While I wholly support the reintroduction of large predators to maintain natural control of prey populations, I have begun wondering how the initial recolonization (and in less natural systems – the future interactions) might bear impact on large predator health.
I started contemplating this issue while reading the Yellowstone Wolf Project reports and following the initially turbulent interactions between packs, within packs as well as the superproductive breeding rates (several breeding females per pack).
This could all be explained with the establishment of a new social order (most individuals were unrelated prior to reintroduction and increased conflict has been reported in, e.g., captive settings where wolf packs are formed not as family systems but system of non-related individuals that have to create and maintain a dominance-subordinance hierarchy) and resource abundance (concerning pup production).
However, I have had this nudging notion that there was something else – something external at play influencing wolf behaviour (possibly through meddling with testosterone production).
It is difficult to find research discussing plant chemistry impacts on large herbivores.
In another post I have presented a hunch of mine – namely, that wolves dislike prey species that predominantly feed on woody plants.
It is clear that plant chemistry (nutrient content, plant secondary metabolites etc.) can affect organisms even as large as humans (see, e.g., Smith, S.J. et al., 2021).
Accordingly, consumption of certain plants might contribute to certain processes in the organisms of large herbivores and, indirectly, these effects could be passed up to predators (especially, if hormonal changes have been induced or, potentially, through alkaloid accumulation).
In places where ungulates have fallen out of natural regulation by large predators and/or where there is an overabundance of certain types of plant resources, ungulates might accumulate compounds that exceed healthy levels.
This post is highly theoretical mostly because there is a paucity of studies investigating such effects even on plant-large herbivore interaction level.
However, if there were such effects and if ungulates overgrazed on specific plant species or if they were constantly exposed to high levels of PSM (e.g., due to clear-cutting and constant regeneration of forest patches after disturbance), they might become accustomed to ‘unhealthy diet’ *just like we become accustomed to, e.g., coffee or other not so healthy substances).
After reintroductions in such places, large predators might be forced to feed on ungulates that indirectly influence hormonal or other processes in the predator’s body.
I was reading about the many conflicts and the particularly intense history of the settlement of the first packs after reintroduction on Yellowstone range.
There was something specifically about the Druid Pack and their initial strife which caught my attention.
There was just too much aggression and also fertility rates that were somewhat excessive within that pack.
From what I have read, during the early phases of recolonization interpack strife should not be as pronounced because there is yet a lot of resources both prey- and land-wise.
But even intrapack strife was at its peak starting from 1995 to many years after.
Later in the reports the intrapack strife also increased due to a less extraordinary reason – the wolves reached high population density and the initially overabundant prey resources were bouncing back to the regular carrying capacity of the natural environment which they had surpassed during the years without the complete large predator assembly on the landscape.
In some ways, it was cruel toward the wolves to reintroduce them to a system of overabundance (due to human fault) and later to observe the wolves killing one another or dying out of starvation because their initial numbers had multiplied to levels that were not natural to the ecosystem that the wolves were to inhabit from then on.
During the initial phases of settlement, tolerance should often more pronounced than intolerance because there is yet space and prey for everyone.
Certainly, the issue might have been rooted in the distribution of the top territories.
The strife would beheightened if some areas were better than others and thus – although there was a lot of land and a lot of good land, the best land with the best resources was still warred for.
Perhaps the strife within the packs (e.g., in the Druid Pack) could be partly explained by genetics or, as stated before, by the assembly of the wolves which was not naturally formed (not a family-based dominance system) although most of the strife concerned related individuals, for example, the Druid Pack adult female sisters.
However, the strife among the females within the pack largely ended with the death of one sister (dominant breeder) and the other sisters did not appear to continue the aggressive trend which might be indicative that genetic disorders might either not have been inherited by all sisters, or that there was only a slight predisposition to mental disorder in the most hostile sister who was killed and that this predisposition was exacerbated by other factors.
When I was reading about Druid Pack, I developed these two intuitions:
1. That the inter- and intraspecific strife experienced by that pack was not entirely ‘natural’, namely, that this was not how it should have ‘gone down’ in a natural, undisturbed environment;
2. That this was not due to some inherent state or only partly due to it (e.g., genetic predisposition or individual psychosis etc.).
My understanding was that there could have been something external that either caused or exacerbated the drama in the Druid Pack (but also other wolf packs) during the first years of reintroduction to YNP.
This was when I began wondering about chemistry and, more specifically, about chemistry of the dietary items.
I was wondering whether there was something about the food resources accessible to the Druid wolves during the initial years that might have affected their hormonal levels (e.g., causing to produce more testosterone or generally upset hormonal balance).
My suspicion was supported by the fact that when the larger male (21) came to rule the pack, he seemed to be less affected by the otherwise heightened levels of aggression and perhaps this ‘immunity’ was due to his large size (larger organisms might be better capable of processing chemicals that act detrimentally on smaller organisms).
Female who was extraordinarily aggressive toward her sisters, might have been unable to handle the new chemical conditions of the reintroduction site which were probably different from her natal range.
Females being smaller than males, she might have succumbed to, for example, abnormal production of testosterone.
The male 21 could have used the extra testosterone to breed with several females and to sire more litters rather than to demonstrate aggression toward his packmates or other packs.
From what I know about Yellowstone, prior to wolf reintroduction, aspens and willows had been suppressed by the elk and moose due to overgrazing.
But this also meant that the ungulates had probably foraged on greater amounts of aspens and willows than was usual for the species.
I could not find information regarding such compounds in aspens and willows, unfortunately, but the if the elk, for example, had been overgrazing on these plants, they might have been affected by their chemistry beyond average and usual rates.
And if the wolves (who had arrived from an entirely different geographic region to begin with and who thereby had not yet adapted to the local environment), initially, were feeding on these overabundant elk who had been for years overgrazing on aspen and willows, perhaps some of the chemical impacts were passed on to the wolves.
These impacts might have dissipated later as the elk abundance was reduced, as the elk adjusted their behaviour and ceased overgrazing, and as the wolves adapted to their new habitat, its prey and chemistry.
(There could be other chemical factors at play on the soil level or water level impacting the wolves naive to the new conditions.)
This could explain the levels of antagonism between packs which was perhaps a bit unusual during a time when the area was largely unoccupied and food stress was negligible (apart from packs who had to subsist on bison during winter due to elk migration).
If the Druid Pack’s environmental setting was somehow even more dissimilar to that of other packs, they might have been affected to an even greater degree.
I simply cannot always accept explanations that ‘this is how wolves act’.
From what I have read and observed, wolves are mostly inclined to live as peacefully as possible.
Their social system allows them a plenty of social contact and exercise (play) which lets steam off extra energy if there were any.
Conflicts with neighbours are equally avoided through intricate mechanisms comprised of olfactory and auditory devices.
There are certainly takeovers of territories and extensions of ranges but such conflicts are frequently characteristic of larger densities, established populations and lower resource abundance.
Wolves appear to be most cooperative and if resources allow, they do not mind sharing, especially, with their relatives.
Therefore, when I read about increased levels of antagonism, I first suspect an external circumstance might be in effect.
There could have been something not giving the wolves another choice or influencing the choice they had.
And it could have been many things (resources, genetics, harsh environment, weather fluctuations etc.).
But the resources were not that scarce. Dispersal was entirely possible. Environment was harsh but the wolves came from British Columbia which was not a Garden of Eden, either.
Which is why I arrived at my musings regarding plant chemistry and its effects on predators through prey biomass.
Notes by Ieva 