related to game sounds are nice to hear when I'm transporting to the field.
As we talk about how game relate to sound, I've learned a lot about spring gobbler hunting. Often guys will get on high ground and listen in the pre-dawn and then try to sneak within 100 yards of a roosted gobbler and setup to call him in. I've have done this and had it work on occasion. But, far more often, the gobbler will go another direction. I find this true when the gobbler is roosted alone or with hens. Why? I have come to the conclusion, over many years of spring gobbler hunting, that it is comfort. I think even deer walking through the woods before light can change a turkey's comfort level in terms of moving in a particular direction after fly-down. There are sounds, natural or manmade that make turkey more comfortable or more warry of moving in a particular direction. A bird hearing soft feeding clucks and purrs in one direction may make that direction feel safer. A bird hearing aggressive cutting from a direction where hens don't normally roost my be concerned. A bird that heard something moving around in a particular direction before light may feel less safe moving that direction after fly-down.
I think there is a similarity in "feeling safe" that makes deer more alert or calm. It comes from many more factors than sound, and in fact sound may even be one of the less important factors for deer. However, I generally feel better about quieter movement in the field.
Right now, I can't convince myself that any sound advantage is worth the other issues with todays wet cell lead acid EVs. I'm hoping that the scale will tip the other direction with the new Polaris Electric UTV partnership with Zero. Cost may still tip the balance in favor of traditional gas. Time will tell.
Thanks,
Jack