10 Animals That Never Stop Growing: A Look at Indeterminate Growth

If you’ve seen videos on the Internet advertising footage of insanely large animal specimens, then what you’re seeing is likely an example of indeterminate growth left to its own devices. Indeterminate growth refers to the function wherein an animal continues to grow throughout its lifetime. The most obvious examples of indeterminate growers are trees, particularly the giant redwoods or bristlecone pines of North America. These massive trees never stop growing and can reach hundreds of feet high so long as they have adequate space to grow. In addition to trees, there exist several animals that never stop growing. Reptiles, fish, and amphibians most frequently rank among the list of indeterminate growers, but several mammals also make the cut. Continue reading to discover 10 animals that never stop growing. 

Lobster

Lobsters (Nephropidae) rank among the most well-known examples of animals that never stop growing. Newly hatched lobster larvae are about the size of a pea, but they grow to massive sizes so long as they aren’t caught by a commercial fishing enterprise, or eaten by a predator. The largest lobster ever recorded came from the waters off of Nova Scotia, Canada, and weighed an impressive 44.4 pounds.

Lobsters can grow to such massive sizes because they frequently molt their exoskeleton. Exoskeletons stop growing once they reach a certain size, so each time it molts its exoskeleton a lobster can grow a little larger. That said, molting is a labor-intensive process, during which 10% to 15% of lobsters die. As long as they possess the requisite energy, lobsters can keep molting and adding new muscle cells. With a lifespan of 45 to 50 years in the wild, it’s no wonder that they can grow to epic proportions.

Goldfish

A relatively small member of the carp family, goldfish can reach immense sizes when given the opportunity. The only thing limiting a goldfish’s growth is its container. If kept in a small aquarium, goldfish typically only grow to 1 to 2 inches long. However, when raised in large tanks or ponds, goldish can reach sizes between 15 and 19 inches long. While most goldfish live between 10 to 15 years, some can live over 40 years, which extends their growth potential.

The largest goldfish on record weighed 67 pounds. Nicknamed the carrot for its orange color, the fish was returned to the  Bluewater Lakes in Champagne, France, after securing the world record. In addition to changing sizes, goldfish can also change colors. If left in a dark space, they will slowly change from an orangish-red color to gray or white. This happens because the pigments in a goldfish’s cells reflect light and give it color. When kept from light, their skin changes over time and eventually loses coloration.

Green Anaconda

Many snake species are included in the number of animals that never stop growing. While they grow quickly until they reach maturity, their growth never ceases but simply slows down considerably. For example, anacondas, or water boas, can grow to exceptional sizes. In particular, the green anaconda (Eunectes murinus) possesses amazing growth potential and is the heaviest snake species. Dubbed Ana Julia by the Dutch research team that discovered her in the Amazon rainforest, the largest documented green anaconda was 26 feet long and weighed 440 pounds.

Red Kangaroo

Very few mammals are included in the list of animals that never stop growing. However, kangaroos rank among the few that do. In particular, red kangaroos (Macropus rufus) reach impressive sizes. The largest living marsupials in the world, red kangaroos are typically 5 feet tall/long and weigh 80-150 pounds. The largest documented red kangaroo was 6 feet 11 inches long and weighed 200 pounds. Due to their immense sizes, they are called Big Reds. Given that kangaroo babies or joeys measure only 1 inch long at birth, it’s incredible that they can grow into such tall and powerful creatures. Unlike humans, their skeletons grow slowly throughout their lives, so it’s possible that some kangaroos could grow even bigger than the largest specimen on record. 

King Crab

Like lobsters, crabs never stop growing. In particular, king crabs, of which there are 121 known species, can reach enormous sizes. They can live for up to 30 years in the wild, although they rarely live that long due to dangers from predators and the fishing industry. To reach their full size, king crabs must continuously molt and grow a new, more spacious exoskeleton. Given that they can continue to grow so long they have enough energy to molt, crabs possess the potential to grow indefinitely. The largest king crab on record, caught near Kodiak, Alaska, weighed 24 pounds and had a leg span of 5 feet.

Crocodile

Crocodiles vary in size, from dwarf crocodiles, average size of 5’9″, 100 pounds, to saltwater crocodiles which on average are 17 feet long and weigh 1000 pounds. Lolong, the largest documented crocodile, measured 20 feet, 3 inches long, and weighed 2,370 pounds. Crocodiles have long lifespans, and the longer they live the bigger they can grow. With such long lifespans, there’s no telling how big a crocodile could grow in the right conditions, though their growth rate slows down the older they get.

Python

Of the many species of pythons that live throughout Asia, the two largest are the Burmese python and the reticulated python. And while green anacondas weigh more than pythons, the reticulated python is the longest snake in the world. Medusa, the longest snake ever documented, measures 25 feet, 2 inches long, and weighs around 350 pounds. Medusa, who lives in Kansas City, Missouri, has continued to grow since being measured in 2011.

Shark

The largest shark species, the extinct Megalodon, was 67 feet long and weighed around 65,000 pounds. Although extant shark species don’t get quite this big, sharks never stop growing. Whale sharks are the largest shark species, measuring up to 40 feet long and weigh 20 tons. While few survive to reach adulthood, those that do can live up to 150 years. The largest documented whale shark was practically 62 feet long with an estimated weight of 42 tons! This beast was caught off the coast of Taiwan in 1987.

Elephant

Elephants are highly regarded for their intelligence, strength, and advanced social skills. They are also the largest living land animals. While indeterminate growth in elephants remains hotly debated, evidence suggests that male elephants never stop growing and that their growth rate merely declines over time. With a lifespan of up to 70 years in the wild, and even longer in captivity, elephants have plenty of time to grow. The largest elephant on record, a male African savanna elephant (Loxodonta africana), weighed 24,000 pounds and stood 13 feet tall at the shoulder. 

Rougheye Rockfish

Also known as the blackthroat or blacktip rockfish, rougheye rockfish (Sebastes aleutianus) belong to the rockfish family. These spiny fish can live up to 205 years and never stop growing. Rougheye rockfish don’t sexually mature until they are 20 to 27 years old. However, few survive to die of old age thanks to threats from predators, which include sharks, dolphins, and seals. The largest documented rougheye rockfish was 38 inches long and weighed 14 pounds and 12 ounces. The largest and oldest specimens live in deeper water, where they like to spend their time near the seabed full of caves and crevices.