Squirrel trials update #5

Last Monday we left for the bay area, but before leaving I stocked the owl box with sunflower seeds and made sure the camera trap was working.

Today I checked the camera to catch up.

After I put smooth plywood under the overhang the squirrels visited the box every day. They were stymied by these latest changes. They climbed about on the tree trunk and peered over the edge of the roof.

The deterrents didn't last long. On Tuesday, the first squirrel broke the sheet metal barrier. I regret not having a marked population of squirrels, and not recording the entry in movie mode. But somehow it reached the hole, and pulled itself in, as you can see for yourself.



The next day the same or another squirrel explored the box for 4 minutes and then made a left-handed side entry. Notice that the little bugger is gripping the upper edge of the roof with one hindfoot. The squirrel with the scratched nose did the same thing.



I am going to watch them for a few days to figure out their secret. Then it's back to the drawing board. Spring travel may force me to postpone further experiments until fall. The redhead just isn't very enthusiastic about watching squirrels and tending camera traps in my absense.

Squirrel trials update # 4

Since the last update I extended the roof to 6 inches. I thought the wonder-rodent couldn't do the yogic stretch to reach the hole. When squirrel encountered the modification it looked over the edge, and didn't even try. It snaked around the corner from the side of the roof where the overhang is only 2.5".

Fair enough. I decided to add 5" vertical barriers to the sides.



This seemed to make it even easier. Now the squirrel could oppose the grip of its hindlegs at 90 degrees, and in one swell foop it did the yogic stretch to reach the hole.



Exiting the box is also a cinch. Though the redwood is smooth, the joints on the corners and sides offer the squirrel more than adequate purchase.

It was time to raise the bar, as they say, which in this case meant enlisting Richard's help again. We covered the box with galvanized metal flashing.



You are looking up at the one area that isn't flashed -- the underside of the overhanging roof.

By 11:00 the next morning the remote alarm inside the box had not sounded, and I was starting to think that maybe, just maybe, I had circumvented wonder-rodent.

"Guess, who hasn't gotten into the box today?" I asked the redhead rather smugly. (Her response, "Who?" was a polite admission that she wasn't really listening, a common pattern in the conversation of old couples and Seinfeld characters.)

Ten minutes later the alarm blasted in its irritating way.

A couple hours later I was gazing out the window and finishing a cup of coffee in quiet postprandial reflection, when the squirrel made a second appearance.

It climbed all around the box on the bark of the tree, mounted the roof, and looked over the edge at the hole. Then it rapidly scratched the metal roof as if trying to dig through. After a thoughtful pause, it went back to edge, leaned over the side, and crawled upside down on the exposed woodwork and entered the hole. It was just like a gecko.

This charged me with determination to do it one better. When the squirrel finished its repast 20 minutes later, I removed the roof and took it to the garage. Fifteen minutes later the undersurface of the roof was one smooth piece of plywood.



Stay tuned.

Squirrel trials update #2

They're very tricky those squirrels. At the moment they are not cooperating.

The day before yesterday I installed a remote passive infrared (PIR) surveillance alarm in the roof of the owl box under a wire mesh cage. Now the alarm will alert the codger when it is time for squirrel observation.

It works nicely. The infrared detector sends a signal from the box to the receiver in the house which produces a maddening 2-tone alarm. There 's a little red light on the transmitter so you can perform a "walk test".



Yesterday morning the alarm sounded briefly on two occasions between 9:00 and 10:00. Though the box was filled with sunflower seed, the squirrels immediately withdrew. I suspect they heard the alarm through the walls of the house (yes, even I can hear it from out there) or they didn't like the red light blinking on the detector.

Wouldn't it be nice if a blinking red light was all it took to keep squirrels out of owl boxes? Well, I'm not buying it. When they are ready or hungry enough the squirrels will be back.

However, the experiment must continue without delay. Late yesterday I covered the light with electrician's tape, but no squirrels have entered the box today.

I'm going to remove the roof of the box to make the food inside more inviting. We need a population of highly motivated squirrels if we are going to solve this problem.

