Padre Island has long been a favorite destination for my parents, and throughout my childhood I’ve been fortunate to keep returning to this remarkable ecosystem. The island is one of the seven Texas Barrier Islands, stretching 113 miles long but less than 2 miles wide. The Barrier Islands separate the Laguna Madre from the Gulf of Mexico and play an important role in protecting the mainland from storm surges and high velocity winds. Padre island’s formation dates only three to four thousand years ago as an early rising shoal. Cyclical submergence, sediment accretion, and erosion continue to shape the island, and wind currents seasonally transform the landscape through migrating dunes. Wind-protected depressions allow for the persistence of marshes, tidal flats produce crucial nesting habitat for birds, and near the island’s center are the grassland plains, where I’ve seen coyotes and caracaras take cover. The ephemeral nature of these habitats is harsh for flora and fauna survival, yet many are somehow able to brave the elements.
Areas near the shoreline permit only salt-tolerant plants, including sea purslane (Sesuvium portulacastrum), railroad vines (Ipomoea pes-caprae) and sea oats (Uniola paniculata). Many reptiles move throughout these sparsely vegetated zones, foraging and basking along both windward and leeward slopes. Across Padre Island, one of the most abundant species is the slender glass lizard (Ophisaurus attenuatus). These legless lizards are skilled at navigating the dunes, and on foot it’s nearly impossible to observe one for a long time. Blurs of their vertical stripes seem like hallucinations under the hot sun, and the waves and wind make them difficult to detect by sound. Many years ago as I walked through the dunes I found a skeletonized juvenile (pictured above) that probably perished from desiccation and was later unearthed by the changing terrain. Last year, I was excited to finally encounter them during the quieter dusk hours. After many tongue flicks, yet again they would slip under the grasses back to their underground worlds.
Glass lizards are so named from their defense mechanism of dropping the tail when caught by a predator, such as a fox, raccoon, or hawk. Astonishingly, the tail makes up over 60% of their entire body length. Depending on where the tail breaks off, the tissue loss is a massive energetic cost, but it grants them to live another day. Of the various glass lizards I’ve seen from Texas to Florida, they have never dropped the tail when handled. Rather, they repeatedly rolled sideways with the mouth closed in an attempt to escape. To the touch, their scales run smooth from any angle, perfectly suited to burrowing and shifting within the soft sand substrate. Like many fossorial reptiles, Ophisaurus takes advantage of existing burrows made by small rodents, and in this coastal environment, those of crabs. In the summer months, females select shallow depressions under vegetation cover to lay around a dozen eggs. Glass lizards have elaborate parental care behaviors as far as lizards are concerned. They surround their egg clutches, raising the incubation temperature by 1°C and consume unhealthy eggs to limit bacterial and fungal growth. Similar behaviors have been reported in close relatives, even mothers aiding their offspring in breaking the amniotic sac(!), implying some of these behaviors may be ancestral to the family Anguidae.
