Florida Manatees -Tough on the outside, but not invincible

Manatees, affectionately known as “sea cows” or “mermaids,” are peaceful herbivorous giants found in fresh and saltwater coastal areas. Despite lacking natural predators in the case of the West Indian Manatees (the ones we find in North America), their population numbers are not as robust as one might expect. This post will shed light on the Floridian subspecies of manatees, honing in on their winter habitats and the impact of both human activity and climate change on their well-being.

Florida manatees are gentle giants who face threats from human activities and climate change. Credit: Keith Ramos/USFWS

Despite their large size, manatees lack a thick layer of fat

Now, manatees are known to be large… but how large exactly? A manatee can weigh over 1000 lbs (~450 kg)! Weights typically span from 440-1300 lbs (200-600 kg), with females being larger than their male counterparts. They are herbivores, eating up to 5-10% of their body weight a day!

One might assume that with their sluggish movement and low metabolic rate, manatees would be on the plumper side, but that’s not the case! In fact, their bones are exceptionally dense, which makes them less buoyant in the water. Their fat layer, often referred to as blubber, is quite thin. This means they can’t endure cold temperatures under 68°F for extended periods.

Cold stress can wreak havoc on manatees’ health

The Florida manatee’s usual habitat extends throughout Florida and can also be spotted around the Caribbean islands. These areas rarely get colder than 65°F (18°C), which is good for them as they are susceptible to cold stress syndrome. This syndrome affects manatees when they are exposed to waters cooler than 68°F. Unlike other marine mammals, manatees don’t have a thick layer of insulating fat. Additionally, they cannot engage in vigorous physical activity for extended periods. This makes it difficult for them to control their body temperature effectively.

Cold temperatures first impact manatees by causing their skin to bleach. But this is just the beginning of their troubles. As their skin deteriorates, they are more prone to developing abscesses and sores. Manatees are natural hosts to algae and barnacles because of their rather slow swimming pace. When they experience cold stress, these hitchhikers become even more prolific. In the end, because their movement is restricted, they cannot forage for food as efficiently as they should, leading to weight loss.

Manatees coming into Crystal River, December 2018. Credit: Naomi Mathew

To escape the cold, manatees take some vacations to natural warmer waters

Florida does encounter occasional cold spells that can persist for some time. Manatees, however, have developed a clever adaptation strategy – they go on their own vacations! During the winter, they are known to journey to Florida’s natural springs, where the water maintains a comfortable 72°F temperature all year round. Additionally, manatees can often be found in areas near power plants where warm water is discharged. They acquire knowledge of these locations from their mothers at a young age. These spots help them stay warm and offer ample sustenance, thanks to the flourishing vegetation in the vicinity.

Locations like Crystal River, Three Sisters Springs, and Blue Spring State Park, among others, are popular destinations for both humans and manatees, especially during the winter months. While these areas are well-regulated and closely monitored to ensure the safety of manatees, there is still a risk of human interference and harassment.

Additionally, power plant runoff areas also pose significant human-induced risks. Manatees tend to stay loyal to the winter habitats their mothers introduce them to and are unlikely to seek out new locations. If these power plants were to cease their warm water discharges, the manatees, driven by their instinct, would continue to visit these areas, even if it puts their lives at risk.

florida manatees
An infographic recap of this post — Credit: Naomi Mathew

Climate change’s potential impact on the manatees and their environment

Climate change has brought about some of the hottest temperatures ever recorded in southern North America, as evident even in the past summer. Alongside rising sea levels and their impacts on the Florida coast, we’re witnessing not only the consequences for human life, which has been widely reported in the news, but also the potential effects on animal life.

As sea levels climb, there are shifts in vegetation that could disrupt manatee foraging patterns. Mangrove barriers, typically safe havens for these creatures and where they graze, are under threat from rising sea levels. This degradation has opened up areas that were once protected, leading to increased boat traffic. As we discussed in our previous post, boat strikes are a significant and life-threatening issue for manatees.

Conversely, we’ve also witnessed prolonged and severe freezes in North America. The stability of the Polar Vortex, affected by the hotter temperatures, has shifted, extending further south into North America. This has impacted certain U.S. states that lack the necessary infrastructure to handle such extreme cold events. All of this raises an important question: How will these extreme weather fluctuations affect creatures that are sensitive to cold? It underscores the importance of comprehending climate change and its wide-ranging impacts to guide more effective environmental conservation efforts.

Thanks for reading! If you want some more information, check out some of the resources we used:

Finally, here is a fun video of a manatee I took during one of my encounters with these gentle giants 🙂

Manatee checking out a UM boat off of Key Biscayne, Florida, April 2019. Video Credits: Naomi Mathew

Naomi Mathew is a PhD student at University of Louisiana at Lafayette. She works on bioacoustics in marine mammals from the Gulf of Mexico. She is the co-founder of Whale Scientists. You can read more about her here

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