Hard nuts to crack

I always forget to kick the pine cones out of the way before I engage in the most strenuous but gratifying of male Freudian rituals: vernal weed whacking.


The wicked looking cones I am speaking of drop like small bombs from the gray (formerly digger) pines (Pinus sabiniana), -- the familiar California endemic that sparsely cloaks the dry slopes of the inner coastal range and Sierra Nevada foothills.

To add insult to injury each spine comes with a blob of pitch.

You won't find a single one in Nevada or Oregon, and they're manna to the western gray squirrel.

Anyway, as I kicked a cone out of the way a large seed popped out and my foraging instinct kicked in.

These nuts, I observed, are bigger than the pignoli the Redhead buys in the market and toasts for salads and pastas.  And if your time isn't worth money they're much cheaper too.

An hour later I was drained by the grueling rite of spring but had sufficient reserves to go back and gather the errant cones which I set beside the garage for solar toasting.

By week's end the thorny scales had opened and relinquished their bounty -- a fistful of nuts the color of roasted coffee beans.

It was time to work on the cones, and I was soon caught-up in knocking their nuts loose.



In my gnarly grip the hooked thorns broke off on the pavement, but I was not spared the pine cone's other revenge -- gummy fingers.

I can sympathize with the squirrels with pitch besmirched cheeks.

Pine nuts are hard to crack, but it doesn't take much to work out a system.

A small bench vice worked better for me than a snub-nosed pliers.

With a turn of the screw you can control the compressive force of the jaws much better.

I cracked 159 nuts and found that 38% were shriveled duds.

I have enough however to garnish our salads next week when the camera trappers rendezvous at the Chimineas Ranch.

PS: Fred the squirrel impersonator and guess who got in trouble 

when someone rubbed his pitch-dabbed cheeks on the carpet. 

Return to El Paso

[This is a feeder trail to "El Paso", with (aaargh) the most common user.]

Since I made such a big deal about "El Paso de las Pumas", I guess I have to write a follow-up.

I waited a month to check the two cams at El Paso, thinking I'd get at least a few bobcat and bear photos, and maybe even a shot of the elusive puma.

Instead, I got 9 pictures of squirrels and one of a female red-shafted flicker. The flicker photo made me feel a little better.



I set another cam on a different segment of the main trail. So I have three cams waiting to ambush a big cat.

[Flicker, uncropped]

I'm not ready to give up on the site, but in the mean time I guess I'd better call the place "El Paso de las Ardillas".

Cone middens and wascally squirrels

Where there are pine cone middens there are squirrels. Figuratively speaking, squirrels and pine trees have been engaged in an evolutionary tango for a very long time. (Read a bit more here.)

The successful pine tree fends off chisel-toothed rodents that attack and eat its seeds before they even germinate. That doesn't mean it bars the wascally squirrels from eating its entire genetic investment. 

It's more of a numbers game.

The tree makes the squirrel work harder for a smaller meal by putting fewer seeds in its cones and arming the cone's scales with painful spines and hooks.  

Have you ever tried to remove the nuts from a pine cone using only your hands and teeth? 

You might succeed with some of the smaller cones like those of Ponderosa pines, but it wouldn't be much fun and it certainly wouldn't be very rewarding, because the seeds are small. 

So tear into a cone with large seeds, like those hooked bombs from our gray (or ghost) pines.

Your lips and cheeks would look like taco meat in no time. If you think that handsome beard would protect you, try removing the pitch without the benefit of solvents. 

Squirrels have responded to the challenge by evolving larger heads and powerful jaws as well as effective ways or munching around those hooks and spines. 

 

The Western gray squirrels here in the Sierra Nevada foothills are hefty bruisers. In addition to acorns they successfully tackle the nasty hooked cones of our gray pines. I doubt that a smaller squirrel could handle them very well.

But these big squirrels are built to take on big cones.

Reference

Steele, M.A. Evolutionary interactions between tree squirrels and trees: a review and synthesis. Special Section: Arboreal Squirrels (pdf)

Exposing the stripper

She was naked and alone. A redwood sapling stripped of her outer bark.

