I was asked if I had some pix to show how to tell various relative ages of marten: Figured more that one might be interested so here's some illustrations.

Adult: no visible bone on the top of the head.



Yearling: 4-7 milimeters of bone showing ; approximate.



Young of the year: 11-13 milimeters of bone; appx.

I didn't know that was how they were aged. Thanks White

Well remember this is just a way to tell their relative ages. Need to cross section a tooth to get the precise age.

Interesting. That is a good bit of info.

I had seen this before and couldn't remember which was which.

I understand but that is a nice quick way to reference what your taking on the line.

Yes it is. Pretty easy to keep track of your age/sex ratios that way.

Thanks Ken.

The is the best piece of information I have seen in a long while. Did not know that at all. Do you mind if I put that on the Canadian site with thanks to you White ?

Go right ahead Ron.

Thank you White, it is done. PM me with some information as to photo credits, where info originated etc. I would like to put this in the next issue of the BC Trapper Magazine.

Folks this is what makes these trappers forums special, useful educational information like this.

It also has the potential of being good for the trapper and the resource. If you can maintain a healthy population, you can trap it indefinitely as long as some external event doesn't intervene. Right now something is going on in my area at the very least and maybe over a larger area. If we had no baseline of what our populations were in the past, we might come to the wrong conclusion about what is happening when things change for a year or two.

can the same "procedure" be used on other critters?

I have seen the same thing in mink and fox. Wolverine all seem to be fully developed by trapping season. A lot of it depends on development of those muscles by chewing. Ever notice how young animals have a rounded skull? The chewing over time, and bone development squash the skull into a flatter, longer shape the older an animal gets. Also the sagittal crest grows larger because that is the point where the temporalis muscle attaches.

100% of my marten catch this year was adult female.

How many was that? Something tells me it was single digits.

1, but I realized the male to female ratio was bad so I pulled the trap.

And none to soon either.

Very good and important info here, I hope all the young trappers read and understand this.

(Old Retired Guy)

I believe that part of the skull is called the sagital crest. As the animal ages the crest developes more. An old marten actually has a crest at the rear of the skull.
I gave all my skulls to Audrey Magoun the last year I seriously trapped marten(90-91). She gave me the oldest one, all cleaned up and had a tooth aged from it. 13 years old.
mt

Great info, I'll definantly use it next year to help keep track of my population. I sure wish I still had the 2 I caught this year so I could start my inventory. They were both males so I guess thats a good sign.

The oldest one I have tooth data for was 14 y/o. A male of course. Haven't seen one that old ever again. What you do see in a steadily trapped population is a declining average age. Now I occassionaly catch a 7 or 8 y/o but most old ones are in the 4-5 range. I have never had a female tooth come back that was over 4.

WOW! 13 years old! I never would have guessed they lived that long. Figured 7-8 was about it. That one must have had all the right moves,(except the last one).
Bearbait; too late. You got the last one.

I've been told you can tell from the sagittal crest on wolves if it's a male or female and the approximate age. Is that true? I have noticed with older skulls (worn teeth) the crest is much larger, but wasn't sure about the male/female ID.

There's an easier way to tell the gender.

LMAO!!

Worn and broken teeth aren't neccessarily an indicator of old age. Many wolves and wolverines will break teeth biting the trap they are caught in. Tooth wear can be caused by what and where a critter normally eats. A marten, mink, wolverine or whatever that lives in an area with sandy soils may chew and ingest a lot of abrasive stuff with his meat, especially in the summer when they may be eating dead fish on the beach or voles with sand in their hair.

Bonnie, the best we can say from the development of the sagittal crest is that it is or is not an adult. We can't be precise in the age of a critter without the use of a tooth. Even then, there are various confidence levels involved. If the animal is very young or very old it may be difficult to say with confidence that the critter was 6 months or 11 months old. Same problem on the upper end.

What's that White? Check the credit card for excess shopping?

Nice skull photos White, explains it clearly. We covered this on the Alaska forum a few years back but your photos are sure to make it easier for anyone to follow.

I have a marten stretcher I mark with a pencil ever year as to the sex and age of my marten. Keeps harvest info right up front and easy to track. 80% of my harvest is juveniles and vast majority males. The longer I stay in an area and the later in the season the more females I harvest. I'm still not 100% convinced vertical sets result in more male harvests.

