River Otters in ANWR
General description:
Adults weigh 15 to 35 pounds (6.8-15 kg) and are 40 to 60 inches (102-152 cm)
in length. On the average, females are about 25 percent smaller than males.
River otters appear to have well-developed senses of smell and hearing. Their
vision is not especially good but may be better underwater than above. Several
sets of strong whiskers are used by the animal in hunting and avoiding
obstructions.
They can run as fast as a man and on hard snow or ice reach speeds of more
than 15 miles per hour (24 km/hr) by alternately running and sliding.
About half of a river otter's time is spent sleeping.
They travel several miles overland between bodies of water and develop well-
defined trails that are used year after year. They may flatten and dig up the
vegetation or snow over an area of several square yards.
Breeding
River otters in Alaska breed in spring, usually in May
One to six pups (usually two or three) are born the next year any time from
late January to June following a gestation period of 9 to 13 months.
The pups are born toothless and blind in a den that is usually a subterranean
burrow. Their eyes open 7 weeks later
Feeding
River otters in Alaska hunt on land and in fresh and salt water
They eat snails, mussels, clams, sea urchins, insects, crabs, shrimp, octopi,
frogs, a variety of fish, and occasionally birds, mammals, and vegetable
matter. Aquatic organisms no bigger than a man's finger are usually eaten at
the surface of the water; larger food is taken ashore.
Social habits
River otters are often found in groups. A family unit is made up of a female
and her pups, with or without an adult male. The family usually travels over
an area of only a few square miles.
Otters travel together and operate as a social unit but do not cooperate in
hunting or share what is caught. They travel over a wide area, and apparently
there are no exclusive territories. Fighting among otters is extremely rare,
although they are wary of strange individuals.
Dangers
River otters have no significant predators except man.
For the last 10 years, between about 1,200 and 2,400 otters have been
harvested annually in Alaska for their pelts.
References
1) Alaska Department of Fish and Game; Text: J.D. Solf and Howard Golden
http://www.adfg.state.ak.us/pubs/notebook/furbear/rvrotter.php
How River Otters are Affected by Oil Spilling
Investigations in Prince William Sound, Alaska, following the Exxon Valdez oil
spill in 1989 revealed that coastal river otters on oiled shores had lower
body mass compared with otters living on nonoiled shores. Otters from oiled
shores had higher levels of several liver enzymes and blood proteins (i.e.,
biomarkers), than did otters from nonoiled habitats. In addition, otters from
oiled areas selected different habitat characters, had larger home ranges, and
less diverse diets than those in nonoiled areas. These observed differences
between river otters from oiled shores and those from nonoiled areas suggested
that oil contamination had an effect on physiological and behavioral processes
in these coastal otters.
-We were also able to determine that ingestion of oil influenced the function
of the otters' gut. Our data indicated that oil ingestion reduced the
retention time of food in the gut
-Thus, it seems that the ingestion of large quantities of weathered crude oil
could reduce absorption of oil hydrocarbons causing a reduction in their toxic
effects.
Oiled otters also performed fewer dives when chasing fishes, representing a
potential decrease of 64% in capture rate of prey. For wild free-ranging river
otters, such increases in energetic costs and decreases in capture success of
prey may tip the scale between life and death.
Exposure to oil may result in a significant physiological damage
Animals requiring an extended period of rehab will likely perish
even low levels of exposure to hydrocarbons may cause significant reductions
in foraging success
Reference
Effects of oil spills on otters
Responses of River Otters to
Oil Contamination: A Captive Study
By Merav Ben-David,
Dept. of Zoology and Physiology, University of Wyoming
and the Institute of Arctic Biology, University of Alaska Fairbanks.
http://www.otternet.com/ROA/oilcontamstudy.htm
costiner"at"mit
Last updated: Dec 1,
03