Growing Up Fast

Studying Steller Sea Lion Development

There is a slight buzz in the air as the team of seven: comprised of veterinarian staff, animal husbandry, and researchers, assembles in the elevator surrounded by no shortage of data collection materials.  The blood collection kit, ultrasound, calipers, morphometric tape, and x-ray machine are all required to accurately track the external and internal development of Perl, a 9-month-old 175lb Steller sea lion (Eumetopias jubatus) pup.  Hard to think of something weighing 175lbs as a pup, right?  But at this weight she outweighs most of the researchers, and thus data collection efforts are done under anesthesia to minimize stress on Perl, and to ensure the safety of her and the data collection team.


Once Perl is safely anesthetized, all hands are on deck and the efficiency of the team is reflective of years of working together. Brandon Russell and Renae Sattler collect blood to track Perl’s developing immune system and health and then move on to recording blubber depths as a measurement of body condition using ultrasound. Casey Brown, Amy Bishop and Brett Long gather Perl’s morphometrics, which include cranial length and width, flipper length, body length and girth, and photos of Perl’s developing canines. Veterinarian technician Jane Belovarac and Dr. Kathy Woodie fluidly track Perl’s vitals and take x-rays of Perl’s fore-flippers’ phalanges, tibia and fibula. In less than an hour of activity, all data points are collected and Perl, fully recovered from anesthesia, has resumed vocalizing and playing with enrichment items.

Measuring Perl’s tooth growth can help improve age estimates in the wild!

If you have visited the Alaska SeaLife Center (ASLC) in the past few years, you may have gotten to see young Steller sea lion pups swimming and playing from our underwater viewing area. To date, three pups have been born of the ASLC Steller sea lion breeding program. This program was initiated in 2009 and was designed to investigate the physiology of the adult female Steller sea lion’s reproductive cycle (i.e. estrus, implantation, and pregnancy), to track the health and development of growing pups, and to better understand these factors as potential constraints to population recovery. Currently, scientists lack physiological and developmental knowledge specific to Steller sea lions, as animals are difficult to access year-round, and especially during Alaskan winters when rough seas and freezing temperatures make capture efforts challenging. However, it is during this time of year, a sea lion is facing significant challenges.


A non-invasive method to accurately age young sea lions in the field is not currently available. In young animals, age can be estimated from erupted canine tooth length but when used alone, this technique has been shown to lack accuracy. Therefore, in addition to dental development, we track changes in the length of pup’s long bones (tibia, fibula, and humerus), the closure of epiphyseal plates (a space between bone plates that lessens with age until maturity in several terrestrial species), as well as external morphometric measurements. The measurements collected from Perl today will be added to the ASLC’s growing pup development database and used to construct a morphometric age determination model for sea lions 1 – 48 months. We hope this model will allow easy non-invasive age estimation of wild Steller sea lions up to 4 years old in the field. This study is one of many projects focused on increasing understanding of factors influencing the decline of this species.

Written by: Renae Sattler

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