Over the past two weeks, we have experienced a few “cold” fronts coming through South Florida. Now, “cold” and “South Florida” sound like an oxymoron, but it does happen. I was actually tempted to put on long pants one day! This change in temperature has an effect on several animals in the area.
Iguanas, for example, can fall from trees when it becomes too cold and they will slow their heart rate so low that they seem to not be alive! Also, we have a lot of birds in the area that have fled the freezing conditions up north and they enjoy this weather. In the water, one mammal species is on the move as the Gulf, river and canal temps become a bit too chilly. That would be the manatees.
From about March to November, it’s common to see these “sea cows” just about anywhere in our area, because the waters are quite warm everywhere.
When we get cold snaps such as we had in recent weeks, the manatees will relocate. Why? They have very little body fat and, just like humans, they can become subject to hypothermia. Waters that are too cold could cost them their lives. When water temps hit 68 to 70 degrees, they will travel.
So, where do they go? It would make sense that they stay in shallow water because that would naturally be warmer. Shallow habitats are home to manatees anyway because they eat plants and seagrass. Waters that are too deep would not allow enough sunlight to grow their food for them at the bottom of the rivers and channels. Close to home an area to find manatees would be the Port of the Islands, just 20 minutes from Marco Island.
Port of the Islands, the “Gateway to the Everglades,” provides a unique setting for manatees. Not too many years ago, a manatee mitigation feature, called a refugium, was built just south of the Port marina. This a place with very stable water temps that several species can shelter in.
Why does this work for the sea cows? Warm, freshwater flows from the Picayune Strand and Fakahatchee Strand of the western Everglades to the basin at Port of the Islands where it meets with the salt waters entering this estuary from Faka-Union Bay. The manmade mitigation feature provides shelter and food for this species here and a safe harbor from boat traffic that utilizes the adjacent channel.
This creates a very unique setting. Freshwater is less dense than salt water, so it sits on top in this environment while the salt water is lower in the habitat. Manatees need freshwater to survive, so this setting is ideal. Although we see manatees quite often in salt water settings, they do indeed need a supply of drinking water. A water balance is very important to them and osmoregulation, the internal balance between water and dissolved materials, shows that their kidneys are developed to help them rid any excess salt when in marine habitats for extended time periods. However, the reliance on freshwater for the manatees living in Florida, known as the West Indian manatees, is important.
The local manatees can get quite large even though they are vegetarians. They can range from 8 to 10 feet long here and grow 800 to 1,000 pounds. These sea cows will eat about 10% to 15% of their body weight every day. That’s about 100 pounds of salad each day!!! (You know what kind of dressing they put on this…? 10,000 Island!) To digest this much food their intestines can be 150 feet long!
They have been equipped with special features on their mouth called prehensile lips which means that the upper lip is split so that both the right and left sides can move almost independently. Seven different muscles are used here to rip and tear plants from the roots.
Their teeth are quite unique as well. Because they chew so much sand and grit with their food supply, the teeth wear down quickly. To compensate for the loss of front teeth they have been provided “marching molars” which means they constantly develop new teeth at the back of the jaw that will move forward and replace the worn teeth at the front of the mouth. This is also true for elephants, the closest land mammal relative of the manatee, and kangaroos.
So, Port of the Islands is an educational destination to find and learn about manatees during the winter months. Several tours are available there to get you to their home for the next several months. Fascinating to see, they are even more interesting to learn about!
Bob is a Naturalist on board the dolphin study vessel Dolphin Explorer. He is also an owner of Wild Florida Ecotours at Port of the Islands. An author and award-winning columnist for Coastal Breeze, Bob wants everyone to know, always, that he loves his wife very much!