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What researchers don't know about the New Mexico ridgenose rattlesnake dwarfs what they do. Holycross and his crew are trying to bridge the information gap in several ways.
First, they want to find out how many ridgenose rattlesnakes live in the Animas Mountains. The species was discovered by ranchers in 1953 and listed as threatened by the U.S. Fish and Wildlife Service in 1978, but no one has a good handle on the total ridgenose population. Researchers are catching and releasing the ridgenose in one canyon of the Animas Mountains, hoping to estimate the number of snakes living throughout the entire range.
"These things are listed as threatened, and we don't know if they deserve it or not," Holycross says. Before Holycross' project began, only 30 ridgenose had been found in the wild. But that total has been increased by more than fourfold during the field study, and during the first 20 days of July, the researchers caught, tagged and released 18 ridgenose rattlesnakes, along with some 20 other snakes.
Holycross also wants to determine whether the ridgenose rattlers in the Animas Mountains are genetically distinct from groups of New Mexico ridgenose rattlesnakes that live in two nearby mountain ranges--the Peloncillos to the west and the San Luis, to the south in Mexico.
The answers to these questions could provide insights for captive breeding of the snakes, if that becomes necessary.
"We are very interested in learning about the natural history, life history, habitat requirements, population size, and the genetics of this little rattlesnake," Holycross says.
But to study the ridgenose, you have to find them, and that doesn't come easy. Holycross estimates it takes five man-days to find one snake. Hence his heavy reliance on volunteers to literally beat the bushes looking for snakes.
The researchers, however, have acquired some ridgenose lifestyle information that helps in the search.
Although rattlesnakes have a reputation as ruthless predators that kill everything in sight, the ridgenose rattler is a shy creature that would rather hide than fight a predator as large as a human. The adult ridgenose is about 24 inches long and approximately as thick in diameter as the width of a quarter. Its name is derived from a distinctive pattern of scales across the snout.
The ridgenose generally live in mountain elevations above 6,000 feet and seem to particularly like rock slides, called taluses, where they can slip away from danger by diving into cracks. But the ridgenose also inhabit patches of thorny locust shrubs, where no human willingly goes. Often, the ridgenose is found in the talus, but within ten feet of neighboring locust.
These rattlesnakes eat only about a half-dozen times a year, but when hunger does strike, the ridgenose doesn't track its prey across rough terrain. Instead, the snake simply positions itself along a pathway where prey is likely to pass. Then, it waits--for days, if necessary--coiled and ready to strike when opportunity arises.
Maturing ridgenose rattlers tend to prefer eating the spiny mountain lizard; they strike and hold, letting venom kill the lizards before swallowing them.
Older snakes appear to fancy rodents and, sometimes, birds. Rodent hunting requires a different style of attack. The ridgenose strikes in a split second, injects its venom, releases the prey and lets it wander off to die. After waiting a few minutes, the snake uses a chemosensory organ located in the roof of its mouth, and its flicking tongue, to track the last steps of its prey. Upon locating the dead prey, the snake swallows it whole, head first.
The reproductive habits of ridgenose snakes are not fully understood. Typically, the male snake initiates mating through a series of overtures that includes flicking its tongue and rubbing against the female. The female must be receptive to this courtship; the male cannot insert its reproductive organs (it has two) unless the female physically opens herself to the male. Females typically deliver between four and eight babies and stay with them for about a week or until the young first shed their skin. After that, the snakes take off for destinations unknown.
"We don't know what happens to the young," Holycross says, although he suspects they spend much of their early life underground or beneath rocks.
If there is a secret to finding the ridgenose rattlesnake, young or old, it is patience.
"They are where you find them, when you find them," says camp cook James Sifert, an easygoing, quick-witted fellow who is a veteran of remote field camps, having spent a summer north of the Arctic Circle studying the musk ox.
A 26-year-old Canadian from Saskatoon, Saskatchewan, Sifert has been on the mountain for 18 days and submitted gracefully to its dry embrace. His curly, reddish-blond hair is dusted with dirt. His legs are caked with black dirt and crisscrossed by scratches. Clad in baggy olive shorts, a faded green tee shirt highlighted with a mix of sweat and grime, and wearing heavy, leather boots, Sifert now splits his attention between the water boiling on the three-burner Coleman stove inside the army tent and some thorns embedded in his hands.
Sifert pours rice into boiling water while Holycross starts a wood fire in the cooking ring behind the tent. He tosses rapidly thawing steaks on the grill, sending up an aroma that is sure to attract other members of the crew, out searching for snakes, back to base camp. This will be a rare, hearty lunch.