As long as you can integrate the light into Hubitat somehow (perhaps a separate question), this would be do-able using a motion sensor (again one that integrates into Hubitat, or however you want to trigger this) and an app/rule (automation) on Hubitat.
However, with what sounds like 150+ ft. between the devices, range would be a concern. Hubitat's Z-Wave docs say the theoretical maximum is about 600 ft (200 m) when using the maximum of four hops between devices, meaning the maximum for a single hop (i.e, no repeaters in between) would be about 150 ft. Outside, you might actually get that, but with buildings or walls in between it will likely be less. The newest generation, 700-series Z-Wave, is supposed to be better at this (might allow 300+ ft. on a single hop), but these new-generation devices are still pretty hard to find (and again, this is theoretical range). I used Z-Wave as an example because it tends to get longer range than Zigbee, though that is another option. Either allows you to extend this range with "repeaters" in between, but these need to be powered (mains or USB) devices, which might be hard to do if there are no buildings/outlets/bulbs in between outside.
Wi-Fi will be of little help, as nearly any sensor you'd want to use with Hubitat for this would be Z-Wave and Zigbee, as would nearly any switch/bulb. (I know a couple Wi-Fi lights that are compatible, but those are rare and wouldn't help you with the sensor.) This is, of course, unless you were thinking of using Wi-Fi to reach the hub and placing the hub near these devices (the hub would definitely need to be indoors-ish...). Hubitat needs a LAN connection for administration, but once you get everything set up, you could let it happily run without that, or you could use a WiFi-to-Ethernet bridge/adapter (probably what I'd do since without access to the admin interface, you can't politely shutdown or restart the hub, much less administer or troubleshoot it).
So, as much as I love Hubitat, unless you had another use in mind for Hubitat besides this, I'm not sure that having a sensor 150+ ft. away outside report to a hub inside which then communicates with the light and tells it to turn on (or whatever) is the best possible use case for Hubitat. A "dumb," local (i.e., at the light) solution might work better for you here, and then you wouldn't need to worry about any of this. But if you have other ideas for home automation in mind, I definitely think Hubitat would work well (there's a reason I've kept mine!) and you could certainly try this idea for deer in addition to those automations. I'd just hesitate to recommend it solely for this one specific purpose. But that's just my opinion.