Rat snakes are significant predators of purple martins, particularly in the Deep South with its warmer temperatures. However, the black rat snake is found in nearly all areas where martins nest. All purple martin landlords should have some kind of snake guard on their housing system poles.
Have you ever wondered how in the world does a rat snake ever find those martins high up in the air in their gourds or houses? A rat snake does not need fantastic eyesight or hearing like a hawk or owl. A rat snake can find his prey in the dead of night and he doesn’t need a hunter’s moon. The rat snake has an organ in the roof of its mouth called the Jacobson’s organ. The snake will flicker his tongue to “taste the air” for molecules of prey and then transfer this information to the Jacobson’s organ. If the snake detects potential prey, he will then continue to follow the scent until he reaches his prey. And if that prey is your purple martin colony, then you better have some kind of predator guard on the pole!
I have been using net traps constructed from bird netting to thwart rat snakes at my previous martin colony in north Florida and now at my current one in northwest Louisiana. I use mainly ¾ inch square netting and this size will catch most large rat snakes when they try to weave through the mesh. The snake will eventually be unable to go forward because his girth is too thick for the mesh squares and he can’t back out because his scales are caught in the netting. I have caught huge rat snakes that had only four or five inches of their thick bodies ensnared in the netting; the snake’s head and neck area would be completely caught by multiple net squares. Other rat snakes are caught in their middle area with numerous mesh squares ensnaring the snake’s body.
However, some smaller thin rat snakes may be able to weave through the ¾ inch square mesh without getting ensnared. These snakes tend to be less than three feet in length and they can still inflict significant damage to your martin colony by killing adults even if they can’t eat them, eating babies and eggs and causing martins to abandon the colony. I have in the past used a combination net trap constructed from both ½ inch and ¾ inch square netting. The ½ inch netting will often catch the smaller rat snakes under three feet in length and smaller in girth than large snakes. But it is difficult to find the ½ inch netting though you can sometimes locate it on the Internet.
The key to successfully using bird netting in many situations is proper installation on the pole. I prefer to create a fluffy ball all the way around the pole and leave NO gaps between the pole and netting so that a snake can’t go UNDER or through an area without any mesh squares. Snakes treat a net trap like they would vegetation. They tend to go through it using their heads to push through the net squares until the snakes are caught. Rat snakes have narrow heads for entering rodent burrows and squeezing in narrow crevices; their heads can easily weave through bird netting.
I tend to create a thick fluffy net trap that completely encircles the pole and presents any rat snake with NUMEROUS open net squares that the snake must try to slide through. The more the better as the snake will have to navigate by turning and twisting as he pushes himself through.
If the netting hangs down and is pressed tightly against the pole, then a rat snake may be able to climb over it without weaving through any of the mesh squares. You want the snake to respond to the netting like he would to vegetation and go through it.
To install the netting on the pole, I first create a simple wire foundation with four prongs protruding out about 10 to 12 inches in different directions from the pole. I have used different kinds of wire, including clothes hangers. I use two pieces of wire and take one and twist tightly on the pole with the two ends sticking out in different directions. Then I do the same with the other piece of wire so that a “crossbar” is created. I tend to place this wire foundation above my winch and the wire is inserted between the cable and the pole.
My net traps may be anywhere from two to four feet above the ground. I have even created net traps at the bottom of the pole so that the netting is on the ground. Height of the net trap is not that important as snakes tend to weave through a properly installed net trap like they would through vegetation.
Now how do I create this fluffed up net trap? First I use thin netting because this netting is best at catching a snake’s scales. Some netting has stiff thick strands and may not be as effective at ensnaring the snake’s small scales. I take a piece of netting that is about two feet wide and maybe eight feet long (could be shorter or longer) and start wrapping it around the four wire prongs. The netting is inserted in the prongs until a fluffy wreath is created all around the pole. I like a relatively thick net trap and may add more netting as necessary. After the “net ball” is created, I bend over the ends of the wire to hold the netting in place.
Even though the wire is twisted tightly around the pole, it still can be a little loose. Also the netting may not be closely “bound” to the pole at the top of the trap and a gap can be formed. You don’t want any gaps between the netting and pole as a rat snake may be able to slip under the netting without getting caught.
So to eliminate any gaps, I use thick zip ties to “close the top of the netting” against the pole. I weave the zip tie through the netting and then pull the tie tight. This action eliminates any gaps and helps to securely hold the wire foundation and netting to the pole. On my three inch square poles, I use three eight inch zip ties fastened together to create a larger one that will easily encircle the pole.
Now I will have one net trap composed of ¾ inch square netting on the pole. To create the second net trap composed of ½ inch square netting, I repeat the same process as with the first trap. This second trap is placed just above the bottom one and now you have a double layered net trap to catch both large and small rat snakes.
This is my method of creating a net trap and there are other approaches that probably work just as well. This method is relatively simple and has caught many gray rat snakes and corn snakes in Florida where I previously lived and black rat snakes at my current location.
Remember: net traps TRAP! That means you catch the rat snake and then you have to get the snake out of the netting! We don’t kill rat snakes and I have never had one die in any of my net traps. You must not let the snake hang in the netting for long periods of times, particularly in the hot sun; they may die under those conditions. I am not afraid of rat snakes so I remove them by grabbing their heads and then cutting the netting from their bodies with scissors. We take the rat snakes for a “ride in the country” and away from our martin colonies.
I have used the double layered net trap a few times at my old Florida martin colony and did on one occasion catch a small gray rat snake that was about two feet long. The snake was caught in his middle section.
Currently all my martin housing poles have net traps. I recently added a double layered net trap composed of ¾ inch and ½ inch netting to one of my gourd poles. I hope to do this with all my other systems soon.
Here are some photos of my double layered net trap. You can see how I attached the clothes hanger wires to the square pole to create the foundation to hold the netting. My net traps encircle the pole including the winch cable. I have not had any issues with the cable going through the netting and the racks/houses raise and lower just fine. If you look closely at the netting, you may be able to see the difference is size between the mesh in both traps.
Here are some old photos of huge black rat snakes caught in our net traps; these photos have been posted on the Forum before.
Steve
