Chapter 3: Emergency Treatment

“Before admitting the pup, caretakers need to be certain they can deliver this level of care to yet another sea otter. As a result, not all stranded pups can be saved.”

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The Marine Mammal Center made a preliminary assessment of the pup’s condition and consulted with the sea otter experts at SORAC.

“She was bright, alert, responsive at that point,” said Karl Mayer. “Temperature was 101.4°F, which is, I would say, slightly elevated but still within the normal range.”

These findings were encouraging, but an animal’s health is not the only factor caregivers consider before admitting a new pup.

Not all pups can make it through a captive rearing process. And what’s more, caring for an otter pup is difficult and requires an enormous amount of resources and dedication – tank space, near round-the-clock care, and fresh seafood for a start. Before admitting the pup, caretakers need to be certain they can deliver this level of care to yet another sea otter. As a result, not all stranded pups can be saved.

There was no time left to search for her mother. This pup was in good health, but needed immediate care. With a minimum three-hour transport time to The Monterey Bay Aquarium, a decision on the pup’s fate had to be made right away.

Could they save her? If not, the only humane choice left would be to euthanize her.

Her condition deteriorated as the moments slipped by.

SORAC made the call: Prepare the intensive care unit at The Monterey Bay Aquarium; a new pup would be coming in. But they couldn’t waste a minute.

A volunteer driver from The Marine Mammal Center arrived at the Monterey Bay Aquarium at 11:30 AM with the pup in a crate. A total of 5.5 hours had elapsed since she was found on Cayucos Beach. Dr. Mike Murray, the Aquarium’s veterinarian, immediately gave her a thorough examination to determine what kind of care she needed. And she also got a name.

This pup was the 501st live-stranded sea otter to enter the SORAC program since its inception in 1984. She was now officially called 501.

“When she got here, she was QAR, which is quiet, alert, responsive,” Mayer said. “The highest category is bright, alert, responsive, which basically means that the animal is vocalizing and is full of vim and vigor. And she was that with the absence of vocalizing.”

As with all strandings, Dr. Murray was concerned about her body temperature and blood sugar level. She had been without food for a long time.

501’s temperature remained normal, a good sign, but they would needed to draw blood to determine her glucose level.

“Significantly below 100 would be an animal that had been in extended interval without any food,” added Mayer.

Tests revealed that 501’s glucose level was 111, indicating that she had likely fed from her mother shortly before stranding and hadn’t been on the beach for long. So, when the PC found 501 washed up on shore, her mother, dead or alive, probably wasn’t far.

In addition to a healthy temperature and blood glucose level, her weight, 2.0 kilograms (4.4 pounds), and hydration were also good. Based on her size, weight, fur, pattern of erupted teeth, behavior, and other factors, Mayer and Dr. Murray estimated that 501 was only three days old. 

Dr. Murray found no injuries, illnesses, or significant complications. So, in 501’s chart he noted that she was a “clinically healthy orphan pup.” But at three days old, separated from her mother, tossed by waves, and transported hundreds of miles, 501’s survival was not guaranteed.

Understand how a scientist ages a pup


“We see pups that come in with relatively superficial but very likely shark-related bite wounds,” Mayer said. “The suspicion that we have in those types of cases is that probably there was a mortal wound to the mother, but she had the pup on her chest. So the shark is coming up underneath a female with a young pup resting. The pup is basically buffered from shark trauma by the mother who dies in the process.”

Luckily, 501 didn’t show any signs of shark attack. But there was no telling what happened to her mom.

The horizon is a long way from shore

Since the weather conditions were mild when 501 was found, she probably wasn’t abandoned by accident, as sometimes happens during high winds and stormy seas. Aquarium staff, looking for clues about 501’s past, reasoned that 501’s mother either purposely abandoned her, perhaps in a last-ditch effort to save herself, or something awful happened to her.

The mystery surrounding what happened to 501’s mom, and why 501 was abandoned, will probably remain unsolved.

The Dr. Murray quickly released 501 to the animal care team.  It was now up to them to set her rehabilitation regime – from her very first meal in captivity to such things as how much and how often to feed her, and even where she’d be cared for.

