Endangered
Species: Sea Otter (Enhydra lutris)
by Annie Bauer
Gae Berry (photographer, copyright holder,
identification) http://animaldiversity.ummz.umich.edu/site/resources/gae_berry/otter.jpg/medium.jpg
General Information:
The animal that I decided to do my report on is the Sea
Otter. The scientific name of the sea otter is Enhydra lutris. “Sea
otters help maintain a healthy kelp ecosystem by limiting the number of
shellfish that feed on kelp. This promotes the growth of kelp forests that are
larger and more productive. Kelp beds provide habitat for fish and other
invertebrates” (e-mail from sea world). Sea Otters well live in the sea. The sea otter lives along
the California Coast and Alaska’s coast line. They like the cold water hence
Alaska. The country that it lives in is North America/Pacific Ocean, Japan,
Kamchatka, and the Aleutian Islands.
“The sea otter has been called “the old man of the sea” by fisherman.”(Sea
Otter).
Physical Description:
“Sea otters are the largest member of the family
Mustelidae. Males weigh 22 to 45 kg and are 1.2 to 1.5 m in length. Females are
slightly smaller, weighing 14 to 33 kg and measuring 1 to 1.4 m in length. The
tail comprises less than a third of the body length. The pelage is brown or
reddish brown. Sea otter fur is the densest of all mammals, with about 100,000
hairs per square centimeter. Since sea otters do not have any insulating fat,
the fur is responsible for maintaining warmth. The hind legs are long and the
paws are broad, flat, and webbed. The forelimbs are short and have retractable
claws. Sea otters are the only carnivorans with just 4 lower incisors. Females
have two mammae.”(Estes 1980; Nowak 1999)
Other:
The
average lifespan of a sea otter is the male sea otters live an average of ten
to 15 years, while female sea otters live an average of 15 to 20 years. Sea
otters are the only mammals other than primates known to use tools. Otters use
small rocks or other objects to pry prey from rocks and to hammer or pry open
their food. They can dive up to 330 feet when foraging for food. Otters rest in
coastal kelp forests, often draping the kelp over their bodies to keep from
drifting away. “Sea otters have a polygynous mating system. Many males
activly defend territories. Disputes are usually settled with splashing and
vocal displays, fighting is rare. Males will mate with females that inhabit
their territory or seek out estrus females if no territory is established.
Males and females bond for the duration of estrus, or 3 days. The male holds
the female's head or nose with his jaws during copulation. Visible scars are
often present on females from this behavior”.(McShane et. al. 1995; Estes 1980;
Nowak 1999).
Breeding Habits:
“Sea otters can reproduce year round. There are
peaks of birth in May-June in the Aleutian Islands and in January-March in the
California population. Delayed implantation produces varied gestation times.
Pregnancy has been reported to be 4-12 months. Females usually give birth about
once a year. Orientation of the fetus may be either caudal or cephalic,
although cephalic orientation is more common near birth. A single pup is born
weighing 1.4-2.3 kg. Twins occur in 2% of births but only one pup can be raised
successfully. Pups typically remain with their mother for 5 to 6 months after
birth. Females that lose a pup will go into estrus sooner than if their pup had
survived. Females reach sexual maturity at 4 years. Males reach sexual maturity
at 5 to 6 years, but may not mate until much later”.(Estes 1980; McShane et.
al. 1995; Nowak 1999; Riedman et.al. 1994).“Females provide all of the parental
care for the young. Pups will nurse until weaned, but start to eat solid foods
shortly after birth. While the mother is foraging, young will remain on the
surface. Pups start diving after two months. Pups learn from their mothers how
to forage and what prey items to look for as well as swimming and grooming
behaviors. The pup remains dependent on the mother for about 6 to 8 months, but
there is considerable variation here also”.(McShane et. al. 1995; Estes 1980;
Nowak 1999)
Feeding
Behavior:
Sea otters will
eat “Abalone, squid, snails and other molluscs; clams; mussels; crabs;
lobster; urchins; sea stars; sea cucumbers; chitons; marine worms; and about 40
other marine invertebrates; and on occasion, marine birds; and in Alaska,
certain fish.”( Sea Otter
Frequently Asked Questions – FAQs). Of the following is the sea otters
predators are “Great white sharks are the primary predator in
California. Ongoing studies in Alaska recently revealed that orcas (killer
whales) are eating more and more sea otters in that region, possibly because
the usual prey (seals and sea lions) are in decline. Other factors that may be
influencing the orcas to eat more sea otters may include natural disturbances
to the ecosystem that occur over space and time, as well as overfishing. Other
reported predators that feed on sea otters include stellar sea lions, coyotes,
bears and eagles.” ( Sea Otter
Frequently Asked Questions – FAQs).
Conservation Efforts:
“Sea otters have been classified as
threatened under the ESA, depleted under the MMPA, and as a "fully
protected mammal" under California state law. Each of these levels of
protection is significant for different reasons. Protection under California
state law, which preceded federal protection under the MMPA or ESA, involves
balancing the needs of otter conservation with economic interests, especially
fisheries along the California coast. Protection under the ESA is of special interest
at this time because the ESA is up for reauthorization in Congress and has been
the subject of contentious debate. Protection under the MMPA is currently
superseded by the listing under the ESA. The MMPA listing will become relevant
only after the southern sea otters' population and range expands to the point
that it is delisted under ESA.” (see Baur; VanBlaricom, this issue)(Why Southern Sea Otters?)
Summary:
There are a few reasons why I picked the sea otter as my endangered animal for this report. The first one is that it is cute and cuddly. Also the other reason is that I love the place that they live I love the ocean and when I grow up and I am out of college I hope actually pray that this creature will still be around because I really want to work with it I want to observe this creature and many others like it that are really smart. I also had to pick an animal in the fourth grade and I well picked the sea otter (I don’t really remember how I chose it) but yet I did. What I really thought is that it would be really easy project because I already knew a lot about the creature. But what really surprised me how much the population has declined. It’s really freaking me out because it was only endangered when I was in fourth grade and now it’s threatened the numbers are not going up. And it is not just like that with this species, it’s like this with many many other species. We need to stop before it gets out of control.
Sources:
Cohn, J. March
1998. Understanding sea otters. BioScience, 48: 151-155.
Sea otter , Encyclopedia of Animals.
SEA OTTERS-STAYING A FLOAT? , By: Churchman, Deborah,
Ranger Rick, 07386656, Jun2005, Vol. 39, Issue 6
Seacoast Secret , By: Dawson, Nancy,
Cricket, 00906034, Aug2005, Vol. 32, Issue 12
http://animaldiversity.ummz.umich.edu/site/accounts/information/Enhydra_lutris.html
http://www.umich.edu/~esupdate/library/96.12/watson.html