I just copied a portion of a spreadsheet with tooth data on it. The column headed CC is the confidence level of the technician regarding that particular tooth's age. The numbers following in the NOTES column give the range of age for that tooth.
Crap ! It won't post as a SS. The column of letters A<B are the confidence levels


Species Date Sex Serial# ID # Age CC Notes


MARTEN Nov-96 M 60 4201 0 A
MARTEN Nov-96 M 61 4202 1 A
MARTEN Nov-96 M 62 4203 4 B 4-5
MARTEN Nov-96 M 63 4204 0 A
MARTEN Nov-96 F 64 4205 0 A
MARTEN Nov-96 M 65 4206 3 A
MARTEN Nov-96 F 66 4207 1 A
MARTEN Nov-96 M 67 4208 7 B 7-8
MARTEN Nov-96 F 68 4209 0 A
MARTEN Nov-96 F 69 4210 0 B 0-1
MARTEN Nov-96 M 70 4211 0 A
MARTEN Nov-96 F 71 4212 0 A
MARTEN Nov-96 M 72 4213 2 A
MARTEN Nov-96 M 73 4214 2 A
MARTEN Nov-96 M 74 4215 1 A
MARTEN Nov-96 M 75 4216 1 A
MARTEN Nov-96 M 76 4217 1 A
MARTEN Nov-96 M 77 4218 2 A


Note on the two I highlighted one is YOY and the other an old adult but the tech can't say with good confidence what the actual age is. The old guy might be at least 7 but could be 8. The yoy could be 7 months but maybe 1 year.

White, I love this kind of info when it comes to skulls. I've cleaned so many and they are each so unique in their own way that I find it fascinating that so much info can be gotten from them.

Here is a pic of three skulls I cleaned a few years back. The largest skull is a grizzly bear, the middle is a large black bear and the bottom one is a wolverine. Just for reference, the dog in the pic is about 65lbs. I don't know the ages of these critters as when I was doing skulls back then I didn't ask the skull owner. Anyone care to venture guesses?

My GUESS is that all three of them are youngsters but the wolverine is older than the black bear and at least as old as the brown bear..but then again, maybe not

Nice job on those by the way.

If I remember correctly, on brown bears the root of the canine tooth has a hole in the end that leads up into the tooth. (my guess is that it provides for blood flow or some such. Bearpaw or Moosecaller could help us here). Anyway that hole remains open well into the bears teenage years.

Thank you Another of my side hobbies...lol

I've got a buncha skulls I'm going to clean this spring for myself of various critters and might take a closer look at what I can see as far as age.

And the reason I was asking about telling the difference between male and female, is I don't normally get the whole critter so I can't TAKE the easy way out to look and see

Right. I understood that but couldn't resist.

There are ways to tell but I can't recall the numbers off the top of my head.

For instance; a male marten skull may be 70mm long but not less than 62mm.

The female may be 53mm but never more than 61mm. These numbers are made up for the example. So if you know the correct parameters, you can tell gender.

Or...you can just look between their legs.

Kusko we've already BEEN THERE!! Can't look between the legs if all you have is a SKULL!!! LOL

Well I found these photos and thought this would be a good thread to put them on.
This was the head from an adult female caught in March. You can see the uterine horns with young starting to form in them. Small circles. Four of them.



The question I would have is in the discrepancy of the next two photos.
I would say from the spacing that this is a two year old. Or older?? The uterine horns look mature enough to say perhaps she is getting ready to begin development of her fetus's considering the swollen nature of them or has had a litter the previous year. Which would be my guess. Or is it just the added year of growth that has done this. From my experience in other animals you don't usually see this unless they have either had a litter or in this case perhaps starting to get ready for development..


Opposed to the YOY class with no swollen uterine horns. Or is it a yearling. It is a Feb or March caught Marten. The spacing seems similiar to your photo of the yearling but I would have guess it at a YOY based on relative size to the other marten. ??


Comments from the Marten Guru's

Man, I miss all the fun when I go out for a day to check my coyote line...

Great photos White. Your first photo is assuredly an adult female (duh!).

Second photo is definitely an adult as well, post partus (meaning that she has produced young in the past, further meaning that she is probably pregnant again, but the blastocysts have not yet implanted on the uterine walls for the current year). Therefore, a minimum of three years old.

Third photo is YOY, with thread-like uterine horns and would not have produced young during the ensuing year.