The question was who was the stripper. Chickadee, titmouse, bushtit? Maybe a nuthatch. Or was it a rodent?

I suspected a dusky-footed woodrat. There was a stick nest only yards away.

Rich thought maybe a Sonoma tree mouse.

We set the camera about 12 feet away and 5 feet off the ground on a metal post, and we waited 6 weeks for a good weekend to make the four and a half hour drive, which was last Saturday.

The camera batteries died after a month, but there were 52 pictures.

Forty four were of grey squirrels and twelve of them were of squirrels on the tree.



There was one visit by a woodrat.



And 4 of deer, who looked only to be passing through..



The evidence is inconclusive. None exposed the stripper.

We'll have to use video to catch it in the act.

The work never ends.

Bobcat food

This is the area where the bobcat passed a few days ago.

Turkeys are an alien (=introduced) species in California, but bobcats and other predators have accepted them without prejudice.

The cam took 0.9 pictures/day here in 12 days, but the majority of the traffic was from this flock of hen turkeys and a couple of squirrels.



When I scoped these pictures out on the trail it was a ho-hum moment.

A couple years ago I would have moved the camera to a new location.

But sooner or later something less common will make an appearance.

So I'll just wait it out a bit longer.

I am not growing more patient. It's just that I have enough cameras now to work several locations at a time.

Animal Psychology for Camera Trappers-Part 1

[A raised forefoot while immobile and staring often indicates uncertainty. This full-frame photo shows an alert young squirrel fixating the camera with hesitation. In the next frame it resumed eating sunflower seeds.]

Many animals are cautious or fearful of unfamiliar objects or situations. This healthy response to the unknown is called neophobia or “fear of the new”.  

I believe that neophobia was the reason my first camera trap pictures of gray fox were in the distance or half out of the frame. After a few weeks the animal(s) approached more closely, and finally became bold enough to examine the camera at close range. 

 

[A jackrabbit assumes a startled stance in reaction to the camera trap. The widely spaced rear feet indicates it is prepared to bolt.]

If there is bait near the camera you might read ambivalence in a neophobic animal’s body language. 

The attraction to the food is strong, but so is the hesitation to approach the strange object near by. The animal may stare at the camera, or stretch its body and creep forward as though it wants to approach and back off at the same time.

 

Or it may approach and sniff toward the camera, then circle and test the air from a different direction. These are manifestations of approach-avoidance conflict.

Caution wanes quickly when repeated exposure to a strange object proves harmless. Since there are neither positive nor negative consequences, the animal habituates to the stimulus.  

Habituation is why we don’t often see neophobic or avoidance–conflict reactions in camera trap photos. 

Also, habituation usually defeats the clever tinkerer who cooks up various repellents for garbage-can bears and bird-feeder squirrels. Fearful reactions wane, unless the repellent is painful or extremely disturbing . The animals habituate. 

[A jackrabbit in a normal resting stance in its form (nest).  The animal habituated to the camera which was staked closer to the nest on three successive nights while the animal was absent. The camera recorded its daily cycle of rest, grooming, and defecation for a week without apparent disturbance.]

Emergence of the bot flies

The grisly subject of botflies revisits me at this time of year, because August and September is when I find them floating in the swimming pool.

My earlier unconfirmed discovery of a bot on a western tree squirrel elicited quite a few comments, including this one by bot fly expert Frank Slansky at the University of Florida. His webpage on the topic is worth a visit.

"Can you clarify-- was that pic of the sq on your website from California? It looked like a western gray squirrel, but I'm not certain.

[CW: Yes, it was a western gray squirrrel.]

