A New Technique to Study Seals Habitats in Alaska

One harbor seal resting on the glacier ice (Source: Jamie Womble/NPS)
One harbor seal resting on the glacier ice (Source: Jamie Womble/NPS)

There are numerous harbor seals (Phoca vitulina) living in tidewater glacier fjords in Alaska. Harbor seals are covered with short, stiff, bristle-like hair. They reach five to six feet (1.7-1.9 m) in length and weigh up to 300 pounds (140 kg). Tidewater glaciers calve icebergs into the marine environment, which then serve as pupping and molting habitat for harbor seals in Alaska. Although tidewater glaciers are naturally dynamic, advancing and retreating in response to local climatic and fjord conditions, most of the ice sheets that feed tidewater glaciers in Alaska are thinning. As a result, many of the tidewater glaciers are retreating. Scientists are studying the glacier ice and distribution of harbor seals to understand how future changes in tidewater glaciers may impact the harbor seals.  Jamie Womble, a marine ecologist based in Alaska, is one of them.

Harbor seals on the glacier ice. (Source: Jammie Womble/NPS)
Harbor seals on the glacier ice (Source: Jamie Womble/NPS).

As Womble put in her recently published paper in PLOS One, “The availability and spatial distribution of glacier ice in the fjords is likely a key environmental variable that influences the abundance and distribution of selected marine mammals; however, the amount of ice and the fine-scale characteristics of ice in fjords have not been systematically quantified. Given the predicted changes in glacier habitat, there is a need for the development of methods that could be broadly applied to quantify changes in available ice habitat in tidewater glacier fjords.”

Map of Wombls's study area(source: Robert W. McNabb).
Map of Wombles’s study area (Source: Robert W. McNabb).

To conduct her research, Womble has used a variety of analytical tools including geospatial modeling (GIS), multivariate statistics, and animal movement models to integrate behavioral and diet data with remotely-sensed oceanographic data. Most recently, she has worked with object-based image analysis (OBIA).

“OBIA is a powerful image classification tool. Many people studying forests and urban areas use it,” Anupma Prakash, a colleague of Womble and professor of geophysics at the University of Alaska, told GlacierHub. “In our case, we could not use the satellite images because the satellite images did not have the details we required. We flew our aircraft quite low so we saw a lot of detail and could identify individual icebergs.”

OBIA offers an enhanced ability to quantify the morphological properties of habitat. Satellite imagery, on the other hand, is not a viable method in Alaska as there are few cloud free days.

 

“We wanted to classify our images into water, iceberg, and brash-ice (small pieces of ice and water all smushed together),” Prakash added. “The color and smoothness of water helped us isolate it. For icebergs the color, shape, and angular nature helped us isolate it, and the rest was bash-ice.” So it is now feasible to quantify fine-scale features of habitats in order to understand the relationships between wildlife and the habitats they use.

Harbor seals on the ice (source: Jamie Womble/NPS).
Harbor seals on the ice (Source: Jamie Womble/NPS).

Thanks to the work of scientists like Womble and Prakash, OBIA can now be applied to quantify changes in available ice habitat in tidewater glacier fjords. The method can also introduced in other geographic areas, according to professor Prakash.  Now that there is a more advanced method to study the harbor seals in Alaska, the hope is that other researchers will use the OBIA method to make further discoveries about key ocean habitats.

Could Glacier Retreat Cause Seals to Wander?

Though populations of harbor seals – the captivating species seen in almost every zoo – are stable in other areas of the world, they are seeing declines in southeastern Alaska. These particular seals use icebergs calved from nearby glaciers as a place to rest and breed, but changes in ice availability are affecting these behaviors, crucial to their survival and reproduction.

Two separate studies, one by the National Park Service (NPS) and one by the Alaska Department of Fish and Game (ADFG), have independently found that seals may be changing their distribution and behavior to match the shifting locations of ice, as glaciers retreat.

Seals taking a break on top of a flat ice berg. (Courtesy of : Jamie Womble/National Park Service))
Seals taking a break on top of a flat iceberg. (Courtesy of: Jamie Womble/National Park Service)

Jamie Womble, leading the NPS research in Glacier Bay, is providing a new way of relating glacier ice extent and harbor seal territory, both in location and seasonality. Womble and her team aim to find the exact distribution and movements of these Alaskan harbor seals. Aerial tracking– flying above the ice and counting the seals–is a method that works effectively in the region. They also glue GPS transmitters to the seals, and track their movements on land-based monitors. These transmitters come off safely during the next summer’s molt, so they present only minimal risk to the animals.

Womble and her team found that “[d]espite extensive migration and movements of seals away from Glacier Bay during the post-breeding season, there was a high degree of inter-annual site fidelity (return rate) of seals to Glacier Bay the following pupping/breeding season.”

Harbor seal wearing GPS tracking device used in NPS research. (Courtesy of :National Park Service))
Harbor seal wearing GPS tracking device used in NPS research. (Courtesy of: National Park Service)

In addition to studying the distances which the seals traveled, Womble and her group also examined the patterns of seal movement in relation to the glacial ice. The team studied the ice distribution within John Hopkins Inlet, which they coordinated with aerial tracking data to examine the relationship between the ice extent and the harbor seals.

John Hopkins Inlet, the main area of research for Womble, is home to Johns Hopkins Glacier and Gilman Glacier which are among the few advancing glaciers in this region. Seals were found to congregate in areas with the highest percentage of ice.

