Aquatic Mammal Species Overview

Aquatic mammals would include various whales and dolphin that come and go throughout the Gulf of Mexico. Another mammal that lives completely in water is the manatee. This lesser known group visits Louisiana when the water is warm and can be found grazing on seagrass and algae.

All of these aquatic mammals are heavily protected and often it is illegal to approach them, but even a distant sighting is exciting and worth watching for.

Here are some marine mammals that may be seen in the Gulf of Mexico off of Louisiana:

Bryde’s Whale - Balaenoptera edeni

The Bryde’s whale is a medium sized baleen whale, but is by no means small. They can reach a length of 40 to 55 feet and a weight of approximately 90,000 pounds. They use baleen to filter out tiny krill and other small schooling creatures including fish from the water. They have been seen to use several types of feeding behaviors including bubble netting and skimming the surface. They normally dive for five to fifteen minutes and are able to reach depths of 1000 feet.

These whales prefer tropical, subtropical and warmer temperate waters worldwide. They have a distinguishing feature that makes them easier to identify. In front of the blowhole on their head they have three distinct ridges. There not enough data to determine the population trends for this whale, but they are protected as are all marine mammals.

Common Bottlenose Dolphin - Tursiops truncatus

There is no more well know or admired marine mammal than the bottlenose dolphin. Its intelligence and seemingly playful nature has fascinated many who have gotten to experience it. Its wide distribution throughout the world’s temperate and tropical waters makes them one of the most often seen by the public. Some groups live in open waters of the ocean, while others choose coastal bays and rivers.

Bottlenose dolphin can reach sizes from six to twelve feet and weights up to 1400 pounds. They are a member of the toothed whales and have a very broad, opportunistic diet consisting of fish and invertebrates. They have developed many methods of catching their prey, some of which are very specialized for specific habitats. They use echolocation to detect their prey and speed, agility and intelligence to capture it. Often these localized predatory methods are taught to younger generations and have been describe as a “feeding culture” by some.

Bottlenose dolphin have a lifespan of 40 to 45 years for males and over 50 years for females. They normally live in groups from two to fifteen, though offshore pods may number in the hundreds. Like all marine mammals they are a protected species in US waters.

Melon-headed Whale – Peponocephala electra

The Melon-headed whale is a lesser know member of the dolphin family. The small head with no distinguishing beak is how they get their name. They can reach a length of 9 feet and weight of 460 pounds. The Melon-head spends most of its time in deep waters of tropical zones where they feed on squids, fishes and crustaceans in fairly deep water. They travel in large pods that range from the hundreds up to a thousand. They are often found following pods of Fraser’s dolphin.

Sperm Whale – Physeter macrocephalus

The Sperm whale is another well know whale, but encounters are less frequent as they tend to inhabit waters of over a thousand feet. This whale is the largest of the toothed whales and also can claim having the largest brain of any animal on the planet, about 17 pounds. The brain is not disproportionate as a mature male Sperm whale can reach a length of 52 feet and weigh in at 45 tons. Females are dramatically smaller, reaching 36 feet and only 15 tons. They all have an extremely large head, which takes up to one third of their body. Females begin to reproduce around 9 years old and have a 15-month gestation period. They can produce a calf once every five years or so, but that calf is 13 feet long and will nurse for several years. Males don’t actively breed until they reach their late twenties and young males often live in their own pods until they mature around 50 years old.

Sperm whales are known for their ability to make deep dives for food that can last over an hour and reach depths of 3,200 feet. They feed on squid and fish and often bear scars from their deep-water battles with prey.

Sperm whales inhabit all oceans of the world, but there is a Northern Gulf of Mexico stock that is present year round, but their numbers grow in the summer months. Whaling took a huge toll on the worldwide population of whales, but that has stopped since the closure of whaling by the IWC in 1988.

Spinner Dolphin – Stenella longirostris

Spinner Dolphins are a relatively small dolphin reaching a length of 7 feet and weight of 150 pounds. They have long slender beaks and their color varies with regions. They are found in all tropical and sub-tropical oceans.

Best known for their acrobatic, leaping and spinning habit and the fact that they tend to travel with schools of yellowfin tuna in the pacific. This last fact has been a problem for them as some tuna boats surround them with nets to catch the tuna below them. Drowning in nets and stress are the two main negative interactions and efforts to reduce these problems are what “dolphin safe” tuna is about. They may also be seen with bottlenose dolphin and humpback whales in Hawaii.

Spinner dolphins are normally swimming in very large groups of hundreds to thousands. They feed at night on fish and deep-water squid, while resting during the daytime. They are considered depleted in status and there are ongoing efforts to protect them.

West Indian Manatee – Trichecus manatus

The manatee is the marine mammal believed to be the origin of mermaid legends. One would have to be at sea a long time for this docile marine mammal to resemble a beautiful girl, but they are amazing creatures and seeing one is always a treat. Most common in Florida, but sometimes seen in Louisiana, the manatee is a coastal dweller and sometimes enters rivers and bays in search of their aquatic vegetarian diet. The manatee can reach a length of 10 to 12 feet and a weight up to 2000 pounds. They can live up to sixty years in the wild, and live in warm waters of no less than 68 degrees. Often they congregate during the winters at natural springs and power-plant discharges, where warmer water temperatures can be found. The manatee is also protected and much effort has gone into eliminating the unnatural causes of death.

Manatee have a gestation period of about one year and give birth to a calf about 4 feet long, weighing 65 pounds or so. They nurse from their mother underwater.

Often the part of the manatee you see is the bristled nose when they take a breath followed by the large, flat and rounded tail as they propel themselves along. They leave a large boil in the water and watching this footprint can track their movements.