Showing posts with label behavior. Show all posts
Showing posts with label behavior. Show all posts

The Great Turtle-Egg Evacuation

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The Deepwater Horizon oil spill is a very, very sad story. No matter how you look at it, the whole thing is spelling disaster.

What is surprising to me is how the event is being labeled as an ecological disaster by the mainstream media. Even though the explosion of the oil platform has left 11 dead (plus 2) and 17 injured, these facts have been essentially forgotten as the yet-contained oil continues to spew into the Gulf of Mexico and its surrounding shoreline. The focus is not unwarranted in most respects, as the consequences of this input of crude into the Gulf and associated cleanup efforts have and will have staggering effects on the ecology of the Gulf of Mexico and the Atlantic Ocean.


Unsurprisingly, an already-struggling effort for effective sea turtle conservation is being hit with very difficult decisions about what to do. Several species of adult sea turtles are running the risk of being cremated alive when caught inside oil slicks being burned. Additionally, as eggs hatch from nests on the beaches of the Gulf, juvenile turtles would face thousands of miles of oil-polluted water in the most vulnerable time of a sea turtle's life.

This last situation is why the US Fish and Wildlife Service, the National Marine Fisheries Service, and the Florida Marine Fisheries Service have developed a plan to relocate an estimated 70,000 sea turtle eggs from almost 800 beaches along Alabama and Florida. Read more here: The Great Turtle-Egg Evacuation


The plan is very risky for turtles inside eggs. As the article states:
"[...] within 12–24 hours of the eggs being laid, embryos attach to an oxygen-supplying membrane. So any movement of the eggs could cause detachment and death [...]."
A former student from my university completed a series of research projects on sea turtle conservation in the last few years which illuminated my perception of the effectiveness of current conservation efforts. This last point about the eggs dying if moved at the wrong point in time is correct, and is a major concern in these operations.

This topic has been a hot one in many email listservs I am subscribed to (especially C-TURTLE), and the point most interesting to me in all of this is the question of how the relocated hatched juveniles will respond to being transported to beaches several hundred miles from where they were laid. The previously-linked article continues to talk about potential affects of this operation on the relocated turtle's behavior:
Moving the eggs is not generally viewed as problematic. "We have adequate data showing that eggs moved with competence at that age have no difference in survivorship to those not moved," said Mike Salmon, a biologist at Florida Atlantic University in Boca Raton. 
But the release could be another matter. "What we don't know is what impact it might have on other aspects of behaviour," says Salmon. 
"The $64,000 question is, if you take hatchlings that would normally emerge in northwest Florida to the east coast," he said, "will they return there, or to the northwest, where they should go?" Because scientists don't know for sure whether imprinting occurs in the nest or after emergence, this remains a mystery.
This point is one where conservation, ecology, and ethology intersect. My favorite! I anticipate some interesting research will come out of this project, especially if local behavioral research-heavy universities (e.g., University of Florida) are asked to become involved. So much is known about sea turtle navigation and spatial perception, but I do not know of any test which has analyzed how moving recently hatched eggs 500 miles away affects the survival of individuals. Normally, this is not a practical situation which would not require testing (and thus, I see why there is a paucity of research on this specific topic).


Finally, it is worth noting that Heppell et al. (1996) found that the most effective contributors to sea turtle conservation were not efforts directed towards very young sea turtle (particularly 'headstarting', or catching recently hatched individuals and raising them for a year before release). Instead, turtle excluder devices (TEDs) attached to shrimp trawling nets offer the greatest positive effect on their survival. I wonder how meaningful this project to move ~70,000 eggs will be in light of these results.


Thank you for reading, I hope you are doing your part to support relief and clean-up efforts in the wake of this ecologically-disruptive event.

Addendum: I could insert lots of opinion on the oil spill, but I'll pass for two reasons: 1) I'm not a geologist, and 2) no one wants to read my whining (not even me). You can read more about sea turtle headstarting here.

Brown-Headed Cowbirds Exhibit Mafia Behavior

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Been a while since my last post. Perhaps I've taken some time off? Nope! School's out for sure, but I'm currently working full time (+ some) with Dr. Ben Pierce in SU's biology department. I spend most of my time in front of a computer, and after a long day of quality excel time, I'm usually just not in the mood to do blahg stuff.


But I'm here for you, right? Yeah.


So today's news isn't really news at all; however, I'm going to guess that the average person on the street has not heard of this problematic species and their interesting behaviors. I've been putting this one off for a while - there's a lot of information, but I think you will find it very intriguing!