In the meanwhile we are getting our daily exercise shoveling snow and chopping ice. We've been snowed in for two weeks now, and it's time to buy supplies (like food!).

Squirrel trials update #1

This is an image that strikes terror into the hearts of owl boxers. Imagine how a screech owl feels with this peering into its home.

Yesterday I replaced the front of the experimental owl box with one having a larger (3.5") hole. The 3" hole seemed a little small and I didn't want to invite home renovation by a squirrel.

The box still contained a lot of sunflower seeds but it was filled with icy snow. Since there's precipitation in the forecast I put a lid on it.

This morning, the squirrels didn't show until 11:00, and the following clockwise sequence shows the reaction of one of them to the owl box modification.



This series assured me that there was no need to worry that a lid would discourage them and delay the experiment. Once the hole was located the squirrel wasted no time entering and feeding on and off for a half hour.

It had a room with a view and periodically surveyed its surroundings, as if to say:

"Hey dudes, this is a gnarly place with all kinds of awesome snacks."

The squirrel trials begin

Owlman recently ran a squirrel out of his squirrel-proof screech owl box. When seen on the video monitor the rodent was comfortably ensconced and showing a morbid curiosity in the video camera which happens to be the size of a walnut. This is a scary thing to see on one's owl cam.

I am finishing up a couple of nest boxes for small owls. It's cold working in the garage, but it has been a nice break from home bound routines and shoveling snow. I'm using redwood siding and shelves from the pantry of a 100-year-old house in Santa Cruz. That scaly old paint is rough on the planer blades, but the planed wood is old growth, wonderful to see, touch and smell.

I was California groovin' in the garage -- planing, sawing, thinking about owls, giant redwoods, old saw mills, and the pleasures of free recycled timber, but bothersome visions interrupted my reverie. I saw a squirrel contortionist stretching like a leech to reach the entrance hole . . . a squirrel scaling an impossible expanse of metal flashing like a gecko . . . a squirrel chewing away at the entrance hole, ousting the resident owl, and looking out the misshapen hole with bug-eyed self-satisfaction.

Then the idea came to me. Why not make an experimental owl box and use it to test various squirrel deterrents?

If you have seen the British documentary "Daylight Robbery" you will get my drift. The script was so imaginative, the sound track so cleverly playful, and Dr. Jessica Holm so charming that it inspired a new wave of backyard squirrel research and wholesome campus recreation like squirrel fishing.

Daylight Robbery was actually a celebration of the eastern gray squirrel's problem solving ability, namely in circumventing obstacles and deterrents to the bird feeders. Last year it inspired me to embark on a similar exploration of climbing abilities in a dusky-footed wood rat .

Now I must train the local squirrels to feed in the roofless owl box and test their intrusion skills when the roof is in place. When they're hooked on the early bird special (black sunflower seeds and peanuts) the performance trials will begin. I'll systematically evaluate the deterrent effect of different sized roofs, flashing, hole position, baffles and so on.



Yesterday I set up the roofless owl box and a camera trap, and at 8:00 this morning two small squirrels were on the scene. Neither entered the box, but they perched on it and ate the seeds I left on the edges.

I didn't bother to check the camera for pictures of the first visit, but rest assured it's ready for tomorrow.

The end of the experiment (for now)

To bring you up to speed -- in the two previous wood rat blogs I recounted several of my embarrassing experiments on the climbing ability of a local wood rat. Because I had misinterpreted the photos and made incorrect assumptions, I was blissfully pursuing an experimental path of self-deception. Then I realized I had underestimated the rodent's gymnastic skills. To wit, it had been shimmying up a 3/4" pipe and negotiating the overhang of the bait station. So I used a "squirrel baffle" to prevent the trickster from reaching the bait station by the "impossible route". That experiment demonstrated to my own satisfaction that the rodent had shimmied up the 3/4" post rather than climb down the 2" PVC pipe, as I had been mislead to believe. That's where we left off.

