When we imagine the Savanna grasslands, we think of them teeming with lions, leopards, kangaroos and gazelles, forming a perfect food chain pyramid. Turns out, things aren’t as hunky dory for the predators in the ecosystem, and this pattern is seen not only in terrestrial animals but also among aquatic creatures.
NEW STUDY CHANGES PERCEPTIONS ABOUT PREDATOR-PREY RATIO
The study, led by Ian Hatton at McGill University, Canada, examined other studies spanning decades on the terrestrial and aquatic ecosystems comprising mammals, invertebrate, plant and plankton communities. They looked at predator-prey dynamics, and also the productivity at each level of the food pyramid. It is logical to think of predator and prey populations as having linear relationships, i.e., when the prey population grows in an area, the predators’ should grow proportionally in response to the increased supply. But, this isn’t true, says the study, after careful analysis of data generated over 50 years.
COMMON POWER LAW DICTATES PREDATOR-PREY RELATIONSHIPS ACROSS ECOSYSTEM
The researchers found that predator populations do not catch up with an increase in their prey. Their numbers increase, but not at the same rate as the prey. This pattern was not only seen in the lions and the leopards of the African Savanna, but also in microbe-eating fish found in the ocean. The scientists were also able to express this relationship mathematically in the form of a power law equation. The equation is able to reliably predict the predator population when given information on the prey. What’s surprising is that the same mathematical function governs every ecosystem’s response to population fluctuations.
THE POWER LAW CAN PREDICT SEVERAL NATURAL PROCESSES
When predators are wiped from an ecosystem, initially the number of prey shows a surge, but over a period of time, the growth rate drops due to decline in reproduction. This reduction in growth rate surprisingly fits the power law equation. It can also define the relationship between the size and metabolism of animals: smaller animals like mice move faster, reproduce more, and have higher metabolism compared to heavier mammals like elephants.
WHAT DOES THIS MEAN FOR PREDATOR-PREY POPULATIONS?
It is still unclear what causes the development of such common patterns across such diverse ecosystems. What is clear is that there is a pattern. We can use it to monitor predator-prey populations to see if any major fluctuation in either could spell trouble for that ecosystem. We could also use this as a metric of how we manage ecosystems for food production, which could possibly have implications on climate change.