From the start, they needed to make an important decision. 501 could have been put on one of two main tracks: a risky life back in the wild, or a relatively safe life as an exhibit otter in a captive environment.

Mayer and the other caretakers decided that 501 was strong enough to have a chance for survival back in the wild.

501 was one of a limited number of pups that SORAC has the resources to handle and rear in this way. 501 would have to face some strict treatment procedures.

501’s new home was an indoor intensive care unit (ICU), which was a 4-feet by 12-feet tank with a haul-out attached to the side. The haul-out was a ledge where 501 could stay dry, which could also be blocked off to control how much time she spent in the water. 

At this age, 501 could easily become hypothermic or even drown without a place to haul out.

Since the eventual aim was to release 501 back to the wild, it was essential that she didn’t learn to associate humans with positive things like food and care. An otter in the wild that looks to humans for this nurturing is an otter that is going to get into trouble. This was a huge challenge for otter 501’s caretakers, as 501 needed round the clock care. 

Otters are quick learners, so people who handle or come into view of 501 always have to wear “Darth Vader” suits. These suits are meant to hide human features and break up the overall human form.

A suit consisted of a welder’s mask with a tinted visor, a rain poncho, and thick gloves—which doubled as bite and scratch protection for the handlers.

Watch as 501 gets fed and groomed

This kind of caretaker might seem cold and impersonal. That was the point. There couldn’t be a bond between her and humans.

If 501 was to seek interactions with people after she’s back in the wild, it could be dangerous for both 501 and the people she seeks out. 501 would have to be captured because of this behavior and spend the rest of her life in captivity.

Otter 501 was either very hungry or wasn’t a fussy eater. When given her first meal in captivity, a bottle of formula made of an appetizing mixture of pet formula, water, and surf clam meat, she finished it all up. 

This concoction, which had been carefully dialed in over the years, had to substitute for the milk from 501’s mom.

A sea otter pup nurses in the wild

As with all mammals, there is little replacement for mother’s milk.

In fact, older stranded pups tend to thrive better than younger stranded pups. In part, because younger pups may not have had time to receive all the immunological benefits of mother’s milk. The difference is even greater for pups stranded when they are less than a week old, as was the case with 501.

During 501’s first five days with SORAC, she received antibiotics to protect her weakened immune system, and gastrointestinal medicine to alleviate discomfort and help her adjust to the formula.

She was also given fluids two to three times a day in addition to the formula.

The fluids were administered subcutaneously (sub-Q), meaning fluids were injected below her skin and then her body naturally absorbed them. 

This method was the least penetrating, compared to intramuscular or intravenous injections. But regardless of where 501 got stuck, she was not a fan of injections.

Luckily, 501 would no longer need the sub-Q fluids once she was able to eat sufficient amounts of solid food, which contained all the water she needed.


Initially, 501 lost weight, dropping from 2.0 kilograms (4.41 pounds) to 1.92 kilograms (4.22 pounds). Pups may lose a little weight while adjusting to the formula and life in captivity. But three days later, with a healthy appetite and attentive caretakers, she hit 2.31 kilograms (5.08 pounds).

“Sometimes they’re still barely breaking even from their stranding weight at that point,” Mayer said. “For a young animal to have that kind of weight gain it suggests that she got onto the program pretty quickly.”

Otter 501 drinks her formula from a bottle

Even so, 501 didn’t gobble down every bottle and caretakers had to be diligent, feeding her roughly every 3 to 3.5 hours, for a total amount of formula to equal to 15 to 20% of her body weight per day.

Her medical chart shows she did not have gas or other gastrointestinal discomforts common in babies, despite the dramatic change to her diet. The chart did note, however, that 501 had a sneezing bout or two, likely from getting formula up her nose.

See 501's growth right after her rescue

Early on, 501 had no problem flopping into the water of her ICU tank. But climbing onto the haul-out, even though it was only an inch off the water, took a little more muscle development. She would have to use her forearms and kick with her hind legs, advanced skills for a newborn.

On June 20th, 10 days after her rescue, 501 hauled out of the water on her own. This was an early developmental milestone, maybe akin to a child first starting to crawl. But unlike a child, this skill helped her stay out of trouble rather than get in to it.