I still harbored a belief that the wood rat could "chimney stem" down the inside of the PVC pipe. As mentioned, he had never descended the pipe, either inside or out, to reach the bait station. But I thought he could do it. He might need to build confidence using the tube horizontally before trying to go down it vertically. With the squirrel baffle on the post, the gently inclined PVC pipe was the easiest route to the bait station. (I didn’t think he was desperate enough to try jumping the 28-inch span). I hoped of course to get that one shot of the rat entering or exiting the pipe.

It rained that night, and when I checked the camera the next morning, two pictures showed the rat stepping off the pipe. It seemed to use the PVC as it would a branch.




Another picture however looked like the rat was peering into the tube.



I looked inside the tube. It was still coated with dust. If the rat had passed through, it would have been swabbed clean.

So I fastened the tube to the overhead branch -- the vertical access route. I was leary he might shimmy down the outside of the tube, so I jury-rigged a baffle from a plastic milk container. There was another potential flaw in the set-up. In an attempt to surmount the milk container he might drop to the top of the squirrel baffle below. From there he could climb up to the bait station. To prevent that scenario I suspended the bait station at the end of the tube, and removed the vertical post.

The peanut butter was untouched the next morning. The baffle had worked. I turned off the camera thinking the experiment was over. But when I came to collect the camera the next day the peanut butter was gone! Wonder rat had circumvented the baffle on the second night, and there were no documenting pictures. The inside of the tube was still dusty. If only I had a camera trap that shot video!

I consulted with neighbor Richard, who advised me to replace my shabby plastic baffle with a two-pound coffee can.

The new baffle did the trick. The next morning the peanut butter was untouched. I had enough. The question of chimney-stemming would have to remain unanswered until some later date. I just can’t believe that this wood rat can’t pass through a 2-inch pipe, but for some reason he wouldn’t have any part of it.

Reflecting on all of this I thought about the advantages of a camera trap that uses video.

That night I was sitting at the kitchen counter as my wife was cooking dinner,

"You know, sweetie, if I had a video-camera trap I could get some fantastic footage. It would be pretty neat seeing that rat in action, wouldn’t it?"

"Yeah, that would be nice", she admitted. "But it would be nice to see the leaking roof get fixed too."

Obviously she wasn't buying it. I guess my timing was off.

Woodrat tricks codger (continued)

Wood rat couldn’t cut the mustard when it came to climbing down a vertical quarter-inch cord. But could he walk across the same cord if it were horizontal? I pulled a quarter-inch cord taut like a tight rope, and repaired the vertical cord that he had almost chewed through. The next morning the vertical cord was dangling and the bait cup was gone. The pictures tell the rest of the story.



He had fed intermittently for a half hour, and cut the bait free in less than a half minute. I revised my thinking. Making the first cut beneath the food wasn’t so dumb after all. If he cut the rope above the bait it could drop into a thicket below, and that would mean a lot more work. Better to cut it free and haul it home in one set of actions.

There was no sign of the cap that held the peanut butter. He must have cached it in his nest for bedtime snacking. I repaired the set up, and the next night was a repeat performance.

Now that wood rat was a habitual visitor, I expected he would go to any length to reach the reward. So I replaced the 1/4" cord with a 1/8th" nylon cord. I figured a really good climber would hang-crawl along the string to reach the feeding station.



Wood rat would have no part of it. On the next two nights he visited the access route as many as 8 times a night, but would stop where the 1/4" line was knotted to the 1/8" line. There he would look longingly in the direction of the bait. It seemed that wood rat wouldn't walk the line if it was less than a quarter-inch thick.

So far, so good. But now I wondered . . . was wood rat capable of "chimney stemming", — that’s what rock climbers do when they brace themselves and "inchworm" between two parallel walls. I wired a 26" length of 2" PVC pipe, the chimney, between an overhead branch and the platform. The only way he could reach peanut-butter-land, I thought, was to go down the tube. I set one camera trap to monitor the tube entrance, and another to monitor the bait station below.

He visited the bait station for two nights, and I assumed that he was chimney stemming.



But a little knowledge can be dangerous. The picture of the hind-foot hooked over the twig showed that he can't rotate his ankles and cling like a squirrel. Therefore, I thought he was testing it in this picture. He couldn't possibly go down the outside of the tube head-first. He had to be going down inside the tube.

