Superpowers for Survival in the Shrub-Steppe By: Sasha Wohlpart & Dr. Dan Beck
On a cool April morning, the sun peeks over the ridge casting an amber glow on a south-facing talus slope, warming the lichen-speckled rocks. It is a beckoning to the Northern Pacific rattlesnakes who have spent the winter entwined in their den, safe beneath the rubble of Columbia basalt. It is now time to bask, to stretch out, to expose the full length of their charcoal-chocolate and white-rimmed bodies to the sunshine for a dose of thermoregulation. It’s time to rev up the metabolism after months of torpor.
As ectotherms, snakes absorb body heat from their environment rather than having to produce their own metabolic heat from the food that they eat. And in the shrub-steppe this is a superpower. Shrub-steppe habitats, with limited water, hot summers, cold winters, and lots of wind, are challenging places for many plant species to thrive. Limited precipitation means that, despite plentiful sunshine, there is very limited plant primary productivity available to primary consumers, like insects, birds and mammals that feed on leaves, roots, stems, and seeds. This presents a particular challenge for a species like the pygmy rabbit who requires a steady consumption of food to maintain its mammalian metabolism. At just under a pound, an adult Pygmy rabbit weighs about as much as an adult Northern Pacific rattlesnake. Yet the rabbit requires nearly 20 times more calories, just for survival, as the rattlesnake!
Pygmy rabbits, like humans, are endotherms, regulating their body temperature using internally generated heat, which is metabolically expensive. It requires them to feed their system by grazing on a lot of big sagebrush, especially in winter, just to survive. On the other hand, because of its greatly-reduced metabolic rate, and because it spends the winter in a cold-induce state of suspended animation, the Northern Pacific rattlesnake, can eat as little as one rabbit-sized meal a year to meet its energy basic demands. How about that for efficiency!
After a few weeks of sunning themselves near the den, Northern Pacific rattlesnakes venture out to forage. They hide from predators like red-tailed hawks under shrubs and in rock crevices, emerging to follow scent trails left by unsuspecting voles or lizards. In this case, it’s not the nose that knows, but the tongue. Another superpower of snakes is their ability to detect even the slightest chemical cues by flicking their forked tongues into the air and on the ground surface. When they pull the tongue back into the mouth, those chemical signals are transferred from the two forks of the tongue into the “Jacobson’s organ” in the roof of the mouth. The Jacobson’s organ is lined with thousands of sensitive chemical receptors that give the snake details about what creature or habitat feature left the chemical signal. The two forks of the tongue deposit the chemicals separately within left and right sides of Jacobsen’s organ so that the snake also can tell from which direction the chemical signal originated, sort of like binocular vision of the tongue. In that way, snakes can follow chemical pathways to track prey, find a mate, detect a threat, or return to their overwintering dens.
When their prey is near, a rattlesnake will strike and inject venom, which serves not only to disable their prey, but to pre-digest it. Venom is a complicated combination of peptides, proteins, and other molecules. Although they can be deadly, many valuable drugs have been developed from snake venoms, including ACE inhibitor drugs used to treat high blood pressure and Batroxobin, a potent coagulant used to stem severe bleeding. Many other drugs developed from snake venom are used therapeutically for the treatment of blood clots, arthritis, cancer and other diseases. Humans benefit greatly from the wonders of nature! The bite of a Northern Pacific rattlesnake is very seldom deadly to humans and is readily treated with antivenin in a hospital. If you are bitten by a rattlesnake in the shrub-steppe (this happens VERY RARELY), you should go immediately to a hospital for treatment.
The dead prey can then be consumed whole by the snake. Yet, how is this possible for an animal with no appendages and a head often smaller than its prey? With a kinetic skull, of course! Snake skulls have many moving parts that are loosely connected, enabling them to move independently of one other—right, left, outer, inner. This allows the snake to open its mouth wide (a superpower I would have appreciated recently when served a portobello sandwich the size of my head!) and wiggle and walk its food into its gullet entirely with its jaw and neck muscles, like some sort of primitive transformer.
With its abundant sunshine, the shrub-steppe of eastern Washington is a haven for ectotherms. The vast majority of Washington’s 20 species of lizards and snakes occur in our region, east of the Cascades. Northern Pacific rattlesnakes have been very successful in our shrub-steppe and open forest habitats leading to robust, populations and wide distributions east of the Cascades in Washington. However, some of our other reptile species living in this habitat appear more vulnerable. The pigmy short-horned lizard, for example, who lives almost exclusively in the shrub-steppe and depends upon specific soil conditions for burrowing and reproduction, is listed as a species of concern due to the threat of habitat loss and degradation. They have superpowers too, though, which help with their survival. Their mottled earth-tone coloration, flattened bodies and spiny profiles make them hard to distinguish from the dry rocky substrate they roam. Even when darting from one sagebrush to the next, or lunging to nab an ant, these masters of camouflage can trick the eye with the flicker-fusion effect, blurring their contrasting skin pattern to confuse a potential predator on their where-abouts.
Every species that inhabits Washington’s native shrub-steppe has its own superpowers, most of which are yet to be discovered by humans. Ecosystem services, such as pollination, water conservation, and soil stabilization, arise from the complex and beautiful web of interactions among these native species (including plants, fungi, microorganisms, and animals), which enables all of us to thrive here. The more stable the strands of this intricate web of interactions, the more resilient will be our environment in times of stress, such as fire and drought. When one strand is weakened or lost, the web is altered in unpredictable, sometimes catastrophic, ways. It serves us to take good care of the relatively few shrub-steppe habitats that remain in our state. Not only do they harbor a host of superpowers and bring us valuable ecosystem services, but they also bring us incomparable beauty. That matters to all of us: people, plants, animals, ectotherms and endotherms alike.
Join us for the 25th annual Get Intimate with the Shrub-Steppe event May 10-12 where you will have the opportunity to learn about, and maybe even meet, incredible shrub-steppe species like the Northern Pacific rattlesnake and the pigmy short-horned lizard. Prepare to be amazed!
Register here for Get Intimate with the Shrub-Steppe https://www.ycic.org/giss
