Saw this earlier but finally have a sec to reply. Like someone mentioned, you really cant compromise on reach for wolves, but unfortunately the native Tamron Z options feel a bit compromised for the price. I was really hoping for better low-light performance from the new stuff but f/6.7 is just... not it for those early Lamar Valley mornings. Basically, the thread consensus so far is that 300mm is way too short and the 150-500mm hunts when the sun is low. Since your budget is firm at $1200, youre kinda stuck in a pick two situation between reach, speed, and price. Honestly its a bummer.

• The Tamron 150-500mm f/5-6.7 Di III VC VXD is the obvious native choice, but that dim aperture makes it a struggle at dawn.
• Dont even bother with the Tamron 70-300mm f/4.5-6.3 Di III RXD for wolves. Youll just end up cropping 80% of your pixels away and regret it.
• Best bang for your buck is definitely adapting. Snag a Nikon FTZ II Mount Adapter and a used Tamron SP 150-600mm f/5-6.3 Di VC USD G2. You can get that whole setup for under $1000 if you check the used boards. Tbh, adapting the G2 gives you more reach and basically the same light-gathering for way less money. It isnt as sleek as native Z glass, but for Yellowstone, reach is king... and your wallet wont hurt as much.

Unfortunately, the Tamron 150-500mm f/5-6.7 Di III VC VXD let me down at dawn. I had issues with focus hunting tho... its the best native Tamron, but not as good as expected.

i actually went through this exact same dilemma when i headed out to lamar valley last year for the first time. i had a 300mm lens thinking it would be enough but honestly those wolves are usually miles away across the meadows. unless youre incredibly lucky, 300mm is just gonna leave you cropping until your photos look like a pixelated mess. the Tamron 70-300mm f/4.5-6.3 Di III RXD is super light and cheap but its definitely more of a hiking or landscape lens than a serious wildlife tool for yellowstone. i ended up grabbing the Tamron 150-500mm f/5-6.7 Di III VC VXD and it worked out pretty well for the budget. regarding your concern about the slow aperture... yeah f/6.7 at the long end kinda sucks for those pre-sunrise shots when the wolves are most active. but honestly with the sensor in your z8 you can just crank the iso way higher than you ever could on older bodies. ive pushed mine to iso 6400 and even 12800 with some noise reduction software and the results were totally usable for social media and mid-sized prints. compared to the massive primes, being able to actually fit this thing in a normal backpack while hiking up to mt washburn was a total game changer. if you adapt an old f-mount lens with an ftz adapter you might save a few bucks but youll lose that compact form factor which sounds like what you actually want. for $1200 the 150-500 is basically the sweet spot for native z mount wildlife right now.