Are Striped Skunks Symmetrical?

Are striped skunks symmetrical? That might sound like an odd question but I have a very good reason for asking. One way camera traps are used in research is to determine the presence of species in an area. At its simplest, think of this as marking off species on a checklist each time one is

Three striped skunks at bait

photographed. At a more advanced level, multiple cameras are used to determine the presence of a species over a wider area and perhaps a range of habitats. In this case, the researchers are striving to calculate more than the mere presence of a species but maybe its relative abundance or more. And in species where individuals can be distinguished, camera traps can be used to conduct a mark-recapture study to make an estimate of population size.


 Much of the published literature I have seen involving individually recognizable animals involves cat species. Think of tigers, snow leopards and cheetahs as animals with distinctive and unique markings. In North America, our distinctively marked species are fewer and when we further narrow the field to the portion of New York where I camera trap, the list is downright pathetic. White-tailed deer (antlered individuals only!), bobcats (still a real rarity around here) and striped skunks are the mammals that come to mind. Perhaps there are others, but these are the ones I am confident in.
I have written about striped skunks before. In this post from last year, I describe numerous individual skunks photographed on my property. One limitation in determining individuals is that some skunks

Bipedal stance of striped skunk

would be photographed in their left profile while others would be oriented with their right profile to the camera. I could pair camera traps and therefore capture images of both sides of  every skunk that passes by but if I were able to safely say that striped skunks had symmetrical body markings (meaning that their left sides matched their right sides), then I would not need to pair cameras and could compare skunk photos regardless of the side captured by the cameras. Make sense?
Since this original idea came to me, I have conducted an incomplete review of the literature and not found anything written on this subject. Perhaps I am not searching properly or perhaps no one has found the need to write about this. But just maybe I have come up with an idea that is worth answering that has not been formally investigated. I thought an easy way to look at many skunks at once would be to attend fur auctions where trappers bring furs of all kinds to be sold. Alas, that plan has yet to make it to the front burner. And another fur season is past. Fortunately, an opportunity presented itself recently and I was able to obtain 162 muskrat carcasses to use as camera trap bait. I chose one large pile rather than several smaller ones and thought this would be the perfect first test of the brand new Reconyx camera I have access to through an undergraduate research grant. With literally thousands of striped skunk images over the last five weeks, I have some evidence to help me answer my question.

First, here is a look at two very white striped skunks. This photo is from a Cuddeback camera I also placed at the bait pile:

Striped skunks at a bait pile

 Let's call these SK01 and SK02. I only have a single image of these skunks during this visit, so there is nothing to help answer our symmetry question, but clearly we have two individuals so our population is at least two.
This next photo is only two days later and is also of multiple skunks but looky looky it appears to be two DIFFERENT skunks (probably three different skunks as that one in the back just seems much blacker than the two skunks in the first image), SK03 and SK04. I will not go through all the skunk photos in this entry and in fact have a student who is trying to tackle that instead. 

Striped skunks and opossum at a bait pile

I have the Reconyx camera set up to take a burst of three photos together and then to take another series of three as fast as the camera can rearm itself. This makes for many many images of the same individual and for my purposes here, it often provided images of rights and lefts of the same individual.

 Let's start with the photo on the right. As this particular stinker walks towards the camera, we get a sense that he/she is symmetrical. There is a bit of a notch in the shoulder area of both sides and the tail is uniformly white. However, we are missing the whole hindquarter. So what we really need are profiles. I will provide you two individuals in this post just to get us started, but before I do you should stop for a moment and guess at my results: symmetrical or no? I will assume those who would answer "Who cares?" stopped reading long ago....










EXHIBIT A: Again, remember that I know this is the same skunk in both profiles because of the almost continuous nature of the photos from the Reconyx camera.

Note the thickness of the stripe on this skunk's right shoulder or front quarter. Now scroll down and see the left shoulder of this same skunk....

Yipes! Look how thick the white mark is on that side. I was a bit surprised as I really thought my efforts were going to show that these guys were symmetrical. Let's look at one more:















EXHIBIT B: Again a right and a left profile from the same individual

Sigh... Again, there appears to be a marked difference. I have considered the idea that in THIS case, the difference may only be perceived due to body positioning, but I don't think that is the answer. Note that the photos are 12 minutes apart. Well, in that entire time this individual was feeding on the bait. I have many photos of this guy and I think these two represent the profiles the most accurately of them all.

