A blog about some of the Antarctica Weddell seal population study field research work and outreach efforts during the Weddell seal pupping season in the Erebus Bay region of Antarctica's Ross Sea. Weddell seal images & recordings obtained under NMFS Permit Numbers 1032-1917 & 17236. More information at http://WeddellSealScience.com
The 2013 Weddell seal pupping seasonis now coming to an end. The Erebus Bay sea ice is melting and breaking up as the pups are left to fend for themselves. They will soon head out into the Ross Sea for the Antarctic summer to start their new lives, and will face difficult times ahead as they hunt for food and try to avoid their predators, Orcas and leopard seals. The Weddell population projectfield research team has now flown off the ice to Christchurch, New Zealand, and will be heading on to various holiday destinations.
As this holiday season approaches, our new Weddell seal project video that tells the story of "What It Means to Be Different If You're a Weddell Seal" is now available as a high definition video free at iTunes through the featured podcast, DiveFilm HD Video. The beautiful photo of Weddell pups in the iTunes Podcast Home Page marquee above is by Montana State University graduate student and Weddell project field team alumnus Jesse DeVoe, obtained under NMFS Permit No. 17236. (Thank you, Jesse!)
This new 12 minute high definition video also has been released in broadcast quality via TelVue Connect on the Roku channel, "The Knowledge Network." This great new Roku channel offers science-themed videos from sources associated with the National Science Foundation.
Featured in the video is some of the most amazing footage ever of Weddell seal pups underwater, filmed by renowned musician, Antarctic diver and videographer Henry Kaiser, courtesy Project B-470 obtained under NMFS Permit No. 15478 and ACA 2003-12. (Thank you, B-470 and HK!) The video also features some of the best of B-009's Weddell project imaging, including remarkable footage of a Weddell seal birth, and numerous shots of engaging Weddell pup and mom interaction, obtained under NMFS Permit Nos. 1032-1917 and 17236.
A friend of mine called the other day to tell me he liked the new Weddell seal video. He also said he wondered, though, just why it is that these particular Antarctic seals are the focus of our study. After all, he asked, why can't all this population stuff be studied just as thoroughly by working with seals that live closer to home--like the harbor seals that congregate down at our local breakwater?
As I began to think more about what he said, I realized that he was asking a very good question--why is it so important to study theseparticularWeddell seals?
So here it is: A list of 10 top reasons why it's important to study these Weddell sealsof Erebus Bay in Antarctica:
Reason #10. This group of Weddell seals in the Erebus Bay area of Antarctica's Ross Sea is a healthy, stable population of high level marine predators. So it's kind of like being able to study a healthy patient if you're a doctor--it helps you to better understand how a healthy population of long-lived mammals works in order to better understand and manage other long-lived species that are endangered or aren't doing as well.
Reason #9. This stable population of long-lived mammals lives its entire life in the most pristine marine environment left on Earth. So this is a rare opportunity to study a healthy population of marine predators that is currently functioning well in a healthy marine environment--and in so doing gain a better understanding of healthy interaction in a healthy ecosystem.
Reason #8. This stable population of Weddell seals, however, is living in a nearly pristine marine environment that is just beginning to experience potentially problematic environmental changes--both natural and man-made--climate change, increased ocean acidification, and possibly an increasing occurrence of extreme environmental events, such as more frequent calving of giant icebergs. These seals can act like as a bellwether of the kinds of effects such environmental changes can have on a previously healthy marine mammal population.
Reason #6. Located very near the main U.S. Antarctic base, McMurdo Station, this population of Weddell seals provides researchers relatively easy access using surface vehicles based at McMurdo Station, with an entire support system in place to ensure vital science support to the researchers.
Reason #5. Tending to be fairly docile toward researchers, these Weddell seals are relatively easy to approach for scientific observation and interaction. This is likely because Weddells do not have a long history of dealing with natural predators on the sea ice during the Austral winter.
Reason #4. These Weddell seals are "philopatric" meaning they tend to return to the same areas where they were born to have their own pups. So even though there is some limited immigration and emigration of seals into and out of the established pupping colonies, for the most part this is a fairly closed and stable population, with predictable pupping colony sites.
Reason #3. The moms and pups are easily detected on top of the sea ice for the first week or so after the pups are born and before they learn to swim because they must remain on the surface, where they are particularly visible and accessible to the researchers.
