Castor: A Universal Attractor

The odor of beaver castor is attractive to many furbearers. Most trappers have access to castors, and preparing them for use on the trapline is not difficult.

Mike Marsyada of West Hazelton, Pa., has been making lure professionally for 34 years and is considered one of the country’s premiere lure makers. Here’s his advice on how to prepare and use beaver castor on the trapline.

THE TRAPPER: Where are the castors on a beaver, and how are they removed?

MARSYADA: There are two castors and two oil sacks on a beaver, located on each side of the vent, or anal opening.

When skinning a beaver, cut from the center of the underside of the tail straight up to the bottom of the vent. Cut again from the top of the vent, straight up the center of the belly to the chin. When skinning out the belly, cut around the edge of the vent on each side.

When the skin is removed from the beaver’s belly, you’ll see a large, slightly bulging mound surrounding the base and both sides of the vent. The castor glands and oil sacks are enclosed in this covering and need to be cut out.
I use a single-edged razor blade, but any sharp knife will work. The castors are slightly above the oil sacks and are surrounded with a thin red membrane. Make a shallow incision in this membrane to expose the castors. Be careful not to cut into the castor; you don’t want any of the watery yellow castorium fluid to leak out.

The castors are much lighter in color than the red membrane and have a textured appearance, like the surface of a brain. Peel the red membrane away with your thumbnail — being careful not to rip the castor — until each one is free of the membrane. They will now resemble two cream-colored sacks connected at the top near their ducts by a small piece of tissue.

Cut this tissue free of the carcass, but leave the castors attached to each other. This makes them easier to dry by hanging them from a wire. If they’re mistakenly separated, they can be dried on a screen rack.

THE TRAPPER: What about the oil sacks?

MARSYADA: Beaver sack oil is attractive to furbearers and is well worth saving.

The oil sacks are visible once the castors have been removed. They’re reddish and about a third of the size of the castors. I hold an oil sack in one hand, pinch the duct near the vent with my thumb and forefinger, and cut the sack free between my pinched fingers and the vent opening. I squeeze the thick, yellowish oil into a jar. If necessary, cut the sack slightly to squeeze the oil out.

Canines are attracted to sack oil. It’s usually used straight, although a few lure formulas call for it as an ingredient.

Once the sacks are empty, I freeze them in plastic zipper-seal sandwich bags, to be used as bait at canine spring hole sets or in mouse hole sets. The oil is a waterproofing agent used by beavers to keep their fur dry and has the body odor of beavers. The odor lasts a long time, and its chemical makeup doesn’t allow it to be dissipated by wet conditions and rain.

THE TRAPPER: Is there a difference in the quality of the castors from large and small beavers?

MARSYADA: Castors are sold by the pound, so the larger and fuller they are, the more valuable they are. However, size isn’t the most important factor. The fuller the castor, the more valuable it is. Full castors from a 2-year-old beaver are more valuable than empty castors, called shells, from a 5-year-old. A lot of times castors from 2-year-olds will be fuller than from 4- or 5-year-olds.

Full castors are round and plump, whereas empty ones are flat. The empty ones still have a good castor odor and work well in lure formulation. They’re just not as valuable on the market because castors are sold by weight.

I normally don’t bother to save the castors on young-of-the-year beavers — kits weighing under 10 pounds — because they’re so small. However, they do have the castor odor and can be used.

THE TRAPPER: Is there a time of year when castor is stronger and more valuable?

MARSYADA: Castors are just as valuable no matter what time of year they’re collected. Again, fullness is the most important factor.  

THE TRAPPER: Is there a difference in the smell or quality of castor from different parts of the country?

MARSYADA: A beaver’s diet determines the strength and type of the castor’s smell, and there are definite differences in the smell of castor from different areas of the country. I’ll probably ruffle a few feathers with this statement, but I’ve used castors from all over the continent, and I’ve had good results with all of it, with just a few exceptions.

Beavers that have no access to tree bark and are forced to feed on just grass and water plants have castors that smell distinctly like horse manure. While this seems to attract beavers of that area, I’ve never found it to be very effective in other areas of the country.

However, beavers in some areas of the Midwestern corn belt have no trees to feed on. Their castor smells similar to regular castor, but with a distinctive odor of its own. It seems to be attractive across the country.
Beavers from the South feed heavily on pine, and their castor has a strong odor.

Probably some of the nicest castors I’ve ever seen or smelled came from three locations, in this order: the interior of Alaska, the northern big-woods country of Maine, and lastly the aspen country of the West. These beavers feed exclusively on hardwoods in the fall and winter.
Don’t misunderstand that statement. I don’t mean castor from other areas has inferior attractant qualities — far from it. It’s just that castor from those three areas is really nice to my nose.

THE TRAPPER: How should castors be stored?

MARSYADA: Castors can be frozen green in paper bags or cardboard boxes for short-term storage, but it’s important to avoid freezer burn. If they’ll be in the freezer any length of time, double-bag them in zipper-seal plastic bags. It’s best to grind and preserve castors shortly after harvest, to avoid freezer burn. You can place green castors in containers, then cover them with glycerine, and they can be kept indefinitely. But if the castors are preserved whole, they get rubbery and become difficult to grind.

If castors are ground and covered with just enough glycerine to moisten them, they have an infinite shelf life. They’ll begin to darken as soon as the glycerine is added and become dark brown, but this does not detract in any way from their quality.

