HOW DO ECOLOGISTS SAMPLE HARMLESSLY?

by Whit Gibbons

September 2, 2002

Amid the clamor about protecting the world's wildlife, efforts by some ecologists to preserve animals go unnoticed by many. I am not referring to strategies employed by environmentalists but to those of researchers exploring biological mysteries while trying to preserve the research specimen. That is, how do you explore certain aspects of an animal's biology without killing the animal?

Killing animals for research was once considered routine and essential to answer certain questions. Numerous scientific publications refer to the dissection of hundreds of turtles to find out what they were eating or how many eggs they were going to lay. Thousands of mammals, birds, reptiles, and amphibians have been killed to determine how much fat they stored, what their reproductive condition was, or what kind of parasites they had.

Finding out the answers to such questions is not a trivial pursuit. Such information is essential to understanding the structure and organization of different species, as well as their role and importance in an ecosystem. But many species can no longer tolerate unlimited destruction. The dissection of a fifty-year-old alligator snapping turtle results in the removal of an important member of a habitat--one that has required half a century to produce. Ecologists now have a variety of techniques that produce answers while leaving the animal intact.

One approach is x-ray photography, a tool in human medicine for decades. Today, x-rays reveal phenomena about animals other than humans, particularly reptiles that lay eggs. This includes all crocodilians and turtles as well as most snakes and lizards. Knowing the reproductive characteristics of a species is essential to understanding its biology. X-ray photography enables ecologists to gather pertinent data about the number and size of eggs, and then return the animal unharmed to its original habitat. A more recent advancement is the use of ultrasound technology to count eggs or embryos in wild animals without harming them.

These nondestructive sampling methods are important to many ecological studies. The advantage in the study of rare or endangered species, when the loss of a single specimen is undesirable, is particularly clear. For example, research in New Zealand on the internationally endangered tuatara, which looks like a large lizard, relied on x-ray photography. Thus reproductive information was obtained, but none of the tuataras were dissected or harmed in any way. The findings were critical for understanding population growth patterns in these unusual animals that are on the verge of extinction.

The dietary habits of wild animals are also an important ecological characteristic for determining how each adapts to and affects its environment. Such information is necessary for proper wildlife management of some species or to understand the position of a species in the food web of a community. One approach used with some reptiles, mainly turtles, is the stomach pump. No ecologist would go so far as to say a turtle likes to have its latest meal flushed out of its stomach, but the approach beats the old-fashioned alternative--dissection. Dietary preferences have been determined for many individual turtles that continue to live happily in their native habitats.

Nondestructive sampling in research ecology is now common for many species of animals, particularly those that are rare, endangered, or that naturally live for many years. For example, few turtles of any species are killed for dissection by ecologists anywhere in the world today because of the advent of these techniques and others. The field of ecology, not to mention many species of animals themselves, has benefited greatly from the development and use of nondestructive sampling techniques.

However, this is not an indictment of researchers who have killed animals in the past or those who kill animals today under certain circumstances. Although research ecologists should proceed in the spirit of modern-day efforts to preserve natural populations, they sometimes have to dissect specimens or place them in permanent museum collections for future study. If such decisions are made judiciously, with an awareness of the impact on the total environment, destructive sampling can make useful contributions to science and society. Today's ecologists are getting better and better at making such decisions.



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