A few words of caution: First, two samples is not enough to draw huge conclusions. And second, the asymmetrical skunks may stand out and were easier to find in my cursory review of the thousands of pieces of data from this camera. But one thing seems certain: Not all striped skunks are symmetrical. That makes the job of estimating their population harder. However, I am a man who tries to look at the bright side of things. I now know I need to photograph skunks from both sides in order to obtain the data necessary to make a proper population estimate. I believe I have just found the justification to ask the grantors for a SECOND Reconyx camera :)

A Valentine's Day tradition

Deer hearts ready for the camera traps
(Seneca Falls, NY 2/13)

My very first post to this blog (here) described the cardiac lesson my wife teaches each year. Part of the lesson involves dissecting deer hearts. Each year she brings the sliced hearts home for camera trap bait and each year "Cardiac Day" happens to fall near Valentine's Day. This year it matched up perfectly. With 14 deer hearts to set out, I knew my two cameras would be busy...




Setting out the hearts

I only set a few hearts at the first set. The first to find them was a gray fox. Note the two photos are a minute apart:

Gray fox taking bait
(Seneca Falls, NY 2/13)

Gray fox taking bait
(Seneca Falls, NY 2/13)

This set was more open than the second one and the only other visitor of note was this red-tailed hawk. Almost missed him!

Red-tailed Hawk in flight
(Seneca Falls, NY 2/13)

The second set is a bit brushier and I put far more hearts in front of that camera. Gray made an appearance here too:

Gray fox
(Seneca Falls, NY 2/13)

The hawk never made an appearance here because it was too brushy, but the crows found the bait straight away. The hearts are too big for the crows to carry, so they chisel out smaller pieces and I end up with massive amounts of photos:

American Crow at bait
(Seneca Falls, NY 2/13)

I also captured a skunk at the second set, but not the first:

Striped skunk taking bait
(Seneca Falls, NY 2/13)

Striped skunk taking bait
(Seneca Falls, NY 2/13)

The deer hearts are now a part of our February tradition. Best. Valentine's. Gift. Ever.

Now, I just gotta figure out what to get her.....

The dust mop and the powder puff II: CHIMERA



The uneasy truce between Powder Puff and Dust Mop described in my last post is holding. In fact, evidence shows that perhaps the relationship has been taken up a notch. Friendship? Bromance? Um, no. But have a look at the foggy photos below and tell me what you would call it:

This is the closest I have seen them. They are even on the same side of the carcass.

Opossum and skunk feeding at carcass
(Seneca Falls, NY 12/12)

Yeah, I'm not sensing total trust here....

Here is an interesting shot. The fanciest tail in all Didelphidom....

Opossum and skunk chimera

Are theses two getting chummy because they are more and more familiar with each other? Each day there is less and less food available on the carcass and each day they seem to tolerate each other more. But correlation doesn't mean causation. I am genuinely curious as to why these two were never photographed together at the start of this set and now I am photographing them more frequently together rather than apart. I don't know. But i do have one other variable to consider: There is a new actor in the night shift. A gray fox made a few tentative appearances and then got comfortable enough with the flash that he settled right into the carcass recently for some venison. Is the additional pressure of the new scavenger on the scene influencing the dust mop and powder puff's relationship? And what clever name can I give to this catish fox? These are the questions that keep me from grading papers tonight.....

The dust mop and the powder puff

Opening day of the regular deer season was November 17th. I found myself, as usual, at my Father's property. It is only the two of us now. The other regulars have all hung up their guns for the last time. So a day hunting typically plays out like this: We get up early and ride double on Dad's ATV out back. We fist bump and head to our different spots. The Van Niel's are tree stand hunters and there are several to choose from on Dad's 80 acres. We hunt for a few hours on our own and then I usually head over to Dad and join him for a bit longer and then we ride back to camp for lunch. After lunch, it may be a quick snooze before the evening hunt, dinner, and usually grading papers for me.

7 point buck
(Fremont, NY 11/12)

The only variation to the routine this year was checking several camera traps while working my way to Dad's treestand. Results will be the topic of a future post :) By the time I arrived at Dad's stand it was noon. It only took a moment to catch up on the events of the day, since neither of us had seen much. But as so often happens in a hunt, everything changes in an instant. I was still settling in when Dad grabbed my arm and whispered "Buck!". I froze. The ettiquite is simple: His stand, his deer. I ducked out of the way and caught a glimpse of the large bodied deer walking slowly across the field. One shot and it was over. Just like that. Dad has been hunting for over 50 years and still gets a thrill out of each hunt.

