Nature’s Food Chains - Carnivores
For creatures not on the top of their food chain, being alert for danger is a matter of life or death.
Animals that are successful in not being killed and eaten are allowed to breed and continue their species, provided they find enough food in their food chain to sustain them. Animals that are prey to others are also predators to the food groups below them in their chain. Each morsel that is ingested gives them energy to continue their life cycle. In a food chain an animal uses about ninety percent of the energy it receives to fuel its body or heat loss and passes on only ten percent to the next ‘user’, the next predator. Prey groups generally have significantly higher populations with typical numbers pyramiding to the top of the food chain.
Animals without enough predators will live on until they can’t find enough food to eat.
They then die of starvation rather than of old age. Predators tend to reproduce as a response to their food supply. If food is abundant, predators will raise large families to enjoy the bounty. When food is scarce predators limit their offspring. Prey numbers may sharply decline, but seldom are they entirely depleted in nature. The ideal in nature is balance between predator and prey. In practice, populations go through cycles of abundance and not react immediately to their food supply. In addition, disease, weather, and loss of habitat affect their numbers. Changes in local conditions may cause populations of a species to be decimated in one area while remaining healthy in another.
Quite often it is man’s interference with nature that upsets nature’s balance.
Since there are hundreds of food chains plus various predators may dine on the same prey, men tinkering with natures balance often have disastrous results. Mongoose was introduced to the big island of Hawaii in an effort to kill rats. It seemed like a good idea. Unfortunately the mongoose had no natural predator there and when their population began to explode, native ground nesting birds were next on the menu. Mongoose was perceived as a problem on Guam and snakes were introduced to kill them. The snakes did control the population, however when they ran out of food, they also began feeding on ground nesting birds. Over half of the ground nesting birds of both the big island of Hawaii and Guam has recently become extinct.
Salmon capable of spawning respond to pollutions of a stream, obstructions preventing passage, even changes in stream water temperature before they can successfully place their eggs. Our land use should seek to restore the habitat we negatively impact. Long term solutions must include habitat improvement for both salmon and prey plus use common sense in the harvesting of each. Simply raising and releasing more salmon will not solve their population problem as larger released numbers may decimate their food supply for the future. The entire food chain must be considered before release. Recently commercial squid fishing was allowed to open in Seattle’s Elliot Bay. Currently millions of dollars are spent to preserve endangered salmon. At the same time their food sources, including squid, smelt and herring are threatened by commercial harvesting. Trawlers that harvest and/or destroy kelp, the nursery to smelt and herring eggs, may be overlooked in their action, but habitat destruction caused by them will decimate the food chain for many years to come.
Through trial and error we have occasionally been able to give nature a boost.
Sterilized predator fish are selectively added to lakes to keep certain pan fish numbers in check. Without the ability to reproduce, the introduced predator eventually dies off and a new decision can be made on whether to reintroduce planned numbers of them, if the problem warrants it.
When we seek to restore nature’s balance it is important that development and land use not negatively affected habitat.
Equally important is that we understand Nature’s entire food chain to have our solutions do more good than harm.