Reason #2. Because of this ease of access, this particular population of Weddell seals has been studied for nearly half a century (>45 years), and an extensive database has been developed during that time that includes information on thousands of mom/pup pairs over several generations.
Reason #1. This longterm population database of a long-lived mammal studied intensively over generations spanning decades is unique in the scientific community, and provides scientists with a dataset that makes possible innovative ecological discoveries as the fields of population modeling and statistical methodology continue to advance.
Oh, and this top ten list doesn't even mention that these amazing animals are the southernmost mammal on Earth! That they are fantastic divers that travel further under the sea ice than any other animal on our planet to birth their pups safely away from other large predators. And that they spend a lot of time nurturing their young and likely passing on valuable survival skills during the nursing period!
The B-009 Weddell seal population study field team lives and works in wooden huts not all that different from the historic wooden huts built by members of Ernest Shackleton's and Robert Falcon Scott's expeditions during the "heroic era" of Antarctica exploration in the very early 1900s. In fact, Scott's and Shackleton's historic huts are located geographically so near the Weddell project field team huts that one cannot help but have a palpable sense of being surrounded by the very history of Antarctic exploration.
B-009 Kitchen Hut Exterior with SunDog and Kitchen Hut Interior Looking Out the Window Toward Mt. Erebus and Big Razorback Island.
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Shackleton's Nimrod Expedition Hut
Built over 100 years ago in 1908 as part of Sir Ernest Shackleton's Nimrod Expedition, the hut is filled with the effects and furnishings from that "heroic era" expedition. Because of the hard work and diligence of the Antarctic Heritage Trust, the hut and its historic contents have been restored for future generations of visitors and scholars to enjoy, learn from and be inspired by.
The Antarctic Heritage Trust describes the decision Scott made to build his second hut at Cape Evans: "The gently sloping ground of this narrow volcanic neck of land with the ramparts of Mount Erebus rising behind and McMurdo Sound in front proved ideal for establishing his base. Originally discovered during Scott’s National Antarctic Expedition 1901–04, the area was named for the large number of skuas that flocked there, but Scott renamed it Cape Evans after the expedition’s second-in-command, Lieutenant Edward ‘Teddy’ Evans. A short distance inland is a large lake named Skua Lake, while to the east the ground rises to form The Ramp and beyond, glaciated slopes rise toward the summit of Mount Erebus. From the hut site there are fine views east over McMurdo Sound to the Trans-Antarctic Mountains and south to the Dellbridge Islands."
White Island. A small volcanic island of the Ross Archipelago in Antarctica poking up through the Ross Ice Shelf several miles south of McMurdo Station. The island is home to an isolated colony of Weddell seals that are trapped there by the Ross and McMurdo Ice Shelves, and the seals' inability to swim far enough under the ice to rejoin the main Weddell seal population in Erebus Bay.
One of the tasks of the Weddell population project is to travel to White Island during the Weddell pupping season to survey, tag, and collect genetic samples from the trapped colony. Last season they found 6 adult females and 3 pups (so 3 of the adults were moms), according to field team leader Thierry Chambert. Here is a short video of a helicopter trip to White Island during a previous season...
Weddell seals are the southernmost mammal on Earth. And this small colony of Weddells trapped at White Island has the distinction of being the most southerly of all--and closer to the South Pole than any other mammal on the planet.
"The minimum distance between the island and open water averages approximately 20 km, but varies annually depending on the extent of sea-ice break-out in McMurdo Sound. Except for a narrow crack along the island’s northwestern side (Stirling 1966), maintained by tidal action and movement of the ice shelf, the ice exceeds 15 m thick within 20 m of shore (Castellini et al. 1984, 1991). There are no other known cracks or holes in the vicinity. A small isolated population of Weddell seals breeds and pups at White Island and uses the tidal crack as its only access to the surface."1
Using historic accounts of earlier explorers and researchers, it is thought that the seals became trapped at White Island sometime back in the late 1940s to 1950s when the sea ice broke out during the Antarctic summer so far south that a small group of seals was able to make it to White Island. However, when the sea ice reformed, the seals that didn't leave the island in time were trapped there. The swim under the ice is further than they are capable of surviving. And they are also likely blocked by the Ross and McMurdo Ice Shelves, as well. Since that historic time, the sea ice has yet to break out far enough south again to free these seals.
