Category Archives: Insects

Insects of the Chihuahuan Desert region.

Monarch Conservation in West Texas

Monarchs roost in a pecan tree in Alpine, Texas

The sun is setting as I sit on the picnic table and just watch. Monarchs swirl around me by the hundreds—or is it thousands? They begin to settle, landing in rows on the bare branches of the old pecan tree near Kokernot Lodge in Alpine. They’re restless though, and burst into flight again when a newcomer tries to squeeze into the row. A swirl or two and they resettle on a clump of leaves. More butterflies float in from the north and jostle for space. I am amazed by the utter silence. A butterfly wing doesn’t even whisper.

Monarch Migration
Monarchs are one of the few insects that migrate in great round-trip journeys from their summer breeding grounds in the north, to sites in the south where they overwinter. In the spring, they head north again. The earliest report of monarchs migrating south was published in a Canadian journal in 1857. The author, W.S.M. D’Urban, noted that monarchs appeared in the Mississippi Valley “in such vast numbers as to darken the air by the clouds of them.” But it took another 120 years to discover where they were going.

In the late summer, as the nights grow cooler and the days grow shorter, a generation of monarchs emerges from their chrysalides that are biologically and behaviorally different from the generation before them. These monarchs won’t mate or lay eggs until the following spring. Their driving instincts are to find food and fly south.

They travel in pulses, often driven by cold fronts that bring the wind from the north, sometimes traveling 150 miles in a single day. Late in the afternoon, the butterflies seek a place to spend the night—in Texas, this is usually a pecan or oak tree near water. Although monarchs do not migrate in flocks as birds do, individual monarchs seem to seek each other out to form roosts of hundreds to thousands of butterflies. The next day, warmed by the morning sun, they will continue their journey south.

When the winds are unfavorable, monarchs stay on the ground, nectaring on goldenrods, gayfeather, and mistflowers. These nectaring stops allow the monarchs to build up fat reserves that will sustain them throughout the winter.

By late September, all of the monarchs from the 5.2-million-square-mile breeding grounds east of the Rocky Mountains funnel into Texas. Most years, the monarchs will travel through Texas along the central flyway, a broad swath of land 300 miles wide and centered on a line between Wichita Falls and Eagle Pass. They are headed for the fir forests of the Transverse Neovolcanic Belt near Mexico City, a place that none have been before, but that millions will find.

Monarch Conservation
D’Urban’s skies darkened by clouds of monarchs are pretty much gone. In fact, some predict that the great monarch migration may be a biological phenomenon that winks out in our lifetime. Illegal logging of forests in Mexico, changing climate in both the overwintering grounds and the summer breeding grounds, and the decrease in nectar and larval host plants are all taking their toll.

A world without monarchs scares people, so many organizations and agencies are jumping on the monarch conservation bandwagon. Yesterday, Texas Parks and Wildlife Department released the Texas Monarch and Native Pollinator Conservation Plan (October, 2015) or perhaps better titled The I-35 Monarch Conservation Plan. Don’t get me wrong. I’m proud of TPWD and the many partners listed in the report for recognizing the critical role that Texas plays in monarch conservation and for wanting to do something about it. But—ahem—that beautiful flyway map produced by Monarch Watch? It’s just an average. Monarchs scoff at sharp lines on human-drawn maps. This year, thousands are monarchs are passing through Fort Davis, Alpine, Marathon, and Terlingua on their way to Mexico. As they have in the past and they will in the future.

Fall Migration 2015

Journey North map of the 2015 Fall Monarch Migration

 

This particular pet peeve of mine is not new. About 10 years ago, I read an article about a monarch tagging project being conducted by the Southwest Monarch Study of Arizona. They were finding that many of their monarchs chose to overwinter in sunny California rather than Mexico. This got me thinking about the Trans-Pecos monarchs. Where were they going?

I eagerly contacted the Southwest Monarch Study and asked to be part of their tagging program. “You’re too far east,” they told me. “Contact Monarch Watch.” Monarch Watch told me to contact Texas Parks and Wildlife and Texas Parks and Wildlife told me we were too far west for our monarchs to be of any interest.

