On January 1, 1929, Bert Lauzon began working for the National Park Service in Grand Canyon, Arizona. Miner Raymond Tillotson held the position of superintendent when Bert was hired. The staff of permanent rangers numbered but ten, so each needed to perform a variety of functions. Lauzon fit that bill perfectly. His knowledge of the trails and river corridor was extensive, his law enforcement experience as Constable and Deputy Sheriff prepared him for sensitive and sometimes dangerous assignments, and his years guiding combined with his own affable personality made him a natural for contact with the public. Furthermore, his comprehension of geology and the history of the region was an asset to furthering scientific inquiry. Lastly, his years as a rancher on the South Rim enabled him to understand the issues with local residents and landholders.

In his capacity as Park Ranger, Bert was often called upon to utilize his vast experience with horses. He rode border and deer patrols in the Park, participated in scientific endeavors and projects, such as the fish plants at Clear Creek, and assisted in wild horse round-ups.

The "Little Horse Trip" was one of the notable pack trips Lauzon participated in with other Park Service personnel. Rumors circulated that miniature horses (supposedly offspring of horses that were isolated in a canyon blocked by a slide) ranged in the Grand Canyon. The size of these mysterious horses varied; with the smallest reportedly being the size of a dog or jackrabbit.

Grand Canyon Park Superintendent Tillotson assigned three rangers (Edwin McKee, Warren Hamilton and Bert Lauzon) to investigate the situation. Mail carrier Tom Gordon along with Deputy Sheriff Fix, and three Havasupai men, Claude Watahomige, Jim Wescogame, and Jack Jones, completed the party.

The group rode from Cataract Canyon to Carbonate Canyon, climbed up to Sinyala Mesa and proceeded in a northeasterly direction to Great Thumb Mesa. There they climbed out of the canyon for the return home.

Bert Lauzon wrote in his notes of the trip:

Jan. 18 (1938) Big Jim was head Councilman and Clark Jack was interpreter. When we explained that we were out to get facts on the little horse proposition the Indians [Havasupais] gladly gave us what information they could and then told us about three little sand rock horses that were in Pachadacobas pasture at this time.

[The smallest measured 48 inches at the shoulder, 53 inches girth, and 67 inches from ears to tail and they estimated the horse to be about 11 years old and close to 300 pounds].

Our Indian visitors explained thru their interpreter that these sand rock horses are descendants of horses that their great Grandfathers ranged in these canyons years and years ago.

The Indians told us that these horses range up the main Cataract Canyon for 30 miles, west on the sand rocks in Grand Canyon to Mohawk Canyon and East to the Big Thumb in Grand Canyon.

In Bert's report to the Park Service on January 28, 1938, he wrote,

It has been reported that under the Great Thumb in the section of the canyon where we now are, that horses 24 inches in height were ranging on the sand rocks but we saw nothing of that size except two last season colts.

The official report to the National Park, written by Naturalist McKee, states:

1. The size of the horses of this area has been greatly reduced in statements given out concerning the area.
2. The canyon blocked off by landslides in which pygmy horses are supposed to have evolved is a myth.
3. The small horses of the area are the normal results of the environment and are not confined to any one limited area or physical barriers.

This report did nothing to quell rumors, and in the 1940s, there were several more reports of the midget horses of the Grand Canyon.

Bert Lauzon's experience on the 1911 river trip with the Kolb brothers, combined with his knowledge of the Grand Canyon, made him a reliable source of information for early river runners.

Loren Lauzon recalled commercial river guide Norman Nevills coming to consult with his father regarding the Colorado River through the Grand Canyon. In his journal entry of July 19, 1938, Bert wrote:

Patrol. Female river scouts arrived at the Kaibab Bridge.

This no doubt referred to Elzada Clover and Lois Jotter, the first women to travel through the Grand Canyon, botanists on a trip led by Norman Nevills.

Lauzon was also on hand when Bert Loper, Don Harris and Chester Klevin hiked from the Rim on a break from their 1939 trip down the Colorado River.