Showing posts with label pinnipeds. Show all posts
Showing posts with label pinnipeds. Show all posts
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linda
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| Ancient paintings of seals from the Caves of Nerja, Spain. Via. |
New research suggests that six seals painted on the walls of the Caves of Nerja in Málaga, Spain, are more than 42,000 years old.
Which not only makes them the oldest human art on record, it also infers they were painted by Neanderthals (Home sapiens neanderthalensis)—who lived in the area at that time and ate seals.
The Homo sapiens sapiens who followed and also painted on cave walls left no images of seals. Their oldest known art is in the 30,000-year-old cave at Chauvet, France.
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| Map modified from Wikimedia Commons. |
The area around Nerja Cave at the southern end of the Iberian Peninsula is believed to be last place inhabited by Neanderthals before they were overrun or interbred into obscurity by Homo sapiens sapiens about 37,000 years ago.
Neanderthals have long been thought incapable of creating artistic works. (*Sigh* Why?)
But the provenance of recently-discovered decorated stone and shell objects is now attributed to Neanderthals.
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| Mediterranean monk seal in cave. Credit: Giovanni Dall'Orto via Wikimedia Commons. |
What's interesting to me is that the seals in the painting would have been Mediterranean monk seals—now one of the rarest pinnipeds on Earth.
Monk seals are believed to have shifted in modern times from beach-dwelling seals to cave-dwellers in order to escape human encroachment.
But maybe—hunted by Neanderthals—they spent time in caves 42,000 years ago too? Could the Neanderthal art have been more biologically accurate than Homo sapiens sapiens' fanciful horses at Chauvet?
I wrote more about monk seals in an earlier post here.
I wrote more about monk seals in an earlier post here.
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linda
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| Ship wake. Credit: Yosemite James via Flickr. |
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| Offshore wind farm wakes. Via. |
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| South Georgia Island cloud wake. Credit: NASA. |
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| Island wakes, Canary Islands. Via Flickr. |
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| Aircraft turbulence wake. Via. |
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| Ship track wakes in the clouds, North Pacific. Credit: NASA. |
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| Comet wake. Credit: NASA via. |
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| Bioluminescent dolphin wakes. Credit: Ammonite via National Geographic. |
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| Icebreaker wake. Via. |
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| Iceberg wake. Via Wikimedia Commons. |
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| Crabeater seal wakes, Southern Ocean. Credit: Steve Nicol via. |
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| Penguin wake. Via. |
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| Ship bow-wake with bow-riding dolphins. Via. |
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| Von Karman vortices, Aletian Islands. Credit: USGS. |
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| Sea turtle wake. Credit: Rosa Say via Flickr. |
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| Sea turtle wake. Via RedBubble. |
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| Surf wake. Via. |
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linda
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| Baby fur seal sleeping on the sofa of a New Zealand home. Via The Daily Mail. |
A baby fur seal crawled through the cat flap of a New Zealand home, hopped up on the sofa and fell asleep. From the Mail Online:
The stunned owner of the house, Annette Swoffer, thought she was hallucinating when she found the pup in her kitchen, hanging out with her cats.
It had made its way from the waterfront at Welcome Bay, New Zealand, through residential streets, across a busy road, and up some steps. 'I was in my office and I heard an awful racket down below,' Miss Swoffer told the Bay Of Plenty Times. 'I thought the cats have brought a rabbit or something in so I went down and had a look—and there's a seal in my kitchen. I thought "I'm hallucinating, this is just wrong". I'm looking and I'm definitely seeing flippers and not paws.'
Miss Swoffer called the Society for the Prevention of Cruelty to Animals—who struggled to believe her at first. 'They were giggling away and I'm saying "I'm not drunk, I'm not lying, there's a seal in my house",' said Miss Swoffer.
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| Sea lion. Credit: lowjumpingfrog via Flickr. |
This reminds me of a filming trip I made to to Mexico's San Ignacio Lagoon many moons ago when an immature sea lion crawled up the ladder onto our live-aboard boat, hopped into a cabin and onto a bunk, where he fell blissfully asleep.
For the next week, he came and went from the boat as he pleased, returning in true Goldilocks-fashion to one bunk or another.
In the end we had to forcibly (gently) evict him before sailing north to San Diego.
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linda
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| Southern elephant seal. Credit: Butterfly voyages—Serge Ouachée via Wikimedia Commons. |
A southern elephant seal has been tracked swimming an astonishing 18,000 miles/29,000 kilometers between December 2010 and November 2011.
That's the equivalent of a roundtrip between New York and Sydney.
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| Jackson's amazing travels. Via Our Amazing Planet. |
The Wildlife Conservation Society (WCS) fitted a male seal named Jackson with a small satellite transmitter on the beach of Admiralty Sound in Tierra del Fuego in southern Chile.
