Uncle Nano 2 - The Hunter

Here's the next one in my series of "Houston Memories Card," based on Sian's Captured in a Card idea and using my May counterfeit kit.  For this card, I used the card sketch challenge posted on the Counterfeit Kit blog.  It's a great  sketch!
This card is also about my Uncle Nano.  You can see the first of his cards in this post.  This one reads "My Uncle Nano used to love to hunt in a place called 'The Big Thicket.'  There were lots of deer and antelope heads mounted and displayed throughout his house, but his real trophies were a boar's head and a rug made from a mountain lion hide.  I remember being totally fascinated by their preserved teeth and marble eyes.  We actually drove up there once. The mosquitoes were so thick that Uncle Nano threw my dad a bottle of 'Off!' insect repellent and shouted,'Here Pete, take a bath!'  I don't think we kids ever got out of the car.  Decades later, my sister Cordelia and I worked with a Realtor to sell the property as part of settling Aunt Vera's estate.  I actually think he sold it to someone who intended to use it as a hunting lodge."
And here's the scrapbook page I made to go along with it:

I don't really know anything about this photograph, as I found it in a book about Latino history in Houston, Texas that I found in my Aunt's house.  I guessed it was circa 1925, as my Uncle looks younger than when he married my Aunt in 1933.  I'll ask around to see if anyone knows any more about it, and I left some space to explain whatever I find out. At first, I thought it must be a military picture, but perhaps my Uncle Nano really hunted on horseback? The other thing I don't quite understand is that the photograph has the name of a Houston photography studio on the back (Cantu Studios), which makes me wonder who took the photograph and how.  Did studios in those days shoot on location? Or did my Uncle Nano bring this horse and his outfit to the studio? Speaking of which, I don't ever remember anything about my Uncle owning a horse! Very curious.  Anyone have any guesses about the photograph or knowledge of photography studio conventions in the U.S. in the 1920's?