Recently I wrote about natural vs. human-caused mortality and how I believe they affect wolf groups and wolf populations differently because natural mortality follows out of the local conditions and its consequences are less disruptive.
In order to substantiate my claims, I decided to follow specific known pack histories where pack members have been lost due to natural mortality (starvation, intraspecific strife, hunting accident, other accident) or due to human-caused factors.
I will use the Voyageurs Wolf Project Reports of 2020/21 (Gable, T. et al., 2021) and 2021/22 (Gable, T. et al., 2022) that delineate pack histories and that attempt to determine mortality causes in many cases.
I will only address adult and subadult survival (individuals that have been recruited into active pack cooperation which usually occurs in autumn with respect to the spring pups).
It is also difficult to distinguish between dispersal and mortality, especially, during the typical dispersal periods (autumn, winter).
Dispersal and pup survival as turnover factors will be discussed in another post.
Huron Pack
In January, 2021 a subordinate wolf of the Huron Pack was attacked and killed by wolves on the western part of the Huron Pack’s territory.
This subordinate could have been born into the pack while Huron Pack was still considered Bowman Bay’s Pack (before they took over Sheep Ranch Pack’s territory) or it could have been a pup of 2019 when the BBP was already residing on their new range (it has not been specified in the report).
In summer and fall 2020, Huron Pack had 6 members (breeding pair, 3 pups, 2 subordinates one of which had joined the pack due to unknown causes because it was not a pup and had not been observed with the pack in winter 2019).
During the time when the related subordinate was killed, a large wolf pack (possibly Bluebird Lake Pack) was seen travelling on the eastern edge of the Huron Pack’s territory but it is now known if the same pack was involved in the mortality.
However, the breeding pair was not left to their own devices and they acquired a new subordinate that was seen with the pack in February and March, 2021.
The other subordinate was likely a former member of the Sheep Ranch Pack who had joined the newly established group after the takeover of her family’s range.
It is possible that this subordinate was the same wolf that had joined the pack previously in summer/fall and that the vacancy left by the death of the related subordinate allowed her to rejoin.
Also, in spring 2021, the former breeding male was no longer observed with the pack but it is not known what happened to him.
It is possible that he was also killed during the same territorial disagreements.
He was an older wolf and could have died due to old age.
The loss of a breeder is a high risk loss (great potential for disrupting the pack) but the breeding female found another mate and produced pups that very April (sired by the new male).
The former group composition (albeit constituted from different members) was also retained with the addition of the joining/rejoining unrelated subordinate.
The new breeding male’s identity is unknown.
However, the pack did not manage to persist.
Huron Pack dissolved in late summer, 2021, and their territory was taken over by the Paradise Pack.
Pack dissolution in summer often occurs due to loss of pups.
The Huron Pack was not long-lived and they moved into the Sheep Ranch Pack’s territory after they had lost their own territory to the new Half-Moon Pack.
The tenancy of the particular territory might be difficult to maintain due to it being crammed amidst other wolf packs some of which had territorial ambitions at the time.
When Paradise Pack took over, it essentially enlarged its own territory incorporating the former Huron Pack’s range (although there does not appear to have been a skirmish and the Paradise Pack perhaps expanded when the Huron Pack had already broken up).
However, despite the high turnover and the instability, the range was utilize by wolves who were locals and it could be that the Paradise Pack, thereby, ensured greater future success for itself because they added these lands to their own range (rather than leaving them vacant to become occupied by a new breeding pair).
They essentially prevented the risks that are associated with too many new packs on too small territories that are surrounded by other packs and that later have to be expanded in order to sustain a family.
Such risks are sometimes the result of pack disruption (which is why exploited wolf populations can be of higher density than stable wolf populations where every family holds a larger range for a longer time).
Similarly, they also resolved their own territorial problems having been equally crammed on a small range among other packs and possibly suffering resource deficiency issues.
Windsong Pack
The Windsong Pack was formed on the old Fawn Crick Pack’s territory.
The breeding male of the Fawn Crick Pack was killed for depredation purposes in summer, 2020, and the territory was taken over by a 1 – 2 year old subordinate wolf which was likely his son who also found a mate.
He also retained his younger sibling in the pack of 3 wolves and it is likely that he took charge over caring for the sibling who was only a pup in 2020.
In the following year, this pack also produced pups and retained the subordinate wolf.
In this situation, although the mortality cause was lethal removal by humans, the pack partly stayed together, the older sibling who took the breeder’s position, also raised the younger sibling who became a subordinate thereby completing the 2020 breeding success on the range.
