Many territorial species use scent-marking in order to ensure avoidance behaviour in unwanted visitors.
Not all but perhaps most of these strategies involve fecal matter or urine that are products of digestive and excretory systems.
As a result, in territorial species urine and fecal matter is not deposited randomly.
While urine is sometimes applied only ‘symbolically’ (not relieving the bladder fully upon each scent-marking effort), fecal matter is probably more closely matched with actual defecation (disposal of metabolic waste).
Therefore, territorial species might have evolved different mechanisms and/or even anatomical features in order to execute the scent-marking operation.
Non-territorial species might also at times regulate where they relieve themselves, for example, in order not to attract predators to their young.
However, territorial species that use fecal matter and/or urine would either adapt to their existing digestive/excretive potential (i.e., adjusting their territories to their diet and foraging habitats) or they would have evolved anatomical characteristics that allow to retain the scent-marking substance for long enough until it can be deposited serving two purposes.
Of course, not all faeces, for example, get deposited with double intent.
Still, it would be beneficial to have evolved special pathways (digestive, excretive but also neural) that would allow to maximize the benefits of deposition.
For example, it is possible that territorial species that use fecal matter/urine for scent-marking purposes, have evolved some type of retention capacity as well as more expressed cognitive control over their bowel movements or bladder.
It is also interesting because regardless of the direction of the underlying mechanism (i.e., whether territorial behaviour adapts to diet or anatomy adapts to territorial needs), such correlation would imply that any given species can maintain a territory which is compatible with their organism.
If there is not enough material (and here fecal matter is of greater importance although in some arid systems urine might also become a limited resource), the species cannot maintain a territory.
Even if the defecation rate is higher than needed for territorial maintenance (counted as number of faeces deposited relative to number of faeces needed in order to scent-mark), some animals might want to avoid foraging very close to territorial boundaries and their favourite foraging patches might exist more centrally in the core areas.
Thence, even if the defecation rate is high enough to ensure the number of faeces accessible, the material might have to be transported from central locations to peripherial locations and if the peripherial locations are very far from actual feeding grounds, this might cause stress to the individual.
If there is an overabundance of material, the consequences are probably not dire.
Small territories with high resource availability rates would allow for boundary maintenance while large territories with low resource availability might be difficult to maintain due to insufficient amount of fecal matter.
This could be a reason why animals with very large home ranges, high daily travel rates and infrequent mealtimes use urine or secretions of other glands rather than fecal matter.
However, overly dense distribution of fecal matter can also lead to, for example, increased pathogen and parasite loads.
Thus, territories should not be too small, either, because this would lead to exposure to harmful organisms.
As a result, territoriality might be closely linked to the health and size of the group or population and finding the right fit between anatomical capacity and health regulation necessities might ultimately ensure that everyone gets a home as large as they can afford to maintain without suffering increased mortality risk.
The size of the territory and its correspondence with the animal’s needs and capabilities might become reflected in the animal’s stress levels.
If the animal finds itself unable to maintain the territory (it is too large) or if the animal suffers from parasites/pathogens (the territory is too small), the stress level might serve as a feedback informing on the inadequacy of the size of the home.
On a partly related note, I wonder how these processes change in an animal during dispersal when there is no longer a need to control defecation/urination rates.
Such change might cause some initial anxiety (unless the young in the species do not participate in territory patrolling and, indeed, the onset of participation might be dependent on the physical capacity to control bladder and bowel movement).
Notes by Ieva 