A simple test could prove it. I stuffed an old sock--yes it was clean--into the entrance of the tube, predicting that he would either pull it out and proceed down the tube as usual, or have to forego dining at the bait station.

When I looked at the pictures the next morning, I realized the rodent had tricked me.




He didn't remove the sock, but there he was on the platform eating the peanut butter. Damn! My design was flawed. I had allowed him two options--go up the post or come down the tube. Not good experimental design. My early assumption that he couldn't climb the 3/4" aluminum post had been wrong. Now I was wondering if he ever came down the tube at all--inside or outside.

So I removed the tube to see if he could climb the post.

Surprise! The next morning's pictures showed the rat on the platform.



He could have gotten there only by jumping, levitating, or shimmying up the post. There were no climbing action shots, but there was this picture of him on the verge of descending with a mouthful of peanut butter. I had the feeling I was finally getting closer to the truth.

If you think you can bear any more of this, stay tuned for the final episode.

Wood rat accepts the challenge

Okay class, today we're going to see how the scientific method can be used to explore an important and unanswered question: how well do dusky-footed wood rats climb?

The irrepressible mammalogist Jack Cranford reported that radio-collared wood rats spent 40% of their time above ground foraging in shrubs and trees, and the late E. H. Vestal described a worried wood rat leaping three and a half feet—a rather squirrel-like achievement. So, it's fair to ask: is Neotoma fuscipes a confident and acrobatic climber? Or a cautious climber? It was time to subject wood rat to some climbing trials and put the camera traps to good use.

Where to begin? Go to the literature! Linsdale and Tevis, in their book "The dusky-footed wood rat" reported a rat climbing a poison oak vine. Poison oak vines come in various thicknesses, but cutting them for experiments can have uncomfortable consequences. So my first question was: can wood rat climb a 3/4" manila rope?

I tied the rope to an overhead branch of oak, and moored the other end to a log on the ground. Only by climbing down or shimmying up could woodrat reach the peanut butter feeding station in the middle of the rope. I hoped for a picture of him clinging to the line like a mountaineer.



Wood rat accepted the rope-climbing challenge, and cleaned up the peanut butter the first night. In fact, he made several visits. I assumed that he descended the rope from the overhead branch. It seemed easier than surmounting the feeding platform. Whatever he did, he did it quickly, because there wasn't a single picture of him coming or going.

Time to "raise the bar". The next night I replaced the vertical rope with a 1/4" cotton clothesline. I also replaced the plywood platform with a bait cup strung on the cord.

No longer could he sit and dine.
He would have to feed while on the line.
Ahah! Two nights passed with nary an image.
Was the 1/4" line beyond his limits?

Or was woodrat digesting in the stomach of a fox or bobcat? It was too easy to discover his limitations, and I wondered whether I had somehow exposed him to danger. I mean, like...gee whiz...maybe he attracted a predator while scurrying about trying to reach the peanut butter.

Okay, let's make it easier for the guy. On night 4, I used the 3/4" rope to make a bridge. All he had to do was walk across the rope to the clothesline where the peanut butter was waiting.





And that's exactly what he did. The next morning's photos showed woodrat alive and well, and eating peanut butter like there was no tomorrow. I could only conclude that he was no match for his crazy ninja Malaysian relatives (see the previous blog, mates). Climbing the vertical clothesline (1/4") was beyond his ability. He seemed a little resentful tugging at the cap and chewing the line, but he wasn't clever enough to cut the cord above the bait. The unfinished meal was still there. I felt a little disappointed and smug at the same time. But all that was to change. Wood rat had some tricks up his sleeve. (Stay tuned for the next episode).



REFERENCES

Cranford, J.A. 1977. Home range and habitat utilization by Neotoma fuscipes as determined by radiotelemetry. Journal of Mammalogy 58(2):165-172.

Linsdale, J.M. and L.P.Tevis. 1951. The dusky-footed wood rat. University of California Press, Berkeley.

Vestal, E.H. 1938. Biotic relations of the wood rat in the Berkeley Hills. Journal of Mammalogy 19:1-36.