With males, it is apparent that the masseter muscle closure method works well. That is, marten from anywhere in North America will show 0-3mm of muscle closure along the sagittal crest if they are YOY taken during the winter (ie, legal season), and will show > 10mm closure if they are ADU. (About 97% accurate).

Females are much more problematic. Some old ADU females (in excess of 3-yr-olds) will not show muscle closure, and size of the uterus should be noted. I see this about 10% of the time, when masseter closure indicates a YOY animal and uterine horn size indicates ADU. Always, when tooth sectioning is completed, these animals are ADU. Thus my earlier comment (on another thread) about the methodology used when looking at harvest ratios.

If any of you (and I would hope all of you) start looking at your catch ratios, I encourage you all to examine the size of the uterus on all females, as this is a better indication of age than length of visible sagittal crest. Also, strive for more than 4 total young (both sexes combined) per every adult female in the harvest.

One of these days I'll take the time to look into posting photos. Once I figure that out, look out!

Again, White, excellent photos to start us on the long journey toward accurate marten aging.

I'd call that one at least a yearling or long yearling just based on what we can see. Remember too that these gals aren't sexually mature until they are about 1 1/2 y/o. Timing of the catch can give a different view of the uterus also. Caught mid-winter, the uterus may not show an indication of past pregnancies because the scars (corpora albicantia ??? is that right Gulo ?) disappear. Also, if you catch a marten prior to the blastocyst attaching to the uterine wall, they disinegrate rapidly in a dead animal. So if you have one hanging for some time between checks it may give an erroneous indication.

I don't think comparison of body size is ever relevant by the time we are catching them.

Good pix Len. Thanks !!

Sorry. The photos I was referring to in my last post were from FamilyTrapper. However, same goes; Excellent photos, Len. Many thanks...

White,
Unfortunately, uterine scars are not persistent in marten (unlike wolves, coyotes, etc., where you can determine history of litter size back a few years). Corpora albicantia and corpora lutea are actually ovarian scars (not uterine) where the egg has developed in the ovary, and then been expelled. In marten, the egg is released, fertilized, from the ovary and descends the uterine horn. This fertilized egg develops to the eight-cell stage (the blastocyst) but, unlike most species, does not implant on the uterine wall (thus, the term, delayed implantation) for several months. The blastocysts are basically free-floating in the uterus, with arrested development. They don't start to develop until they implant (usually late winter). Thus, you can flush the blastocysts out of the uterine horns with water and a syringe during most of the winter, and count these little guys, giving an indication of population productivity (had they not been harvested).

It gets real complicated, and most of you are probably rolling your eyes. If there is interest, I'll go farther into this...

So just to be sure I understand what you're saying;

The YOY will show 3-10mm of closure to go before the bone is no longer visible. In other words, still shows 3-10mm of bone whereas the adult will show 3mm or less visible bone.

Gulo


You have my attention. I have been around a fair bit of this type work while working part time at the Montana Fish and Game Lab in Bozeman while attending college. It was here that looking at uterine horns etc was introduced to me and I have used it a lot in my classrooms as a teacher and with my kids. I found it to be fascinating It is really fun to show people how many young an animal has had the previous year etc in such animals as mentioned.
As you mentioned, and for the readers here. Fand G would look at scars in the ovary for the number of eggs that were released by a female. And compare this with the number of scars left on the uterine horns. The number of young that had implanted on the uterine horns and thus given birth to.
Some good info here
http://en.wikipedia.org/wiki/Corpus_luteum

(corpus al·bi·cans (lb-knz)
n.
The white fibrous scar tissue in an ovary that results after the involution and regression of the corpus luteum.

How realistic is this for the untrained eye. I would like to try this. Just looking I could not find anything. Maybe a microscope would be what is needed. Also on a first year breeder. Bred in say July on her first cycle. How would the uterine horns look in Dec/Jan as compared with a YOY and Adult breeder in terms of development of the uterine horns. Guess what I am looking for is could you say that she is a first time breeder due to the lack of development compared to a previous breeder yet substantially more developed that a YOY?

This is what a marten uterine horn looks like the last week in March. Three young. Gulo when would you expect for these to be born. Looks like april to me.



The blastocysts on a January wolverine. Three young forming.


This was an interesting head shot. Notice the indent on the growth in the right photo.