Aerial image of harbor seals. (Courtesy of :National Park Service))
Aerial image of harbor seals. (Courtesy of: National Park Service)

“Tidewater glacier fjords in Alaska host some of the largest seasonal aggregations of harbor seals in Alaska,” Womble told GlacierHub in an interview. Many of these tidewater glaciers – glaciers that run into the sea and calve frequent icebergs – are thinning, and a few have begun retreating.

In particular, rapid retreat on the east side of Glacier Bay is leading to decreased seal pupping. During this critical season when the pups are newborn, mother seals and the weaning baby seals use flat icebergs to rest. “By 2008, no seals were pupping in Muir Inlet, and fewer than 200 seals were counted in McBride Inlet near the terminus of the McBride Glacier, the only remaining tidewater glacier in the East Arm of Glacier Bay,“ the NPS team stated in a recent report.

John Hopkins glacier, one of the few advancing glaciers in southeastern Alaska. (Courtesy of :Peter Makeyev/Flikr)
John Hopkins glacier, one of the few advancing glaciers in southeastern Alaska. (Courtesy of: Peter Makeyev/Flikr)

In a report, ADFG  emphasizes the importance of  studying  “…why, how, and when harbor seals use glacial habitat, and whether the rapid thinning and retreat of Alaskan glaciers associated with climate change could negatively affect harbor seals…” Their research documented similar instances of glacier thinning and retreat and they are also monitoring seal movement, as well as other topics, including seal diet, seal weight and bodily composition and disturbances by tour vessels. Though ADFG began their work in Glacier Bay, the same site as the other team, they moved their research to Tracy Arm Ford’s Terror Wilderness Area – more than 200 miles to the southeast.

The ADFG team has attached transmitters such as SPOT  to track the seals. These beam data on location, heart rate and other biological indicators up to satellites. To gather data, the researchers depend on the seals surfacing to breathe or rest, since the satellites cannot receive signals that are released underwater. The tracking for both research projects was most important during winter months, since researchers were interested in monitoring movement and feeding after the summer breeding season. (More tracking information, here)

Harbor seals, said to be awkward on land, use icebergs as a place of safety from predators. (Courtesy of :Jamie Womble/National Park Service))
Harbor seals, said to be awkward on land, use icebergs as a place of safety from predators. (Courtesy of: Jamie Womble/National Park Service)

ADFG also saw regular return rates for the sea populations which they studied. They hypothesized that they may travel to find food in the winter, but still return to Glacier Bay in the summer for the safety that icebergs provide from land-based predators. Icebergs are also important sites for the animals to haul out, since many beaches are entirely covered during high tides.

The ongoing research conducted both by Womble’s group and by the Alaska Department of Fish and Game show how recent changes in glaciers have already had large effects on the seal life cycle, specifically pupping. Continued monitoring of seal reproduction and movement in the context of glacier retreat will allow for predictions of the future of this important species in a critical section of its range.

Roundup: Students, Seals and Skiers Visit Glaciers

Survival of a Tropical Glacier

A glacier in the Peruvian Andes is shrinking more slowly than was previously thought. Careful examination of long-term satellite images is the key. Previous research has not separated snow and ice as accurately.

William Kochtitzky, a student from Dickinson College, presented a poster about glacial changes on Peru’s Nevado Coropuna volcano. They did not experience any difficulties combining SPOT and Landsat data. They were able to acquire a SPOT image that was taken within three days of a Landsat scene, allowing us to calibrate our glacier classification scheme and have greater confidence because our SPOT and Landsat images are consistent with each other. This research has the potential for immediate policy implications in Peru.

Professor Benjamin Edwards (left) and Will Kochtitzky (right) conducted a 2015 field season at Coropuna, Peru
Professor Benjamin Edwards (left) and Will Kochtitzky (right) conducted a 2015 field season at Coropuna, Peru

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A Really, Really Big Problem: The Continuing Saga of Jumbo Glacier Resort

There’s a mountain resort in the East Kootenays with a mayor and a council, but without infrastructure, buildings, citizens or a tax base. If that sounds bizarre, well, it is—yet just another twist in a tale that has taken on aspects of the absurd since the idea of a ski resort in the wilderness of the Purcell Mountains first began percolating over two decades ago. Opposition was fierce then and remains so today. In fact the proposed Jumbo Glacier Resort (JGR) has polarized a community perhaps more than any other major development in British Columbia—at least one involving the seemingly innocuous, fun-loving pursuit of skiing.

Karnak Peak, Jumbo Pass, BC; September

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Counting Harbor Seals in Glacier Bay

Glacier Bay National Park has historically supported one of the largest breeding aggregations of harbor seals in Alaska (Calambokidis et al. 1987). Harbor seals are an important apex predator and the most numerous marine mammal in the park; however, harbor seals have declined by up to 75% from 1992-2002 (Mathews & Pendleton 2006). The most recent trend estimates from 1992-2009 suggest that the decline in seals has not abated or reversed (Womble et al. 2010). The magnitude and rate of decline exceed all reported declines of harbor seals in Alaska, with the exception of that at Tugidak Island (Pitcher 1990). Declines of harbor seals in Glacier Bay are of concern for several reasons.

Aerial photo of harbor seals ashore at Spider Reef in the Beardslee Islands of Glacier Bay National Park. NPS

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