Animal model answers questions about environment

Birds were dying on an island off the coast of Florida, and people didn’t know why. A group of conservationists wondered if the culprit might be a pesticide sprayed into the air to wipe out mosquitoes. The explanation quickly came from an unlikely source in Wisconsin.

For several years, Warren Porter, a professor of zoology at UW–Madison, has been working with faculty and staff across campus to develop a computer model that could predict how animals, living on a real landscape anywhere on Earth, would respond to specific changes in the environment. The model could answer questions, such as how warmer temperatures would alter the activity patterns of squirrels in southern California or how removing the forest canopy in Yellowstone National Park would affect the elk that took cover under it during winter.

“If we fail to answer questions like these, we will continue to lose species – and their genomes, the biological libraries that have accumulated information for billions of years – from this planet,” says Porter.

But many of the models that had been designed to address ecological concerns, he adds, were inadequate: They didn’t take into account the complexity of factors involved in the interaction between animals and their environment. To achieve a more sufficient model, Porter needed to integrate animal morphology, physiology and behavior with features of the climate, topography and vegetation of a particular area.

“Models are always an approximation to reality,” he explains. “You design them to ask specific questions. As the questions become more complex, the models become more complex. As computers have gained more power, we have been able to continue to add complexity and to solve very difficult problems.”

At the heart of Porter’s integrated model is an understanding of energy transfer between animals and their surroundings. For instance, the animal’s physical properties – body size, fur thickness, body temperature and breathing rate – help determine how much energy it needs to survive. The animal’s behavioral patterns, such as how often it reproduces or how active it is, also are important factors.

To apply this information in a real context, scientists must also determine how much energy is available based on environmental factors, including rainfall, temperature, vegetation, topography, sun exposure and time of day or year. The model, which incorporates remote satellite sensing and large-scale global climate models, can determine this.

Because Porter’s model integrates all this information on animal physiology and behavior and climate conditions in a predictive model, the scientist says, “it can help us understand what the critical processes are that affect life processes on earth and how specific changes in environmental conditions may modify or even terminate those life processes.”

The model, he adds, also could help scientists solve unanswered questions about what’s already happened. For example, the model could answer how the distribution of mosquitoes that potentially carry diseases harmful to humans and other species might change when the ground is wetter than usual, or how much more water livestock will need when the outside temperature is two degrees warmer.

With its specificity and complexity, the model could determine parameters crucial for determining a species’ potential for growth and reproduction, exposure to pesticides or pathogens, migration times and patterns, and possible sites ideal for conservation, says Porter. Based on the model, Porter says scientists could make recommendations on the most effective habitats for free-ranging animals, which could maximize productivity while minimizing environmental stresses.

Patented by the Wisconsin Alumni Research Foundation, Porter’s system for examining the effects of environment on animals already is answering important questions. For instance, Porter and his colleagues have used it to understand key factors that led early hominids to walk upright, instead of on all fours.

It also has helped the conservationists who contacted the Wisconsin zoologist about three years ago, shortly after the large number of birds started dying off the coast of Florida. Porter was able to use the integrated model to determine how much air the birds would have been breathing. Getting enough oxygen is critical for metabolic processes, which supply energy to the body.

Given the known levels of pesticides in the air before the birds died, Porter calculated daily pesticide inhalation. It was toxic over a short period of time, he says. The Wisconsin scientist forwarded this information to the American Bird Conservancy. A week later, he says, they presented his findings at an Environmental Protective Agency meeting in Florida.

“The next day,” Porter recalls, “the EPA announced that they were moving to ban spraying of that pesticide on the island.”

Porter notes that the integrated model, and the results it already has produced, would not have been possible without the unique, interdisciplinary nature of the UW–Madison campus. In the course of his career as a professor at the university, Porter has taken 33 courses in 14 academic departments – an activity, he says, that has enabled him to gain the expertise and collaborations needed to develop such a complex model.