Saturday, January 19, 2013

Sandhill Cranes - Mycotoxins


In an ecosystem rife with bobcats, coyotes, alligators, vultures and snakes, it's rare to see a dead animal without any apparent wounds. So when I stumbled on this scene in Kanapaha Prairie I asked myself, what could have done this? I recently posed this same question to a group of fans on my Facebook page and surprisingly, two of them had the right answer. 

Sandhill cranes fly over Kanapaha Prairie - Gainesville, FL -  Photo ©Mac Stone

The sandhill cranes' arrival in Florida is the sure sign of winter. They come in with the staccato trumpet calls that pierce the morning air and echo through the prairie's live oak rim. Their migratory populations have ebbed and flowed over the years on the prairie, some years with over 1,500 individuals and other years only a few dozen. There doesn't seem to be a solid explanation for this, but some believe its due to the amount of dog fennel that grows up to 6 feet high and gives the cranes a natural barrier from potential predators like coyotes and bobcats. Without the vegetation, they simply pass over the prairie and onto greener pastures. 

Sandhill cranes at sunrise on Kanapaha Prairie - Photo ©Mac Stone

One of my favorite things in the winter is to go out and photograph the sandhills at sunrise. When polar fog exhales from the wetlands, their silhouettes dot the horizon and make for some great images. On these mornings though, I'm not the only one stalking birds. If sandhills usher in the day with their calls, then coyotes are the denizens of the night. Their mad cackling can be heard from a mile away and I can't help but wonder while I'm sitting around the backyard fire, what they're howling about. No matter how close they sound, every time I go looking for them they're nowhere to be found. After their raucous nights, though, I'm always certain to find the remains of their prey in a cloud of feathers on the cold prairie floor. 

A lone coyote stalks a flock of sandhill cranes on Kanahapa Prairie - Photo ©Mac Stone

So it was curious to me, the morning I stumbled upon the dead sandhill, left untouched. Then I started replaying the previous day's events and images, and I knew the answer immediately. Out of the flock of cranes I had been photographing the day before, when all others flew away as I approached, there was one crane who stuck around. At first it looked like it had an injured wing as it fumbled about,  hopelessly attempting to fly. 

Sandhill crane infected by mycotoxin, fusariotoxin - Kanahapa Prairie - Photo ©Mac Stone

Not wanting to stress the bird or cause it any more pain if its wing really was injured, I stayed back and watched it for a while. It was really sad to watch. The crane would call out to its flock in a broken shrill and the others didn't respond. It's limp neck eventually lost all mobility and hung low as if paralyzed. In the deeper water, it could barely keep its beak high enough to breathe. I apologize for the graphic photos.

Sandhill crane infected by mycotoxin, fusariotoxin - Kanahapa Prairie - Photo ©Mac Stone
Finally, I wrote it off as a strange injury and went home knowing it would soon turn into food for the prairie. The next morning when I saw the sandhill laying dead in the water where I saw it yesterday, I wondered how long through the night it suffered, as this was almost certainly the same bird. The images of its broken body were hauntingly fresh in my mind, so I did some research to see if anyone else had documented this behavior. What I found was alarming. 

According to the National Wildlife Heath Center, this paralysis and eventual death is caused by a toxin produced by a fungus found in corn and peanuts, called mycotoxin, or more specifically, fusariotoxin. Fusariotoxin will cause a flaccid paralyses of the neck and wing muscles as well as neurological damange. Wild migratory waterfowl like cranes poisoned by this fungus have thus far only been documented in Texas and New Mexico from contaminated grain fields. Cranes can ingest the fungus while foraging during low temperatures when other food sources are unavailable. Who's to say where the bad corn or peanuts were eaten; it could have been in Georgia a few weeks prior. According to biologists, there are about 300 cases in Florida each year, but this series of photos is the only ones I could find in Florida, although I've seen this condition twice on Kanapaha Prairie alone (if there are other accounts of this in Florida, please let me know in the comment section below). 

Thanks for reading. If you'd like to read up a little more on this strange condition, click here, or here. Also, as a side note, I did not do an autopsy on the bird, so for scientific purposes I have to say that based on my field observations alone, I put mycotoxins as the probable cause of death. 

Sandhill crane, probable cause of death: mycotoxins from molded grains - Kanahapa Prairie - Photo ©Mac Stone

12 comments:

  1. O no very sad image i am very shocked after visit your last 2 images. Otherwise all images are fantastic !!

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    1. Thanks.. I know the photos are a little tough to see, but trust me, it was much harder to watch.. thanks for looking, I promise to post some more positive photos next week :)

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  2. Mac, that was a great post and explanation of the events. While, the photos are tough on the heart, they are powerful and evoke many thoughts in my head. I appreciate you sharing them despite the visual shock. - Steven Llorca.

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  3. I witnessed this same thing about a week ago off of the Lower Myakka Lake in Sarasota County. I assumed the bird had an internal injury. Thanks for doing some stellar research, always enjoy your posts and images!

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    1. Really?! According the papers I've read, I can't find any documentation on sandhills affected by these toxins in Florida.. that's very interesting. thanks for sharing!

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  4. Although only based on your observations, your conclusion sounds plausible. Thanks for the informative piece and photos.

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  5. Saw one doing the same thing on the lower Myakka in Charlotte County. Thought it got infected by something or hit by a car from it's movement.

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    1. yeah, it's really strange to see.. not sure what to make of it at first, right?

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  6. found in corn you say---- what do "hunters" use to draw deer to their blind... could it be corn what do dove hunters use to salt a field ... could it be corn? what do folks use to deter squirrels from raiding the bird feeder .... could it be peanuts... if only they knew the unintended consequences of an inconvenient truth.

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    1. Well, it's hard to say where it comes from.. could be hunters, could be people feeding birds, could be fallow fields from farmlands. Luckily this isn't a widespread epidemic, instead something that affects a very small percent of the population.

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  7. Wow, cools pics, even the one with the dead Crane :( But apart from that they are really cool. I'm not very good at taking photos of birds but I will perserve!! Cheers!

    Shooting My Journey x

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