We paced the distance as we walked up on his buck. 193 yards. I snapped a few photos of my proud papa and then got down to the messy work. Truth is, I enjoy gutting a deer (or any animal for that matter). Besides being "The Eviscerator" I am also the butcher. But the reward is venison for us and a carcass for the camera trap.

I selected a location in our short hedgerow simply becuase it was close enough to the house to check easily. The carcass has been out for several weeks now and the cast of characters has not changed.

THE DAY SHIFT: The diurnal crew is all-avian. A murder of crows and a single red-tail hawk. I have up to seven crows in one frame but the one below is my favorite.

THE NIGHT SHIFT: The nocturnal crew is decidedly furrier and toothier. I call them the Dust Mop and the Powder Puff.

Dust Mop -- This was the first image of the opossum that I obtained and it was so unglamorous that I had to laugh. The poor opossum has quite the image problem already without me plastering unflattering photos all over the internet.

To be fair, let's have a look at a good hair day:

 

In fact, opossums can be downright cute if given the right light, a bloody carcass and an open mind:

Opossum on deer carcass
(Seneca Falls, NY 11/12)

Powder Puff -- My other nighttime visitor has more of a dramatic flair. This one knows how to make an entrance. Powder Puff makes the most of her assets and owns this carcass the moment she sets foot on the stage.

An unexpected benefit of the carcass is that Powder Puff is no longer tearing our lawn to shreds in search of grubs. This is clearly the same skunk from a previous post.

For weeks, the day and night shifts never crossed paths. No skunk or opossum photos in the day and obviously no crow or hawk photos at night. But in addition, the night shift and day shift didn't intermingle within their respective tours of duty. Not surprisingly, no photos of hawk and crow appeared and no photos of skunk and opossum were captured. But that changed recently. A few nights ago, numerous photos of Dust Mop and Powder Puff in what I would like to believe is a tentative detante.

Opossum and striped skunk
(Seneca Falls, NY 11/12)

Skunk diggings and droppings

Striped skunk
(Seneca Falls, NY 8/12)

"Did you tell your Father about the skunk?" Laura said over dinner the other night.
"Skunk? What skunk?" I said with a forkful of food poised at the ready. You see, this is the time of the semester that I challenge my introductory mammal students to a friendly game of "who can see the most mammal species and their sign". The checklist is displayed in the classroom and of course, the honor system is the rule of the land. I had yet to see a skunk, but apparently one was in the lawn the previous night when Danika got home and she stayed in her car for a few minutes to let it gain some distance before coming into the house. (At right is a photo I took earlier this summer)

Lawn damage from skunk
(Seneca Falls, NY 11/12)

I poked around the yard with a flashlight a little with no luck. But the next morning, I did some scouting and found that this guy has been busy in my yard for some time now. What you see in the photos are diggings made by a skunk to search for grubs and other invertebrates. Raccoons do this as well and I am not sure how to tell the difference. I am certain I read an account recently*, so i will have to search for it (and with the magic of electronic editing, amend this entry to make it look like I knew what I was talking about the whole time!). The photo to the left is a particularly deep hole. Note the penny for scale.
*AHA! I found reference I was thinking of. Elbroch's Mammal Track & Sign says (p. 698-99) that skunk digs are conical with the dirt thrown back only a short distance while raccoons have the debris pile farther from the hole.

Now, it is important for me to tell you that I am not a fanatic when it comes to lawn care. In fact, I am not much for yard work of any kind. I look at the digging as an interesting piece of natural history and perhaps a bit of soil aeration. There are several patches in both the front and back yards. Below is a photo that gives you an idea of the extent.




Skunk diggings for grubs
(Seneca Falls NY, 11/12)

 One more photo as I don't think these are showing up well (compensate for quality with quantity is the theory here...):

Skunk digging in lawn
(Seneca Falls NY, 11/12)

The skunk or skunks have left some scat behind as well:

The piles are similar to each other and I must admit that I would be hard pressed to call them skunk without the circumstantial evidence of the holes and the sightings. I checked the camera in the back yard and found this:

Striped skunk
(Seneca Falls, NY 11/12)

But a camera trap capture doesn't count. The sighting must be of a live animal. So last night I took the headlamp out again. This time I didn't make it 15 feet from the door before I could smell him. I heard some movement only 10 feet away and off he scurried! It appeared to be the same white-backed individual captured above. I watched as he waddled under my daughter's car. I have to remember to warn her.....

