Posted by: Wild Instincts | February 25, 2016

Fostering Black Bear Cubs

We have rehabbed over 100 bear cubs over the years. The majority are orphans who have been separated from their moms after emerging from the den. There are those, however, who have been admitted as young infants; those who are orphaned from their moms while they should still be in winter sleep.

When we get young cubs admitted when bears should be in their dens, we contact our network of bear biologists looking for potential foster dens.

Over the years, especially when the bear population was not as healthy as it has been in recent times, we had a choice of several different bear research projects. Researchers place radio telemetry collars, now GPS tracking collars, on bears for a variety of projects.  Generally, when a tracking collar is put on as part of a long term project, the batteries will need to be changed, the collar maintained and the collar fit checked. For bear research, these activities are best accomplished while the bear is in the den.

Cubs are born in January, during bears’ winter sleep. Bears will typically stay mostly in their dens until the first part of April around here; weather dependent, of course, but typically. Cubs are then of an age and strength to keep up with mom as she sets about putting back on the weight she lost over the winter and teaching them to be bears.

Researchers usually start going into the dens late February on into March. This gives any cubs in the den time to mature enough to be mobile enough to move out of the way. When mom is tranquilized, she could roll onto them so they need to be big enough to crawl out on their own.

This timeline gives us a variable window of opportunity in which to find suitable dens. A suitable den would be one that contains a nursing mom.

In the last few years, many of the bear research projects have ended, due either to the completion of project life or budget cuts which means we have less windows of opportunity to choose from.

While the search is on for a suitable den, we are busy raising cubs. They typically get fed every 4 hours. We feed a formula specially compounded for bears. It has 30% protein and 50% fat. Because they have it pretty cushy as far as being warm and getting all they want to eat, they grow a lot faster than their wild counterparts. We try to make sure they don’t grow too big too quickly. Otherwise they would have an unfair advantage and outcompete their wild foster siblings. Placing rehab cubs in wild dens only to have them outcompete and displace the wild cubs would defeat the whole purpose of wild fostering.

We feed only one at a time, letting the other cry. People have asked about this. Wild cubs in a den are subjected to lots of stressors – availability of mom’s milk, quality of mom’s milk, competition from siblings, weather and temperature fluctuations inside the den, etc. Cubs in care have little stress. Temperature is constant and comfortable. They have top quality nutrition and almost as much as they care to eat. Stressors help wild animals develop properly and be prepared for life in the wild. Crying is a stressor in captivity that helps them develop what is needed to be wild. Feeding one at a time also reduces the number of people handling the cubs to a minimum which also is needed to keep them wild.


Not a very stressful life!


Once researchers notify us they have a suitable den, they let us know when they will be going in to process it.


There’s a suitable den down this hill.

On that day, we pack up the orphan(s) we have, extra formula, an inverter and heating pad to keep the bottle(s) warm for many hours. The den can be a 3-4 hours away in one direction!  We make arrangements for the other animals in our care.

We hit the road to meet the research team. There is often a walk through the woods to get to the den.

Many times the researchers have students or other guests along. This group of people is kept a distance away from the den until the bears are ready to be removed from the den.


Guests get instructions on what will happen and why.

An experienced person quietly approaches the den. The sow is tranquilized using a pole syringe. Tranquilizing wildlife in real life is not like on TV. It takes 10-15 minutes for the drug to take effect-providing her weight has been guessed correctly. Once she is totally anesthetized, the cubs are pulled out and placed in jackets of observers to be kept warm while mom is processed.


Not a very stressful life!

She is pulled out of the den – not an easy task to move 200 pounds of Jello.

She’s weighed, measured and any blood work needed is drawn. While some are doing those tasks, others are doing collar maintenance. Everything is done quickly and efficiently.

Several decades ago, a dab of Vicks Vapor Rub was put on her nose before she was put back. The thinking then was by the time the Vicks wore off, the cubs would smell like her and all would be fine. We now know this or any other scent masking is totally unnecessary.

When everything is finished, she’s placed back in the den (again moving 100’s of pounds of jello is not easy). The cubs are tucked into still sleeping body and everyone leaves.

Until the sow is tranquilized and someone is in physically in the den handing out cubs, no one knows how many cubs there are.

How many cubs there are in the wild den is probably the most important question for fostering cubs. Many years ago two cubs was average. That number has been creeping up over the years – now four is not uncommon.

If a sow has four cubs she is about at the maximum number she can support with success. Sometimes a sow can support five. This is where the past research data is so important. We can make judgments on how many she can support by how many she has raised in the past, what her body condition is like, what the previous year food supply was like, and what the weather has been like.

There have been years when we have been in over a dozen dens over several days. Each had too many cubs of their own to introduce a foster. Our cubs were well traveled those years!

There have been a couple of times the den lent itself to what we call Drop & Run. If we’ve processed all the dens and run out of excellent options, we may go back to a den that was an okay option. Instead of tranquilizing mom and second time just for the sake of giving her an extra cub, we will do a Drop & Run. It’s pretty much what the name implies. We will take a cub, quietly sneak up to an entrance of the den and drop the cub onto Mom. Yes. A couple times it has been dropping a cub ONTO Mom from a second hole in the den. Otherwise it’s getting the cub into the den, close to the other cubs. Then observing, ready to quickly make a hasty retreat if necessary. To this day it has never been necessary. Mom pulls the stray cub in and it becomes part of its new bear family. Obviously, this is the risky method of foster placement and not our first choice.

Our last resort is to keep the cubs and raise them to release in the fall. We have done this very successfully, but we would much rather see them been raised by an adult bear.

With fostering there are always tough decisions. When fostering two in an era of large bear litters, there are tougher decisions. We need to either foster both cubs or keep both cubs. That doesn’t mean they both have to go to the same foster mom. They could each go different foster moms. The problem is that if we take a gamble on placing one and then can’t place the other in any other den, we have one very young lone cub to raise. The risk of that cub imprinting to people is very high. If we have two cubs, then they teach each other how to be bears.

Bet you didn’t think wildlife rehab had such a gambling component! We never know when or what will be the next animal through the doors. In 2014 we raised 15 cubs, in 2015 only five.

We make these tough decisions for the absolute best interest of the animal based on decades of experience. Even with all this experience, it doesn’t get easier.



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