White17...
Sorry I'm not being real clear. On male marten, YOY animals will have the sagittal crest visible all the way back, the full length of the skull, or the masseter muscle closure will only be about 3-5mm (where the muscle has coalesced together) from the rear end of the skull (from the lambdoidal crest). The remainder of the sagittal crest is visible, and there is usually a gap between the muscles which may be several mm wide. FamilyTrapper's last images above, if indeed they are both males, both of them are YOY animals. That is, very little muscle closure. On the other hand, if that last photo is of female heads (I can't tell scale), the one on the left is undoubtedly a YOY, while the right one is probably a YOY, but should look at uterus size for verification.

FamilyTrapper...
Really nice photos! Uterine scars (again, not persistent in marten, so lets not go there) are where blastocysts (developing embryos) have implanted on the uterine walls and go through their development until perturition (birth). It is the number of fetuses that developed, but not precisely the number of young produced. You've still got to take into account resorption of fetuses in times of stress and stillborn fetuses. Gets real complicated (sorry; I guess I'm an egghead).
The blastocysts that are flushed out of a marten uterus are a little less than 1mm in width. Thus, you pretty much need a dissecting scope to verify numbers. I usually flush them (with water, flushed through a 3-4cc syringe, 20-ga. needle, inserted near the ovary and flushed down through the uterus toward the vaginal end) into a petri dish with water. Under good light, and if your eyes are better than mine, you can see and count these little dudes.

I feel at this point that I should provide a disclaimer. In actuality, guys, I'm nothin' more than a trapper, tryin' to do the best I can to maintain trapping, yet maintain the resource the best way I know how. All this biological mumbo-jumbo really does have a point to it.....

FamilyTrapper...
On your top photos, I agree. Looks like an April, maybe early May, parturition date, based on the size of the fetuses. That's pretty advanced fetal development for March. Usually, they're not that far along.

On the other hand, you are down there in the delta country...

The female with young was taken with a 22 the last week of march. She had refused a set and was climbing a tree near the set. My son got pretty excited about it that was the end of story. Had I know I would have left her. Does one flushing push out the blastocysts? What is the most you have found in a female. What seems to be the average?

Very interesting! Wish some of my college courses would have been this interesting. And my wife thinks I'm wasting time when I'm "on the Trapper's Forum again!"

Keep the info and pics coming!

How do you go about getting teeth aged? Is it something you can get setup to do with F&G?

Does one flushing push out the blastocysts?
Yes, one flushing per each uterine horn flushes out all unimplanted blastocysts. You can usually talk a local high school into letting you borrow a dissecting scope for counting.

What is the most you have found in a female. What seems to be the average?
I believe the most ever encountered was 6. My sample size is well over 1,000 adult females flushed over a 20+ year period. The average varies from year to year, but overall, is probably between 2 and 3 blastocysts.

How do you go about getting teeth aged?
My recommendation is Matson's Lab in Milltown Montana. Gary Matson has more experience than anyone in doing this. He used to take teeth directly from trappers, I believe, and it also used to be about $8.00-$10.00 per tooth. Turn-around time is about a year, so you have to be patient. At this point, I'm not certain if Craig Gardner (Furbearer biologist, ADFG, Fairbanks) is collecting a large sample to age. From what I understand, his funding has been cut dramatically. You may also want to see what White17 has in mind.

This past spring Gulo and Craig and I exchanged a three-way email about the marten on my line and their ages. Craig had expressed that he was seeing similar results (very low juvenile counts) in the critters he was cutting up. He also mentioned a low blastocyst count from some areas. (I think we may be seeing the fruits of that this year but thats nothing more than an uninformed opinion) Craig's heartburn was that he had no funding for tooth aging and maybe no money to continue this particular work.

It seems to me that this would be a worthwhile thing for us to help out with funding. I think it would be imperative that Craig have control of the funding rather than the Department. Maybe Gulo can tell us how to structure things so that is attainable.

Anyway, I think it's something that could eventually benefit the resource and in the long run, trappers. I have no idea how much we would need but again Gulo can provide guidance there.

So I think this would be a good place and time to discuss that and see if there is any interest.

Take a poll, wise one.

Is this just your experience, Ken? Has this been tested in other areas of the state? Are you getting a large sample of your catch actually aged, or is your info coming from using skulls.
mt

That's my interpretation from several hundred teeth aged over several seasons on my line Mike. I'm pretty certain that the average could only decline to a certain level before there were no more to trap.

