Tuesdays with Turtles – NPR morning Edition
Now you know what to do when you hit Jekyll island, GA (no, don’t Hyde!)
NPR : Loggerhead Turtles Draw Georgia Tourists
It helps that they’re such handsome beasts.
Similar Posts
Sea Turtle News o' the day – Global warming edition
ScienceDaily: Scientists Warn Of Climate Change Risk To Marine Turtles
North American marine turtles are at risk if global warming occurs at predicted levels, according to scientists from the University of Exeter. An increase in temperatures of just one degree Celsius could completely eliminate the birth of male turtles from some beaches. A rise of three degrees Celsius would lead to extreme levels of infant mortality and declines in nesting beaches across the USA.
Like a lot of other reptiles, the sex of the hatchling is dependent on nest temperature. Warmer temperatures make female turtles (my mnemonic was hot females!), and even warmer temperatures just kill the eggs. But, I wonder if the turtles would adapt by nesting a little earlier. I don’t think it is yet clear when turtles decide to nest. If it is based on sea temperature, then they would eventually figure it out. This paper from 2004 appears to conclude that loggerheads in Florida do nest earlier than before, so there is hope.
John F. Weishampel, Dean A. Bagley, Llewellyn M. Ehrhart (2004) Earlier nesting by loggerhead sea turtles following sea surface warming Global Change Biology 10 (8), 1424–1427
The onset of spring, noted by the timing of wildlife migratory and breeding behaviors, has been occurring earlier over the past few decades. Here, we examine 15 years of loggerhead sea turtle, Caretta caretta, nesting patterns along a 40.5 km beach on Florida’s Atlantic coast. This small section of beach is considered to be the most important nesting area for this threatened species in the western hemisphere. From 1989 to 2003, the annual number of nests fluctuated between 13 000 and 25 000 without a conspicuous trend; however, based on a regression analysis, the median nesting date became earlier by roughly 10 days. The Julian day of median nesting was significantly correlated with near-shore, May sea surface temperatures that warmed an average of 0.8°C over this period. This marine example from warm temperate/subtropical waters represents another response of nature to recent climate trends.
So the truth lies somewhere between easy adaptation and giant swarms of frustrated female turtles!
Tuesdays with Turtles – Why Adult Turtles Die so You Can Eat Fish
An interesting paper featuring a North Carolinian turtle researcher Larry Crowder from Duke University:
Blackwell Synergy – Conservation Biology, Volume 21 Issue 1 Page 79 – February 2007 (Full Text)
Abstract: Although some sea turtle populations are showing encouraging signs of recovery, others continue to decline. Reversing population declines requires an understanding of the primary factor(s) that underlie this persistent demographic trend. The list of putative factors includes direct turtle and egg harvest, egg predation, loss or degradation of nesting beach habitat, fisheries bycatch, pollution, and large-scale changes in oceanographic conditions and nutrient availability. Recently, fisheries bycatch, in particular bycatch from longline fisheries, has received increased attention and has been proposed as a primary source of turtle mortality. We reviewed the existing data on the relative impact of longline bycatch on sea turtle populations. Although bycatch rates from individual longline vessels are extremely low, the amount of gear deployed by longline vessels suggests that cumulative bycatch of turtles from older age classes is substantial. Current estimates suggest that even if pelagic longlines are not the largest single source of fisheries-related mortality, longline bycatch is high enough to warrant management actions in all fleets that encounter sea turtles. Nevertheless, preliminary data also suggest that bycatch from gillnets and trawl fisheries is equally high or higher than longline bycatch with far higher mortality rates. Until gillnet and trawl fisheries are subject to the same level of scrutiny given to pelagic longlines, our understanding of the overall impact of fisheries bycatch on vulnerable sea turtle populations will be incomplete
Adult sea turtle killing by humans occurs due to
- Harvest, killing them deliberately for food
- Incidental bycatch in fishing nets
- Habitat loss
The paper focuses on long line fishing and its effects on turtle mortality. So, if like me, you’re not a fisherperson, what is long line fishing and what are some other kinds of fishing techniques that have effects of sea turtles? Well, the Duke Project GloBal research team on studying bycatch has a nice primer. Some highlights:
- Longlines: As the word suggests, longlines are very long (>10 km) lines of 2000+ individually baited hooks that drift close to the surface and are used to catch tuna, swordfish, halibut, etc. Crowder’s paper suggests that while each individual longline hook has low probability of catching a turtle, because of their number and ubiquitousness, they catch many many turtles.
- Gillnets: These are giant rectangular mesh nets, either stationary or drifting, that catch marine life indiscriminately. There’s not much that can be done by way of reducingsea turtle catch in gillnets, except monitoring, observation and just using less of them
- Trawls: Big funnel shaped bags that catch fish. Bottom trawling fishing boats used to, and still catch turtles at an alarming rate. Trawls are now (at least in the U.S and other “developed” countries) required to be outfitted with Turtle Excluder Devices (TEDS) to let turtles swim to safety.
- Purse Seines: These are weighted on the bottom and float at the corners. They are indiscriminate, and especially hard on dolphins. It appears that mitigation efforts aimed at reducing dolphin mortality have the unintended effect of increasing sea turtle catch. Battle of the cute species!!