From there he swam:
- 1,000 miles/1,610 km north
- 400 miles/644 km west
- 100 miles/160 km south
Along the way, Jackson meandered inshore through fjords and ventured offshore beyond the continental shelf.
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 Aerial Patagonia by Julia Whitty is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. |
All this in search of the fuel that drove his travels: fish and squid. From the IUCN Red List description of the species:
Foraging elephant seals combine exceptionally deep diving with long-distance traveling, covering millions of square kilometers while traversing a wide range of oceanographic regions during periods of up to seven months at sea. The seals spend most of their at-sea time in particular water masses that include frontal systems, currents and shifting marginal ice-edge zones. Studies of foraging locations suggest that seals are sensitive to fine-scale variation in bathymetry and ocean surface properties (sea-ice concentration, sea surface temperature).
In the course of his travels, Jackson was also diving deep—a skill at which elephant seals excel.
Different satellite tracking studies (pdf) have shown that during the seven months they're living offshore southern elephant seals typically spend only a few minutes breathing hard at the surface before making repeated dives of 20-minutes or more duration to depths of 1,300-3,300 feet/400-1,000 meters.
Some female elephant seals have been recorded making 2-hour-long dives. And some have made dives to more than 4,600 feet/1,400 meters. From the Red List:
Southern elephant seals are prodigious divers and routinely reach the same depths as their northern counterparts. Dive depth and duration vary during the year and between the sexes, but normally range from 300 to 500 m deep and from 20 to just over 30 minutes in duration. A maximum depth of 1430 m was recorded for a female, following her return to sea after the moult. Another post-moult female dove for an astonishing 120 minutes, which is by far the longest dive ever recorded for a pinniped.
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| Southern elephant seals. Credit: B.navez via Wikimedia Commons. |
At the end of his peregrinations, Jackson returned to the same beach he'd left from on Admiralty Sound. His satellite tag should continue to transmit until early next year when it will cease transmitting and fall off.
The WCS research is part of their ambitious goals in the region:
The information WCS gathers will serve as a foundation for a new model of private-public, terrestrial-marine conservation of the Admiralty Sound, Karukinka Natural Park (a WCS private protected area), and Alberto de Agostini National Park. It will help build a broader vision for bolstering conservation efforts across the Patagonian Sea and coast.
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linda
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| Antarctic fur seal (right), Weddell seal (left), Penguin Island, South Shetland Islands, Antarctica. Credit: © Julia Whitty. |
How do you assess the health of a marine invertebrate—namely Antarctic krill—when there's no historical baseline to measure it against?
In an intriguing piece of detective work reported in PLoS ONE a team of researchers from China and the US turned to analyzing old seal hairs to determine changes in abundance of krill in the past century.
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| Antarctic krill. Credit: Uwe Kils via Wikimedia Commons. |
Antarctic krill, Euphausia superba, is a keystone species in the Southern Ocean and the primary consumer in a foodweb supporting fish, penguins, seabirds, seals, and whales.
They school in swarms of up to of 30,000 individuals per cubic meter and are perhaps the most abundant animal on Earth, with a total biomass estimated at ~379 million metric tons.
In the video below (starting at 00:01), you can see humpback whales bubble feeding on krill in Antarctic waters.
There's evidence of a decline in krill biomass in parts of Antarctica in the past 30 years—but when did it begin?
To look deeper into history, the authors analyzed core samples from lake sediments near an Antarctic fur seal colony on King George Island in the South Shetland Islands off the Antarctic Peninsula.They dated the fur in the cores via stable carbon (δ13C) in the samples. They inferred the abundance of krill in the seals' diet via the nitrogen (δ15N) isotopes in the fur. From the paper:
Since Antarctic fur seals feed preferentially on krill, the variation of [nitrogen] in seal hair indicates a change in the proportion of krill in the seal's diets and thus the krill availability in local seawater.
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| Antarctic krill grazing on algae living on the underside of sea ice. Credit: Uwe Kils via Wikimedia Commons. |
Their results indicate that krill began to decline in the diet of fur seals in this part of Antarctica nearly a century ago. That time frame correlates with increasing sea surface temperatures and dwindling sea ice. (See my post Life Inside the Sea Ice more about the relationship between krill and sea ice.)
From the PLoS ONE paper:
In this region for the past decades, the sea ice shows a decline trend, and this is in coincidence with the decline trend in krill populations. Like the seal [nitrogen] values, the sea surface temperature anomaly in Southern Ocean (50°S) also shows an obvious increasing trend for the 20th century, and the significant correlation between them... suggests that the inferred decreasing krill population is linked with warming ocean and declining sea ice extent.
The paper:
- Relative Changes in Krill Abundance Inferred from Antarctic Fur Seal.PLoS ONE. 2011.DOI:10.1371/journal.pone.0027331.
