Dispersion in wolves has received plenty of scientific attention yet many of its aspects are still unknown due to the great potential by wolves to disperse and the varied dispersal patterns within the gray wolf species as well as within all the wolf species.
A decent overview of gray wolf dispersal patterns and determinants has been provided by Morales-González, A. et al., 2021.
It was also the study that I used (mainly for the compiled references to other studies) in order to attempt a more in-depth data analysis after I developed a certain ‘hunch’ as a response to the wolf dispersal studies (or comments in studies not dedicated specifically to dispersal) I had read.
However, currently I am unable to perform any investigations into the matter and I thought I would begin with this post noting my suspicions.
Namely, I have formed this intuition that wolf long-distance dispersal which cannot be explained by wolf population densities, nor geographical obstacles, might assume two prevalent directions which cannot be prescribed a cardinal direction globally because these directions depend on ancient colonization patterns by the species and these patterns differ among continents, regions etc.
I believe that wolves, upon undertaking long journeys, might move in directions that either follow the ancient colonization route or that ‘retrace’ them (moving toward the cardinal direction whence original dispersal was initiated).
To give an example, wolves in North America might be prone to take either southward or northward direction because most of migration started in the north and there might be some genetic triggers that encourage and predispose the individual (for example, by provoking a sense of greater security or familiarity) to take these routes.
The individual would not move straight north or straight south but the general direction would be considerably more northward or southward than it would be eastward or westward.
On the contrary, for example, Europe was colonized from Asia and that would create a pattern of east or west prevalence in long distance dispersals.
Genetic memory is a theoretical concept that has not been supported with scientific evidence.
However, genetic memory is also defined as an inherited memory that is not associated to sensory experience and I think that, in the case of wolf dispersal, sensory experience would be involved by comparing the present environmental conditions with those of the past that, through different mechanisms, have been ‘stored’ as a legacy.
These mechanisms would be different between wolves that follow the ancient route and wolves that retrace its direction.
For example, individuals that follow the direction might simply be descendants of generations of a multitude of early colonizers.
These early colonizers were, for some reasons or others, predisposed to take certain actions and to make certain types of decisions.
The same physical traits that stimulated the original decision making could have been passed down to the modern day individuals.
On the other hand, wolves that ‘retrace the direction’ might not be ‘remembering’ it but rather relying on the genetic familiarity with the landscape of origin.
That is to say, in the regions where wolves originated and spent their early hundreds and thousands of years, wolves also accumulated specific adaptations and responses to their environment.
As wolves colonized in other directions, they moved through new landscapes and new environments where they also adapted over time.
In the regions that have been colonized most recently, wolves have had the least time to adapt.
Therefore, unless the genetic inheritance has been lost to genetic drift and adaptation, wolves might feel more familiar with (better adjusted to) environmental cues that their morphology and ecology, essentially, evolved in for the better part of their journey on the respective continent.
It might be, however, difficult to disentangle geographic effects from genetic effects.
For example, the ancient wolves chose their routes in accordance with the terrain and the terrain might not have changed as substantially in some situations which is why the decisions by the ancestor and the descendant could be similar merely due to the landscape configuration and the choices that it leaves.
In other instances, the landscape might have changed profoundly affecting the modern day wolf’s decisions and making them dissimilar to those of their ancestors.
However, not only habitat suitability could be perceived as a ‘promised given’ in the direction whence ancestors came – wolves might also experience a greater reliance on finding a mate because long-colonized regions are likelier to be populated than recently colonized areas.
In fact, this could be a strong driving mechanism favouring wolves that ‘go back’ (countered only by population densities and hardship to carve out a new territory in places with resident wolves).
Finding a mate is a crucial dispersal motivation and upon moving in the wrong direction (the direction formerly not taken by most wolves) could prove unwise of lack of other wolves and unsuitable habitats lie that way.
However, there have always been the individuals blazing the trail and taking that risk which is why wolves are very successful at colonizing and recolonizing new areas.
The personality or genetic, or behavioural traits determing who would be the pioneer and who would bring their genes back to the ‘Old World of Wolves’, might affect the direction taken if the direction was at all founded on the ancient migration patterns.
I believe this would be interesting to study.
There are case studies, for example, where wolves have begun their dispersal nearby but with temporal separation (several years apart) and their dispersal pattern is rather unidirectional ending up in rather the same place (even in the same pack) (e.g., Mech, L.D., 2020 and Gable, T.D. 2003).
These unidirectional dispersal patterns could not be entirely explained with the topography and its predeterminants.
If the individuals are related and if they come from the same natal pack, the uniformity in their decisions might be based on their genetic, behavioural and experiential similarity.
