Trans-Pecos Rat Snake (Bogertophis s. subocularis) Feeding on Bats in the Wild

A photo essay by Daryl Eby

The conditions were great as I left my house at Study Butte in southern Brewster County, Texas on the evening of July 26, 2008. The temperature was in the upper 80s, winds from the south, high humidity, no moon and overcast skies. It had rained over the past two days and there were still numerous puddles even though the ground had mostly dried out. Conditions looked great for observing and photographing herps as I drove along Hwy. 170 from Study Butte toward Lajitas and Presidio making several interesting herpetological finds along the way.

Crossing over a bridge on the River Road (Hwy. 170), I noticed what appeared to be a DOR Bogertophis s. subocularis. Disheartened at it being a DOR, I parked my car and headed back to the bridge in order to remove the tangled corpse from the roadway. My disappointment deepened when I realized that it was a blond phase. Then I shouted (to who I’ve no idea, my son was sound asleep in the back seat), “It’s not dead. It’s constricting a mouse!” I practically skipped as I ran back to the car to get my camera. I could not believe my insane luck…a blond phase Trans-Pecos Ratsnake feeding in the wild.

With camera in hand, I had to force myself to calm down and slowly approach the feeding snake without disturbing it. It either didn’t notice me or didn’t care. It was busy.

Look closely at the photo subocularis-01. That black spot to the left of the snake is actually a drain or vent hole in the bridge. Photo subocularis-03 shows a series of those holes across the width of the bridge. I have since noticed similar holes on several bridges.

After the snake stopped constricting and started to feed, I zoomed in for some closer shots. Looking at the view finder, I had yet another major surprise. The snake was eating a bat…not a mouse as I had first thought. See photos subocularis-04 and subocularis-05. Swallowing a bat cannot be that comfortable. See photos subocularis-06 through subocularis-08.

After finishing, the snake headed straight for one of those little vent holes in the bridge. See photo subocularis-09. It looked like I was about to get my final shots as it disappeared beneath the bridge.

Then I made yet another suprising observation. The snake wasn’t leaving. It was foraging. It crawled halfway in and started probing every nook and cranny in that hole. See photos subocularis-10 and subocularis-11 Unfortunately, it didn’t find any more. However, if you look closely at photos subocularis-04 through subocularis-08 of the snake swallowing the bat, you will notice a bulge already present. That bat was at least the snake’s second for the night. It emerged from its honey hole, looked around, and headed back in for another look. See photos subocularis-12 through subocularis-14.

As I continued to observe the snake foraging, I noticed a truck approaching in the traffic lane that the snake was occupying, so at this point I intervened and rescued the snake from the roadway effectively ending this night’s observations.

It has long been known from the examination of stomach contents that the natural diet of Bogertophis s. subocularis was made up of small rodents, birds, mice, bats, and lizards, but few observations of the species actually feeding in the wild have been reported on. Alan Tennant once observed a “fat and happy” suboc with a full belly sitting coiled on a rocky ledge just beneath a layer of young, flightless Mexican Free-tailed bats (Tadarida brasiliensis) (Tennant, 2006) (Dusty Rhoads, 2008).

Click the thumbnail to see a larger image.

On the evening of August 7, 2008 I returned to the same bridge on Hwy. 170 in order to attempt continue my observations of predation on the bat colony by Bogertophis s. subocularis.

Approaching the underside of the bridge, I nearly stepped on a three- foot Bogertophis s. subocularis. This snake was the normal color phase. It was actually crawling toward the portion of the bridge that had heaviest population of bats. I hoped the snake would continue on its path toward the underside of the bridge. I suspected it was heading there to forage for the occasional bats that I had seen land in the brush and shrubs at the bridge’s edge or perhaps to forage along the guano covered ground under the bridge.

Unfortunately (or perhaps fortunately), the snake decided to take refuge in a small borrow instead (likely in response to my presence). See photo subocularis-15

I thought I would just wait the snake out and hope that it would resume foraging. After waiting awhile, I developed a plan to intervene and increase the odds of the bats coming in range of the burrow entrance. From its concealed position just inside the opening of that burrow, it began feasting on bats. In total, the snake attempted to eat five bats. It subdued and ate the first, third and fourth with no trouble at all (other than some apparent difficulty swallowing their pointy wings). The second bat easily escaped from a poorly secured bite. The fifth bat that the snake attacked put up a frantic struggle and escaped after being firmly bitten and aggressively coiled in a failed attempt at constriction. See photos subocularis-16 through subocularis-26. The snake then showed no apparent interest in a sixth bat. I’m not sure if it had a full stomach, was disturbed by my presence, or was just leery after having a difficult time with the fifth bat.

Click the thumbnail to see a larger image.

All photos © 2008 by Daryl Eby