I gave up, but the monarchs haven’t. In fact, the frequency of the monarch migration through west Texas seems to be increasing. Don’t quote me on this. It’s just a hunch without any supporting data. But it is an interesting research question. How does the monarch migration fluctuate over time and what are the triggers that cause a shift of the central flyway? What does long-term climate research predict for our region? Will El Nino patterns increase in frequency, resulting in wetter Fall weather and increased nectar sources for monarchs?

Conservation plans need to be pro-active and prepare for a changing future. I know that it’s easiest to focus on what we see today and concentrate on urban areas because funding is often about numbers (how many school children can you reach per dollar spent?), but if you’re truly interested in monarch conservation, think broadly and include west Texas in your planning.

In the meantime….
As I climb off my soapbox (will someone please hold the ladder?), I have some suggestions:

1) Plant for fall migration. You’ll read a lot about the need to plant milkweeds for monarchs. Milkweeds are important, it’s true, but in the fall, monarchs need nectar sources. A 2006 study of lipids (energy storage molecules) in migratory monarch butterflies showed that once monarchs get to Texas, they pause to nectar and build up their lipid reserves before continuing on to their final destination in Mexico. These lipid reserves are critical to their survival over the winter. Texas wildflowers are critical to their survival over the winter.

2) Go to the Big Bend Chapter of the Native Plant Society of Texas Facebook page and post an image of plants that you’ve seen monarchs use for nectaring. Let’s develop a list specific to this area for homeowners, landowners, and government officials that can be used for everything from large-scale restoration projects to home gardens.

GoldeneyeGregg's MistflowerAnnual Goldeneye
Texas GayfeatherMilkweedThistle
Fall blooming flowers such as sunflowers, mistflower, Annual Goldeneye, Gayfeather, milkweeds, and thistles provide important nectar sources for migrating monarchs.

 

3) While we would all like to think that our backyard gardens are Making A Difference, here’s what the 2006 monarch study has to say: “The popularity of butterfly gardens and native plant landscaping may enhance pollinator populations locally, but will never be of sufficient magnitude to compensate for the losses of native nectar sources from rural habitats.” Damn.

This isn’t to say that you shouldn’t be planting your monarch café. Please do. But also think bigger. Did you know that there are over 4 million miles of roadsides in the United States? I don’t know how many in Texas, but I’ve driven over 1,000 of these miles within the last week, so I can tell you that there’s a bunch. Thousands of miles of roadsides fenced off from grazing animals and protected from development.

The Texas Department of Transportation is responsible for managing these roadsides. They even have a wonderful document titled Roadside Vegetation Management Manual: Guidelines for Levels of Vegetation Management. Take a look at it. It’s great.

Unfortunately, when I called TXDOT one year to register a complaint about the mowing of a huge stand of gayfeather in full bloom, I was told the guidelines are “suggestions, not policy.” I think Texans and Texas deserve better than that. Make yourself familiar with the guidelines and work with your local TXDOT office to let them know that you care.

3) Post observations to Journey North. The only way they’ll know about the monarchs of west Texas is if we tell them.

Also posted in Chihuahuan Desert, Plants

Puddle Parties: Just Hanging Out With The Guys

Puddle PartyI should know better.

In hot pursuit of a butterfly, I came around a bush and WHOOSH! I was immediately enveloped in bright yellow and pumpkin orange confetti. I’d stepped into the middle of a puddle party.

Puddle parties are social gatherings for butterflies. Dozens of butterflies—almost exclusively male and often young—will congregate in a single spot to sip from mud, a pile of excrement, the blood of fresh roadkill (I’ll spare you the visuals for that one), or even turtle tears (No, seriously. Check it out!).

The butterflies are searching for sodium, an ingredient that’s typically pretty scarce in a nectar-feeders diet, but critical for egg production.