Visitors to an ever-shrinking pond...

Drying pond
(Seneca Falls, NY 7/12)

It has been dry this year and the pond in our backyard is barely earning its name. But the mud pan is good for tracking and I imagine that the small pool of water concntrates prey making it easier to catch. The camera trap is not visible in this photo but it is attached to the willow tree in the background left. BTW, this end of the pond is now completely dry so I moved the camera to the deeper end yesterday.

The mud is just littered with raccoon tracks, so it was no suprise that I captured several really nice coon shots.

Raccoon family
(Seneca Falls, NY 7/12)

I love this photo! What an action shot. Each of the youngsters is actively searching for food. The young coons will stay with their mother all summer and may even spend the winter with them. I hope to keep getting photos of these guys and watch them grow. I can't tell if that is an eye shine in the backgound. Evidence that it may be is this next photo of four young

Raccoon and four young
(Seneca Falls, NY 7/12)

Among the raccon tracks, I found a single set of skunk tracks. We only have one species of skunk in NY, the striped skunk. I have had no shortage of skunk photos this year. Check out other entries here.

Striped skunk
(Seneca Falls, NY 7/12)

Skunk and raccoon tracks have some similarities. They are both about the same size and both have five digits on the front and rear. But there are some obvious differences. The digits are not aligned the same and are much shorter on the skunk. Skunks also have some really long claws on the front feet. So when I found this skunk's tracks among the coons, it was pretty obvious.

Striped skunk track (rear)
(Seneca Falls, NY 7/12)

Striped skunk track (left)
Seneca Falls, NY 7/12)

The final track I wish to share is a little different. This one is on the camera itself! At first, I brushed it off as a raccoon. I have had experiences with coons climbing my cameras before but this one didn't look right for coon. We are looking at the print to the right of the flash. Note that only four toes are showing. That in itself doesn't eliminate coon. It is common for a toe (or two) to not show in a track, but it had me thinking of who would leave a four-toed track. The answer: rodents. And when I looked at the photos from the camera I found this:

The unmistakable tail of a gray squirrel. Look at those long whispy hairs on the edge. Here is the whole squirrel for comparison:


Gray squirrel
(Seneca Falls, NY 7/12)

Signs of SPRING: skunk mating season and blackbird flocks

Common Grackle and Red-winged Blackbirds
(Seneca Falls, NY 3/12)

Although the thermometer seems to have been set at "Spring" for the past few months, the calender is finally agreeing. I checked the cameras today and found two genuine signs of spring. First, two photos of migrating blackbird flocks. I see Common Grackle and Red-winged Blackbird. Interesting fact: Red-wing males migrate before females and establish territories. When the females arrive, they seem to select males largely on the territory they have selected and held. The Red-wings on my wetland are already singing.

Red-winged Blackbirds
(Seneca Falls, NY 3/12)

Female Red-winged Blackbirds are not black nor do they have red in the wing. I have been doing a bit of mist netting with my students lately and i look forward to cathcing some Red-wings with them. The males are so much larger than the females that they take a different size band. That is not all that unusual in the bird world, but it IS unusual for the species of birds that I work with. I wish this photo wasn't so blurry, but you take what you get!





My other sign of spring is a set of two skunk photos taken only a few minutes apart. I assume the first photo is a female and the second is a male following her scent. I have no proof of this but I can support my idea. First, I experienced almost exactly the same thing almost exactly one year ago in exactly the same spot. Last March, I had this camera on the same tree and wrote this. Second, I do not get photos of skunks this close together outside of the breeding season. Even this year, where I had more skunk photos in February -- more different skunk individuals -- I did not have skunks trailing so close behind each other. Compare the two skunks photographed to the ones shown here to see if these are known or new skunks. What do you think?

 Thirteen minutes later:

Thirteen minutes doesn't feel like he is "hot on her heels" but consider a few things. How do they find each other in the first place? Probably by scent. So a male crosses a fresh scent of a female and he starts to follow. By the time he is photographed above, he has narrowed the gap to 13 minutes between himself and the female. Presumably, she is meandering a bit; looking for food. Presumably, he is not and that is how he can continue to get closer and closer.