This one always gets intetesting. I hunted the Trans Pecos for many yrs.

Whitetails and mule deer could be found on certain ranches. So....do they cross breed or not? Game biologist says they can. But he says the fawns survival rate is almost non exsistent.

I tend to agree they do cross, but I also believe their survival rate is higher then what the bio told me.

About 10 years ago my FIL hunted a ranch and a guy killed a whitetail with a mule deer rack.

The lease foreman swore it was a cross bred

I didn’t believe it until I saw the pic

So I am gonna say it’s possible

I talked to a TPWD biologist too and he concurred it's possible. 'Only way to tell definitely if one is one is by a blood test. That can't be cheap.

A whitetail buck will breed a mule deer doe and they do on occasion, but a whitetail doe will not breed with a muley buck.

I've seen a WT buck chasing mule deer doe.

I've seen a mule deer forkie chasing a WT doe.
My cousin killed a cross MD/WT in Pecos County in the mid 80's. The metatarsil gland is a good way to tell if it is a cross. I have a 35mm photo of the buck and the metatarsil gland.
Here is a link with photos of a WT, MD and Hybrid cross. Second article has a picture of hybrid buck with more detail.
https://www.fs.fed.us/rm/pubs_other/rmrs_2012_heffelfinger_j001.pdf
http://www.deeranddeerhunting.com/deer-s...s-and-mule-deer

This was what I was told also when we hunted in Childress...

Whitetail and mulies will cross breed. I grew up in CO and they take a few every year out in the plains. Shot one myself in Yuma County on a spread an old family friend owned about 20 years ago. I was just meat hunting and found a small buck running with some mulie does and he seemed a little "off" when they busted out of a draw. His gait was different than the females. I popped him and when I walked up his rack was weird too, 3 points per side with one side being a normal type mule deer rack and the other going up like an elk rack with 3 points on it. His tail was flared like a whitetail but had a black tip on it and he lacked the black skull cap on a mulie.

I took the dressed carcass to the DOW office in Brush, CO and they took a few measurements and tissue samples. A few months later they got back to me and said the buck was a hybrid of the 2 species and that they see a few every year. They like to see them shot and really don't want them around. He ate just fine but was kind of a weird looking deer. I regret never taking a photo since it will probably be the only one I ever shoot.

I wish I could remember the article I read but, one article stated that the whitetail buck is more aggressive than the mule deer buck, hence the main reason whitetails breed mule deer doe.
An uncle of mine in Idaho hated whitetails. Said they would be the ruination of the mule deer herd.The whitetails stuck mainly in the valleys and the mule deer the mountains until the snow pushed them down.

In areas where they overlap the mule deer takes precedence in my line of thinking

We have both on our family land where I live and hunt. I have no doubt it's possible but I think it's rare and the results are usually poor. I've read some articles where the breeds were crossed in controlled settings and the resulting fawns had a much higher mortality rate. That said, I've seen some racks that looked like a WT on one side and a Muley on the other.

As for "aggressiveness," I've yet to see a Muley of any size yield to a WT. In my limited observations over the last 20 years or so, they typically give each other space but neither seems to be an aggressor. Admittedly, in most of these observed occasions, the Muley buck was the larger of the 2 species.

Here's a mulie my buddy shot down on our place off I-10 and the Pecos River. Had several mulie doe with him and the typical huge mule deer ears/body and white face.