The sodium-sipping males pass on their salty nuptial gift to the females during mating. Studies have shown that female butterflies that receive sodium from their male partner have larger eggs which produce more fit offspring.

But why is sodium-sipping a social event? Why not just go find your own puddle? Or bloody rodent. Or whatever?

Sleepy Oranges

As passing on sodium to your mate gives you a distinct evolutionary advantage, so does hanging out with the guys. There are benefits to participating in a puddle party.

Benefit 1: It’s easier to find the “good stuff” if you just follow the crowd. Male butterflies use visual cues to recognize brethren of the same (or similar) species. Once they see a gathering (a sure indication that someone’s found a good puddle) they’ll join in, swelling the ranks of the party.

Benefit 2: You’re less of a target. Puddle parties typically take place on the ground where the butterflies are more vulnerable to predators such as lizards. If you’re by yourself, you’re easy pickings. In a crowd though, there are a lot more eyes to watch for movement and you become “one of many” when your puddle party explodes into flight to avoid a predator (or an oblivious photographer).

Benefit 3: If a little advertising is good, then a whole lot of advertising is even better. Many butterflies have bright colors that warn “I don’t taste good, so save us both a lot of hassle, and don’t even try to eat me.” Gathered together in a puddle party, the message becomes a bit stronger: “WE DON’T TASTE GOOD, SO SAVE US BOTH A LOT OF HASSLE, AND DON’T EVEN TRY TO EAT US.” And if you try, we’re all going to fly away in a huge WHOOSH and you won’t be able to focus on a single one of us anyway. Ha!

Two-tailed swallowtails

IMG_5457

Not all butterfly species participate in puddle parties. In my experience the most social of the butterflies appear to be swallowtails, blues, and sulphurs. Blues and sulphurs have grand mixed-species parties with marine blues hanging out with Reakirt’s blues or Sleepy Oranges mixing freely with Cloudless Sulphurs.

But swallowtails seem to be more aloof. Two-tailed swallowtails, those yellow and black beauties that soar high overhead, prefer to gather with others of their own species. Pipevine swallowtails may not be quite as picky and have been known to crash another swallowtails party.

It’s easy to host a puddle party in your yard if you have a butterfly-friendly garden (see my story on Butterfly Gardening for more information on that subject!). Choose a bare patch of dirt or sand, pour some salty water over it, and wait for the party to begin. It helps if your puddle stays damp for awhile, so you might want to put the sand or dirt into a shallow dish (such as a terracotta plant saucer) and keep adding salty fluids as it dries out.

Butterflies are fascinating creatures that do a lot more than just flit from flower to flower. While we know a lot about butterfly taxonomy, there’s still much to learn about butterfly behavior. So grab your binoculars, settle in, and just watch. Who knows what you’ll discover!

 

Also posted in Chihuahuan Desert Tagged |

White on White

Sunset at White Sands National Monument

Imagine this.

You’re standing in the Tularosa Basin of New Mexico during the last ice age—let’s say about 30,000 years ago. A huge lake shimmers in the background. Herds of mammoth and camels squelch through the mud leaving long lines of tracks. Packs of saber-toothed cats and dire wolves follow, waiting for the opportunity to hunt.

The lake is not unusual for this time period, nor this geologic setting. The Tularosa Basin is completely enclosed, bound by mountains to the east, west, and south; and Chupadera Mesa to the north. Water that drains into the basin has nowhere to go, so—depending on the climate—it either accumulates or it evaporates.

During the last ice age, water accumulated. Temperatures were cooler, evaporation wasn’t as rapid, and there was simply more water. At least eight lakes dotted the basins of the northern Chihuahuan Desert in Arizona, Texas, and New Mexico.

But the giant lake of the Tularosa Basin (now known as Lake Otero) is different. Although the water sparkles and shimmers, it’s not “pure.” The mountains surrounding the basin are partially composed of gypsum deposits hundreds of feet thick. As rain or snowmelt flows across the surface, the water slowly but surely dissolves the minerals of the rocks, and carries them away in solution to eventually accumulate in the lake.

