I am pleased to report that the San Diego Zoo’s sun bear mother Marcella and her two cubs are doing very well. (Read Suzanne’s previous blog, Sun Bear Cubs: Multiple Personalities.) Now six weeks old, the youngsters have pudgy, round bellies and rolls of flesh that indicate mom is feeding them well. They are big enough that Marcella cannot cover them both completely at the same time, so their increased bulk should act as a buffer against the cold weather.
The hard work of dealing with twins is something Marcella struggled with the first few days. She often appeared exhausted and overwhelmed. I am sure human mothers of twins might know something about how she felt! Fortunately, for the last several weeks Marcella seems to have gotten the upper hand in her den. Now that the cubs are bulkier, they get longer periods of rest and make fewer demands on her time. This means Marcella, too, gets good rest. She also seems more relaxed now that the cubs are older and will allow them to cry loudly for several minutes while she slips out of the den for a quick meal. Sometimes the cubs sleep right through her absences and she gets some quiet alone time with her keeper, enjoying a quick peanut butter or honey treat.
Sun bear cubs, like pandas, are born with their eyes closed. This is generally related to their short gestation time. A lengthy window in utero means the brain can develop more fully and the infant is born with eyes open, like in humans. The sun bear’s short gestation window of about 100 days, including some period of delayed implantation, means that the cub’s brain has more growing to do after birth. This additional neurological development is necessary before the eyes can be fully utilized by the cub.
Both of Marcella’s cubs now have their eyes at least partially open. What a different world it must seem to them now that they can see! For instance, we first became alerted that eyes were opening when a keeper peeked into the den while cleaning the area. A cub got its first glimpse of a human and let out a loud squawk! What a surprise it must have been to the cub to see someone other than Marcella.
The cubs can be seen scooting across the den floor when they are alone in the den. They aren’t strong enough to walk yet, but they propel themselves with their back legs, sometimes making little circles as they search for comfort. Often, if they bump up against their sibling this is enough to quiet them, and both cubs will rest together until mom returns from foraging.
We haven’t yet examined to cubs to determine gender or to get weights, but this will come with time. We didn’t get a chance to pull the first cub, Danum, until he was nearly five months old. With our second cub, Bulan, we got our hands on her sooner, at about 2.5 months of age. With each progressive litter Marcella seems more tolerant and willing to cooperate with these health checks. When we are able to pull the cubs, we can share some of their biometrics with you.
Suzanne Hall is a senior research techinican at the San Diego Zoo.
I’m surprised that you treat them so differently than the Panda cub. Xi was weighed and sexed by the time he was two days old and every day after that. Is Marcella so much more dangerous then Lun Lun?
Marie,
In a sense. Marcella is not as adapted to handling as is our panda group. She is also a bear we believe was rescued from a life as a pet, separated from her own mother at too young an age and not well handled by the humans around her when she was very young. As a result, she and the other adult Bornean sun bears in the US have to be treated carefully. Even under the best of circumstances sun bears are known to be aggressive and dangerous and can do a lot of damage with their very sharp claws.
I always find it interesting to read the history of the animals. Rescued as a pet ?? I recently had the pleasure of talking to a bird keeper and found out that many of the birds on exhibit at another zoo were also rescued in a similar fashion, having been taken from the nest at an early age. It saddens me to hear such stories, knowing that species are becoming endangered in such a manner.
Marcella is doing an excellent job in taking care of her cubs. I can’t wait to find out more!