Monarch Migration: butterfly faces challenges along the way north and south

It was over three years ago that I started the RTSea Blog with an inaugural entry about the Monarch butterfly and its annual migration from the United States to Mexico. Not much of an ocean conservation subject but I linked it to the plight of white sharks and their migratory routes.

That was in May of 2008 and now the Monarch butterfly once again appears here, this time regarding how the Monarch butterfly is able to last through its entire journey and how researchers are tracking these butterflies in a manner, once again, similar to sharks: tagging.

The Monarch is an endangered insect due to the ongoing loss of deep forest habitat in Mexico. The trees are being cut down, usually illegally, and this limits the Monarch as it migrates south to the tropical forests in southern Mexico and the Yucatan peninsula.

Amazing as this annual migration seems, it is even more unusual because of the fact that many of the Monarchs do not live to make the entire journey, but their offspring know to continue southward, or northward depending on the time of year. Scientists are not sure as to why the Monarch has this ability to know where to go when born and they have yet to conclusively agree on how these insects are able to migrate from point A to point B and back again. Antennae which are sensitive to the magnetic fields around the planet is one of the more common theories - a concept that is used to explain migratory behavior in birds and even sharks.

As reported in the Kansan.com, a large population of Monarchs passes through Kansas, feeding on some of their primary food sources: nectar from milkweed and the Biden flower. In Kansas, there is an organization named Monarch Watch that monitors the butterflies' migration and conducts "tagging" of the Monarchs so that they can better determine the actual migratory route. Butterflies from across the central to eastern United States head south to a much smaller area in Mexico before heading northward in the early Spring.

Monarch Watch holds a one-day tagging event and this year's event drew 500 people of all ages to come see these butterflies and participate in learning more about the migration. According to Orely Taylor, ecology professor and founder of Monarch Watch, “Everybody needs to get out and experience the wild. We need to get out and enjoy nature, and this is one of the opportunities to not only enjoy and participate in this incredible phenomenon, but also to contribute to science by learning about these butterflies through their tagging.”

Just as there is concern over the Mexican government's ability to effectively police the forests and prevent poaching of the trees that the Monarch butterfly seeks at the end of its migration, so it is in Kansas that conservation groups wish to ensure that there is sufficient food for the butterflies as they pass through. Much of the butterflies' food source in Kansas grows in wetlands and wetlands across the nation are continually threatened by urban development. Monarch Watch makes available Monarch Waystation Seed Kits that allow concerned citizens to grow the various types of plants that the butterflies depend on for growth to sustain them through their journey.

If people can become interested in tagging and feeding an endangered butterfly - something that they can see, that flies right into their own backyard literally and figuratively, geographically speaking, then perhaps they can come to appreciate other animals around the world that migrate as part of an evolutionary pattern of self-preservation. Perhaps, as I mentioned in my very first blog post, the Monarch butterfly and great white sharks still have a lot in common.

Turtles and Sharks: long migrations studied in the South Atlantic

Animal migration is one of nature's most mysterious presentations of animal behavior. What makes an animal travel great distances? How are they able to do it in a relatively straight path? Why do they use the same route year after year? Just how are they so good at it, while I can get lost in the local Costco?

One vast body of water where several marine species migrate but where mankind has not spent much time studying these movements is the South Atlantic, between South America and Africa. However, two recent studies have shed some interesting light on the long migration paths taken by leatherback turtles and blue sharks. Both of these species are threatened with possible extinction, so the more we know, the better we can manage our conservation efforts.

As reported in the Proceedings of the Royal Society B, researchers from England tagged and track the migratory routes of leatherback turtles for five years, from a breeding colony in Central Africa to feeding grounds in the southwestern Atlantic. Using satellite tracking tags on 25 females, the researchers found that the turtles followed three migratory paths, often traveling in remarkably straight lines.

One female turtle was tracked along a path that totaled just under 4,700 miles and took about 150 days of nonstop swimming to complete. The researchers are keen to know the "when and where" of these journeys to ensure that commercial fisheries do not take advantage of the turtle's singular purpose and place themselves right in the turtles' paths. The researchers are hoping to avoid a large decline in leatherback turtles in the South Atlantic as has happened to leatherbacks in the Pacific.

"All of the routes we've identified take the leatherbacks through areas of high risk from fisheries, so there's a very real danger to the Atlantic population," said University of Exeter professor Brendan Godley.