Now, jump forward about 20,000 years. The climate is changing. Temperatures are rising and there is less precipitation. The mammoths and camels no longer roam the lake shores. The dire wolves and saber tooth cats have disappeared. The lake is drying up.

As the free water evaporates, millions of tons of dissolved minerals become concentrated in less and less water. Knife-like crystals of selenite begin to grow in the supersaturated muds of the lake bed. Eventually, the water of the lake is gone and the crystals lie exposed. Battered by the wind, cracked during freeze/thaw cycles, broken as animals walk across them, tiny chips and flakes of gypsum from the crystals are ground down into pure white, sand.

The wind picks up the sand grains and bounces them across the landscape. They begin to accumulate around rocks, bushes, and anything stable enough to stop their movement. Sand dunes begin to form.

Take another giant step through time. Pay your admission and enter White Sands National Monument, an amazing system of gypsum sand dunes. These gypsum dunes are quite rare. They require a set of specific conditions to form: a source of gypsum, arid conditions (so the gypsum won’t just dissolve away), and the wind to pile everything up. The three largest gypsum dune systems in the world are in the Chihuahuan Desert (White Sands, Guadalupe Mountains National Park, and Cuatro Cienegas, Mexico).

Although the dunes seem barren, they’re actually teaming with life. But you need to be on your toes (or more likely, your knees) to see much. Many of the animals spend their days dug into cool burrows in the sand or tucked into the shade of a bush.

But the main reason that you may not see anything is because the animals have changed color to blend with their environment. Instead of the normal browns and tans of the desert, the animals of white sands are bleached blondes.

This color adaptation is exciting to researchers. After all, the dunes are only about 7,000 years old, so to find white versions of common animals shows speciation moving along at a fairly rapid clip.

The Bleached Earless Lizard (Holbrookia maculata ruthveni) shows the greatest adaptation to its environment of all the lizards at White Sands. On the dark, volcanic rock surrounding White Sands National Monument, the earless lizard is a dark brown. The populations at White Sands are nearly pure white.

Bleached Earless Lizard

A Bleached Earless Lizard blends into the white sand.

This adaptation was probably originally a matter of natural selection. A dark animal on white sand is an easy target for a predator. Since the Bleached Earless Lizard is active during the day and prefers open habitats, the darker lizards would have been removed from the environment, leaving lighter and lighter animals to breed.

Today, predators are probably still picking off darker lizards, but the lizards themselves have changed their way of looking for a suitable mate. Field and experimental studies have shown that White Sands males will display preferentially to the lighter White Sands females when given a choice, thus continuing the selection for lighter animals. Although the Bleached Earless Lizard is considered a subspecies of the general population of Holbrookia maculata, these behavioral changes may indicate that a new species is in the making.

Bleached Earless Lizard

Bleached Earless Lizard (Holbrookia maculata ruthveni)

While other reptiles and animals such as pocket mice and crickets all show adaptation to the white sand, perhaps the most astounding group (evolutionarily speaking) are the moths.

Not much was known about the moths of gypsum dunes until 2006 when lepidopterist Eric Metzler was invited to conduct a long-term study at White Sands National Monument. He established a three km-long transect that cut across the four habitat types within the dune field: open dunes with no vegetation, interdunal spaces, the edge of the dunes, and open habitat outside the dune field.

Using light traps, Metzler and his colleagues collected moths at 11 sample sites along the transect. What they found was astounding. Among the thousands of moths collected were 24 undescribed species in 7 families. As you would expect, many of the new moth species are white or very pale in color.

As Metzler’s study shows, there is still much to be learned in the gypsum dune fields of the Chihuahuan Desert. So the next time you visit White Sands National Monument or venture out into the gypsum dunes at Guadalupe Mountains National Park, take a moment to wander. Watch for movement and holes in the ground. Imagine the life under your feet and admire the resourcefulness of the plants and animals that live here. Perhaps you, too, will discover a new species.

Also posted in Animals, Chihuahuan Desert, Geology, Landscapes Tagged , , |