From Running Water to No Water: In Search of Desert Bats

A glimpse of aboveground running desert water in the Hoarusib River of northwestern Namibia (Photo by Theresa Laverty)

After three weeks of traveling through northwestern Namibia in search of water where I net for bats, I now have a much better appreciation for the term “desert oasis.”

Driving north on the heavily corrugated gravel road from Sesfontein to Puros last week, we passed through some extremely arid areas. Upon reaching Puros, however, we reached the beginning of a flowing section of the Hoarusib River—a stretch of water about 7.5 miles (12 km) in length—accompanied by the wealth of biodiversity you find around desert water.

The field team- Young Explorer Theresa Laverty and field assistant Archie Gawuseb- stop for a lunch break under an Ana tree while they search for water (Photo by Theresa Laverty)
The field team, Young Explorer Theresa Laverty and field assistant Archie Gawusab, stop for a lunch break under an Ana tree. (Photo by Theresa Laverty)

For three nights, field assistant Archie Gawusab and I netted along this stretch of ankle-deep water. We caught a diversity of vesper bats and molossids (bats with long, free-hanging tails), while thankfully avoiding the capture of a confused Hartmann’s mountain zebra just outside of Puros. Now that the moon is waning, the skies are finally getting darker, landing us more bats in the net.

A little vesper bat appears to smile just before releasing back into the night (Photo by Theresa Laverty)
A little vesper bat appears to smile just before we release it back into the night. (Photo by Theresa Laverty)

Given the permanence of water in this area, quite a few cattle wandered in and out of the riverbed canyon each day among the springbok, oryx, and elephants. It’s rare to find livestock so far down these rivers, but the flowing water and riparian vegetation supports them in a region that receives on average about three inches of rainfall per year.

Cattle make their way down the Hoarusib River to feed (Photo by Theresa Laverty)
Cattle make their way down the Hoarusib River to feed. (Photo by Theresa Laverty)

While working in the evenings, small flies and gnats filled the air and I am pretty sure I inhaled several pounds of bugs while processing bats next to the calmer portions of water in the river. It is worth mentioning that the flood lines in the dry riverbed downstream of this flowing water were well above my head, a reminder of the dramatic impact that flash floods can have. Luckily, we did not experience the Hoarusib River at its extreme.

Flood lines in the Hoarusib River above Theresa's head (Photo by Archie Gawusab)
Theresa points to the flood lines high above her head in the Hoarusib riverbed. (Photo by Archie Gawusab)

After those three nights, water was much harder to come by as we made our way back to the Hoanib River (the area where we began netting in late December). While searching around at an old spring up the Mudorib River, we spooked off a pride of lions from the shade and watched them cross the golden, grassy hillside. The water was gone, however, with just a few wet rocks at the bottom of holes the elephants must have dug as the site dried out.

After two days searching for water, I ended up just re-netting at some of the previous Hoanib River sites to check for any indications of change in bat species use or diversity over time, but even one of our first field sites had dried up forcing us to move about a quarter mile (300 meters) upstream instead.

Sunset at a spring in the Hoanib River of northwestern Namibia as we setup for an evening of mist netting for bats (Photo by Theresa Laverty)
Light from the sunset reflects off a spring in the Hoanib River as we set up for an evening of mist netting for bats. (Photo by Theresa Laverty)

We made it back to Sesfontein this morning (January 11, 2015) and will be re-netting at the spring in town tonight. With just one week left in the field, I recently completed our rough field schedule and I am preparing for the return to Windhoek.

It is difficult to believe I will be sitting in class in Montana again in just two weeks time. It is still too early to contemplate that notion, however, so best to get back to focusing on the matters at hand: the areas where people, their livestock, and big (and small) game all share the same water holes. It sure will be hard leaving the Kaokoveld.

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Meet the Author
My name is Theresa Laverty, and I am a PhD candidate in Colorado State University's Department of Fish, Wildlife, and Conservation Biology. I study the community ecology surrounding desert water sources in Namibia. More specifically, I examine how large mammalian herbivores, via their direct and indirect effects on vegetation and insect communities around rare, aboveground water bodies, could impact bat communities that prey on insects. My research takes place along the ephemeral desert rivers of the northwest, where elephants, giraffe, black rhinos, and many smaller herbivores live among the livestock of traditional pastoralists. I hope you enjoy reading my posts from the field!