At the same time, researchers from the University of Florida were tracking the migratory routes of the blue shark. Working with a Brazilian team of researchers, Felipe Carvalho, under the supervision of renown shark expert Dr. George Burgess, Director of the Florida Program for Shark Research, began tagging blue sharks along the Brazilian coast. The question was whether the tracking results would show a migration that would link shark populations in both the southeastern and southwestern Atlantic.

Blue sharks are heavily fished in the South Atlantic and within coastal territorial waters some nations are trying to determine how to best manage the remaining populations. By showing a migratory link between these separate locations, it emphasizes the need for multinational cooperation. As it turned out, one of Carvalho's blue sharks, tagged off the coast of Brazil, was detected off Africa 87 days later.

“This is the first evidence of the transatlantic migration of a blue shark from the southwestern Atlantic Ocean to the southeastern Atlantic Ocean. We thought this migration might be happening, but we never had the data before to prove it,” Carvalho said.

More and more, we are finding species that travel along oceanic highways, making incredible journeys over and over again. Navigating by prevailing currents, or visual cues, or even by the Earth's magnetic fields - all have been suggested as possible theories that could account for the animal's amazing accuracy.

Whatever the method, it is important for us to understand these migrations and their purpose and use that knowledge to protect rather than take advantage of leatherback turtles, blue sharks, and so many other species that roam the seas.

Read about tracking leatherback turtles from the Associated Press.
Read about tracking blue sharks from Physorg.com

Green Sea Turtles: coastal foraging puts endangered turtle at risk

Perusing the other ocean conservation blogs, I came across an interesting post written by Jesse Senko, marine researcher and seafood consultant for the Blue Ocean Institute - an ocean conservation non-profit headed by Dr. Carl Safina. Jesse writes of the challenges faced by green sea turtles as they forage through coastal areas. While tagging of sea turtles has produced important data regarding their long distance movements, not much is known about their shorter coastal movements, which actually constitutes the greatest part of their activity.

Although protected by law in Baja, Mexico, the green sea turtles are subjected to lax enforcement and protection and many turtles are lost to poachers or drowning in fishing nets. The turtles' dilemma in Baja reminded me of the supposedly protected white sharks, the juveniles of which can often be found in local Baja fish markets.

Daily movements of green sea turtles

Large marine vertebrates, such as sea turtles, are particularly vulnerable to human impacts due to their long lifespans, late maturity, slow reproductive rates, and extended migrations. Like most large marine vertebrates, sea turtles play key ecological roles in their environment when they are abundant. Green sea turtles are especially important in coastal areas because their grazing behavior significantly reduces nutrient cycling times in seagrass pastures.

In Baja California, Mexico, green sea turtles are protected by law, but lack of enforcement, coupled with drowning in fishing nets and illegal poaching has led these turtles to the brink of extinction. The majority of green turtles that are killed in Baja California are juveniles inhabiting coastal foraging areas; thus, understanding their movements and habitat use in this environment is a priority for conservation efforts. Nevertheless, while researchers have tracked the long-term movements of mainly nesting sea turtles, there is very little known about the short-term movements of green turtles in coastal foraging areas. Understanding this aspect of their biology is particularly important because green turtles spend the majority of their lives in these environments where they come in direct contact with fishing nets and poachers who often sell their meat on the black market.

Above: Jesse Senko (author) holding a green turtle before it is released

Recently, a team of biological scientists set out to better understand green sea turtle fine scale daily movements in a coastal foraging area along the Pacific Ocean in Baja California, Mexico. They developed a novel tracking device to conduct their study. The tracking tag consisted of a buoy that housed a GPS logger to record turtle movements and a VHF transmitter to locate the tracking tag. The researchers tethered the buoy to six green sea turtles. They found that green turtles were active throughout 24-hour periods while moving large distances over surprisingly short time periods. “We were surprised to see how far some of the turtles moved over temporal scales as short as one or two days. We had some turtles that moved total distances as far as 29 kilometers (18 miles) and occupied areas as large as 1,575 hectares (6 square miles) in a single 24-hour period”, said Senko, the study’s lead author.