This assumes a more or less constant rate of in-migration from refuge areas surrounding the trapline. I suspect it would change measureably in the situation that now exists on my line. I believe some external event has moved my population to some other area and now critters are beginning to move back in. They seem to be overwhelmingly adults. It would be interesting to see how those ages compared to previous average ages.

So where do I place my bid for "white17's February 2011 trapline adventure" to benifit marten research??

You need to survive 2010 first. But you do have a point. We should probably let you make the first bid on the next auction.

It's not the first bid I want the rights to!

HAHA You'll have to earn the last bid.

LOL.
Don't I know it!

It was good training for you.

Gulo: does the development of the masseter muscle depend at all on what the critter is generally eating ?

Wow $8-$10 a pop. What does it entail? Just a cross section and ring count? Polishing? Just a guess.

W17...
I don't know; good question. I suspect that if food is inadequate, there would be less development of the musculature. Seems to me it would be the old "nature vs nurture" argument.

FT...
Yeah; spendy. It entails decalcifying the tooth, slicing it serially on a microtome (as I remember, about 16 microns thick), staining, mounting on a slide, and reading the annuli. Really pretty simple, but takes some pretty spendy equipment.

Back to W17...
I really like your idea of furthering the marten science. It would be a good question to pose to Craig, and I can certainly take the lead on questioning him, if you want to assign that to me (or you can ramrod this thing; let me know). At this point, is furtherance of the science best attained by additional tooth sectioning, or would it be better to assist Craig with understanding the diet questions (i.e., stable isotope work)? To me, both are important. I think Craig is currently in New Zealand, so we may need to wait a couple weeks before we can run this by him, if that's what you suggest we do.

Well I would certainly think you and Craig can better assess his needs than any of us can in terms of what aspect to direct the funds toward. Consider yourself assigned and thanks for volunteering. How much money do you think we'd need to raise to be meaningful ? Which activity would provide the most benefits per dollar ? How do we keep Craig in control and not the department ?


Back to the food: what I was wondering about the muscle development was this. Say a critter grows up in an area where he encounters food that is harder to chew than his more affluent relatives 200 miles away but the same age class. Would the act of chewing tougher food accelerate the rate of growth of the masseter?

Just a word of caution about what your money will actually buy with the stable isotope work:

People who do that type of work generally look at nitrogen and carbon isotopes. The nitrogen isotopes merely tell if, or how much, of their nutrition comes from the sea (as in salmon consumption)... not real relevant for marten. The carbon work tells how many trophic levels have been passed and how rapidly tissue turns over in particular organs. It doesn't tell what prey species have been consumed. There's a new, budding technology called Qauntitative Fatty Acid Signature Analysis (QFASA) that is designed to tell which species are included in the diets of other species. It's not mature/reliable enough at this point to sink money into because it still has a lot of kinks that need to be worked out. It's one of those emerging technologies that give good results within a particular set of limitations.

The bottom line is that we need to ENSURE that the method we support, if any, will answer the questions at hand, and supporting the stable isotope research won't tell you anything about how prolonged trapping affects the age structure of marten populations. As long as that's understood, and everyone's happy with supporting some other research goal, then funding ongoing research might be in order.

Whuh! Many thanks Caz...

I've not been directly involved (have never done it myself), but was under the impression that stable isotope work (using isotopes of carbon and nitrogen, as you said) would give us an indication of actual dietary components. The guy at UAF that Craig is working with wanted samples of red-back voles, red squirrels, mushrooms, high-bush cranberries, etc., that he could "signature" for looking at marten meat, fat, bones, hair, and claws, indicating that he could use each marten component to get a different "slice" of the life dietary history. Thanks for the heads-up. We should definitely look further into this and know what the capabilities are before we invest any green.

And too, Cazador, you are quite right. They are two dramatically different potential projects (the tooth sectioning versus the dietary components). It is imperative that we look at cost/benefit of either project.

"On the other hand", I'll talk with Craig when he returns, and his priorities, while not necessarily the same as ours, should be weighed.

Give us the wisdom, sensei17...

As in wisdom teeth ?

ttt

Very cool, alot of good info in here. W-17 are you aware of a NYS biologist who has been doing Marten studies for a while now? If not, seems to me you two could have a good conversation and share some thoughts. If interested P.M. me for contact info. Thanks!!

No I'm not but I'd like to talk to him and pick his brain. Thanks!

Talking about ageing marten, what about size?
How long was your biggest marten? Largest I have caught in northern Alberta is
37" nose to tail. I trap approx 150km south of NWT border.