A Simple Sea Cow Question, Or So You Think

A simple straight data graph, population counts in blue, mortality reported for the year in red (c) Ben Jewell

It’s been manatee madness lately at WaterNotes and a great question came in to me via email the other day: how many manatees are there left in Florida?

Well. A little over 3,800. That’s the simple answer. The more detailed answer is that the synoptic surveys carried out by the state for 2009 reported back a count of 3,802. But the numbers posted since 1991 – when surveys became a requirement – show a wicked variation and almost volatility in the counts (as you can see from the straight data graph above).

For an endangered species you would expect that we would have a definite headcount of sea cows but it simply isnt feasible. Current YTD mortality numbers are also available online. If we began the year at 3,802 then we’re somewhere near 3,600 at the moment. Two hundred animals have been lost. “Undetermined” causes of death leads the way, followed by “cold stress” and then “perinatal” for lost calves. Of course all this says nothing for those elusive manatees that were not counted this past year or the calves that have been born since the survey took place. So are we really down by two-hundred animals? Or have we added a few dozen calves in the few months?

Its just impossible to say. Environmental education, like so many other fields, is only as good as the data and research that a naturalist’s answer is based on. And in some situations the best answer we can give is just a snapshot of the wider issue going on. How many manatees are there in Florida? “Well, a little less than four-thousand. We think. Maybe.” Unless you’re interested in going further down the rabbit hole, that might be all the answer you’ll get at any nature center in the state.


4 Comments to “A Simple Sea Cow Question, Or So You Think”

  1. That’s the general answer (around 4000) I give my students also. We are in the middle of prime manatee viewing country here, but so many of them have never bothered to visit our manatee laden springs in the winter.

  2. The great thing about being a hydrologist is that so much more “hard” data, or in this case “wet”, is available, often online and in many cases real time. That being said, great graph!

  3. Ok, I’m going to open a can of worms here, but the data on Florida manatees is so obviously statistically unstable that no inference could really be made from it except for a range. Also, manatees were historically migratory, why do we expect that they stay in one general area? Furthermore, why do we keep attracting them to certain areas? One article I read in the Florida Today (ok, it’s so not a scientific journal) stated that the FPL plants that draw them raise the IRL temperature by 5-8 degrees. Isn’t that doing significantly more damage than leaving the manatees to their natural behaviors? Don’t think I’m one of those “manatees with mash potatos” people, I just think they’ve been commercialized into something that they aren’t.

  4. Jamie you bring up some good thoughts. I definitely agree with you that the “statistics” aren’t worth a whole lot. If you look at the raw data that FWS posted to their webpage you’ll notice that some years are omitted entirely (like 2008) because of bad weather and in other years they surveyed three months in a row and posted each number. I’ve never done any analysis on the stats – they’re not my data – but the simple graph above shows what a crazy prospect it is to get even something as simple as a headcount on the beasts!

    They are migratory and the surveys attempt to take advantage of that by holding the counts in winter months when manatees are expected to migrate to those warm water zones they need for survival. But they don’t always show a strong migration pattern, particularly if we have a warmer than typical winter. Water temps of 68F seem to be the tipping point.

    The FPL artificial “saunas”, as I like to call them, are a point of contention. It could be altering their natural instincts to migrate to other areas and researchers are pretty sure that mothers pass on knowledge of migration routes to their calves. Which begs the very important question: if we remove the FPL sources, and the manatees are dependent on them for winter time survival, will they know where else to go to seek refuge in cold water episodes? You could argue that we’re doing damage by altering their environment so considerably but the world they now inhabit is so altered in many other ways that this one is apparently a small blip on the veritable radar. Then again cold stress is always one of the leading causes of mortality, so perhaps the artificial saunas should be more heavily discussed in the conservation circles.