Modifying A Feeding Nipple
How to reduce the risk of aspiration in young squirrels
Shirley J. Casey, WildAgain Wildlife Rehabilitation Inc.
This article was first published in Wildlife Rehabilitation Today, Fall 2003/Winter 2004 with all rights reserved.
Aspiration of formula by very small and young squirrels in the rehabilitation setting seems to be a common problem. It is often caused by the rescuer or rehabilitator not carefully controlling the amount of fluid into the squirrel's mouth during feeding.
Generally, the risk of aspiration can be significantly reduced through the use of a 1cc syringe to feed squirrels weighing less than 100 grams and pushing the plunger very, very slowly. However, the size of the syringe tip opening may still allow too much fluid for them to swallow safely with each small push of the plunger.
Some rehabilitators also express concern that the hard syringe tip is not at all like the mother squirrel's nipple and seems to be painful on tender mouths, causing the squirrel to initially resist this method of feeding. Placing a plastic nipple on the end of the syringe can help control the flow of formula and effectively soften the feeding instrument that is placed into the young squirrel's mouth.
The selection decision of the size and shape of the nipple to place on a syringe should be based on natural history of the species, safety, and effectiveness. A lactating squirrel's nipple is about 1/4-1/3 of an inch in length (see photo of the lactating Golden-mantled ground squirrel above.). After a young squirrel places its mouth around the mother's nipple, it pushes or pumps on the mother's chest with its front paws, assuming a comfortable and safe position. Once in position, the infant only sucks and swallows a small amount of fluid at a time.
Currently, the choice of nipples used by rehabilitators varies widely. These include some with very small openings that are made of hard plastic, such as the Interlink™ cannula (Baxter™) or teat infusion cannula. Others with small openings are softer, such as the white nipple from the Mothering Kit™ (Classic™ products), Zoologic® elongated nipple ®, Catac™ nipple, or the soft I.V. catheter. While being softer, experience shows that some of these nipples collapse or stick to themselves after only a few uses, are difficult to pull formula up into the syringe, and may be difficult to clean. (The photo at right shows various nipples. From left:soft I.V. catheter (trimmed); Interlink™ cannula: teat infusion cannula; white nipple from the Mothering Kit™: Catac nipple; and Zoologic® elongated nipple.)
Most of the nipples mentioned above are much longer than the mother squirrel's nipple (some up to 4 - 5 times longer) and can cause improper swallowing if the young squirrels suck them too far into their mouths, risking aspiration. Some rehabilitators trim the nipples to make them shorter and decrease these risks to the squirrel.
In 2001, Colorado rehabilitator, Venice Kelly attempted to address these concerns by modifying the nipples. She liked the white nipple from the Mothering K™ it for its suppleness, durability, and easy cleaning but thought it was too long. She cut it in half and put it on the syringe, easily drawing formula into the 1cc syringe without having to remove the nipple from it. The risk of aspiration seemed to be reduced because it was now easy to only have the tip of the nipple in the infant squirrel's mouth. However, the infant squirrels could not hold the syringe with their paws and seemed to be in a very uncomfortable position during feeding, pumping their front paws into the air.
She found that the Zoologic® elongated nipple had a wider base onto which the squirrels could place their paws. But the nipple was long and, in her opinion, was more difficult to clean.
To gain the benefits of both of these nipples, Venice trimmed off the tip from the Zoologic® elongated nipple, placed the Mothering Kit™ nipple on the 1cc syringe, and pushed that nipple tip through the opening in the base of the Elongated nipple (see photos).
The infant squirrels seemed to adjust quickly to this modified nipple. It fit snuggly over the 1cc O-ring (slip tip) or Monoject™ (luer lock) syringe and the amount of formula given could be controlled very easily and effectively. Additionally, this modified nipple was soft and approximately the same length as their mother's nipple. When an infant squirrel took the nipple tip into its mouth, the base of the Elongated nipple stopped them from sucking the nipple in too far. The base was wider to hold or pump. Plus, it was easy to draw formula through the nipple into the syringe as well as to clean after feedings.
Rehabilitators using the modified nipple have consistently reported that the infant squirrels have adjusted to the nipple very quickly and seem less stressed. The pinkies also seemed to make fewer "fish-breathing motions” when eating. She found that using the modified nipple on a 1cc syringe for squirrels weighing less than 100 grams markedly reduced aspiration incidences.
After squirrels' front teeth are fully erupted, they are able to nurse from a 3cc syringe without a nipple. Use of a nipple on a syringe after their eyes are open and chewing solids is not recommended, as it can result in them biting off the nipple tip and choking or swallowing it. And since the plunger diameter of the 3cc syringe is smaller than the diameter of larger syringes, the rehabilitator can better control the flow of formula and reduce aspiration risk.
The Mothering Kit™ (Classic Products) and Monoject™ syringes are available from various veterinary suppliers, including UPCO® and Jeffers®. The Zoologic® elongated nipple and O-ring syringes are available from various wildlife rehabilitation suppliers.
Note: Rehabilitators placing the shortened nipple from the Mothering Kit™ on larger syringes for feeding rabbits have also reported excellent results.
Many thanks to Venice Kelly for this new design and sharing it with rehabilitators!
Shirley Casey, co-founder of WildAgain Wildlife Rehabilitation in Colorado, has rehabilitated 1,700+ squirrels since 1986. She conducts a two-day seminar on squirrel rehabilitation and is co-author of WildAgain's Squirrel Rehabilitation Handbook.
Note: If you are not a rehabilitator and are reading this article to learn how to feed a juvenile squirrel, you need to know that effective care of wildlife requires much more than just the use of appropriate feeding supplies and diets. State and sometimes federal permits are also necessary to possess and care for wildlife. Please take the wild animal to a permitted and knowledgeable wildlife rehabilitator promptly. Improper care can result in serious health problems for wildlife.