Alligator Gar - A Keystone Species in America's Freshwaters - Animal Corner (2024)

The Alligator Gar (Atractosteus spatula) is not just any fish; it’s a living testament to the wonders of evolution. This freshwater giant, with its lineage tracing back to the time of the dinosaurs, is a marvel of nature. It is one of three species of Gar in genus Atractosteus, and there are no recognised subspecies for any of these Gars.

These top-level, freshwater predators stand out amongst their peers, with their unique features and behaviours. They thrive in the freshwaters of very specific regions in the USA, but are very adaptable to waters with varying saline levels. From the ultra fresh, to brackish and estuary environments.

While the Alligator Gar doesn’t have any recognized subspecies, its very existence speaks volumes about the rich biodiversity of our planet.

Appearance & Characteristics of Alligator Gar

The Alligator Gar is a colossal being and amongst the largest species of fresh fish in the world. There are some reports that they can reach lengths of up to 10 feet and weigh over 350 pounds. These reports are anecdotal however, and there is no scientifically verified measurement to support this.

The largest ever recorded and verified, was caught in 2011 and estimated to be around 70 years old. It weighed in at 327 lbs 148 kg) at a length just over 8 feet 5 inches. On average, they are more likely to be around 6 feet (1.8 meters) and 100 lbs (45 kg) in weight. Still massive for a freshwater fish by all accounts.

This makes it one of North America’s freshwater titans. Its body is streamlined and powerful with an elongated snout, reminiscent of an alligator. Their jaw is lined with rows of sharp teeth, with a double layer on their top jaw – making it a formidable predator in its habitat.

It has a thick armour with diamond-shaped ganoid scales that offer protection against predators. These scales are more like that of a reptile, particularly an alligator or a turtle than of a fish. With an enamel like outer layer, covering an inner layer similar to bone.

Because of their ancient heritage, the Alligator Gar is often noted to be a ‘living fossil’ They maintain some of the characteristics of their ancient ancestors – notably a spiral valve intestine which many similar species discarded through evolution long ago. They can also breathe in both water and air through a special kind of swim bladder which is a remarkable characteristic to maintain from their ancient past.

Distribution – Location and Habitat

The Alligator Gar’s domain is fairly well defined and stretches across the freshwater systems of the southeastern United States. From the expansive Mississippi River Basin to the warm waters of the Gulf of Mexico, this fish can adapt well do different water environments. It has a particular fondness for slow-moving waters.

Whether it’s the tranquil bayous, vast lakes, or the backwaters of lowland rivers, the Alligator Gar thrives in these serene environments, making them its home. They are most commonly found in the Mississippi River and valley, across the southern states from Mexico, up to Texas and right across the Gulf Coast states to Florida and Georgia.

In the northern part of their range, around Missouri and Kentucky they are less populous than in the southern range, particularly around Louisiana and Mississippi.

The Lifestyle & Behaviour of Alligator Gar

The Alligator Gar is a solitary fish by its nature. Often seen floating near the water’s surface, it might appear lazy or inactive. But don’t be fooled! This behaviour is a strategic hunting tactic. As an ambush predator, the Alligator Gar waits, camouflaged and patient, a few feet below the surface of the water, for unsuspecting prey to venture close. When the moment is right, it strikes with great speed and accuracy.

They are primarily nocturnal hunters, and opportunistic in their hunting. Depending on the availability of food they may also resort to scavenging to find sustenance.

Diet & Nutrition of Alligator Gar

The Alligator Gar is not picky when it comes to food. They are mostly piscivorous with a primary diet that consists of a variety of fish, particularly small bait fish, such as the gizzard shad. They will also eat larger carp and buffalo fish and hardhead catfish. Depending on their local habitat, they may also eat invertebrates such as small blue crabs, waterfowl and other small birds. They have even been known to eat small or baby turtles.

The specific diet depends on the water in which the Alligator Gar is in. Brackish water, swamp areas or freshwater river all provide different food for the fish to eat.

Whatever the environment, their sharp, formidable teeth play a crucial role, allowing the gar to grasp and hold onto its prey, ensuring it doesn’t escape.

Predators & Threats to Alligator Gar

Humans, both directly and indirectly are the biggest threat to Alligator Gar populations. Through habitat loss, and historically overharvesting and culling, the fish has become locally extinct in some areas, and populations continue to decline in others.

Other than the human threat, there are only a few predators that these fish need to worry about. Their armour like scales provide excellent protection for mature fish, and even in the egg, nature has given the Gar some exceptional protection. That is because the bright red eggs of the Alligator Gar, intriguingly, are toxic to many would be predators, including humans.

Mammals, invertebrates and birds are all at risk from the toxins in Alligator Gar eggs, but interestingly, other fish and reptiles are not. So predators that might take advantage of their immunity to these toxins for a meal, are egg predators such as the Bluegill.

One predator that will eat eggs and is also geared up to take on an adult fish, is the Alligator and these are their biggest predator. They have strong enough teeth and jaws to get past the Gar’s tough exterior.

Alligator Gar Reproduction

Being oviparous, females lay eggs that are then fertilized externally. A single female can lay thousands of eggs at a time, and they usually do this in very warm, shallow waters. They release their eggs once males start to exhibit ritualistic movements around the female to trigger the release of the eggs. They are then fertilized externally by the males, who release a milt fluid onto the eggs.

The male then plays a protective role, guarding the eggs against potential threats. There is a short gestation period of around 6 to 8 days. Once hatched, the young gars start their life as larvae, and around 10 days after that, they embark as tiny fish on their journey of growth and survival.

Lifespan of Alligator Gar

As with most ancient species, the Alligator Gar is a very long lived fish. With a lifespan commonly extending up to 50 to 70 years, they experience various life stages. From the vulnerable juvenile phase to the sub-adult stage, where they learn the ropes of their habitat, and finally to adulthood, where they reign supreme, the Alligator Gar’s life is a journey of challenges and triumphs.

It takes around 10 years for the female Alligator Gar to reach sexual maturity and around half of that for males. Most of their growing however, is done in the first 1 – 2 years of life.

Population and Conservation

Alligator Gar are known as an important fish in the waters they swim, because they help to keep their ecosystem in balance. They are an effective keystone species, but at one time they were seen as a nuisance fish, and a threat to sport fish or food stock that make up part of the human diet.

As such, these fish were commonly culled and overharvested in some areas, where populations have now become locally extinct. This was the case in much of the historic range they had in the northern United States. Now that they are known to be a valuable asset to their environment, some areas have actively tried to reintroduce these fish to areas where they are extirpated, particularly as a method to control other invasive species, such as the Asian Carp.

Despite the recent acceptance of their importance, the once-thriving populations of Alligator Gar have continued to see a decline in recent decades. The main reasons for this are habitat loss, overfishing, and human interference.

Conservationists and biologists in the last two decades have begun to implement measures to protect and rejuvenate the Alligator Gar populations. Legislation has been introduced locally in some areas to encourage population monitoring, management and restoration in their natural range.

Despite their various challenges, the Alligator Gar is listed as a species of ‘Least Concern’ on the IUCN Red List.

5 Fun Alligator Gar Facts for Kids

• Breathing Marvels: Alligator Gars can breathe in water and on land, thanks to their unique swim bladder!
• Scaly Armor: Native Americans once used their tough scales as arrowheads.
• Friendly Giant: Even with their fearsome looks, they rarely pose threats to humans.
• Incredibly Ancient: They’ve been around for over 100 million years, witnessing Earth’s many changes.
• Baby Beacon: Young Alligator Gars have a light-sensitive spot on their snouts, aiding them in hunting.