Field Report From Parker Levinson, MSU MS Student and Field Crew Leader:
It’s hard to believe the end of the season is here. We’ve been working hard the past couple weeks to complete surveys, which are crucial for the resight part of the project. The tags we put on the seals are simple plastic livestock tags so the only way to know if a seal has survived from one year to the next is to physically locate that seal in our study area and record that specific tag number. We’ve already done that for females who have had pups, but we haven’t recorded all the lone adults in the study area, so surveys allow us to record all the seals present in the area and determine annual survival rates.
Mairan Smith reading and recording tag numbers on a survey. Photo credit: Parker Levinson.
By completing numerous, systematic surveys, we’re also able to figure out how many seals are present in the study area. Although we tag every pup in the study area, some adults do not have tags. During a survey, we record how many untagged animals are around so we can better estimate the entire population size.
Lastly, surveys help us understand colony attendance patterns. On average, a Weddell female will breed 2 out of every 3 years. During the years when she is not breeding, she might come back to the study area to mate in which case we would record her during a survey, but she may also go somewhere else on her "off" years. Recording who is present in which years helps us understand what environmental variables cause a seal to show up even when she isn't having a pup.
Our study area is about 75 square miles so it takes a fair bit of time to survey it in its entirety. We split up into groups and map out survey routes the night before to ensure we cover the entire study area. Normally, we also record mom and pup pairs; however, we have a lot of seals this year, so to increase efficiency, we’re focusing our final few surveys on lone adults that are in the area as we’ve already recorded the mother/pup pairs. With three teams of two people, we can cover the entire study area in about 9 hours.
Surveys have been really interesting this year. We’ve had a handful of animals show up that we haven’t recorded in over a decade. For example, last survey we recorded a male wearing tags “9501A” who hasn’t been seen in our study area since he was tagged as a pup in 2009. We’ll see if he continues to show up in future seasons.
A male Weddell seal guards a breeding hole by Tent Island. Photo Credit: Avalon Conklin.
We’ve also seen a handful of one, two and three year old seals coming back to the study area, Typically we don’t see these younger seals until much later in their life. It’s pretty exciting to see and record these individuals to mark that they survived the earlier years of their life as juvenile survival is relatively low. These seals tend to be a lot smaller as they haven’t reached full adult size yet.
Covering so much ground in a single day allows us to see a lot. Last time we saw both an emperor penguin and an Adélie penguin, which was quite exciting! The emperor penguin was quite curious about our snowmobiles.
An emperor penguin walked a couple hundred meters to investigate our snowmobiles after we had stopped.
Photo Credit: Parker Levinson.
We're completing our final survey in the next couple of days before our time in the field comes to a close. Then, we'll transition to cleaning and organizing our gear as we get ready to redeploy back to the United States.
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