Not a bunch of pretty pictures this week. However, a few of you may appreciate the commentary. I have been attempting to better manage marten for several decades, both in Alaska and in Idaho.The extent of the annual harvest is young-of-the-year animals. One of the things I looked at over many years and many thousands of trapper-harvested animals, was the average number of blastocysts in the adult females. This could be used to predict next year's crop. I would excise the reproductive tract out of adult females, flush that uterus with water, and count the number of potential youngsters she could have produced if she was not removed from the population. It gets pretty complicated. The fertilized egg would divide to the 8-cell stage (pictured) and the development would stop (suspended animation) until late spring, when the blastocyst would implant on the uterine wall and continue growing (delayed implantation). In marten, breeding is in the fall (before trapping season begins) and birthing is after the trapping season closes. Therefore, these adult females are pregnant during the entire season and potential litter size can be determined.


This is the reproductive tract from an adult female marten. Ovaries on the right, vaginal orifice to the left.



These two photographs are blastocysts (fertilized eggs in the 8-cell stage). They are approximately 1.0 mm in diameter and can be seen with the naked eye. The photos, however, are through a dissecting scope.

Must smaller than counting placenta scars that I am use to

I thoroughly enjoy the biology lesson. I didn't know that marten also employed delayed implantation. I knew otters did.

Bear also, right???? I guess I figured bears were the only ones. Are there any other animals?

How many females would a trapper have to check toget a fairly decent average for his area? Only mature females, correct? Would YoY females be pregnant?

In order for a trapper to "manage" his marten population would his take of marten have to be the major source of mortality?

If a trapper knows the average fetus number is there a way for the trapper to also know, or estimate, the average survival percentage of those young?

In 1979 I was fairly new to Alaska. Me and another guy had just finished the winter with a catch of over 200 marten. The Novi had an ice jam somewhere, or maybe it was on the Yukon. Anyway, the whole lower Nowitna valley was flooded. I spent a week in a tent on a high spot. Figured all the voles/Shrews would have drowned. Bad news for marten. The next November, right near the Nowitna mouth, I could barely keep the marten out of my traps!

Back around 1986, Gary Bamford, trapped the Hog River country, told me there had been a Feb. rain the winter before. Covered the snow with ice. His marten catch the next year was considerably less.

Thank you, Jack, for sharing your priceless knowledge .

Here's a different rendition, in pencil, to contribute.

Beautiful Sharon

Wild turkey hens can suspend the semen from a single mating and fertilize another clutch of eggs if first or second nest is destroyed...

beaverpeeler, Robert Martin, and others - Bears display delayed implantation. Also, most mustelids (otter, fisher, wolverines, badgers, weasels, etc, as well as mink, but their delay period is very short) and some skunks (interestingly, the eastern spotted skunk has no delayed implantation, the western spotted skunk has a delay).

martentrapper - I always figured that only 20 adult female marten were enough to give an indication of next years' crop. More important, though, is the ratio of total young:adult females in the harvest. If trappers can keep that ratio at 4:1 or better. they will probably have a decent crop the following year. I certainly agree, however, that winter chinooks (thaws with rain in January, February, or March) is a death knell for microtines, and will have profound effect on survival of YOY marten in spring and early summer.

Mike, from what I remember reading the average number of kits per litter, that survive into their fist fall is something like 2.1. I also want to say that the average number of blastocysts was about 4. Maybe Jack will weigh in on that.


While delayed implantation is an interesting subject, I think and even more interesting subject is induced ovulation. I believe it is thought to occur in marten and maybe some other mustelids.

Jack, maybe you can talk about the various reasons for this. I can see it being valuable in a species where the density is low (wolverine) or in species that do not reach sexual maturity early in their lives.

Your thoughts ??

Isn't blastocyst number an indication of the health of the female? The healthier she is the more kits she will have. So counting blastocysts would be about as good an indication of next years marten pop. health as you could get.
I assume the only way to KEEP your young to adult female ratio at 4 or more would be to stop trapping when you see it being less. But how many marten do you need to catch to get a good grasp of that ratio? I see you already more or less answered that question. 20 adult females is enough.
Without the ability to control the weather, to control the microtine population, and to control kit survival, I don't see how one could really "farm" his marten population. You might get lucky some years but just as likely what you "expect" to be a good year based on the last years harvest could end up being a bust.

In fall of 1990 I returned to my trapping cabin on the lower Nowitna after a 5 year absents . The whole lower Nowitna was mostly untrapped since 1985. In addition, I had an airplane. I used the airplane to lake hop the Little mud drainage on the east side of the Novi. The trapping cabin was in the white spruce lowlands and most of my effort in there was with a snogo. The Little mud was black spruce with some very mature forests and 2 different burns of different age. I had been lake hopping the mud for the 3 previous years. The first year was a learning time, both flying and trapping. The next 2, 88 and 89, was serious trapping. 88 and 89 were over 100 animal seasons.
The 90-91 season was the worst trapping season I ever had. Both the Novi basin and the mud. I actually trapped out of the mud at it's head and into Boney creek going east. Lots of 7ECA size lakes there. I ended in Feb. 91 with only 50 marten. Something I had no control over had effected the marten and there just weren't many around.