When it comes to nature, I take after my mom. While my dad thinks an unruly shrub needs a good pruning, my mom happily lets sweet-pea plants sprawl across the yard. She’s the one who saves worms on the sidewalk and tries to make necklaces out of fox vertebrae. She’s no hippie. Like me, she’s just fascinated with nature and science.
So it wasn’t surprising to me that she brought up the idea of tagging the blue-belly lizards that live in our yard.
One summer day, we caught one. We put him in a pickle jar and thought about how to tag him. My mom had the epiphany: green paint. That way we could pick out our lizard from his friends, but he could still camouflage in the flowerbeds.
For a couple years after that, we’d look out the kitchen window and say, “There’s ole Green-Tail.”
Turns out we were doing just what the real scientists do.
Wildlife biologists want to track animals without compromising the animals’ behavior or survival. Scientists use colored bands, radio trackers, fur dyes, even under-the-skin scanning tags to identify individuals in a population.
But sometimes the process fails.
In the January issue of the journal Nature, a team of French researchers reported that flipper-band ID tags threaten the survival and reproduction of king penguins. They found that flipper-bands can damage flippers and reduce swimming speed. Banded, slow-swimming birds spent more time looking for food, so they missed out on breeding.
This is a major problem – not just for hungry, cock-blocked penguins but also for researchers. If a tracking method changes an animal’s behavior, then the study results are useless. The situation is man-made, unnatural.
How can biologists keep this from happening?
Dirk van Vuren, professor of wildlife, fish and conservation biology at UC Davis, has spent a lot of time thinking about that question. Van Vuren studies mammals like marmots, skunks and bison. He said traditional methods like ear tags and radio collars are usually trustworthy.
“Most of these have been employed for decades,” said van Vuren.
A popular method is the passive inducible transponder (PIT) tag. A PIT tag is inserted under the skin of an animal. If the animal is caught again, the researchers use a scanner to read its unique identity. Van Vuren said that this technique causes minimal damage, and the animals heal quickly.
Tagging isn’t just for the wilderness. Here in Davis, there’s an invasive population of Eastern fox squirrels (see The Quad). Many of these squirrels were subjects in an experiment to test a new kind of animal birth control. The test-squirrels were marked with silver ear tags and black fur dye. You can still see these punk squirrels on campus.
The most risky tagging method is radio telemetry. The radio transmitters that broadcast the farthest and longest are also very heavy. Animals like moose can wear heavy devices, but smaller animals get weighed down.
The penguin failure brought the problems of tagging to my attention, but biologists wrestle with the issue all the time. One solution is for scientists to monitor each other. Van Vuren said researchers must include their tracking or tagging methods in their papers. Fellow scientists review scientific papers, and if the scientific community doesn’t approve, the research isn’t valid.
But not even van Vuren’s tagging techniques are foolproof; nature has ways of fighting back. Once, he was using cage traps to catch dusky-footed woodrats when a coyote grabbed an unattended trap. The coyote scampered off with its new doggy-bag.
“We finally found the trap 300 feet away with the woodrat in it,” van Vuren said.
Maybe the coyote was doing research of its own: how to bewilder humans.
MADELINE McCURRY-SCHMIDT would love your story ideas. E-mail her at firstname.lastname@example.org.