But this does not hold true in all cases (some of the unidirectional dispersers were not related and did not disperse from the same pack).
The studied individuals lived in North America and dispersed in northward direction although more pronouncedly so in one case study while in the other the direction was also strongly inclined toward east.
As I began looking through more case studies (most of which I was already superficially familiar with), I found both support and contradiction to my theory.
I realized that more time has to be dedicated to analyzing these patterns because:
1.
Ancient colonization routes should be better understood.
For example, North America was colonized from far NW, not really from the N.
It might be necessary to determine whether eastward colonization was substantially less predominant than southward colonization;
2.
It should be determined what constitutes a ‘predominant direction’ (the threshold angle above which, for example, NW becomes N etc.);
3.
Even if based on ancient colonization events, dispersal patterns might be different in species that have remained relatively similar to the ancestral trait sets and that have adapted to a great measure (e.g., wolves in Midwest, US might have retained more of the environmental adaptations of their ancestors than wolves in the southern states or Mexico).
4.
‘Long-distance dispersal’ is not defined easily, either.
Long-distance in one continent and in some regions might be considerably longer than long-distance in another continent and in other regions.
For example, wolves dispersing in North America can move through vaster areas of contiguous or almost contiguous wilderness achieving greater distances.
Wolves in Europe, meanwhile, have to disperse through areas of intense anthropogenic impact and the subsequent risk factors.
In some regions, dispersal might be limited by geographic factors such as peninsulas, coastal areas, mountain ranges.
For example, long-distance dispersal in Norway and Sweden might be biased toward the north or the south simply because these countries are elongated and the east-west directions are bound by the seas as well as difficult terrain (mountain ranges).
Individuals might not feel more inclined to travel shorter distances eastward or westward but there simply is a shortage of land to travel compared to north-west direction.
If wolves are restricted in their movement or the movement involves great risk, the average dispersal distance might be shorted in such regions.
It might be even necessary to estimate dispersal distance probabilities (possible distances) and then to compare them to the actual dispersal distances in order to see if, on a local scale, some dispersals are longer than others (even if they do not appear extraordinarily long on a regional, national or global scale).
Coincidentally, dispersal distance can be determined by wolf population density.
In areas where wolf population density is high, wolves might be forced to travel long distances merely to leave the ranges unavailable for settling.
However, if wolves are later faced with ‘no wolf lands’, their dispersal distance might be affected by the need to keep moving in order to find other wolves (mates).
I do not suppose that the latter two considerations would need to be factored in to determine the dispersal distance threshold.
5.
There could be other confounding factors such as, for example, tendency by many animal species to align themselves with the magnetic poles or magnetic fields.
Birds are a famous example but see also, for example, Červený, J. et al., 2011 and the references of this study.
For example, northward direction and aligning with the magnetic pole might be difficult to disentangle.
6.
In consonance with the landscape-mediated decision-making, there could be other factors affecting wolf dispersal (ultimately, habitat selection) behaviour that we are not aware of.
For example, while the range of many wolves coincide with coastal areas, not many wolf populations can be found specifically on the coast (although they might use the coastal area for travelling purposes etc.).
I am not excessively confident with this impression but I think that wolves are likelier to inhabit and to benefit from coastal areas in more northerly regions and regions where the sea / ocean is inhabited by species that can provide large carrion or that can be hunted on ice while in the south or in areas without large acquatic mammals, such regions could be deficient in vegetation (salty, dry, rocky, high altitude) and inhospitable for the associated prey species.
If wolves tend to the avoid the very coastline in some regions, the proximity to sea which can be sensed over a distance might affect their dispersal patterns, especially, in areas where such prey-poor coastal habitats are extensive or predominant.
***
Recently I have been reading that pre-dispersal forays might determine the direction that the dispersing individual eventually takes (already explored options).
Characteristic to a species with a large territory size, the dispersal direction in wolves might be thereby determined also by the neighbouring groups and the permeability of their ranges.
Beside the obvious dispersal into vulnerable or recently vacated (regarding range or breeding position) neighbouring territories, dispersing wolves might find it easier to attempt to travel through some neighbours’ territories but not others (e.g., larger groups vs. smaller groups).
The former experience exploring the neighbouring ranges as well as the overall accessibility of the different neighbouring ranges could determine the direction.
However, I do not suppose this would affect the results of analysis if the sampling effort was great enough because the permeability of the neighbouring territories can be rather stochastic.
In some places, nevertheless, ‘strongholds’ could aggregate in more optimal habitats which can fall under a certain geographic distribution (e.g., habitats on the west parts of the region are better than those on the east part).
Notes by Ieva 