"The issue is that there is only one known species of Cuterebra (C. emasculator, the "emasculating" bot fly, which actually doesn't emasculate its hosts!) that normally infests tree squirrels, and it only occurs east of the Mississippi. So there are three possibilities about the squirrel you photographed:

1. There is a western spp of Cuterebra that typically infests sqs which has not yet been 'discovered' and identified by entomologists;

2. The eastern species of Cuterebra that infests squirrels has somehow spread to the west coast, perhaps because some of the eastern gray squirrels that were introduced on the west coast were infested with Cuterebra;

3. The squirrel you photographed was 'accidently' infested by a species of Cuterebra that typically doesn't infest squirrels. Each species of Cuterebra is fairly specialized in its 'typical' hosts-- one species of Cuterebra may typically infest only wild mice, another only wild rats, another only rabbits, etc. But sometiumes an 'odd' host gets infested, such as a raccoon or house mouse-- sometimes even cats, dogs and people, although there are no species of Cuterebra that typically infest these animals. They just 'accidently' get infested when they encounter some bot fly eggs laid in the habitat of the 'typical' hosts.

"I think #3 would be the most likely explanation for that squirrel-- when running on the ground it may have encountered some eggs of a mouse-infesting or rabbit-infesting Cuterebra and became infested that way. Larvae of the mouse-infesting species often settle in the groin area of mice.

"Anyway, it's probably a very rare occurrence, but if you see other western tree squirrels with these bot fly lumps ('warbles), please let me know. And if you know any folks out your way who are wildlife rehabilitators, please ask them to keep an eye out for Cuterebra-infested sqs that they get in for rehab. Larvae should be removed (they can be carefully pulled out using forceps from a live squirrel through the hole they normally make in an animal's hide, and preserved in alcohol (isopropyl or ethanol). If I could get some photomicrographs of such larvae from western tree squirrels, we should be able to publish a paper about this since it would be a very unique situation.

So readers there you have it. Keep your eyes peeled and contact Frank if you see warbles on Western tree squirrels. (Don't bother him with eastern tree squirrels -- he already has plenty of bots from them.)

Back on the mountain

Rich disappeared as soon as he unpacked, but I knew where to find him. He was sprawled in the weeds next to the snake pit eyeing a western diamondback through the zoom lens of his Nikon. (Yes, that's his picture.) He crawled a little closer for another shot and the reptile lurched over the edge and bellyflopped on the bottom of the septic tank. It sounded like a deflated tire hitting a cement floor.

"Wow!"

"A flying snake!"

We were back at the Cleary Reserve, supplied for an overnight with carne asada, beans, tortillas and tequila. And oatmeal. It was 3 weeks since our last visit.

The "camera trapline" was waiting. So we put on our boots, grabbed our gear, and headed for the nearest cam at the bottom of a gulch.

Such a promising set -- a giant fir across a stream bed. The old veteran had lain there for several decades. I knew when I saw it that it was an occasional game crossing. It was made for camera trapping. A bay tree was growing at a suitable distance to anchor the camera. If a bear or puma crossed the log, I'd still get a full body shot.

There was a promising sign, too. Something had dug out the area where I had prepared the scent cocktail-- crab juice stinkum (aged for 7 months) and castoreum.

I disarmed the camera of its bear guard, and noted the number of exposures -- 20. One a day. Not bad.

Oh no. The first picture was a self portrait of two sorry looking codgers. It was taken as we were "walk testing" the camera 3 weeks ago. We looked a little like trophy hunters posing beside a fallen giant.



We clicked through the rest of the pictures.

Bear and puma hadn't found the tempting cocktail, but a juvenile gray fox had. Notice the blocky puppy look. It still has some growing to do.



This fox decided to give the scent cocktail a thorough butt-scrubbing, known in the technical literature as an anal drag. Dogs are good at this sort of thing, and it probably explains the dug out section of the log.



Oh yes. A couple of squirrels visited, and one dashed across the log.



Hmmm. Gray foxes and western gray squirrels. No surprises here.

We shouldered our packs and moved on to the next camera beyond the mouth of the gulch.

(Continued in "Back on the mountain-part 2")

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 #3

This is a progress report. We haven't yet solved the squirrel-in-the-owl-box-problem. But I believe we are getting closer.

The squirrels aren't early birds. Usually I hear the alarm between 9:00 and 10:00 AM and dash to the window to see what's going on. By then the squirrel is in the owl box. The regulars seem to be young of last year, perhaps siblings.

