Why Do Animals Live Such Short Lives?
Humans have been trying to answer this question for years, but until recently, most of the lifespan information came from keeping records of captive animals. While these records show how long animals can live, the information can be misleading. Captive animals are protected from drought, floods, fires, and predators; they are fed regularly and receive medical attention if injured or diseased. This care helps them live long and healthy lives. However, wild animals do not have these advantages. They live only as long as they can defend themselves and find food. For information on this and to ask questions you are curious about, you can look at the relevant online companies on internet pages and examine them in detail from here.
Average Lifespan in the Wild
It is very difficult to determine the age of wild animals, but research is finding answers to some questions. Fisheries biologists have learned to read the growth rings formed in scales, fin spines, ear bones (otoliths), and vertebrae to determine age. During periods of rapid growth, the rings are far apart, but during winter months when growth slows, the rings are close together. By counting the areas of concentrated rings, a biologist can tell how many winters have passed. This aging method is more accurate in the North, where seasonal temperatures are extreme, but it is not entirely accurate, as conditions other than winter occasionally slow growth. Some turtles also form annual growth lines on their shells. In the case of the box turtle, these lines are considered reliable for the first five years and quite accurate for the next ten. However, once the turtle reaches fifteen years of age, the lines no longer have any value in telling its age.
Age Determination in Mammals and Average Lifespan of Insects
Biologists can determine the ages of some mammals by examining their teeth. In sheep and goats, the number and type of teeth indicate age, but the wear on the jaw teeth indicates the age of a deer. As deer age, certain parts of their teeth wear down from use. By examining the amount of wear, the deer's age can be determined. This method is quite accurate up to about eight and a half years, but by the time the deer reaches this point, the teeth become too smooth to be of any help. As the teeth wear down, the deer cannot feed properly. As a result, very few deer live more than ten years in the wild. It is believed that the males of some species of bighorn sheep show their age according to growth segments on their horns; however, the segments remain the same after twelve or fourteen years, so older males cannot be accurately aged. Whales have a waxy plug in their external ear. This ear plug grows with age, and scientists believe that its alternating light and dark layers represent a series of annual growths. If this is true, whales are believed to have much longer lives than they actually do. Zoologists once believed that whales lived for 150-200 years, but wax-like ear plugs from hundreds of whales hunted in Antarctica show that none of the whales are older than 60 years. It would be almost impossible to try to track a wild bird to see how long it actually lived; however, ornithologists have been able to age some wild birds from information gained through banding efforts. On June 1, 1935, a banded fish eagle was found dead. According to the band record, they discovered that this fish eagle, which had been banded as a chick on June 19, 1914, had survived in the wild for almost 21 years. A European black-headed gull was recaptured twenty-four years and ten months after being ringed, and a Caspian tern was collected twenty-six years after it received its ring. Records like these give an idea of lifespan potential, but very few small birds reach old age in the wild, as predators and accidents often shorten their lives. Animal size does not necessarily indicate lifespan. The age of a wild lion is comparable to that of a domestic cat; larger dog breeds have shorter lifespans than smaller ones, and a Shetland pony may live longer than a normal horse. As a rule, however, larger animals live longer in the wild than smaller ones. One reason for this is that smaller creatures face more dangers. Rising waters from a heavy rain can drown a small creature or destroy its home and food source, but may only cause a larger animal to get wet or be inconvenienced. Predators also prey on smaller animals such as rabbits, mice, birds, and insects. So you can see that there is a certain amount of safety that comes with size. Smaller animals may also live at a faster body rate than larger ones. This means they may breathe faster, have faster heart rates, and eat more food relative to body size to produce the energy needed for this faster pace. As a result, the body of a smaller animal wears out faster, like an engine that is constantly run at high speed.
Most insects live less than a year. Many cannot withstand cold weather outside of the egg stage, so they live out their entire life cycle between spring and fall. Some insects, like the mayfly, live as adults for only a few hours because they do not and cannot eat. Their entire existence is devoted to finding a mate and reproducing. The adult mayfly accomplishes this task in a maximum of eighteen hours. Despite their short lives as adults, these insects may spend one to two years in the larval or nymph stage before maturing into adults. Cicadas, which live for three to six weeks as adults, spend two to seventeen years as nymphs. The activity of a creature can also determine its lifespan. A queen bee, who spends her time laying eggs in the hive, can live up to five years. Worker bees, on the other hand, do not live longer than six to twelve weeks. During this time, they collect pollen and produce honey. For both workers and queens in an ant colony, long lives are the norm. Queen ants live fifteen to twenty years, and workers can live as long as ten years. However, the queen termite surpasses them all, living fifty years or more. Centipedes and scorpions live for five to six years.
