WANDERING HOODED SEALS PUZZLE AND CHALLENGE NOAA's STRANDING NETWORK
Sept. 22, 2006 — Hooded seals, Cystophora cristata, are often called ice seals due to their preference for Northern ice sheets. However, this summer there was an increase in Hooded seal sightings and strandings throughout the entire Eastern seaboard. Members of the NOAA Fisheries Service Marine Mammal Health and Stranding Response Program are unsure what is causing the hooded seals to travel to climates that appear to have an adverse impact on their health. (Click NOAA image for larger view of hooded seal taken this summer. Click here for high resolution version. Photo courtesy of Maryland Department of Natural Resources.)
Although seeing a hooded seal resting on a beach is not necessarily an unusual occurrence along the East Coast, seeing one basking in the hot sun can be alarming. "We don't necessarily picture a hooded seal resting on a hot sunny beach in Florida, where the air temperature is still in the 90s," said NOAA Fisheries Service biologist Jenny Litz. Hooded seals, so named for the inflatable sac, or 'hood' that is found on top of the nose on adult males, are typically known to frequent the pack ice of the Northern Atlantic. "We get concerned when we see them out of their natural environments," Litz added.
Hooded seal pups are usually born in March or April. According to NOAA Fisheries Service biologist Ulrika Malone, these pups have the shortest known lactation period for any known mammal—only four to five days. After that, the mother abandons them and they are on their own. These highly migratory animals generally are considered to be solitary, except during the breeding and molting periods. Biologists have known for a while that hooded seals often travel well outside their normal range, which extends from New Jersey and further north, primarily north of the Gulf of St. Lawrence.
This summer biologists have seen hooded seals from Maine to St. Thomas in the U.S. Virgin Islands. The occasional summer stranding is not considered abnormal due to the animal's extensive migratory habits. Hooded seals usually strand in the late winter, from January to March. Biologists say that during a typical year, approximately 25-35 hooded seals strand in the Northeast, with approximately zero-two in the Southeast. However, a total of 55 hooded seals have stranded (47 in the Northeast and 8 in the Southeast) all along the East Coast of the U.S. and down into the U.S. Virgin Islands so far in 2006, with the majority of these occurring in the months of July, August and September. In addition, a large number of animals have been sighted swimming close to shore, all along the Eastern seaboard. (Click NOAA image for larger view of hooded seal taken in August 2006. Click here for high resolution version. Photo courtesy of Marine Mammal Stranding Center.)
Most of the animals that are coming ashore are called "blue-backs." "We call them blue-backs because their coloration is light grey on the stomach and dark blue or grey on the back and head, representing the juvenile stage of the animal," biologist Malone said. "The animals coming ashore are severely dehydrated, suffering from heat exhaustion, sun burn and often alopecia (hair loss)." Trained marine mammal stranding professionals from the NOAA Marine Mammal Stranding Network observe the hooded seals, and if they determine that an individual is unhealthy, they attempt to place them into rehabilitation.
In rehabilitation, the hooded seal is kept cool by air conditioning and buckets of ice, and nurtured back to health with the ultimate goal of being released back into the wild. Due to the extreme volume that has been observed this summer, many of the rehabilitation centers on the East Coast have reached capacity. As a consequence, the Stranding Network has collaborated and transferred seals between rehabilitation facilities along the East Coast in order to recuperate as many animals as possible. In total, both the Northeast and Southeast have seen 21 hooded seals enter rehabilitation facilities. Of these, eight already have been released back into the wild with a very short rehabilitation time.
The anomaly of an influx of ice seals in the summer has been observed before, most recently in 2001. During that year, scientists noted a similar trend in that the number of hooded seal strandings increased with the majority occurring during the summer. Currently, about 75 percent of the sightings from 2006 have occurred in July, August and September. Although scientists are unsure about what is causing the high number of strandings, some have speculated that this increase could be due to the pack ice breaking up earlier, a large pupping year or some other unknown environmental factor. Unfortunately, not much is known as to what is causing this increase. However, every stranding must be seen as an opportunity to learn more about the biology of these threatened animals. "Perhaps eventually, we will be able to predict these particular wander-lust years, and be able to plan accordingly within the stranding network," Malone added.
To report a stranded seal, or any other stranded marine mammal, call the NOAA Fisheries Service Stranding Hotlines.
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