Happy Birthday Sea Lions! Did you know that most sea lions are born in June? Their moms have this amazing ability to delay egg implantation (clever mothers!) So in honor of their 23 millionth birthday, we're offering some special activities online and at our facility in the Marin Headlands throughout June!
Happy Birthday Zalophus Californianus
Yes, it's true! Most California sea lions are born in June. This is because female sea lions have the ability to delay egg implantation so that they can give birth at a time that gives their pups the best chance of survival. Very cool!
So as a tribute to all the sea lions out there, The Marine Mammal Center is celebrating their birthday throughout June with special activities at the Center and online!
Watch this slideshow of the birth of a California sea lion! Photos by Suzi Eszterhas.
Let's Celebrate!
Join us Friday June 15th - Sunday June 17th for some birthday fun!

- 11am, 1pm & 3pm: Docent-Led Tours. Our usual great guided tour with added sea lion trivia! Click here to book a tour!
- 11am - 3pm: Salty the Sea Lion is visiting us from our friends at PIER 39! Take your photo with him and wish him happy birthday!
- 12.30pm each day: Cake and songs. Join us on the front porch with Salty the Sea Lion to sing Happy Birthday and eat cake! (First 100 guests get a cupcake!)
- All day: Activity Stations. Make your own sea lion birthday hat, feel the fur of a sea lion pelt, examine skulls and more.
Sea Lion Webcam
As you may know, PIER 39 is one of the best places to see healthy, wild California sea lions. If you can't make it in person to see them, our friends at the PIER have installed a webcam! Click the link below to get connected to sea lions!
Send a sea lion birthday e-card!



Whether you know someone with a birthday in June or just want to tell-a-friend about our sea lion birthday celebrations, send them one of our great sea lion birthday cards!
Send in Your Sea Lion Birthday Wishes!
6-year old fundraiser Anastasia, from Marin, popped by yesterday (June 14, 2012) with a handmade birthday card for the sea lions and $22 that she raised from her lemonade stand! Seals, sea lions and otters are her favorite sea animals and she says that this money will help feed our patients.
THANK YOU ANASTASIA!
$1 buys 1 lb of fish for our hungry pups. Follow her lead and give a seal a meal today!
Let's talk about the birds & the bees... (and size does matter!)
- Pupping season is late May through July, but most pups are born in June!
- Mating season is July through August.
- Once a female gives birth, she has a month off before she is able to get pregnant again (if a male sea lion seems worthy!)
- Females have some choice as to how many and which males to mate with! Males have to put on a show to attract females and size does matter, because larger and stronger males are more successful at getting their attention!
- Females give birth to a single pup following a 8-9 month growth period (very similar to humans). But unlike humans, full gestation in California sea lions includes a period of delayed implantation, when the fertilized egg stops growing and remains dormant for a period of 2 1/2 - 3 months, so they are essentially pregnant for almost a year!
- Delayed implantation allows pups to be born when environmental conditions are best for their survival.
- Most pups weigh 13 to 20 pounds (6 to 9 kg).
- California sea lion moms are great! Most commonly, pups stay with their mums for 5 - 6 months, but they sometimes stay with mom for up to a year. Moms feed them and teach them the ways of the world during this bonding period.
- Moms recognise their pups by smell and vocalization making reuniting with them on crowded sea lion beaches, much easier!
Other California sea lion facts...
- The female California sea lion can outlive the male by an average of 5-10 years in the wild.
- A male California sea lion weighs approximately 3 times more than a female.
- Males reach 850 pounds (390 kg) and seven feet (2.1 m) in length. Females grow to 220 pounds (110 kg) and up to six feet (1.8 m) in length. They have a "dog-like" face, and at around five years of age, males develop a bony bump on top of their skull called a sagittal crest.
- Non-breeding subadult male sea lions are called “bachelors.” Think of that next time you’re watching the popular television show of the same name!
- The repetitive barking noise that California sea lions make is unique to their species. Male sea lions tend to vocalize more than females. And females tend to vocalize to communicate with their pup, unlike males, who vocalize to simply be loud and obnoxious (just kidding, they vocalize to mark and defend their territory).
Learn more about California sea lions on our educational pages.
Ex-Patient Steep Stairs Gives Birth to a Pup!

Female California sea lion, Steep Stairs, was rescued by the Center on March 18, 2012 in Santa Cruz. She had a shark bite wound and a bump on her stomach. That "bump" turned out to be a baby sea lion! Our veterinary staff knew that the sooner we got Steep Stairs back out to the familiarity of the ocean, the better, so we quickly treated the wound and released mom-to-be back to the wild after just four days in our care.
Steep Stairs gave birth to her pup on Sunday morning, June 10, 2012, in southern California. Our friends at the Channel Islands Marine & Wildlife Institute (CIMWI) who have been observing the animal, noted that mom and pup exhibited normal bonding behaviors, were vocalizing loudly, sniffing each other and mom used her mouth to help the pup get into position for nursing.
Like The Marine Mammal Center, CIMWI is a rescue and rehabilitation facility for sick, injured and orphaned marine mammals located in southern California (south of The Marine Mammal Center's range). CIMWI is part of the Marine Mammal Health & Stranding Reponse Program under the direction of NOAA's National Marine Fisheries Service. CIMWI is the only authorized organization to respond to and rehabilitate pinnipeds and cetaceans for Ventura County.
Photos by Eric Maffre and Ron and Barbara Barrett, volunteers with the Channel Islands Marine & Wildlife Institute (CIMWI). www.CIMWI.org







