Wildlife Research: A Squirrelly Business
Date: Aug. 29, 1997
Editor: D'Lyn Ford (505) 646-6528, dlford@nmsu.edu
LAS CRUCES -- Patience, perseverance and a tasty mixture of hand-cracked pecans and old-fashioned oats are the ingredients for successful squirrel research.
Scientists recently perfected that recipe for studying how New Mexico's rock squirrels deal with snakes in the desert.
"These species have been together for thousands of years, so they have kind of co-evolved," said Pat Arrowood, an adjunct professor with New Mexico State University's fishery and wildlife sciences department.
For example, researchers think the rock squirrels are developing resistance to snake venom. At the same time, the snakes may be developing better venom all the time, Arrowood explained. "It's kind of an arms race between the two."
Human medicine could benefit. "If the antibodies the squirrels have to the venom can be isolated, then that might prove useful in helping protect humans against snake strikes," she said.
Arrowood and researchers from the University of California-Davis and Appalachian State University in North Carolina also are hoping that studying the rock squirrel will shed light on the California ground squirrel's plight.
"In California's central valley, the ground squirrels have trouble distinguishing non-poisonous snakes from poisonous snakes, because they've been isolated from encounters with poisonous snakes for about 10,000 years," Arrowood said. "The rock squirrels in New Mexico, which are the closest living relatives of the California ground squirrels, live in an environment that has many more snakes."
In Aug., the researchers picked two sites in the Las Cruces area to study the squirrel/snake interactions -- Aguirre Springs and a field on the west end of NMSU's campus. Before beginning the research, the scientists needed some study subjects.
"First, we had to catch all the squirrels that we could in an area," Arrowood said. The researchers sprinkled the pecan and oat mixture on the ground near the squirrels' burrows leading to cages that trapped the squirrels without harming them.
Then the researchers waited.
When the cages filled, the researchers anesthetized the squirrels to tag their ears and paint numbers on their fur with hair dye for identification. The researchers noted the squirrels' sex, weight and burrow location before releasing them back to their homes.
Once they had identified about 90 squirrels at the two sites, the scientists started the research trials. It rained. It hailed. They waited.
"In a trial, we select a particular squirrel to be observed for 20 minutes without a snake present, then we put a snake near the squirrel's burrow and videotape the reactions," Arrowood explained.
The snakes were fitted with saddles and then tethered near the burrows. Researchers could easily step in if necessary to make sure that the squirrels and snakes did not hurt each other.
"Some of the squirrels were very cautious at first, but in a matter of seconds they overcame that and just proceeded directly to the snake," Arrowood said. "They did a lot of tail flagging -- moving the tail back and forth with their hair all spread out. Sometimes they vocalized. These reactions may warn other squirrels and/or direct the snake's attention to them and away from a burrow full of pups."
Sometimes the squirrels actually bit the snakes, and the snakes were not timid about striking the squirrels. "But the squirrels at the campus site seemed to recognize that the snake bites are not lethal," she said. "The squirrels leapt back when they were struck, but they immediately came back at the snake."
Next, the researchers will review the videotapes. They'll look for differences in behavior depending on the squirrel's sex, age, location and whether or not the snake used was poisonous. "They'll spend the rest of the year analyzing the tapes and making a chart of the different behaviors and all the reactions," Arrowood said. "They may go through a videotape 10 or 15 times. That'll keep them plenty busy."