Why do some animals live much shorter lifespans than humans and others much longer? What determines the lifespan on an animal?
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Although not a hard rule lifespans are largely determined by metabolism. All mammals have roughly the same number of heartbeats and breaths in their lifetime. Short lived animals have a very high metabolism and larger animals tend to have a lower metabolism. Humans sort of mess up this calculation because we have a lot of medicine, pretty good diets, and other preventative measures that make us have a longer lifespan that would otherwise happen in the wild.
There are many factors, but typically the larger the animal, the longer the lifespan. And cold blooded will live longer than a similar sized warm blooded.
There are always exceptions though
For most animals, it mostly has to do with energy usage (aka metabolism). Generally, the higher an animal’s metabolism, the shorter it’s lifespan will be. Animals that spend a lot of time chilling out and not doing anything energy intensive (whales, turtles) live a very long life, whereas animals that are high energy (rats, flies) live a much shorter life. This also correlates to size because larger animals tend to have a slower metabolism. Metabolism causes a lot of wear and tear on cells, which eventually leads to death. There are a few other factors that scientists believe play a part and it is still a debated topic to this day
Interestingly, there is a general trend that larger species have longer lifespans, but within one species, the smaller the specimen, the longer the lifespan. There are, as always, exceptions.
The former half of this statement is about metabolic activity vs size–little critters are all hopped up on the gogo juice. The latter half–well, I’m not really sure.
You all have seen lots of examples of big species living longer than smaller species.
My favorite example of differently sized individuals within one species is dogs. Due to human intervention, there is an enormous amount of variation in dog sizes from about 1 pound adult weight all the way up to over 200 pounds. Among dogs, smaller breed dogs have average lifespans (with medical care) of well into their teens whereas giant breed dogs typically are considered elderly at 8 or 9 years of age.
Its not a straightforward question as every animal has a maximum possible lifespan determined primarily by its ability to regenerate cells, and this in turn in governed by telomeres, their length and the presence or not of telomerase (this is the genetics answer).
Other than that, maximum lifespan is limited by how the animal functions everyday and what factors might degrade its cells and/or cause new cells to be created in healing and replacement.
Factors that shorten life could include hormonal stress, food source, physical stress, toxins, or a whole lot of other factors. Basically anything that makes an animal perform above its resting state or directly attacks it; and buses… they really shorten life expectancy.
Edit. many wrong comments on this question. You cannot associate size with life expectancy, and while metabolism can play a part it is by no means definitive.
Everyone has mentioned the facts about metabolism and body size correctly but it’s important to note that median/average lifespan does not just refer to what age an animal will die from old age.
The statitistics also include death from other factors such as disease or predators. Hence expected Lifespan is also determined by an animals ability to fend of these predators or diseases. For example humans technically are apex predators hence we have much larger lifespans compared to our cousins the chimpanzees despite being “similar”, because we have developed ways to fight off predators. Conversely cheetahs are thought to be great hunters so you’d think they would have a large life expectancy, and yet it’s no more then 15 years, possible because they have a very week immune system, making them prone to contracting diseases
The lifespan of an animal is determined by many things, including how big the animal is, what kind of food it eats, how often it has babies, and whether it lives in a dangerous environment. Smaller animals usually live shorter lives than bigger animals because they have a higher metabolism and burn up their energy faster. Animals that eat lots of fresh food tend to live longer than animals that eat lots of processed food. Animals that have lots of babies tend to have shorter lifespans than animals that have fewer babies. And animals that live in dangerous environments tend to have shorter lifespans than animals that live in safer environments.
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