Age Determination - Pinnipeds

Trying to determine the age of an animal can be difficult. There are certain features that can assist in this determination, however, many researchers will rely on straight length to place animals in a life history category (an age class).  At the bottom of this page you can find standard lengths for various age classes for California sea lions from the published literature. However, with experience you will be able to pick out many of the other features that will alert you to whether an animal is a neonate, an adult, or somewhere in between.

Keep in mind that there are also anatomical features that can be examined during necropsy to determine for example, if an animal is sexually mature, and therefore considered an adult.



Below you will find some helpful hints on determining age in pinnipeds.  CLICK on an image to see an enlarged view.

Age Determination 01   California sea lion TEETH start off white, but become progressively BLACK-PIGMENTED with age.

DID YOU KNOW? The front, or INCISOR teeth normally have TWO CUSPS in this species, one in the front and the other in the back, as shown above. If you look closely you will also notice that this pup has oral ulcers.
02-age-determination   Open-mouth photo of a FETAL SEA LION (a STELLER in this case). The DECIDOUS, or "baby" teeth are just beginning to show through the gums.
03-age-determination   The same fetus viewed from the side.
04-age-determination   The teeth of a YEARLING SEA LION, showing MINIMAL TOOTH STAINING, and the almost equal length of the canine tooth with the last incisor.
05-age-determination   This is the mouth of a JUVENILE SEA LION showing the PERMANENT INCISORS AND CANINES that are partially erupted. Note the normal BLACK surface DISCOLORATION and the BLUNT CONICAL SHAPE of these young adult teeth. This animal also has a small oral ulcer.
06-age-determination   As the teeth continue to age and erupt, they appear LONGER and LESS BLUNT.
07-age-determination   Teeth of an ADULT MALE California sea lion.
08-age-determination   Teeth of an ADULT MALE California sea lion.
09-age-determination   Mouth of a GERIATRIC captive SEA LION showing MARKED TOOTH WEAR and BLACK PIGMENTATION. This animal was greater than 25 years old.
10-age-determination   A younger captive sea lion showing PREMATURE WEAR of the INCISORS AND CANINES due to inappropriate chewing behavior. This bad habit required surgery to repair!
11-age-determination   Another captive SEA LION showing EXTENSIVE TOOTH WEAR, similar to the previous photograph.

straight lenghts csl