Raise like rabbits
Rabbits are herbivorous animals of relatively small size, hunted by many carnivores and super-carnivores, therefore they are located just above the base of the food pyramid. To survive, they have developed different strategies, such as a body adapted to flee at high speed, a panoramic vision that allows them to monitor their surroundings, an excavating capacity to build underground galleries to take refuge, twilight activity, and an outstanding reproductive rate. They are fast growing animals, early sexual maturity, large litters and short breeding. Just unlike a whale, an elephant, or a human.
The 13th-century Italian mathematician Leonardo de Pisa, known by the nickname Fibonacci, introduced a method to estimate the number of pairs that a pair of rabbits could produce in a year. The result was the Fibonacci number series, in which each number is calculated as the sum of the previous two. Thus we have: 0,1,1,2,3,5,8,13,21… in one year 144 pairs of rabbits are obtained. It may not seem like much, but the second year the number rises to about 46,000, the third to almost 15 million, and the fourth to more than 4,800 million couples! Fortunately for ecosystems, rabbit mortality is very high and the actual reproductive figures are much lower.
The Fibonacci series has an interesting peculiarity, any number divided by the preceding one, always gives a value close to 1.61803, the golden ratio. In nature this series is found in the shell of the Nautilus, a marine mollusk related to octopus and squid, in the geometry of pineapples, in the arrangement of flower petals, or in the leaves of many plants. It also has applications in economics, computing, optics, botany… It is a series as fruitful as that of the rabbits from which it originated.
However, if conditions change, a virtue can become a problem. In the last centuries humans have extinguished or drastically reduced the number of predators, and in addition, we have introduced rabbits in places where there were none, as in Australia. As a result, European rabbit populations grew uncontrollably to become a pest in much of the world. Neither the fences, nor the traps, nor the shots, nor even the toxic gases managed to stop the advance of the rabbits. For this reason around 1950 some biological warfare initiatives were launched. It was used a myxomatosis virus, a mild disease in the South American rabbit, the original host, which instead killed more than 99% of European rabbits. Intentionally introduced to France and Australia, it killed millions of rabbits in a few years. In addition to regulating rabbit populations, this experiment allowed us to see how coevolution occurs between a pathogen and its host. Over the years, rabbit populations have developed resistance to the virus, and the virus, in turn, has attenuated virulence, thereby not killing its host and thus facilitating transmission.
Humans do not breed like rabbits, but we are starting to become a global pest. Pandemics are natural regulatory mechanisms to deal with population imbalances.