Unfortunately, this was a special moment that she wouldn’t share with her mother.

Follow 501's development on a timeline


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Otter 501 Can’t Choose Her Meals Yet, But You Can.

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Special Features

This Page All
  • AAS: KM Age

    Ask a Scientist: Karl Mayer – Determining the Age of PupsUnderstand how a scientist ages a pup

  • Shore to Ocean

    Video Clip: Shore to OceanThe horizon is a long way from shore

  • Karl & 501 in ICU

    Video Clip: Karl and 501 in ICUWatch as 501 gets fed and groomed

  • Otter Nursing

    Video Clip: A Wild Pup NursesA sea otter pup nurses in the wild

  • AAS: KM Sub-Q

    Ask a Scientist: Karl Mayer – Subcutaneous FluidsLearn about Sub-Q from a scientist

  • 501 Bottle Feeds

    Video Clip: 501 Bottle FeedsOtter 501 drinks her formula from a bottle

  • Growth Chart 1

    Growth of Otter 501 to 12-days OldSee 501's growth right after her rescue

  • Milestones 1

    Otter 501′s Development to 14-days OldFollow 501's development on a timeline

Chapter 1: The Ocean is Cold but Mom is Warm

Chapter 2: Less than Ideal Rescue

Chapter 3: Emergency Treatment

Chapter 4: Species in Danger

Chapter 5: No Substitute for Mom’s Cooking

Chapter 6: The Surrogate

Chapter 7: Furry New Friends

Chapter 8: Release

Chapter 9: A Wild Sea Otter

Ask a Scientist: Karl Mayer – Determining the Age of Pups

Are sea otters born without teeth?

Karl Mayer: No, they’re born with teeth. Usually neonatal pups have 6 to 12 teeth erupted in the gum line. The 6 to 12 teeth include: 1 set of upper incisors (2 teeth), upper and lower canines (4 teeth), and possibly upper and lower 1st premolars (4 teeth) and lower 2nd premolars (2 teeth). These teeth are all deciduous, meaning that they will fall out and be replaced by permanent (adult) teeth as the pups get older.

How do the teeth grow in?

KM: Sea otters wind up with a full set of 32 permanent (adult) teeth by about 8 to 10 months of age. Dental development follows a relatively predictable pattern of eruption and replacement. Within the first 2 to 3 months, deciduous premolars and permanent incisors are fully erupted. The central 2 sets of incisors are the first permanent teeth to emerge, usually between 4 and 7 weeks of age. Sea otter pups do have deciduous central incisors, but these teeth are very small, probably non-functional, and often never emerge through the gum line. The deciduous upper caniniform incisors are replaced by permanent teeth by 7 to 9 weeks of age; and deciduous canines are replaced by adult teeth between 14 and 18 weeks of age. Adult molars are fully erupted by about 22 weeks of age (there are no deciduous molars). The final permanent teeth to fully emerge are the 2nd and 3rd premolars (at 32 to 36 weeks of age).

So by the teeth that are present, or not, can you estimate the age?

KM: We can compare the tooth eruption pattern in a stranded pup or juvenile with that of known-age pups to get a rough estimate of age. For example, if an early weaner strands and adult canines are just starting to erupt, we might estimate age as 13 to 15 weeks; whereas, if canines are fully erupted and adult molars are starting to come in, we might put the pup at more like 18 to 20 weeks of age.

What are all of the characteristics that you use to determine the age of pups?

KM: We consider a variety of factors: dental eruption pattern, length, weight, behavioral development, presence of a remnant of the umbilical cord (whether dried or moist), and whether the animal passes part or all of the meconium (an infant’s first feces) in the first 24 to 48 hours. A still-moist remnant of the umbilicus and passage of meconium, in addition to the birth dentition described above, would characterize a neonate. If the pup is over a week old, dentition would probably be the primary factor in determining the initial age estimate, but this may subsequently be modified based on behavioral observations: is the pup able to haul out on its own, swim directionally, roll back-to-belly, etc.? Length and weight-at-age are probably the most variable determinants, and may be influenced by various factors, including condition of the mother, nutrition and caloric intake during dependency, and cause(s) of stranding. Frequently, stranded pups and juveniles may be undersized for their age due to chronic malnutrition prior to abandonment or by separation from the mother.