Additionally, breeding was not disrupted.
However, the territory was taken over by less experienced and younger individuals of which only 1 (the older sibling and the new breeder) could have had a proper knowledge of the range and the prey while the new mate and the pup were possibly only learning the local conditions.
This could be a reason why the two pups of 2021 were also killed for depredation purposes – they were not experienced and as they had to begin hunting on their own (May, 2022 – denning season when wolves tend to split up and hunt in smaller groups or individually), they took misguided decisions.
Obviously, there was a larger problem because the former breeding male had, too, attacked livestock and it cannot be claimed that the problem appeared only after the loss of the old breeders.
This demonstrates that the removal of a pack member for depredation purposes led to two more younger and inexperienced members to repeat the mistake.
Moonshadow Pack / Blood Moon
In January 2022, the pack lost its breeding male which in scientific literature is considered a very high risk loss.
Cause of death was starvation which could have been augmented by other health issues.
The pack was immediately taken over (late-January) by a new male who had immigrated into the territory after it had roamed around the area for a while.
Apparently the new male had learned about the vacancy by chance or by following the health status of the local breeders upon his visitations into other packs’ territories.
It is also possible that the new male confronted the old male and while there was no fight resulting in injury, the old breeder may have been chased away and kept from rejoining his pack which led to starvation.
It is the VWP team’s best guess that the new male took over the breeder’s role in the former pack because it could have been an altogether newly formed pack, as well.
Thus, this occasion of natural mortality attests to a less disruptive takeover where, potentially, most of the pack mates stayed together and the territory was inherited by ultimately the same pack only with a different leader.
It is not known yet whether Blood Moon Pack reproduced in 2022 and if this led to non-disrupted reproduction.
Lightfoot Pack
In late January, 2022, the breeding male was killed by other wolves.
This caused instability in the pack because the VWP team rarely observed them travelling as a group after the demise of their breeder.
However, it does not appear that the pack dissolved.
The breeding male passed on at the end of the report season which is why it is not known yet what happened afterward – this information should be published in the 2022/23 report.
But the VWP claims that the breeding female likely did not find a new mate, nor she produced a litter of pups.
I cannot analyze this situation due to lack of follow-up story.
Tamarack Pack
While I have not discussed the impact of death of pups in this post, these mortalities of no lesser importance because in many packs, without pups, only the breeding pair remains to take care of the territory and to provide for the pack during winter (but winter body conditions might be of importance during the following reproductive season).
Even if the few remaining wolves who are not enforced by the ‘pup power’ manage to hold their own against neighbours, in new packs this can prove not to be sufficient for pack persistence because the territory cannot be expanded, either.
Pup survival, I believe, is essential in new populations or populations with high turnover (such as Voyageurs wolf population lately which I assume is due to high pup mortality and, hence, small pack sizes).
Tamarack Pack was one of the packs that started the 2021 breeding season with a pair of breeding wolves but their pup(s) did not survive and the pair remained alone for the second autumn.
This was apparently a vulnerability that a nomadic pair of wolves (the new Stub-tail pack) exploited to take over their territory.
The Tamarack Pack did not dissolve (the breeding pair did not split up) after the takeover.
Instead they moved slightly to the north.
But the breeding female of the pack was shot illegally in March, 2022 and her former mate became a lone wolf and did not manage to attract a new mate and to stay in the ‘old-new’ territory.
I suppose, in this story, both the death of the pup(s) and the death of the breeding female played a part because: 1) the Stub-tail pair could take over the Tamarack Pack’s territory; 2) without any additional pack members, the breeding male likely had no incentive to stay on his range and to expect meeting another female, especially, because much of dispersal seems to occur before March and after March, it might have been more dismal to expect meeting somebody new.
Similarly, perhaps hormones were at play, as well.
For example, if hormonal levels change after the winter’s territorial/breeding season, the altered hormonal concentrations in late March / April might cause individuals to make decisions that are different from those they would have made while feeling ‘feistier’ (more territorial with greater incentive to mate).
This is another aspect to natural vs. human-caused mortality because much of natural mortality occurs during winter when wolves likely have a different mindset and different urges.
The timing of the mortality might be of importance, as well, because it determines at what hormonal and social stage the wolves would be in their annual cycle and how their subsequent behaviour and decision will be selected.
It could even affect the resource availability in form of new mates (if most of dispersal occurs in specific seasons providing more abundant floaters that can fill the vacancies).
Similarly, while dispersal also occurs in spring, breeders might find it less easy to accept new partners at a time which is subsequent to the actual breeding season.
Notes by Ieva 