The researchers also found that turtles were active throughout day, night, and crepuscular (dawn and dusk) periods of activity. “These results indicate that turtles were active throughout 24-hour periods, and did not show preferences for certain periods of the diel cycle (one 24-hour period). Given our findings that turtles moved large distances over short time periods and were active throughout 24-hour periods, conservation strategies intended to protect this endangered species may ideally need to encompass the entire coastal foraging area rather than focus on a few high use zones”, added Senko.

Above: Tracking a turtle

The full study in Journal of Experimental Marine Biology and Ecology can be found online at: http://wallacejnichols.org/wallacejnichols/Research/Entries/2010/9/2_JEMBE__Movements_of_green_turtles_in_Baja_files/*Senko_JEMBE_2010.pdf

Studying Pacific Blue Marlins: scientists enlist the aid of sportfishermen

Cruising throughout the warmer waters of the Pacific, the Pacific Blue Marlin is one of the most magnificent of the top or "apex" predators to roam the seas. But as with many other pelagic sea creatures, not much is known about them. A majestic mystery.

But that is slowly changing through the help of a seemingly unlikely source: sportfishermen. The Pacific blue marlin is a highly prized catch in ocean sportfishing; landing such a fish can entail hours upon hours of strenuous effort, making it one of the pinnacle goals of the sport. But rather than lose the fish to a trophy photo or dinner plate, the marlins are being released after being tagged with satellite tracking tags.

Stanford University's Hopkins Marine Station, home to the Global Tagging of Pelagic Predators (GTOPP) program, has been working for nearly a decade on tagging a variety of ocean predators, ranging from billfish - like the marlin - to tuna, great white sharks, and more. Headed by Dr. Barbara Block, GTOPP has uncovered migratory patterns that were heretofore unknown, such as the migratory patterns of white sharks traveling from the California and Baja coasts to a large area in the Pacific, dubbed the White Shark Cafe, and then back to their respective coasts year after year.

Working with sportfishing tournament organizations, such as the Hawaiian International Billfish Tournament, GTOPP has promoted catch-and-release techniques that allow the researchers to tag the animals with electronic tags that can record a variety of information including global position, speed, and depth. Ultimately, the tags come free and upon reaching the surface, release their stored data to satellites for study by an anxious and waiting team of researchers.

GTOPP researchers just recently completed launching a series of ten tags on Pacific blue marlin caught as part of the Hawaii's big marlin tournament; an event called the Great Marlin Race due to the long distances that the marlin can cover. They are waiting to see what new surprises the tagged animals will reveal as they patrol the open sea.

In 2009, several tagged marlin traveled a distance of more than 1800 miles, from Hawaii to the Marquesas Islands. In addition to such a long distance, what made this remarkable to the researchers was the fact that the animals crossed the equatorial region, which is unusual due to its warmer surface temperatures and lower oxygen content - not a normally hospitable environment for a high energy-consuming animal like a marlin.

"The equatorial region is such a significant boundary for so many species, it was really surprising to see that three long tracks went right across it," said Randy Kochevar, Hopkins Marine Station marine biologist. "We don't really know a lot about the marlins' patterns and their behavior. It appears that rather than traveling to a particular place to spawn, and then spending the rest of the year feeding, like tuna, it seems like they are constantly spawning and they sort of come and go from place to place."

So, while some tagged predators have defined certain migratory routes or oceanic highways, like the white sharks traveling from the coasts to mid-Pacific, other animals appear to roam the seas, perhaps directed by yet undiscovered stimuli. Enlisting the aid of sportfishermen in events like the Great Marlin Race, can be an effective means to learn more about these important ocean predators while allowing the fishermen to engage in the most challenging aspect of their sport - and at the same time preserving the species rather than see it hanging tails-up from a local dock.

The Shark Free Marinas Initiative is another organization that encourages catch-and-release techniques for sportfishermen, politically avoiding a more confrontational approach (banning sportfishing altogether) by taking an incremental step toward shark protection and confrontation. While some people may debate the hooking and reeling in of sharks or marlins as unnecessarily cruel, it has proven itself to be one of the more effective methods for enabling scientists to tag and track these animals.

"What we hope to learn from this work," says Stanford marine biologist George Shillinger, "is basic information about these animals' life histories. We want to know where they go to feed and where they go to breed. We want to understand how they use the ocean in which they live and, ultimately, how we can manage their populations to ensure that they remain plentiful."

Read more about GTOPP and the Great Marlin Race at their website.
Read more about marlin tracking and see a brief video through Stanford's Hopkins Marine Station.