Since my last report they visited and fed in the open-topped box for a week. Then I put the roof back on, and they had to get past the overhang of 2.5".

As expected, there was no contest. They just hang over the front and enter.

After a week of regular morning visits I extended the length of the overhand from 2.5" to 6.75". Again, they didn't miss a beat. Their rotational ankles make it easy to cling to the front edge of the box and reach the entrance.

This afternoon I extended the roof to 9". The squirrels will have to span 11" to reach the hole from the front edge of the roof.

I expect they'll start coming in from the side, where the straight line distance to the hole is 6.75".

I just hope they don't lose their appetite for sunflower seeds, so we can finish the trials in the next two weeks.

Oh yes, something else is going on, too. Yesterday's squirrel had a bloody patch of skin on one side of its face, and this morning another squirrel showed up with a bloody snout. Has mom become a pre-partum crankinpuss, and is she kicking butt when last year's litter shows up in the nest? I wonder.

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."

Magic squirrel mulch

An incense cedar fell across the flume during the last storm. Evidently the tree had been injured when it reached a height of about 40 ft.



The original shoot is the gray stub on the left. It died back from the damage, and eventually became a bird's nest cavity.

Two new shoots replaced it and grew into the two logs you see laying across the flume. These forked shoots were off center, and as they grew they placed an increasing strain on the trunk. This year they strained the trunk to the breaking point. Heavy winds were all it took to snap the trunk.



The trunk was hollow, but squirrels had packed it with cedar bark stuffing. It smelled good, and I started to dig it out like a terrier in a rat hole.

"I wouldn't do that", warned the redhead, "it could have fleas and all kinds of things.

"My God, there's squirrel hair in it! Tail hair!" I exclaimed. "Why this is a multi-generational squirrel nest!"

"Remember when your house had the flea infestation and your parents threw out your bird nest collection?"

"That was different," I answered. "This is self-sanitizing nest material filled with terpenes and secondary compounds. Just smell it. It's wonderful." The redhead backed up a step.

"C'mon!" I pleaded. "It smells just like cedar pencils."



Finding a fallen tree can be a cheap thrill for a biologist, especially one with cabin fever.

As we walked home I hatched a plan.

Three days later I returned to the scene and packed three grocery bags with magic squirrel mulch. It looks great around the camellias. The redhead hasn't noticed yet. When she does, I'm going to tell her, "It's special. You can't buy it at the garden center".

The Firestone press

It's that time of year again folks. The weather is cooling off, the oaks are a'droppin' acorns, and the annual squirrel Wanderung has begun.

The little troopers are not only looking for nuts, but young squirrels are starting to disperse, and along the way they encounter highways and American commuters. That's where some of them get the Firestone press.

It's fatal, but it's one of the realities of squirreldom.

If you find this a little sad, listen to this masterpiece by Ray Stevens, and you'll feel better.

Incurable bone chewers

That moose antler was a gift from my older daughter. It was already weathered and chewed by a porcupine when a grad student found it in northern Minnesota. My daughter bugged the grad student until he gave it to her, and then she shipped it to me in Virginia. It arrived in a very large box. A gift for a goofy dad. Yes, biologists are a little weird.

I made this cool sign out of it, and I liked it a lot, so when we moved to California I hauled it along.

It's a bone of contention. Every now and then the redhead discovers some useless but sentimental thing that I saved from the past (like the antler), and gently reminds me that she jettisoned all kinds of useful things when we packed off to California.

My daughters and I respond to these observations the same way.

"You married me (him). You knew what I (he) was like. I (he) can't help it. Biologists are a little weird."

Her point of course is well taken, a gentle reminder of the tolerance and sacrifices of a biologist's spouse.

Well, back to the story. It didn't take long for the squirrels to discover my eponymous moose antler, and we developed a routine. I hear the unmistakable sound of rodent gnawing antler, stop what I am doing, sneak around the garage, and suddenly but quietly make my appearance.

The squirrel stops gnawing, but doesn't flee.

"What in the hell do you think you're doing?!"

