 |
Marine Mammal Care Center |
| ||
|
|
|
About Seals and Sea Lions Click here for animal news at the Center! Several species of seals and sea lions inhabit California coastal waters, four of which are commonly seen in Southern California waters. These animals are of the order Carnivora, suborder Pinnipedia (fin footed). Seals and sea lions have streamlined bodies, hairy coats, and large eyes. They have whiskers located on either side of their snouts, which can be moved back or stiffly forward. The whiskers act as a sense organ that helps in navigating and locating prey. They can see and hear relatively well on land and underwater. Native “true” seals (phocids) include harbor seals and northern elephant seals. These seals lack external ear flaps, have small front flippers and swim primarily with their rear flippers. On land they scoot on their bellies like caterpillars. Local sea lions or “eared seals” (otariids) include California sea lions and northern fur seals. These animals have small external ear flaps and very large front flippers, which they use for swimming. They can move quickly on land by tucking their rear flippers under their bodies to run on all fours. Pinnipeds are expert divers. They eat a variety of fishes, crustaceans, and cephalopods. They usually swallow their food whole and headfirst. Seals and sea lions occupy different marine zones. Some frequent shallow waters near land while others, such as the elephant seal, swim hundreds of miles from land during different seasons. They must return to land for the birth of their young. Why They Strand Natural Ailments Seals and sea lions are susceptible to natural disease processes, including bacterial infections, viral infections, liver diseases, respiratory ailments, and cancers. They are also affected by a wide variety of parasites. Additionally, they can strand due to malnutrition or failure to thrive. Natural Injuries Great White Sharks (Charcharodon carcharius) prey heavily on several species of seals, and account for some injuries inflicted on pinnipeds.
Ratfish (Hydrolagus colliei) grow to a maximum of about three feet and inhabit Northern California waters as well as the colder, deeper waters in Southern California. They are rarely seen in less than 100 feet of water in Southern California. They can be distinguished by their lack of scales and the venomous spine at the base of the dorsal fin. It is this spine that can inflict injuries on Northern Elephant Seals, who normally feed in deeper waters.
Broken bones can be the result of interactions with predators, in-fighting, boat strikes, storms or surf. Any of the injuries above, if gone untreated, can become infected and develop into abscesses. Human Interaction
Boat strikes arise due to the difficulty involved in spotting marine mammals in the water. Sea lions, especially, frequent marinas and areas of heavy boat traffic, and can surface unexpectedly.
Natural, Cyclical and Toxicological Events
El Niño is a cyclical, global climate event that changes the temperature of the ocean water. This usually affects the availability of the normal food sources for marine mammals.
More information on Domoic Acid can be found on the University of Southern California's Caron Lab page on Harmful Algal Blooms. |
|
|
||
|
|
||
|
|
||
|
|
||
|
|
||
|
|
||
|
|
||
|
|
|
|
|
||
|
|
||
|
|
||
|
Cookie Cutter Sharks (Isistius brasiliensis) prey on fish and some marine mammals, especially northern elephant seals. Growing only to lengths of 2-3 feet, they are slow swimmers and deep water dwellers named for the circular bites that they takes out of their prey.
Bat Rays (Holorhinus californicus) often bury themselves in the sand on the ocean floor to catch unsuspecting prey. Unfortunately, pinnipeds sometimes stumble across the rays, which hide in the sand on the ocean floor, and end up on the receiving end of the large stinging barb located at the base of the tail.
Gill nets, monofilament line and fish hooks are the unfortunate side-effects of two groups of mammals (humans and pinnipeds) competing for the same resources.
In late February or early March, the Care Center tends to see an influx of Northern Elephant Seal pups. These animals, born in January, are nursed for a month and then expected to hunt for themselves, as the parents do not teach foraging skills to their offspring. The pups that arrive in early spring are usually malnourished and dehydrated, while those admitted later in the season are usually suffering from one of the natural injuries or ailments listed above.
Domoic Acid Toxicity is the indirect result of a natural algal bloom. A particular algae (Pseudonetzchia spp.) is consumed by filter-feeding organisms like sardines, anchovies and shellfish. At times the algae metabolizes into a neurotoxin. When the affected fish are eaten, the toxin is transferred to animals higher in the food chain. California Sea Lions are particularly affected, and will exhibit disorientation, loss of muscle coordination and seizures.
