California sea lion (Feeding habits – reproduction – conservation) – Video

I filmed this video in the Sea World, Saint Diego, California, USA during December 2014.

Source: www.fishconsult.org

Feeding habits: California sea Lions (Zalophus Californianus) are carnivorous having fish being their favorite food including herring, mackerel, pompano, salmon, capelin and squid. They also feed on crabs and clams.

The quantity of fish consumed by sea lions depends on their size as well as the abundance of fish in their habitats. Sea lions may use their sensitive whiskers to locate food. They will generally hunt close to the shore as long as their food is sufficient otherwise they move to deeper water looking for food while they become vulnerable to their predators of Killer Sharks and Whales.

Sea Lion swallow their food without chewing or tear it into chunks using their sharp teeth. They also use their back teeth to break the shells on clams so that they can consume what is inside. Adult California sea lions eat about 5% to 8% of their body weight per day (7-18 kg/animal/day).

During the breeding season, adult males fast for a few weeks when defending their territories for ensuring mating opportunities.

Stones are often found in the stomachs of sea lions. Variety of reasons have been suggested for swallowing stones including ballasting while swimming, stop irritation from intestinal parasites or assisting in digestion.

Breeding and Reproduction: Male Sea Lions are mature at about 6 years of age. However, in most instances they won’t end up mating until they are 9-10 years old of age, after they attain full size and are able to attract and compete for females. The females will begin to mate when they are about 3 years old.

During the mating season, males use their barks to intimidate other male Sea Lions that happen to be in the area. A male of California sea lion with established breeding territory on the beach, breads with around 15 females or even more in one season.

Pups are born on land after a gestation of 11 to 11.5 months; a female generally give birth to one pup each year. On average, newly born pups are about 75 cm and 6 kg. It is interesting to know that the female vocalizes during and immediately after the giving birth while her pup instinctively replies. This helps establish the mother-pup bond. Generally only one pup will be born at a time with occasional twins. Nursing lasts for six to twelve months

The pups immediately start to consume mother’s milk which helps them to grow at a fast rate and also to develop the layers of fatty blubber that pups need to stay warm. Blubbers should be formed so pups can survive upon their first entry to the water accompanying their mother.

In addition to mother’s milk, pups begin eating fish at about two months of age, and then they are ready to move into the waters. When pups know how to swim, they are taught by mothers how to hunt for fish even though they will continue to get their main nutrition from drinking the milk from mother till the end of nursing during which pups are also taught to stay away from predators especially their brownish color during the first six months makes them vulnerable to predation before they acquire the normal color through two molts. During nursing, vocal cues continue to be the most important factor in mother-pup recognition.

Threats to sea lions: The main threats to sea lion populations include:

Natural predators: Common predators of California sea lion are killer whales and large sharks. However, it is believed that mentioned predators do not pose a significant threat to healthy adult sea lions that can easily swim faster than Killer Whales and Sharks. However, young and weak sea lions are easier for these predators to capture. The efficient sensory system enables sea lions to feel their predators as they come close by.

Hunting by humans: thousands of years ago, California sea lions were hunted for subsistence. In the late 1800s they were hunted commercially for their hides. In fact, in 1899 the United States Fish and Game Commission concluded that California sea lions were too numerous, and several thousand were killed intentionally as a means to control their over-abundance.

Although the Killing of sea lions was banned whether generally or in particular locations, fishermen continued to shot sea lions because they believe sea lions consume significant quantities of fish which is seen a real threat to their commercial fishery, particularly salmon.  Fishermen also believe that Sea Lions ruin fish nets and equipment.

Miscellaneous threats: Sea lions are facing various threats such as entangling in nylon fishing nets causing severe injury or drowning. The ingestion of plastic debris can cause obstructions in the digestive tract.

Protection and conservation: At present, there are International Laws to help protect Sea Lions from becoming extinct. The laws also target to help protect their natural environments. Today, it is illegal in many areas to hunt, harm, or kill a Sea Lion. In California, there are limits to where boats can go so that Sea Lions aren’t as likely to be struck by them. According to the U.S. Marine Mammal Protection Act (MMPA) of 1972, it is illegal to hunt or harass any marine mammal in U.S. waters. There are various means to enforce the banning which include rewards which are offered for the reporting of such illegal activities. The penalties for the illegal hunting range from fines to jail time to a combination of both.