It hesitates and looks at me bug-eyed, and then discretely makes off into the canopy.

"That's more like it!" I continue. "And kindly leave my damn moose antler alone!"

It's all false bravado, of course. I actually don't mind them eating the antler.

The fact of the matter is that rodents are incurable bone chewers, and antlers are just bones, though very special ones. Hardly anything, except metastatic cancer grows as fast as deer antlers in velvet. When the growth is complete the cartilage is thoroughly embedded with calcium, phosphorus and various trace elements, and as the velvet peels the buck, stag or bull undergoes a personality change. It's a hormonal thing. Testosterone, the evil hormone that confuses rational thought transforms relatively docile velvet-antlered male deer into aggressive, anorexic, sex-crazed hard-antlered fiends.

In due course, the deer that survive the hunt shed their proud adornments and their sex-vanity, and the antlers lie there in the snow or on the damp duff.

Then come the "antler collectors" and the antler eaters. Antlers are worth money these days, and a lot of antler or shed collectors are good capitalists. They want to beat the competition. They also know that if they wait too long, the rodents will start to eat the antlers, and diminish their value. So they like to start looking early, and this can be a problem. When people are wandering around the woods in the dead of winter and deer are living on hard times it can put the deer at a disadvantage.

On the other hand, the shed eaters -- mainly rodents and rabbits are just responding to their physiological needs. They're capitalizing on a concentrated source of calcium and other minerals found in bone. Only a small percentage of the calcium in the mammalian skeleton is dissolvable and can be accessed for fetal growth, lactation, and the unending growth of the incisor teeth. So external sources of calcium are important. Calcium is an abundant element, but it's a lot easier for a rodent to gnaw a bone that chew limestone.

My casual observations of bone-gnawing squirrels suggest that it occurs year round. Consider this a hypothesis. I assume that the demand for calcium for the ever-growing incisor teeth is more or less constant, and assume that bone-gnawing is also a continuous habit. Who's going to do the experiment? Or who's going to direct me to the published results? So many questions!

Meanwhile, this old fool watches his moose antler slowly shrink, and verbally abuses the squirrels who come and go and help themselves. Yes, biologists are a little weird, but we're harmless, sometimes lovable, and we sure know how to have fun.

Got you under my skin

Notice anything unusual about this squirrel?

Yeah, I've noticed that it's a male too, but that's not unusual. (Arrow "x" is there only for reference.)

What I'm talking about is the dark thing hanging down from the squirrel's belly? Can you see it? Look again below the scrotum. Arrow "y" points to it.

The luckless rodent seems to be carrying an alien from the underworld of the Arthropoda. What you probably see is a repugnant swelling with an oozing sore, a warble. It's the domicile of a bot, the parasitic larva of the bot fly.

As flies go, bot flies are rather pleasing. They are hairy, somewhat blocky in build, and resemble bees. They have small or vestigial mouthparts. The raison d'etre of their brief adult existence is reproduction, and during their quiet interlude under the skin of squirrels they accumulate the energy stores needed to go forth and procreate.



There are 34 species of the bot fly genus Cuterebra in the US, and their larvae, the bots, must feed on small mammals, mainly rodents and rabbits in order to reach maturity. Each species of Cuterebra has its preferred host. In other words, gophers, wood rats, white-footed mice, and squirrels have their own dedicated species of bot fly, but they are not totally loyal to one host. Occasionally they meet up with the wrong host. Forty species of insects, including bot flies have been known to "accidentally" parasitize people in the US.

Finding a bot on your own body or in something you intend to eat is not a pleasant experience. In the southern US, only 2% of squirrel hunters were reported to eat bot-infected squirrels. The rest of them got really turned off. So a lot of hunted squirrels cycle back into the food chain without benefit of human digestion.

The fly bot is the closest thing to the slimy xenomorph (read Alien) from Planet LV-426 that exploded from the chests of its human hosts. Surely you remember Sigourney Weaver and aliens that got scarier with each new movie.

