When the Rains Come…

The video of a rain storm at Hueco Tanks will give you an opportunity to experience a rain storm in the desert. without getting wet and without having to wade out of the area through six inches of water…

The rain started while we were in the cave with the Upside Down Tlaloc.  We moved to this location after water started rushing down into the cave on both sides of where we were standing.  On a dry day one can look at the rocks and see the wide black lines where the waterfalls are during the rains.  The waterfalls dry up almost as soon as the rains stop, although there are some areas in the park where one can see water seeping down the rocks for several days.

The rainy season here is July through September.  Our total annual rainfall is eight to ten inches per year.  That is very little, but it is amazing to see the number and variety of plants and animals that thrive in this environment.  For example, remember that mud-covered toad we showed on the Fauna page?  There are actually two species of these amphibians in the park.  We have seen the pollywogs in the water, and in August of 2014, on one hike, the young toads were everywhere; it was difficult to walk without stepping on one.  The toads survive the dryness by burrowing underground, emerging only when there is enough water that they can reproduce.   Here is a photo of the other species of toad, Couch’s Spadefoot, and one of a young Red-Spotted Toad.

There are also multiple species of animals that live in the huecos and the ponds.  Possibly the most numerous are the mosquito larvae.  The most unusual or unexpected was the leeches we saw in the pond behind the Mescalero Dam in the summer of 2013.  That summer had a lot of rain, so many of the huecos retained their water for a long time.  The result of that was that at least one of the three species of freshwater shrimp that live in the park, the Tadpole Shrimp, got very large.  It was clear from looking at one of the huecos on the top of North Mountain that these shrimp had grown big enough that they had to molt, because we saw a lot of their ‘shells’ floating or on the edges of the huecos.  Even though the huecos on the top of the mountain are exposed, many are deep enough that they retain water for a long time.  One of the amazing things about the huecos is that whether the water is clear or muddy, the life in them is teeming and very active.  And even when the water level is down to one half inch or less, the creatures in them behave as if there was far more water than there is.  In other words, they don’t need a lot of water to thrive.   The other two types of shrimp that can be found in the huecos are the Clam Shrimp and the Fairy Shrimp (which are difficult to photograph well).

Normally, the life cycle of the shrimp is about two weeks.  That is long enough for the eggs to hatch, the shrimp to mature, mate and lay eggs, before the waters dry up and they die.  The presence of shrimp eggs and possibly other eggs, is why one should never walk in a hueco with a sandy bottom.  The eggs stay in the sand in a dormant state until the next significant amount of rain.

When there is significant rain in the park, there are several places that become lakes.  Laguna Prieta, on the west side of North Mountain often has water, and sometimes floods a larger area.  The area on either side of the Mescalero Dam similarly frequently has water, especially on the side toward Comanche Cave.  The vegetation growing on both sides of the dam, such as Seepwillows, Goodings Willow, and Scouring rush, indicate that these areas are prone to flooding.  A similar area that becomes a huge lake is in the area between East Mountain and the East Spur.

In the summer of 2013, for the first time in at least 20 years, the area behind the Interpretive Center became a huge lake, with enough water that it extended under the bridge by the Cottonwood trees and covered a large area on the other side.  This was the result of three inches or so of rain in the space of one week.  That lake lasted at least until January, and possibly longer.  There were a number of migratory water birds that really enjoyed having the lake there.  The lake returned again in 2014, after we  got 3.5 inches of rain in one day.  The lake is not as big, and is receding much faster this year.

Something we often fail to consider is how the various animals in the park get their water.  Water is often not easily accessible, so the animals have to be creative about how they get it.  One obvious sign of animals seeking water is prickly pears that have been eaten.  The Javelina as well as pack rats and possibly others will eat the cactus pads to get water.

Another water source, not so often seen, is that insects can get water from animal scat, even when it appears dry.  This photo shows a large number of Marine Blue butterflies on Javelina scat when the scat is fresh.  A couple of days later, the scat was looking very dry, but there were still butterflies on it looking for moisture.  

© Susan L. Stone 2015                   rovingstones@me.com