Map usage courtesy U.S. Department of Commerce.
So, how is it that a small colony of Weddell seals trapped at White Island for over half a century and isolated from the rest of the Weddell seal population in Erebus Bay has managed to survive and successfully reproduce?
Because White Island is subject to the same tidal rise and fall of the ocean as is any other island, a tidal crack in the fast ice surrounding the island is maintained year around by that tidal movement. However, because the island is located in the Ross and McMurdo Ice Shelves, the ice surrounding the island is very thick--as deep as 45 feet in places near the island. The White Island seals have access to the ocean to hunt via this very deep tidal crack. To give birth on the surface of the ice, somehow these seals make their way up to the surface of the ice shelf through this deep tidal crack. Even more mysterious is how the Weddell pups born on top of the ice shelf are able to survive the steep drop down through the deep tidal crack to reach the ocean below to learn to swim and hunt.
One thing is for certain: despite great challenges to their survival, this colony of hardy seals has persisted for well over half a century to live and pup at this isolated colony, cut off from the general population of Weddells many miles away. How long they will continue to persist is a mystery; and equally so, whether the sea ice will ever again break out far enough to free these seals so that they may rejoin the Erebus Bay colonies.
The Weddell seal population field team makes two annual visits by helocopter to the White Island Weddell colony to survey, tag, and collect genetic samples from these seals, and has been doing so for many years. While the seals are unable to mix with the general population of Erebus Bay, they are still originally of the Erebus Bay Weddell population. The Weddell population project collaborates with other Weddell research groups to make census information and genetic samples available for further study.
Geneticists have determined that, "The White Island [Weddell seal] population showed altered reproductive dynamics compared to Erebus Bay [Weddell seals], including highly skewed sex ratio, documented inbred mating events, and the oldest known reproducing Weddell seals."2
According to scientists studying the genetics of these isolated seals, "The extensive amount of data available about the White Island population provides us with an opportunity to better understand the origin and fate of such Weddell seal colonies, and, by extension, of other small and isolated population of large mammals."3 This kind of insight may also be useful in better managing threatened populations of other large mammals elsewhere in the world--populations facing habitat loss or other challenges to their survival.
You can access our Google Earth Explore the Ocean videos by installing Google Earth, and ensuring that the Ocean layer and the Explore the Ocean layer are both selected.
Then click on the image to the right and enjoy Google Earth's Explore the Ocean Layer!
What does it mean to be different if you're a Weddell seal in Antarctica? Our new project video explores individual variation in Weddell seals studied by the Weddell population project research team, and what such individual variation might mean for the future of this southernmost mammal living in the most pristine marine environment on Earth.
Over the years the Weddell project has published a number of scientific papers on various aspects of individual variation in Weddell seals. Among the most recent project publications is a fascinating paper on whether frequency of pupping--how many pups a Weddell seal mom has over her lifetime--is a fixed or real characteristic of these seals, as opposed to a chance, or random, occurance. Researchers found that this life history characteristic involves a fixed trait and, interestingly, one that continues to be expressed in harsh environmental conditions.
Weddell seal survey days are long ones for the field team. The team will cover the entire Erebus Bay study area in one 24 hour period to count, identify, and record every seal encountered during that single sweep. To accomplish this, the team will travel by snowmobile to the all different Erebus Bay pupping colonies, and move quickly through those colonies to record every seal they come across.
This survey information is recorded in both the small field books the researchers carry and the hardy handheld field computers they use on the ice. Back in camp after the survey, data entered into the field books will be compared with the data entered into the field computers to ensure accuracy of the count. Lead scientist Jay Rotella notes, "For each seal observation, we record the date, location, seal tag numbers, sex, age class. For females with pups, we also record that they are a pair. For a subsample, we also collect a very small tissue sample for genetics work and record that. If we weigh the seal or outfit it with a swim tag, we also record that information."
Since Weddell seals spend a good amount of time in the water, they may not be visible to the team when it moves through an area on a particular occasion. To address this, 6 to 8 full surveys will be conducted over the pupping season. This makes it more likely that the researchers will encounter every seal in the study area at some point during the survey period, and so achieve an accurate count of the entire Weddell seal population in the study area for the current season.