If you don’t have a grinder, simply slice, chop and dice castors with a sharp knife into small pieces and cover with glycerine. Grinding or chopping helps them blend better with other ingredients when used in formulation, but if you’re going to use just straight castor, larger pieces work fine.

Never store or ship unfrozen castors in plastic bags or buckets because they mold quickly if kept in plastic, even during a short four- or five-day shipment. Ship unfrozen green, semi-dry, or dry castors in paper bags or newspaper.

THE TRAPPER: How is castor dried, and why?

MARSYADA: Personally, all the castor I use is in the semi-dry state, I think it gives off the best odor when worked in my formulations. But this is relative to the individual lure maker’s wants.

I simply drape a connected pair of castors over a horizontal wire and let it hang for two days. Then I flip them so the sides that have been touching each other are exposed to the air and dry for another two or three days. Depending on humidity and air flow, it takes from three to five days to produce semi-dry castor.

Dry castor, sometimes called “barkstone” in old lure formulas, is allowed to dry for at least a year. It nearly turns to dust when ground.

Check with your buyer to see whether he wants castor green, semi-dry or dry. Green castor is cleaned and frozen or shipped immediately after harvesting, with no drying time.

THE TRAPPER: What’s the best preservative for castor?

MARSYADA: I use glycerine, but I know some very reputable lure makers who use glycol, mineral oil, vodka or Everclear. It’s a matter of individual preference.

THE TRAPPER: You’ve said that castor can be tough to work with in some lure formulations.

MARSYADA: There are certain essential oils that can overpower castor, just as there are some that will make the castor odor “grow” in formulation. Lovage, though very expensive, is an example of an oil that will fire up castor. Bill Nelson was very fond of adding asafoetida gum to his castor to fire it up. Even cocoa will strengthen castor to a degree.

However, oils such as spearmint and peppermint have an opposite reaction. The castor makes these oils grow to a point where they overtake everything else in the formula. Tonquin also has a tendency to grow when used with castor. Use these products sparingly in formulas until you see how each reacts.

THE TRAPPER: Castor is sometimes called a universal attractant to all furbearers. Is this true?

MARSYADA: I have yet to find an animal, other than mice, that didn’t like castor. From bears to deer, cats to canines — even down to weasels — everything likes it.

While castor can be used alone to catch or attract most animals, I believe it is better used in formulation as an additive in attractors.

Different species respond to castor in different ways. To canines, it is a food/curiosity attractor. To felines, it is a food/pacifier odor. It makes them feel at ease and makes them want to rub. To the weasel family, it is a food/curiosity odor, in varying degrees. For example, a mink is drawn not for food alone but out of curiosity of what a beaver is doing there. Whereas to the wolverine, it means there’s beaver meat somewhere.

Muskrats will respond somewhat to castor, but I’ve never seen where it was more than a casual response. There are plenty of better attractors for muskrats.

As I mentioned, mice are not that fond of castor. With all the castor I’ve hung to dry over the years, I’ve never once had mice chew on any or bother it in any way. They simply ignore it. They’ll chew oil sacks in a second, but leave the castors lying beside them untouched. I’ve never figured out why.

THE TRAPPER: How do beavers respond to castor?

MARSYADA: Their response is the most diverse of any furbearer. Some react in fear when they smell strange castor in their territory, while others exhibit pure rage. Location, time of year and the beaver’s age have little to do with it. It seems to be the temperament of the individual beaver that determines its response.

Sometimes the response you want is not the one you get. A beaver that was pinched at a castor set might avoid any set using castor for the rest of its life.

On the other hand, some beavers become so angry at the smell of strange castor that they come in to the set at full speed to destroy the castor mound. I’ve seen angry beavers hit a set sideways and smash the mound with their tail.

This is why I no longer make foothold castor-mound sets in shallow water. A beaver reacting strongly to castor will sometimes fire a shallow trap. I make castor mound sets where I can carve a trap shelf about 10 to 12 inches deep in front of the mound, so the beaver can plant its back feet to exit the water and get caught by a hind foot. This way a sideways swimmer, tail-slapper, or fast swimmer with its front feet tucked in or full of mud won’t fire the trap with its body or debris.

THE TRAPPER: Can you give readers a lure formula for beavers, using castor?

MARSYADA: A simple yet effective beaver lure can be made as follows:

4 oz. ground or chopped semi-dry castor
2 oz. glycerine
3 drops anise
3 drops valerian
6 drops apple essence

THE TRAPPER: Can you share any castor-based predator lure and bait formulas?

MARSYADA: Here’s a fine canine lure:

4 oz. ground or chopped semi-dry castor
2 oz. glycerine
1?4 oz. asafoetida tincture
10 drops tonquin musk

An unbeatable bobcat lure:

4 oz. ground or chopped semi-dry castor
2 oz. glycerine
1 oz. mink glands
10 drops pure catnip (not imitation)
3 drops pure quill skunk essence

A basic predator bait:

Cut 1 gallon of beaver meat into egg-sized pieces. Spread this meat on a screen, salt it, and let it set on the screen for a day. Then place the meat in a plastic container and add:

1 pint honey
6 oz. glycerine
2 oz. castor
1 oz asafoetida
1?2 oz. tonquin musk

Stir with a stick and cap the container. Let stand for a few days, and every time you pass by roll the juice around in the container to coat the meat chunks. The bait is ready to use in a few days and will last all season.

Bob Noonan of Canaan, Maine, is a field editor for T&PC.

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