Using Time Lapse Cameras to Document Year-Round Steller Sea Lion Presence at South Marble Island and Graves Rock in Southeast Alaska
Alaska Department of Fish and Game – Steller Sea Lion Research Program
During summer 2016, ADF&G researchers installed autonomous time-lapse cameras at six sites as part of our effort to observe, year-round presence of Steller sea lions in Alaska. Two of these cameras were deployed in Glacier Bay National Park (GBNP) at Graves Rock and South Marble Island. The camera system consists of a modified, watertight, Pelican case which contains a Canon DSLR camera body, zoom lens, and an external battery pack. The camera is pointed out a clear acrylic viewing window installed on the side of the Pelican case. The battery is connected to compact 20 watt solar panel and both the Pelican and solar panel are mounted to a wooden frame which is in turn secured to the ground via a combination of heavy mass (e.g. sand bags or rocks), temporary anchors (e.g. climbing nuts), and adhesives (e.g. 2 part epoxy resin). The tower is then camouflaged with paint, netting, and if available any vegetation dislodged during installation (Figure 1). The camera system has an adjustable timer, 256gb memory card, and supplemental solar power so it should in theory allow for >1year of uninterrupted observations. Mother Nature is hard on equipment, however, so we visit our cameras several times per year to ensure they’re still functioning as intended.
FIGURE 1. These images show the time lapse camera installed at South Marble Island. A) The gold star indicates the location of the camera overlooking the haulout in the foreground. B) The camera was camouflaged using a combination of paint, netting, and local vegetation. C) The elevated vantage point means that the camera captures the entirety of the haulout. D) We can use images captured by this camera to identify permanently marked Steller sea lions and then ascertain population trends- for example sea lion T244 was marked at Marmot Island in 2004 and has been documented at South Marble Island repeatedly including this photo from 2012.
Alaska Department of Fish & Game (ADF&G) biologists have been studying the life history of Steller sea lions (Eumetopias jubatus) throughout their Alaskan range for more than 50 years. In some areas such as the western Aleutian Islands, populations have declined about 90% since the 1970’s and have not recovered. Meanwhile, overall eastern population counts have been increasing roughly 3% per year during this same timeframe. Sites in and around GBNP in northern Southeast Alaska were first colonized during the 1980’s through 2000’s and have seen even higher annual growth. This region saw an overall average increase of about 8% per annum, with yearly growth as follows: Graves Rocks ~4%, South Marble Island >16%, and Inian Islands >14%.
You might be wondering “How do scientists know that the Steller sea lions from the declining sites aren't just moving to Glacier Bay where conditions are apparently better for some reason?” Well, researchers from a number of agencies have been permanently marking a small number of Steller sea lions from various sites, tracking their movements during annual surveys, and using that information to determine the overall population survival rate.
FIGURE 2. Glacier Bay National Park has two of the fastest growing Steller sea lion (SSL) haulouts (indicated by stars in the left image) in Southeast Alaska- Graves Rock, a rookery, and South Marble Island, a haulout. We placed a time-lapse camera at each site during 2016. In the right image of South Marble Island, one normal location for SSL aggregations has been circled and the camera system is indicated by a star.
The rugged coastal Alaskan sites preferred by Steller sea lions are extremely remote so the simple act of just getting there to survey what’s around is very time consuming and as they say, time is money, especially on a boat. What’s more, these surveys only really provide a short glimpse of what’s going on out there. As such, even if you encountered sufficient workable weather windows (that’s a really big if), sending people to most sites multiple times per year is prohibitively expensive. However, in recent years digital cameras, batteries, and solar panels have seen vast improvements coupled with decreasing costs which means that deploying a year-round automated observation post (i.e. autonomous camera) has become a reasonable supplemental tool for collecting sea lion survival data.
The South Marble Island camera was deployed during mid-August and has not been serviced since then, so we don't currently have any data from that site. The camera at Graves Rock was deployed during July and serviced during mid-August. Nautical conditions on-site during August were challenging, with large waves sweeping through from all directions (Figure 3) so surveying Steller sea lions from the boat was not a good option. However, the camera was unaffected by these swells which is precisely why we deployed the camera in the first place. The 4400+ images captured by the camera have not been analyzed yet, but a quick review showed that marked Steller sea lions are clearly visible throughout the deployment period. We’ll know more about whether our camera systems are viable or not when we get back to service them again this winter.
FIGURE 3. On-site conditions at Graves Rock during our mid-August camera service trip included 8’ swells from the south, which were wrapping around the islands and arriving from all direction at all times. These confused seas made it very challenging to view sea lions from the boat (left), however the camera was not affected by similar conditions as indicated by the image it took on the right.
Last updated: December 2, 2016