The difference of course is that aliens are fictional. True, they are all pretty much based on biological themes, though embellished and recombined to be extremely scary. Bot flies and their parasitic larvae however are REAL. So let's concentrate on the kinds of zoological reality that gave the producers of Alien its wildest ideas. There's a good reason for this, because our youth often confuse reality and fantasy, and in the age of intelligent design people seem to be losing their curiosity about biology and the natural world.

You will recall that the infective phase of the Alien life cycle is the Facehugger, which leaps onto the head of the human host and shoves an egg down its throat. This is extremely disconcerting for the human host. Cuterebra have far more finesse.
The female uses olfactory cues to home in on the nests of rodents, and simply lays her eggs on the vegetation nearby. When the eggs hatch the tiny bullet-shaped larvae (the first instar) zero in on body heat and attach themselves to the passing rodent.

There is no need for forced entry. The tiny larva crawls undetected into the body through the eye, nose, or mouth -- for that matter any opening they find, natural or otherwise.

The Alien's embryo (the "crawler") settles in the thoracic cavity and matures in a remarkable 24 hrs. Our baby bot (the first instar) on the other hand, takes about a week to migrate from the point of entry to a comfortable space beneath the skin, often in the squirrel's hindquarters. There it prepares its lodging for the next several months. The first order of business is to rasp a small breathing hole to the outside word. It also uses this porthole as a latrine, periodically expelling its liquid brownish excreta on the surface, which the squirrel periodically grooms away.

For the next month and a half the bot is the squirrel's constant companion. The squirrel's body reacts to it by encapsulating it in a fibrous sac, not unlike a mummy bag which seals it off from the rest of the body. The host's white blood cells and antibodies also increase. but this has little effect on the bot. It is basically a couch potato. Its daily routine is to lounge in its mummy bag, feeding continually on tissue fluids and cellular debris.

When it reaches the stage known as the third instar, it's almost as big as the end of your thumb. But unlike the Alien, it doesn't explode through the body wall, killing its host and scaring the hell out of everyone. On the contrary, it goes gently into that good night of pupation by squeezing through the breathing pore and dropping to the ground. There it burrows and undergoes its final transformation. It may emerge as an adult in another month or pass into a diapause and emerge next year.

It is hard to say how squirrels and other bot-infested rodents feel about all of this. They seem to carry on normally and ignore the bot, but in the laboratory at least, rodents become inactive about the time the bots emerge, and we may infer from this that harboring a bot has its discomforts.

What else? Well, if you are a nestling squirrel and unfortunate enough to be selected by several bots, you may not live long. If you are an adult female and the bots settle in your back side (as they often do) you may develop a pseudo-scrotum, and fool all the other squirrels. Male's with a bot-infested scrotum on the other hand may sport an appendage that resembles a duffel bag, but this renders them reproductively useless for the time being.

The affinity of bots for the scrotum accounted for the name Cuterebra emasculator, but Drs Bob Timm and Robert E. Lee Jr showed that scrotal bots don't affect subsequent reproduction. Unlike a lot of other parasites, bot flies don't practice "parasitic castration" upon their hosts.

If that wasn't so, a lot of southern squirrel hunters might be wearing camou codpieces made of fly screen.


References

Baudoin, M. 1975. Host castration as a parasitic strategy. Evolution 29:335-52.

Bennett, G.F. 1973. Some effects of Cuterebra emasculator Fitch (Cuterebridae, Diptera) on the blood and activity of its host, the Eastern chipmunk. Journal of Wildlife Diseases 9:85-93.

Jacobson, H.A., D.C. Guynn, and A. Hackett. 1979. Impact of the bot fly on squirrel hunting in Mississippi. Wildlife Society Bulletin 7(1):46-48.

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Squirrel episode at the owl snag

As fledging day approaches the fickle finger of fate continues to thwart my efforts to photograph screech owl fluffies. These are trying times.

I've gotten only 8 photos since last week -- a few blanks and a couple of screech owl butts as the adults entered the nest cavity. Part of the problem has been poor sensor alignment. Then the controller batteries went out, and today the camera batteries were dead.

