Steller Sea Blog

Whales Share Phylogenetic Relationship with Dogs

During the Eocene, some 53 million years ago, the earth was home to a species of hoofed-mammals known as Pakicetids. Based on the anatomy of their fossil remains palaeontologists have established that Pakicetids looked somewhat like dogs with hoofed feet and long, thick tails. They are also believed to an early ancestor of whales based on the shape of their auditory bulla, a bone located in the inner ear. The shape of the ear region in Pakicetus is highly unusual and only resembles the skulls of whales. The feature is diagnostic for cetaceans and is found in no other species. The teeth of Pakicetus also resemble the teeth of fossil whales, being less like a dog’s incisors, with a serrated triangular shape, similar to a shark’s tooth, which is another link to more modern whales. Given their evolutionary relationship I found the article below to be rather interesting.

Poop Patrol
by Monique Keiran, Canadian Geographic

A Black Labrador named Tucker is helping researchers determine why orcas summering off southern Vancouver Island are dying off.

Tucker lends his nose to science by standing in a moving open-decked motorboat and sniffing the wind to detect orca scat floating on the surface of the Strait of Georgia and Haro Strait. His human colleagues, including Sam Wasser, director of the University of Washington’s Center for Conservation Biology, scoop up the greenish brown goo and later analyze its hormone levels.
“Killer whale scat doesn’t stay afloat long, and it’s about the same color as the water,” says Wasser, who uses dogs to study elephants, caribou, spotted owls and other at-risk species. “Without a dog, we’d have a hard time getting enough samples.”
Because Tucker can smell the poop from a long way off, the researchers needn’t crowd the whales. Preliminary analysis of hormones in the scat suggests that boat traffic stresses orcas.
The results from samples collected since 2006 also indicate the whales’ preference for chinook salmon may be causing them to starve. Stress hormones in the scat peak and thyroid hormones plummet from September through December, when the salmon are at their scarcest. Thyroid hormones help regulate metabolism. When the animal starves, levels drop and metabolism slows. Wasser says the hormone levels mirror observed orca death rates.
“In 2007, thyroid levels in the samples were highest, and no whales died. They were intermediate in 2006, when there was five percent mortality, and lowest in 2008, when mortality increased to eight percent.”
More samples are needed to confirm the results. Wasser and Tucker will return to the straits to patrol for poop this summer.

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Early whales gave birth on land: study

WASHINGTON (AFP) – Early whales gave birth — and probably rested and mated — on land, according to a study published Wednesday that examined 47.5 million-year-old fossils discovered in Pakistan.

The “stunning discovery” reinforces the belief that modern sea-dwelling mammals originated from terrestrial ancestors, said H. Richard Lane, director of the National Science Foundation’s paleontology program, which funded the research.

The team that discovered the Pakistan fossils in 2000 and 2004 were initially baffled when they found whale skeletons so close together, said team leader Philip Gingerich of the University of Michigan.

“When we first saw the small teeth, we thought we were dealing with a small adult whale, but then we continued to expose the specimen and found ribs that seemed too large to go with those teeth,” he said.

“By the end of the day, we realized we had found a female whale with a fetus.”

The fetus was positioned for head-first delivery, like land mammals but unlike modern whales, according to the study, published in the online journal PLoS.

The positioning indicated the whales still gave birth on land, said Gingerich.

Other clues — such as the whales’ big teeth that would have been well-suited to catch and eat fish — suggested to researchers that the mammals lived most of their time in the sea, but came on land to rest, mate and give birth.

The primitive whale couldn’t travel far on land, although “they could support their weight on their flipper-like limbs,” said the study’s authors.

“They clearly were tied to the shore,” according to Gingerich. “They were living at the land-sea interface and going back and forth.”

The discovery gives unparalleled insight into how the early whale gave birth and how it transitioned from land to sea, according to the researchers.

The fossils’ species “occupies an intermediate position on the evolutionary path that whales traversed as they made the transition from full-time land dwellers to dedicated denizens of the deep,” the authors said in a statement.

“Specimens this complete are virtual ‘Rosetta stones,’” Gingerich said. They provide “insight into the life history of extinct animals that cannot be gained any other way.”

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