Take home message? Catching fish causes a lot of turtles to die. While trawl fishing is the worst culprit, it is also the most studied and the technique for which a viable mitigation strategy exists. THe other kinds of fishing are less studied, and there is precious little that can be done to avoid sea turtle bycatch.
Happy fishing!
Tuesdays with Turtles – Travel Edition
It’s travel all the time for sea turtles. Of course, the great turtle race is finally on, and windy’s in the lead, my pick billie’s in second place, a mere 30 miles behind. There’s a new turtle in the race, Colbertia, named in honor of Stephen Colbert, in third place. Anything that gets turtles some attention is good.
But this is only a 500 mile sprint. PBS’ nature series had a one hour documentary on an 8000 mile, one plus year journey of a loggerhead turtle from her juvenile feeding grounds in Mexico to her adult breeding ground in Japan. It’s great to spend an hour at that close proximity to a turtle. But to me, the other animals, the dolphin pods, the giant fish swarms, the hammerhead sharks, the other sharks, the jelly fish, those little fish that eat parasites off the turtles and sharks kinda stole the show. There is something about thousands of animals of the same species doing something in concert.
Anyway, nothing more to say, except that 8000 miles is a long way at a mile an hour. I don’t think any of us can appreciate the mindfulness and sense of purpose (do turtles have these qualities, or do they just keep on chuggin’?), not to mention the huge amount of luck it takes to get it done.
Tuesdays with Turtles – Green Turtles Deluged?
I mentioned recently that elevated temperatures from climate could skew sea turtle sex ratios towards females. The featured news article highlights research which speculates that storm surges caused by increased hurricane (they call them cyclones in Austraila and India) intensity from climate change might lead to the flooding of green turtle nests in Florida, hastening their extinction. Why only the greens? Because they nest later than the other turtles and tend to be around during the height of the Atlantic hurricane season.
We know from previous research that loggerhead turtles have been nesting earlier because of elevated temperatures. Will the greens catch up. More pertinently, will there be enough survival of the early nesters of this generation to keep a viable population going while the whole population adapts? As with all climate change suspense thrillers, only time will tell… Depressing, at any rate.
News in Science – Cyclones may blast turtles to extinction – 15/05/2007
More severe tropical cyclones expected as a result of climate change may lead to the extinction of the green sea turtle in some areas within 100 years, researchers say.
The cyclones are expected to threaten how well the turtles nest and hatch eggs, placing pressure on already endangered populations, some of which are also threatened by fish trawling.
Researchers including PhD candidate David Pike, from the School of Biological Sciences at the University of Sydney, report their findings online in the journal Oecologia.
The researchers studied more than 40,000 sea turtles nests on an uninhabited, 38 kilometre stretch of beach along the Atlantic coast of Florida from 1995 to the end of 2005.
Each night during this period researchers surveyed the beach for turtles emerging to lay eggs, or for tracks of turtles that had already deposited eggs.
The stretch of beach is home to the loggerhead, green, and leatherback sea turtles, which start nesting at the beginning in April and end in late September.
This nesting season largely coincides with region’s tropical storm season, which runs from June to November.
Leatherback turtles (Dermochelys coriacea) and, to a lesser degree, loggerhead turtles (Caretta caretta) get around this by nesting and hatching earlier.
Only nests laid late in the season are inundated with seawater during storm surges.
But green turtles (Chelonia mydas) nest last.
Their entire nesting season occurs during Florida’s tropical cyclone season, which means their nests and developing eggs are extremely vulnerable to being washed away and killed.
Researchers are concerned that increases in the severity of tropical cyclones in the future may cause green turtle nesting success to worsen.
Fishing Major threat to Turtles
Well, not the least bit surprising, sea turtles have always been very difficult to track, and we’re finally getting verification that, gasp, turtles’ lives cannot be described in simple juvenile = open sea, adult = coast behavior.
BBC NEWS | Science/Nature | Fishing ‘major threat’ to turtles
Until now scientists have believed that young turtles live in the open ocean, but change to a coastal habitat when they reach a certain size.
But researchers working in Cape Verde found that most adults nesting there retain their open water behaviour, with the attendant risk posed by longline boats.
“The bottom line is that we thought juveniles experienced this risk out in the open ocean with longline fisheries,” said Brendan Godley from the University of Exeter.
“We thought that if you got them past that, then unless they’re being taken by inshore fisheries, you’re OK,” he told the BBC News website.
“But now you’ve got adults exposed to longline fisheries, which is very worrying.”
Tuesdays with Turtles – Must See TV Edition
PBS is showing a nature film following a loggerhead turtle on a looooooong journey.
Voyage of the Lonely Turtle
Sunday, April 15, 8:00pm
CHANNEL 4 (UNC-TV)F. Murray Abraham narrates this account of a 30-year-old female loggerhead turtle’s journey from Mexico to Japan (its birthplace) to lay eggs. During the yearlong trip (travel speed: 1mph), she passes an array of marine creatures, including blue whales.
Here’s a press release on the show, sounds great, don’t forget to watch (or record!): April 15th at 8:00 PM.
One Comment
Comments are closed.
“Dont Hyde” !! Ha, ha, thats so funny.. “Dont Hyde!” ROTFL