"When the effort to tag all the pups born into the McMurdo population was initiated an effort to walk through the pupping colonies and record all the individuals present, along with the tag numbers, was begun. These 'census' efforts were generally repeated at least seven times each pupping season and the census tallies became the central part of the growing database."
"Initially, data from these census undertakings were recorded in a standard field notebook," Siniff explains, and that practice continues to this day. "In the mid 1980s, small handheld computers became available. This started a process of developing a data entry system that could be used to record tag numbers and the other data as we moved through the pupping colonies."
"Ward Testa was instrumental in this development at this time, and wrote the first data entry program which contained routines that checked each entry as it was entered to make sure the new data were consistent with what was already in the data base. This data checking routine proved extremely valuable in limiting the number of mistakes entered into the data base."
More work on improving the field computers was done by Michael Cameron, who worked as a PhD student with Don Siniff on the Weddell project for a number of seasons. Siniff notes, "In the late 1990s Michael Cameron contributed significant upgrades to what Ward Testa had developed, and we purchased new field computers as they came on the market. This was essential as the database was continually increasing in size and the data checking programs needed additional computer storage space and increased speed."
"In 2002 the project moved to Montana State University with Jay Rotella and Bob Garrott as lead principal investigators. The data entry program was rewritten by the Montana State University program in order to take advantage of the upgrades in handheld computers and bring the data entry software up to date. Since its arrival at MSU, the database has been subjected to analyses taking advantage of the fact that the McMurdo population database currently consists of over 80 percent known-age individuals."
This season, the team is using a new field computer called the Trimble Ranger 3, shown in the photo below, which includes GPS capability.
Notes Siniff, "The database now consists of perhaps the most complete record on marked individuals that have been seen repeatedly over their lifetimes. These data can now be subjected to advanced statistical analyses, using the latest programs and models that make up a major area of study focusing on multiple mark-recapture data. A number of population statistics can be accurately estimated from such analyses, including the investigation of ecosystem measures whose influence on the dynamics of the Weddell population can now be explored in detail."
It started with viewers posting the video on various blogs, then ramped up rapidly when Reddit picked it up. And now, it just went completely viral as HuffingtonPost.com posted an article about the video and posted the YouTube video, itself.
She's back! And she's making Weddell seal population project history.
The B-009 field team was working in the Hutton Cliffs area of Erebus Bay when they located a remarkable mom and her new pup. According to project lead scientist Jay Rotella, this extraordinary Weddell mom, known in the project database as SPENO 5970, is now 30 years old and has given birth to her 21st pup. This makes her among the oldest Weddell seals recorded in the 45 year history of the project, (the oldest on record being 33). At 21 pups to date, she is the project record holder for producing the most pups over a lifetime. We first wrote about this Weddell super-mom last season, when she was located by field team members in 2012 at Hutton Cliffs.
Project lead scientist Bob Garrott working with the field team in Antarctica took this photo yesterday of field team leader Thierry Chambert affixing a tag to the new pup's rear flipper as mother SPENO 5970 looks on.
As with all of SPENO 5970's previous 20 pups, her new pup was born at Hutton Cliffs pupping colony in the Erebus Bay study area. Weddell seals are philopatric, meaning they show a strong fidelity to the area where they were born, and usually return to the same area to have their own pups.
SPENO 5970 was born in 1983 at a pupping colony in the Erebus Bay study area referred to as Glacier Tongue North Base. This pupping colony is relatively close to the Hutton Cliffs pupping colony, where all of SPENO 5970's 21 pups have been born over her reproductive life to date.
After SPENO 5970 was born at North Base in 1983, she disappeared from the Weddell population for two years before first returning to the study area as a two year old youngster in 1985. She returned again in 1988 and 1989 as a pre-breeder, meaning she had not yet had a pup. Then in 1990 she returned and gave birth to her first pup at Hutton Cliffs.
Project lead scientist Jay Rotella notes that what is so remarkable about this Weddell mom is that she has had pups at ages 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 29, and 30. Weddell seal moms live an average of 15 years, and usually have around 2 pups every 3 years, so this long life and frequency of pupping is quite unusual. "She had pups in every year from 1990 to present except for 1993, 2010, and 2011," says Rotella.
SPENO 5970 with her 21st pup in a photo by field team member Terrill Paterson.