Video Clip: Shore to Ocean

Otter 501 washed onto the beach like some discarded piece of plastic, tumbled in the surf and unable to return to the sea where she was born—where her mother once was. Was her mother still out there, past the pounding waves? Did she lose 501 by accident or by intention? Was she even still alive somewhere out there in ocean?

Video Clip: Karl and 501 in ICU

After preparing a bottle of formula for 501 and donning his Darth Vader outfit, Karl enters the intensive care unit to feed 501, give her a bath, and then groom her.

Video Clip: A Wild Pup Nurses

Watch a sea otter pup in the wild nurse from its mother.

Ask a Scientist: Karl Mayer – Subcutaneous Fluids

at - What does subcutaneous, or sub-Q, stand for?

What does subcutaneous, or sub-Q, stand for?

Karl Mayer: Under the skin.

Why do you use this method of giving fluids compared to intravenous or intramuscular?

KM: Sub-Q is the easiest type of injection, and the least risky for the animal. Our skin is covering our entire body, so it’s the largest organ, and therefore provides the largest potential area to give an injection, but still have the body absorb the fluids relatively easily.

Do they not like that?

KM: No, they don’t at all. The otters need to be restrained to administer the injections, so there is risk involved. The fluid itself is called lactated ringers solution, which is an electrolyte solution. The amount of fluid prescribed will depend on size and condition of the otter. Young pups might typically get 50 milliliters at a time, three times per day. The fluids are injected via syringe through a butterfly catheter, which is a needle attached to a flexible line. We insert the needle into the sub-Q layer and inject the fluids. The fluids create a pocket in the sub-Q, which is then absorbed relatively quickly by the body.

The difficulty in this procedure, and the primary focus, is ensuring that the animal is adequately restrained and that the needle is inserted into the sub-Q layer where you intend it to go. The restraint is critical because the pup is uncomfortable, vocalizing and trying to wiggle away.

Once you’re done with the injection, if you pinch the skin where the needle went in, the injection hole will seal itself pretty quickly, keeping the fluids from leaking back out of the sub-Q pocket. Sometimes, as the pup rolls around on the haul-out surface, fluid may be pushed out of the pocket and get into the fur. Even though the fluids are an electrolyte solution, and contain nothing that will damage the fur, the wetness can cause slight matted areas to develop. So, we have to be conscious of the fur condition as well, while they’re on sub-Q fluids.

How did you determine when sub-Q fluids were no longer necessary for 501?

KM: Sea otters get most of the water they need through the food they eat. So in 501’s case, daily solid food consumption in grams has to provide her with enough fluids to equal, or exceed, the amount being offered subcutaneously. Based on food component analyses, we know that most of the prey types we feed the pups are about 75% water. If she’s getting 100 ml of sub-Q fluids per day, and I know the solid food that she’s getting is 75% water, then I divide 100 by 0.75, which is about 133 grams. That’s the amount of solid food that she needs to exceed, on a daily basis, for us to delete the sub-Q fluids.

Video Clip: 501 Bottle Feeds

When it came to feeding, 501 didn’t get the benefit of having mother’s milk. The Monterey Bay Aquarium had to provide the best nourishment possible as a substitute. In this case, it was dog formula mixed with water and surf clam meat. 501 quickly put on weight, then moved to a solid food diet.

Growth of Otter 501 to 12-days Old

This graph shows how big Otter 501 grew from her rescue to 12-days old. Her weight was measured in kilograms (1 kilogram equals 2.2 pounds). Some days, she got weighed more than once. The difference seen on these days of multiple weigh-ins had a lot to do with when she was fed.

Otter 501′s Development to 14-days Old

This informative chart shows a timeline of special events and developmental milestones for Otter 501, from birth to 14-days old. The white timeline, to the far left, represents 501’s entire time in captivity. A small part of this timeline is magnified to the right, which shows the details during this period of time.