Determining animal life spans has always been dicey

  •  Thursday, February 8th, 2024  Animalsforkids

    How long do different animals live? Man has been continually trying to answer this question for ages, but until recently majority of the life-span information emanated from keeping age records on captive animals. While these records disclosed how long animals could live, the info was misleading.

    Captive animals remain secured from fire, drought, flood, and predators; they are nourished regularly; and if injured or diseased, they receive medical attention. This care makes them live long, healthy lives. However, wild animals lack these advantages. They live only as long as they find food and are able to defend themselves.

    Determining the age of wild animals is very tough, but research is providing some of the answers. Fisheries biologists have learned how to read the growth rings formed in the scales, ear bones (otoliths), fin spines, and vertebrae of fish to determine age. Some turtles form annual growth lines on their shells. In the box turtle, these lines are considered trustworthy for the first five years and quite accurate for the next ten. But after the turtle attains fifteen years of age, the lines cease to be of any value in telling age.

    It is possible for biologists to determine the age of some mammals through the study of their teeth. The number and type of teeth are indicative of age in sheep and goats, but jaw teeth wear reveals a deer’s age. As the deer gets older, some portions of its teeth are worn away due to use. By probing the amount of wear, the age of the deer can be fixed. This method is quite accurate up to 8½ years, but once the deer grows older than that, the teeth wear is of no help.

    The whale possesses a waxlike plug in its external ear. This earplug gets lengthier with age, and scientists are of the opinion that a set of its alternating light and dark layers signifies one year of growth. If this is in fact true, whales have been assigned with much longer life spans than they in reality have. Zoologists once upon a time believed whales lived 150-200 years, but the waxlike earplugs from 100s of whales caught in the Antarctic fishing grounds demonstrate that none of the whales was older than 60 years.

    Ornithologists (zoologists who study birds) have been able to age some wild birds through banding efforts. A banded osprey found dead on June 1, 1935 was banded as a nestling on June 19, 1914. That means it lived almost for 21 years in the wild. A European black-headed gull and a Caspian tern were found twenty-four years and ten months and twenty-six years respectively, post receiving their bands.

    Animal size is not a good indicator of life span. Smaller breeds of dogs have longer life spans than larger ones; wild lion’s age compares with a domestic cat’s; and a Shetland pony can live longer than a regular horse. Nevertheless, larger animals, as a rule, do live longer in the wild compared to smaller ones. Among mammals, elephant’s life span is believed to be longest. Among birds, golden eagle tops the list.