Because of the longterm dataset of the Weddell seal population project, the researchers are able to keep track of the animals in the study area and access data on over four decades of seals and several generations. Working with the extensive database, Jay Rotella was able to determine that of SPENO 5970's first 20 pups, 10 were females and 10 were males. "Of those offspring, 2 sons and 2 daughters have been seen again, which is right in line with what we'd expect based on other analyses [indicating] that roughly 20% of the seals make it to adulthood."
Of SPENO 5970's surviving offspring, two daughters have returned to the pupping colonies to give birth themselves. One of those daughters is 22 years old and has produced 13 pups so far. One of that daughter's pups--a granddaughter of SPENO 5970--has gone on to have 5 pups herself.
SPENO 5970's daughter 8731AA with her new pup (SPENO 5970's granddaughter) in a photo by field team member Terrill Paterson.
"Through her own pups and those of her daughters and grandaughters, she is responsible for 40 pups so far," notes Rotella. And this does not even take into account how many offspring she may be responsible for through her sons!
SPENO 5970's daughter, 8731AA, in a photo by field team member Terrill Paterson.
So, what can Weddell seal researchers learn about these seals by tagging them? Well, it turns out, a lot!
When a small, uniquely numbered tag is attached to the rear flippers of a Weddell seal, the researchers record a substantial amount of data on that animal. Lead scientist on the Weddell project Jay Rotella notes, "For each seal observation, we record the date, location, seal tag numbers, sex, and age class. For females with pups, we also record that they are a pair. For a subsample, we also collect a very small tissue sample for genetics work and record that. If we weigh the seal or outfit it with a swim tag, we also record that information."
Since 1968, over 22,500 Weddell seals have been tagged by the Montana State University based Weddell seal population project, and their information added to the extensive project database. This means that the B-009 Weddell population project has recorded vital information on over four decades, and several generations, of Weddell seals in the Erebus Bay study area, making this one of the longest running population studies ever of a long-lived mammal, and providing a database that is unique in the field of population ecology.
The researchers know how many seal pups survive to return to the pupping colonies as adults (around 20% of female pups survive to return as adults), how long the seals live (the oldest seal recorded in the study to date is 30 years old), how many pups the females have over their lifetimes (anywhere from 0 to 21 pups over a lifetime, recorded to date), and which of those pups survived to return to the study area to have pups of their own.
For well over a decade, many of the Weddell seal pups have been weighed at three different stages of their nursing period, which lasts approximately 45 days. Researchers weigh a select number of pups to determine their mass (weight) at birth, at the mid-nursing period, and at weaning. Some Weddell moms have been weighed during that nursing period, as well. So, the mass of these seals at various points in their lifetimes is also a vital part of the extensive project database, and central to the mass dynamics work of the Weddell seal population project. Unfortunately, due to the delay in the field season start this year because of the government shutdown, very few Weddell pups and moms will be weighed this season due to lack of data regarding accurate dates of pup births to correspond to those animals' weights.
In 2010, the project began a pilot study of Weddell seal pup swimming behavior during the nursing period. Co-Principal Investigator Bob Garrott developed a small temperature tag to attach to a select number of pups' flippers to record the surrounding temperature at six minute intervals over the course of the nursing period. This simple temperature recording tag allows researchers to know how often and for how long pups are in the water during the crucial time in their lives when they are learning to swim and interact underwater with their moms. Here's a project video on Weddell seal pup swimming behavior and survival, and the temperature tag study...
For about a decade, the researchers have also taken genetic samples from a select number of seals, and are developing a genetic archive of this population to enable even more discoveries in the future based on genetic analysis.
By recording the birth date, birth location, re-sightings, and reproductive histories of these seals, and determining a select number of the seals' weights at various stages of their lives, as well as recording the swimming history of a select number of pups, the researchers are able to use all of these data to determine whether there are correlations with environmental changes and variation, and to assess the effects of extreme environmental events on this population of Weddell seals.
Lead author of this fascinating study, project PhD recipient Thierry Chambertnotes that, "Interestingly, results also suggest that the expression of these individual reproductive differences tended to remain constant across varying environmental conditions." Females that were "robust" reproducers tend to reproduce at higher than average rates even in harsher environmental conditions. As Jay Rotella puts it, "When the going gets tough, the tough stay--and they keep on producing pups!"
Viewers can learn more about individual variation in Weddell seals in a new project video to be released later this month, so please stay tuned!
