What Are The 10 Animals That Never Stop Growing in Size and Weight

If you have watched online videos showcasing incredibly large animals, you are likely witnessing a result of unknown growth. unknown growth is when an animal keeps growing throughout its life. A prime example of this is seen in trees, such as the giant redwoods or bristlecone pines in North America. These enormous trees continue to grow as long as they have enough space.

Apart from trees, there are various animals that exhibit indeterminate growth. Typically, reptiles, fish, and amphibians are common examples, but some mammals also fall into this category.

Below is a list of 10 animals that never stop growing in size or weight.


Goldfish, a smaller member of the carp family, can grow quite large if they have enough space. Most people who’ve had goldfish know that their growth is limited by their environment. In small aquariums, goldfish typically only reach 1 to 2 inches in length. However, in larger tanks or ponds, they can grow to be 15 to 19 inches long. Some goldfish can even live for more than 40 years, which allows them to reach their full growth potential.

Interestingly, goldfish can also change colors. When placed in a dark environment, they gradually shift from their usual orangish-red hue to gray or white. This transformation occurs because the pigments in their cells interact with light, affecting their coloration. In the absence of light, their skin changes gradually, resulting in a different appearance.

Green animals Anaconda

Many snake species fall into the category of animals that keep growing, although their growth rate significantly slows down after reaching maturity. For instance, anacondas, also known as water boas, have remarkable growth potential. Among them, the green anaconda stands out as the heaviest snake species and the second-longest, trailing only the reticulated python.

The largest recorded green anaconda measured 17.1 feet in length and weighed nearly 215 pounds. Occasionally, reports surface suggesting the existence of giant anacondas deep in the Amazon, with claimed lengths of 35 to 40 feet. While theoretically possible, these reports should be approached with caution and skepticism.

Kangaroo Animals

Among mammals, very few continue growing throughout their lives, and kangaroos are one of these exceptions. Red kangaroos, in particular, can attain impressive sizes if given the space. They hold the title of the largest marsupials globally, standing at heights of up to 6 feet and 7 inches and weighing over 200 pounds. Australians affectionately refer to them as “Big Reds” due to their immense stature.

It is remarkable that these creatures, which are born at just 1 inch in length, can grow into such tall and powerful animals. Unlike humans, their skeletons grow slowly over their lifetimes, raising the possibility that some kangaroos may exceed the size of even the largest recorded specimens.

King Crab

Crabs, much like lobsters, exhibit continuous growth throughout their lives. King crabs, in particular, can attain immense sizes as long as they remain undisturbed. With origins traced back to hermit crabs, there are now over 121 known species of king crabs. Among them, the red king crab stands out, boasting a carapace that can grow up to 11 inches long and a leg span of 5.9 feet. In terms of weight, these crabs can be quite hefty, with some reaching up to 28 pounds.

In their natural habitat, king crabs can live for up to 30 years, although many don’t reach this age due to threats from predators and the fishing industry. To achieve their full size, king crabs must periodically molt and develop a new, more spacious exoskeleton. Since they can continue growing as long as they have enough energy to molt, crabs possess the potential for indefinite growth.


Crocodiles come in various sizes, ranging from the moderately sized dwarf crocodile to the massive saltwater crocodile. The saltwater crocodile is the largest among them and also holds the title of the largest living reptile. These creatures can attain tremendous proportions. For instance, Lolong, the largest officially measured crocodile, reached a length of 20 feet and 3 inches, weighing a staggering 2,370 pounds. Currently, the world’s biggest crocodile, Cassius, measures 17 feet and 3 inches in length.

Crocodiles also boast remarkably long lifespans, which means they can continue growing for extended periods. Cassius, for instance, is estimated to be around 100 years old. With such lengthy lifespans, there’s ample opportunity for them to achieve impressive sizes.


Similar to anacondas, pythons are another group of animals that exhibit continuous growth throughout their lives. Among the many python species found in Asia, the Burmese python and the reticulated python are the largest. Burmese pythons are among the heaviest snakes, surpassing most other species in weight, while the reticulated python is typically considered the longest snake in the world by many scientists.

Medusa, officially recorded as the longest snake ever, measures an astounding 25 feet and 2 inches in length and weighs approximately 350 pounds. Reticulated pythons undergo periodic shedding of their skin, and with each molt, they can grow a bit larger. Despite their relatively shorter lifespans, averaging between 12 to 20 years, these pythons manage to achieve remarkable lengths during their relatively brief existence.


Megalodon, the largest shark species ever known, could reach an surprise length of up to 67 feet and weigh around 65,000 pounds at its heaviest. While today shark species are not quite as massive, they continue to captivate both scientists and the general public. Sharks display indeterminate growth, meaning they keep growing as long as their environment permits it.

The whale shark, the largest fish globally, can grow up to 40 feet long and weigh a staggering 60 tons. Although few of them survive to reach adulthood, those that do have the potential for exceptionally long lives, with some scientists estimating they can live up to 150 years.

Other famous shark species like the great white also exhibit continuous growth, not just in size but also in teeth. They continually grow new teeth and may produce over 20,000 teeth throughout their lifetimes.

Elephant Animals

Elephants are renowned for their intelligence, strength, and advanced social abilities. They also hold the title of the largest living land animals. Given their enormous size, it’s no surprise that they make our list of animals that experience continuous growth. While the concept of indeterminate growth in elephants is a subject of ongoing debate, evidence suggests that male elephants do not cease growing; rather, their growth rate decreases as they age.

With a lifespan of up to 70 years in the wild and even longer in captivity, elephants have ample time for growth. The largest recorded elephant, a male African elephant, weighed a staggering 24,000 pounds and stood at an impressive height of 13 feet at the shoulder.

Rougheye Rockfish

Also known as the blackthroat or blacktip rockfish, rougheye rockfish belong to the rockfish family. These spiny fish have exceptional longevity and continue growing throughout their lives until they pass away. Incredibly, some rougheye rockfish can live for up to 205 years. Because they don’t reach sexual maturity until they are 20 to 27 years old, it’s understandable that they spend a long time in the growth process.

Despite their lengthy lifespans, only a few of them survive to old age due to threats from predators and fishing activities. However, those that do make it can reach lengths of up to 38 inches and weigh as much as 40 pounds. The largest and oldest specimens are typically found in deeper waters, where they prefer to dwell near the seabed, often in caves and crevices.

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