29

Don’t Tread on Her

I felt a squishiness under my hiking boot, almost like I had stepped on a fresh cow patty, and then immediately heard the explosive rattling of an angry Black-Tailed Rattlesnake under my feet. I looked down at my left shin and could clearly see two puncture marks, little over an inch apart. As the annoyed large female Crotalus molossus back-circled twice and then crawled off rattling my first thought was Well, I’ve always wondered what this would feel like.

August 8, 2002 was the day my life and the life of that rattlesnake collided ever so briefly. I was a new assistant professor at Cornell University, and I was collecting in Skeleton Canyon, in the Peloncillo Mountains of southwestern New Mexico. My goal that day was to collect two species of lizards that were part of a study on genetic diversity across the southwestern sky islands, a series of beautiful mountain ranges that rise above the desert in that part of the world. I had worked that canyon a few times before, sometimes even hiking alone, carrying my lizard lasso, scanning the rock walls for lizards. That particular morning, fortunately, I was accompanied by my first doctoral student, Lauren Chan, and we were just hiking into the canyon when the snakebite happened.

I had been working in the sky islands of southern Arizona and New Mexico for a few years, and my husband Harry Greene and our colleague David Hardy, a Tucson anesthesiologist, had a long-term study on Black-Tailed Rattlesnakes in the neighboring Chiricahua Mountains, so I was familiar with these docile serpents. This species is so calm it is rarely involved in snakebite incidents. To be bitten by one you really have to be unlucky enough to step on it, and that was just not my lucky day. In retrospect I see how this happened. It was morning, and the sun had just crested over the canyon walls, creating dappled shadows on the yellow and brown oak leaf litter that lined the ground—a perfect match to the yellow and brown diamonds of blacktails. Perhaps she had been coiled there all night and was just warming up in the morning sun to start her day.

What happened next was a chaotic, yet coordinated, blur. Within seconds I felt an odd sensation in my joints and a distinct burning sensation at the site of the punctures, an indication that this had not been a dry bite. David Hardy, who was interested in rattlesnakes from both natural history and public health aspects, always emphasized the need for field biologists to have a snake bite protocol in place and, especially, to know the location of the nearest hospital that stocked antivenom. So, according to our plan, Lauren and I headed to the clinic in Douglas, Arizona, about an hour away. The pain in my leg was getting steadily worse, and it took all my mental energy to keep it at bay. The sensation was of burning, like I was being branded, but the iron tool never left my skin. I could feel the front of tissue-destructive venom creeping up my leg, and I imagined a band around my knee and willed the pain to stay below it. Of course, no willing in the world keeps venom from doing exactly what it evolved to do, which is to break down cells and spread through tissues. But my mental exercise helped me manage the pain and keep us as calm as possible, despite that adrenaline was rushing through our bodies. Lauren was flying down the highway to Douglas, driving over 90 miles an hour, and I remember looking over at her and seeing a bead of perspiration running down her forehead.

At the Douglas clinic I allowed myself to feel relieved, maybe everything was going to be okay. They immediately put me on morphine to manage the pain, and after convincing the doctor that I was sure I was bit by a rattlesnake (and yes, I am SURE it was not a coral snake), he started my first vials of antivenom, delivered intravenously. I was airlifted to a Tucson hospital in a helicopter that was mostly windows, with a nurse by my side. That flight over the desert flats, with the sky islands jutting up below me, while on morphine, was one of the most spectacular experiences I have ever had. The clinic had contacted Harry, and he and David Hardy would meet me at the hospital in Tucson. I was safe now.

Then began the roller coaster. Mine was not a simple envenomation, and several factors contributed to a serious condition that eventually required surgical intervention (Hardy and Zamudio 2006). Because this was a defensive bite, the fangs penetrated well into the muscle bundle on my shin and delivered venom deep within. I received antivenom treatment, which slowed tissue destruction, but the venom of blacktails is not included in the cocktail of venoms used to produce a polyvalent antivenom. In theory, this antivenom is effective for rattlesnake bites by all species but will differ in efficiency across species, especially if some have unique components to their venom. Another telltale sign that my envenomation was unusually deep is that I never developed the skin blebs and blisters that are typical of rattlesnake bites. By the time my antivenom course was completed, it was clear that the amount of tissue damage in my shin was extensive and, without surgical intervention, it would compromise the entire muscle bundle and possibly my lower leg. Three days after my bite I underwent an emergency fasciotomy to relieve the pressure in the anterior compartment of my lower leg caused by the large amount of necrotic tissue and inflammation.