Last weekend I was convinced that the problem was squirrels. My late afternoon visit began well. It was the first time I saw the male owl in daylight. His 'owl camou' really worked -- dark facial streaks obliterated closed eyes, and his ear tufts were at full mast. He didn't look awake, but I had a feeling he was sleep-faking.

Well that's cool, I thought. If the male is roosting here, the nest hasn't been abandoned.

There were only two pictures on the memory stick, so I raised the camera on the fiberglass pole, and tried to adjust the senor's position better. (I am embarrassed to say I forgot the periscope.) I had trudged up the slope to sight-in on the camera's position when I noticed two dainty gray squirrelettes lounging on top of the snag. They must have just weaned, and yes, they were cute. But their proximity to the owl nest only 4 feet below was too close for comfort. My warm and cuddly feelings weren't there. They didn't understand boundaries, and needed to find another tree.

I made a pathetic attempt to scare them off by tossing short twigs. They hardly noticed. Then I resorted to a long dead tree limb, but these efforts were equally laughable because I was endangering the camera. Finally the squirrels scampered down the snag and climbed a nearby oak.

I was again sighting-in on the camera when I was distracted by a big squirrel chasing one of the youngsters down the snag it had just climbed. This did not look like play or maternal discipline. They scuffled on the ground, someone squeaked, and the small squirrel broke free and bounded down the slope with big squirrel in hot pursuit. They scrambled up another tree, and -- OH NO -- big squirrel caught little squirrel again, and there was more squeaking. At this point little squirrel literally bailed out, free-falling about 25 feet to the ground, where he bounced on the leaf litter, and apparently none the worse for wear, ran down the slope and out of sight.

As if that wasn't enough excitement, I now heard a wheezy cough behind me.

"Chunka-chunka-chunk! . . . chunk-chunk-chunk!".

Another squirrel -- and a very large and agitated squirrel at that, was peering beyond me toward the victorious squirrel in the tree. Was this the mother of the vanquished weanlings? (I could see from its revealing posture that it lacked testes.)

"Chunka-chunka-chunk", replied the attack squirrel.

A chunka-chunk duel went on for a full minute, and then petered out.

The squirrel episode neutralized my funk about my bad luck with the owls. I've seen squirrel chases and rough and tumble play, but this looked like child abuse by the neighbor next door. What was going on?

Pack on my back, I looked up for the screech owl as I started home. I was almost directly beneath him, and though everything appeared as before, I noticed that his head was tilted down. He was watching me through squinted eyes. The bird was definitely sleep-faking.

Recluse in the snag

Three days ago at 6:13 PM a squirrel climbed down the snag and aroused the resident screech owl (who looked pretty scary to me). During the next two nights the owl took 143 pictures of its own comings and goings. Or should I say owls? If there is a pair, I can’t tell them apart.

The cavity is in a black oak and looked unused. So I was prepared for disappointment this afternoon when I went to check the camera. For nearly two weeks I have been using a new toy -- a telescoping fiberglass pole -- to raise the camera up to the level of tree cavities. This tree was second choice.

I expected a bonanza of pictures from my first choice -- a much-pecked flicker-sized cavity about 25 feet up. It had all the signs of occupancy, except the presence of a bird. The edge of the cavity had been chipped away and enlarged recently.

It was a bear of a job getting the camera into position, because when it is 25 feet overhead you can’t really see exactly where the camera's sensor is in relation to the cavity. From one angle they look like they are face to face. Then you move uphill to confirm it, and the camera looks too low. So you make adjustments and check again. And again. The other problem is pole-wobble. Even when anchored with guy lines, the slightest breeze wobbles the pole, which fools the sensor, and the camera goes wild taking pictures of moving vegetation.

After failing with a cavity that had "active nest" written all over it, I settled for one that was 12 feet up.



It looked abandoned, but I got a nice surprise. There were many shots of the little guy checking out the camera and the scenery.



And then there were shots of it clinging to the entrance.



And (whoohoo!) I got three pictures of the owl in flight.



Now to improve the set-up so I can get that picture of mini-raptor with limp deer mouse in talons.