Residing in the Southern USA & Mexico, brown-headed cowbirds (Molothrus ater) are obligate brood parasites (some male BHCs pictured on the right in a trap described later). This terminology means that females BHCs do not (and cannot, I assume) construct nests and must lay their eggs in the nest of another species of bird in order to have a successful clutch. The cowbird eggs hatch earlier than the 'normal' eggs and yield large chicks with very big mouths to feed. Guess who's the bad guy here:



Yikes! The parental birds feed the biggest and most obvious beak - which will often be owned by cowbird chicks. This would be fine and dandy in the world of biology, if it weren't for a tiny detail. BHCs used to be restricted to what wildlife biologists call 'edge habitat', as illustrated in this figure:



Essentially, when one has a grouping of a certain type of habitat, the edges are susceptible to different pressures than the inner portion of that type of habitat. Cowbirds got their name because they were found following the wake of edge habitat created by cattle trails in the 1800s. Nowadays, cattle drives are rare, but suburbia and habitat fragmentation are everywhere:


For species that "live life on the edge" (sorry, I had to), life is good. For the affected species... not so much. Problems arise when this brood parasitism spells certain death for the nest fate (i.e., success) of, say, endangered species. Brown-headed cowbirds, which used to have a more limited range (and then restricted to edge habitats), must now be controlled in areas under management for endangered species of birds.


A classic example of this BHC control is performed on Fort Hood in central Texas. Fort Hood has been a leader in environmental protection and the protection of endangered species. Many an environmental/biological researcher has earned his or her Ph.D. working on their property - and with good reason. Specifically, Fort Hood is the largest remaining breeding ground for the endangered species of bird, the Black-Capped Vireo. Before controlling for BHC,  vireo nest fate was zilch - guaranteed zero percent nest success if parasitized by BHC. Now, the military facility invests a lot of time (and money) into maintaining brown-headed cowbird traps like this one (this is actually a photo I took out at Fort Hood this year):




The premise is simple. The birds can get in, but not out. A door allows someone to enter the cage and handle the birds as necessary. Food and water is provided. Generally, when one BHC is inside the cage (bait), other BHCs will fly over and into the cage to investigate, trapping themselves. Females are euthanized and males are released (only females lay eggs). This simple, if labor-intensive, control has had a hugely positive impact on restoring the black-capped vireo population. The numbers are a bit fuzzy, but I think in the late 80s, Fort Hood had around eighty nesting pairs, and at current they have around five thousand nesting pairs.


So what's new? If you're any sort of bird person, you've probably heard all of the above, if not for the details. The story here is a study released by the University of Florida in 2007 which gave evidence for mafia behavior in female brown-headed cowbirds. ScienceDaily reports on the article (found here). If all of the behavior described above wasn't enough to make you have a distaste for brood parasitism, this article may be the kicker for you. What the researchers, including primary author Jeff Hoover, found was that female brown-headed cowbirds would ransack the nests of birds who rejected the parasitic eggs laid in their nests. It's worth noting that female BHC lay eggs in a nest over a period of days (2-4?), and so they are involved in some parental care of their young - watching to ensure the nest isn't abandoned, checking to see that the eggs have not been pushed out of the nest, and even feeding the chicks after hatching.


Hoover et al. observed Prothonotary warbler nests (a truly beautiful bird which accept BHC eggs almost 100% of the time) and found several interesting things:
"Retaliatory mafia behavior in cowbirds makes hosts' acceptance of cowbird eggs a better proposition than ejection," Hoover said. "The accepting warblers in our study produced more of their own offspring, on average, than those where we ejected cowbird eggs."
The researchers also found what they called "farming behavior." This means that after a warbler rejected the female BHCs eggs, the BHC would force the female warbler to make a new nest, sync her egg laying with the warbler, and parasitize this new nest. This final step happened 85% of the time the farming behaviors were observed. A male prothonotary warbler is pictured on the right (photo credit).

I hope you learned something after reading this truly lengthy post. Thanks for sticking it to the end.

NOVA Series - Lizard Kings

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Perusing some other blogs, I discovered a fascinating NOVA series on monitor lizards titled "Lizard Kings."


NOVA is well known for their awe-inspiring filming, and this program certainly does not come up short.

I'm posting this because it's free to watch online, visit their website and click "Watch online." The whole program runs at 52 minutes.


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