Something never before seen among wolves is taking place on the Northern Range of Yellowstone Park. The two pregnant Slough females finally entered their traditional dens up on the steep slope at the mouth of Slough Creek, but the new "unknown" pack has either scattered the rest of the Sloughs or the Sloughs left, and the two Slough females seem to be pinned in their dens by the unknowns. The status of the denned females isn't known, but because of the high water requirements of a lactating wolf, they or their pups won't last long confined to their dens like this.
The weather has been poor, so there has been no tracking flights to try to locate the other Slough wolves or other packs.
Update 4-19. I believe Kathie Lynch may have the complete story by tonight. Meanwhile, this is a brief update from talking with Rick McIntyre and trying to distill all the information. Today is day number 7 of the unknown pack's occupation of the area around the Slough's den site.
When Rick McIntyre and folks showed up on the morning of April 13 to look at the Sloughs, instead they found 9 (of the 12) wolves of the unknown pack all around the Slough den site. Later that day the signals of Sloughs 377M and 490M were picked up to the west, but the signals of the pregnant Slough alpha female 380F, and pregnant 527F were not heard. McIntyre walked about a mile down the closed Slough Creek road and picked up their signals from inside the natal den.
Ever since the unknown pack has come and gone. All 12 of the "unknowns" were at the den site today. In between the Slough females have been seen out of the den briefly, eating snow. McIntyre thinks that due to the extremely wet conditions prevailing, they probably have snow melt water to keep them going. From time to time other Slough wolves, but not the big males, have come and entered the dens too, with as many as 5 Slough wolves in the den at one time.
The unknown pack has one pregnant female. Although they have no functioning radio collars, the pregnant female is not their alpha female. This pregnant female seems to have been the most aggressive of the 12 new wolves. At one time she seemed to try enter the natal den. A number of times the unknown pack members have crowded around the Slough natal den in an excited manner, but there is not good evidence they entered. The den might be a good defensive location for the time being.
It is possible that this seige, or whatever it is, will end when the unknowns lose interest or the pregnant subordinate unknown female has her pups in the open or decides to head home. I wonder if she would try to use one of the empty Slough dens?