Blatant World. Bowhead Whales swimming in the Arctic Ocean, Taken Dec 1, 2009. From Flickr.com.
Staying young impossibly long
There are animals that stay young much longer than we would ever expect (1, 2, 3, 4, 5). It is not only that they live longer than their cousins: they stay fertile and maintain a youthful body for most of their lives. They have incredible longevity.
Imagine that we didn't have menopause. Imagine that we didn't have to suffer through our senior years. Imagine that we can live until 100 or even longer maintaining the body of a 30 year old. And then, only in the last 2 years of life that we experience aging.
That's what Brandt's bats and Bowhead whales do.
Brandt Bats: living more than 4 decades
Bats are fascinating creatures. They are the only mammals that fly; they use echolocation for tracking and catching food. They are exceptional pollinators. In fact, some fruits are dependent on bats for pollination, like bananas and and mangoes. Those fruits - and others - would disappear without bats.
The insect-eating Brandt's bat is about 0.25 oz or 1.5 teaspoons in size. Some of those very long-lived Brandt’s myotis bats roost in caves in Siberia. In 2005, a bat was captured for examination; it had a numbered band that had been placed on it in 1964. That bat was at least 41 years old (6). The "old" bat was checked out and released back into its cave.
zdenek_macat. Brandt's bat (Myotis brandtii). Shutterstock ID 2039508098.
Brandt Bats: Incredible longevity for a mammal with its size
Here's what is fascinating. Bats (and naked mole rats) are the longest-lived mammals relative to their body size (7). Humans are also relatively long-lived mammals based on their size. As a general rule, the larger an organism is, the longer it lives (8 - 9). The graphic below shows the relationship of age (x-axis/based as log-years) and weight (y-axis/based as log-kg).
Hijab, J. (2022). Lifespan versus body mass: Notice how small mammals group to the bottom (low weight) right (longevity). Bats are the most bottom/most rightward.
Hijab, J. (2022). Lifespan versus body mass: weight (log) is on the Y-axis and age (log) is on the X-axis. A whale is is shown as 105 or 100,000 kg and an age of 102 (or ~200 years).
Some of this is necessary, given the logistics of size and lifespan. When you achieve a large size, it means that you have had to have the time to get to that size. This means that smaller creatures live shorter lives, as we see with mice and rats. However, there are only 19 species of mammals that are longer-lived than humans when you correct for their body size. Eighteen of those species are bats (7)!
Brandt Bats and Bowhead whales demonstrate cancer resistance
Brandt's bats - like the naked mole rat - keep their non-aging phenotype for most of their adult years and are incredibly cancer resistant (7, 10, 11, 12). One curious finding for the diminutive Brandt's bat is a mutation in the Growth Hormone receptor. This may be the clue that allows the bats to remain small, increase longevity, and decrease their incidence of cancer (10). Growth hormone insensitivity (through growth home receptor mutations) has been strongly associated with increased resistance to cancer and diabetes in humans and mice (13).
Bats have also been found to have multiple genes that are unusually active in DNA repair and maintenance activities (7).
Bowhead whales clearly demonstrate the relationship of body size and longevity. Bowhead whales can be more the 54,000 kg in weight and live more than 200 years (8). Some whales have reached 100,000 kg in weight.
Bowhead whales follow the lead on our long-lived bats and naked mole rats. They stay fertile well into adulthood and maintain resistance to disease as they age as well as a resistance to developing cancer (11, 12, 14, 15).
What other creatures demonstrate longevity?
Interestingly, most of the creatures that enjoy extreme longevity (living hundreds of years) live in the water. Clams, bowhead whales, Greenland sharks, sea urchins easily live 200 or more years. The only land-based creatures that have lived more than 200 years are the Giant Tortoises.
In conclusion, aging is not a foregone conclusion for all animals. Clearly, there are many animals that defy the odds. And this does not even scratch the surface on animals that live centuries or are thought to be immortal (particularly invertebrates like quahog clams, sea urchins, hydra, and sponges).
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