Arizona’s Audacious Otters


Elizabeth Blaker

(Published in Northern Arizona’s Mountain Living Magazine – select ‘Articles’ tab to see other writing samples)

Kerry Christensen bent over the unconscious otter and clamped his lips around its mouth to resuscitate it, while fearing it would awaken and bite his face off. Christensen had gotten himself into this mess by becoming a biology graduate student at Northern Arizona University. Soon after arriving on campus, he found himself slogging through snow drifts carrying an armload of dead rabbits to a barn where 20 ill-tempered, snarling Louisiana river otters awaited a meal. Playing nursemaid to this ravenous mob of carnivores was not exactly what he’d imagined, but it was all part of a plan hatched by the Arizona Department of Game and Fish to reintroduce otters to the Verde River.

Otters have lived in Arizona for millennia – 10,000-year-old otter bones were found in a cave in the Grand Canyon – though historical accounts suggest they have never been numerous. Mountain men trapping along the Verde, Salt, and Gila Rivers rarely mention them in their journals. In 1886, Edgar Mearns, an Army surgeon and naturalist with a bristling mustache and observant eye, shot a river otter at Montezuma’s Well. He sent it to the American Museum of Natural History where it was designated as a new sub-species, Lutra Canadensis sonorous, or, the sonoran river otter. The last sonoran otter was trapped in 1953. A few tantalizing, but unconfirmed, sightings have been reported since then in lonely, secret canyons along the San Juan in New Mexico.

River otters are smaller cousins of sea otters, weighing around 30 pounds.   As their name suggests, they dwell in rivers, creeks, lakes, and ponds, but sometimes along the seashore.  Sleek furred mammals, they are related to weasels, badgers, ferrets, and wolverines.  Otters live in family groups that hunt and play together. The female otter makes her den in the burrows of other animals, such as beaver or muskrat, and has even been known to evict the resident animal from a desirable den.  Here she births a litter of several cubs which she cares for tenderly. Observing otters in the wild can be difficult, as they are aware of your presence long before you see them.

Kerry Christiansen and a veterinarian  implanted radio tracking tags in the abdomens of the captive Louisiana river otters– collars will just slide off an otter—a surgical procedure requiring general anesthesia. One of the otters went into cardiac arrest, but Christiansen brought it back from the brink, and fortunately, it didn’t bite his face off. The otters were released into the Verde River in February 1982. For the next year and a half Christensen tracked the otters, sometimes from a plane, but mostly on foot.  With his equipment strapped to his back, he would stand on a rocky outcrop holding up his radio antenna, listening to static on the receiver. If an otter was nearby, his receiver would beep. He followed the beeps into rugged country along the Verde and East Verde, up West Clear Creek, Fossil Creek, Wet Beaver Creek, but the otters were elusive.  When he finally did find one, it was a bedraggled carcass. He wondered what had become of the rest of the gang.

Some of them must have survived, because now there is a thriving population of otters along the Verde and its tributaries. They delight in raiding the Bubbling Ponds Fish Hatchery, selectively eating the juicy and slow swimming endangered roundtail chub and razorback suckers in the research ponds. Biologists there have had to install special fences to keep them out.

The subject of what river otters eat has been a point of contention between people who are in favor of reintroducing river otters to the Grand Canyon, and those who fear that the otters would decimate native fish at their spawning grounds.  Christensen’s research shows that river otters eat primarily fish, including the Gila sucker, roundtail chub, Carp, and catfish, but no trout, while Dr. Paul Polechla, a biologist recently hired by the Nature Conservancy to survey otters in the Verde watershed, has found that they eat a lot of invasive crayfish, especially in the summer, and fish in the fall and winter, including trout. But perhaps the controversy is moot. A couple of years ago park ranger Jessica Bland spotted a river otter at Pierce Ferry on the Colorado River just below the Grand Canyon. Otters can travel surprisingly long distances over land, as well as swim. There is no barrier preventing them from entering the Grand Canyon if they want to go there.  They could be there already.


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Did Human Anscestors Use Tools 800,000 Years Before Lucy?

 E. Blaker

Human ancestors were using stone tools and butchering animals for meat 800,000 years earlier than previously thought, according to a paper published in the science journal, Nature, last month.  A multinational team of scientists discovered the fossil remains of butchered animals in Dikika Ethiopia, not far from the site where evidence for stone tool making was found, but the stone tools are hundreds of thousands of years younger than the newly discovered fossils.

 “This discovery dramatically shifts the known timeframe of a game-changing behaviour for our ancestors,” says Zeresenay Alemseged, a paleontologist of the California Academy of Sciences. “Tool use fundamentally altered the way our earliest ancestors interacted with nature, allowing them to eat new types of food and exploit new territories. It also led to tool making – the precursor to such advanced technologies as aeroplanes, MRI machines, and iPhones.”

In early 2009, a group of scientists led by Dr. Alemseged found a smaller than six inch long piece of fossilized rib bone from a cow-like animal and a short length of thigh bone from another grazing animal the size of a goat. The fossils had weathered out of a sandy layer of rock in the harsh, treeless canyon-lands of the Ethiopian desert.  What makes these small pieces of bone special is that they bear the cuts and scrape marks of purposeful butchering.

 “Most of the marks have features that indicate without doubt that they were inflicted by stone tools,” explains Dr. Curtis Marean from the Institute of Human Origins at Arizona State University, who performed the mark identifications.

                But how can scientists be sure the cut marks on the bones were made during ancient times, and not recently? To find out, the marks were examined using a special kind of scanning electron microscopy. The technique allows analysts to not only clearly see tiny details of the cut marks, but also to determine the chemical composition of the surface of the fossil. By comparing the chemical makeup of the interior of the cut marks with that of the uncut surfaces, the researchers were able to ascertain that the cut marks were of ancient origin.

To determine the age of the fossils, the researchers needed to know the age of the rock layers encasing them.  So they measured the proportions of two forms of argon gas trapped within tiny crystals when the rock was formed. Geologists calculate the age of the rock using the known rate of change of the gas from one form to the other.

 “We can very securely say that the cut-marked bones date to between 3.42 and 3.24 million years ago, and that within this range, the date of the bones is most likely 3.4 million years ago,” says project geologist Dr. Jonathan Wynn from the University of South Florida.

This begs the question of who, back in the hazy dawn of human ancestry, used the stone tools to butcher these particular animals. Who was in the neighborhood back then?  “The only hominin species we have in this part of Africa at this time period is A[ustralopithecus] afarensis, and so we think this species inflicted these cut marks on the bones we discovered,” notes Alemseged.  The most famous human ancestor, ‘Lucy,’ was a member of this species.

But so far, no stone tools or the evidence of their manufacture have been found that are as old as the recently discovered animal bones bearing the cut marks.  There are no rocks within 6 kilometers of the area that are big enough to be used as tools, or for tool making.  Were Lucy’s kin able to plan ahead well enough to bring the tools with them?

 “This new discovery will cause us to refine our ideas about dietary and cognitive evolution in our early ancestors,” said Leslie C. Aiello, an anthropologist and the president of the Wenner-Gren Foundation in New York, who was not involved with the project. “It would be nice to have some stone tools from this period and more than two bones as evidence; however, this is enough to demonstrate that there is still a lot to learn about these early phases of hominin evolution.”

Shannon McPherron, a paleontologist from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany summed up the next challenge: “ One of our goals is to go back and see if we can find these locations and evidence that at this early date they were actually making, not just using, stone tools.”

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Out for a snowshoe ramble on McMillan Mesa

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