Over the next two years I worked hard to regain my mobility. The surgeon who did the fasciotomy told me that I should expect to limp for the rest of my life. I thought to myself, You are just an MD, you might know about means, but you don’t really understand variance. My husband, who knows me best, has said that was the best prescription the doctor could have given me. Nothing like some spite for motivation! A month after my accident, back in Ithaca, I started the long process of building up the damaged shin muscle, the one that lifts your foot up toward your shin (the technical name of this muscle is tibialis anterior). Excessive damage to this muscle causes foot drop, such that your toes do not clear the ground and requires compensation by elevating the knee. I knew that to have a normal gait I needed to reach that magical neutral point, and making that mark became my obsession. I did everything I could to build up that muscle that had been so damaged by a big load of venom. Approximately a year into my recovery my progress began to slow because of the formation of scar tissue that was binding the tendons and muscles in my shin. One possible treatment is scar excision, a surgical procedure that removes the scar tissue that hinders movement. This procedure can potentially have diminishing returns because, of course, any surgical intervention also creates scar tissue. This time, with no emergency decisions being made, I did my homework, read about the procedure and its likelihood of success in my case, and interviewed multiple surgeons to gauge their experience before selecting a young doctor in New York City. That surgery increased the mobility in my toes and got me a few more degrees of upward foot movement, past the critical neutral point.

I improved enough to be able to walk with a normal gait and return to hiking, running, and other activities. I made it a goal to run a recovery marathon (because why not?), and with the help of many running friends I trained on the running trails in the state forests around Ithaca. I ran my first marathon in Mexico City with my good friend Gabriela Parra, just a few years after my accident. We then did some repeats the following years, in Chicago and Washington, DC. It took many years and uncountable hours of work, and each time I crossed a finish line I imagined that little muscle getting stronger and stronger. Now the 11-in fasciotomy scar on my shin has faded, and it is just a part of me. Most of the time I even forget it is there.

Fieldwork will always involve danger. Especially when working in remote places, any number of accidents can happen and turn a fun and productive scientific endeavor into a life-threatening situation. Venomous snakebite accidents, although very rare, are among those. I have always had a healthy respect for venomous snakes, but I never feared them. I have always told my students that if we take the right precautions we can reduce the probability of animal-induced accidents, and the largest threat to us in the field is likely to be interactions with other humans. To this day I believe that is true. I have been the most scared in the field when we happened upon humans, sometimes even armed, and did not yet know their intent. Being isolated, with no immediate escape, and with no one to turn to for help is especially difficult for women in the field. That feeling of vulnerability is no fun at all. In contrast, most of my encounters with venomous snakes in the field have included only the excitement of spotting them, admiring their beautiful patterns and scales, and marveling at how they make a living.

After my accident, I wondered whether my relationship with venomous snakes would change. Would I fear another encounter so much that I would not enjoy fieldwork anymore? Would I blame rattlesnakes for what I went through? Some things did change. The first couple years after the bite I was hyperaware of movement on the ground, even if just a hopping insect or blades of grass blowing in a breeze. My brain was hypervigilant. If twigs or stems brushed up against my lower legs I would start and immediately look down. It took a few years for these reactions to pass. I still dislike walking through high vegetation where I cannot see my feet, even when wearing snake chaps. But I adapted and have since had great field experiences in snaky places and many safe encounters with rattlesnakes, jararacas, and other pit vipers—back to our relationship of admiration and healthy respect.

I have thought often about that female blacktail in the last 20 years. Rattlesnakes are long-lived, and it is conceivable that she still lives in that same canyon, still wakes up every morning to the warmth of the early morning sun rays, just as she did that day. I wonder if she had litters every couple of years and how many times she unobtrusively watched hikers go by, undetected. I hope she did not get killed with a shovel or machete by someone after a rattle trophy. I hold no grudges and certainly do not blame her for protecting herself. We share something in common. If I were tread on that way, you can be sure I would have bitten too!