Excrement, secretions and urine have been commonly studied as scent-marking behaviour elements in many species.
It has been concluded that these droppings and discharges can communicate an array of messages from individual recognition to reproductive status to group status to territorial claim to resource use notices etc.
However, I have been considering an additional purpose that excrement, secretions and urine might serve, i.e., that of self-diagnostic tool.
Changes in the content or the degradation rate of these materials or their interaction with external abiotic or biotic agents are used, e.g., in human medicine to perform diagnostic procedures.
While we utilize lab equipment and quantifiable / visually detectable etc. readings of the results of the testing, such readings could be achieved also through other mechanisms (predominantly, olfactory cues) that do not call for laboratory conditions and that might be used by animals in order to analyze their own droppings and discharges and to follow possible changes that could be indicative of deteriorating body condition, presence of parasites, pathogens or other signals and warnings of ‘medical’ nature.
Changes can occur internally (inside the organism) or externally (upon interaction with the outside environment, its microorganisms, temperatures, humidity etc.).
While the external environment is always variable and this variance determines the ‘state’ of the material and its transformation rates, some changes might be more notable (dramatic) than others alarming the animals of their condition or the condition of their habitat.
This could serve both on individual level (analyzing one’s own droppings and discharges) and on group level (where group latrines or allomarking etc. are involved).
This could be a wild assumption but animals might even mark different parts of their range in order to follow the reactions of their own physical state in response to the exploitation of these habitats.
If the chemical reactions and the corresponding olfactory cues (or the rate of degradation of these marks) are greatly altered on the entire range or in a particular feeding patch, the animal might make further decisions regarding their health risks with respect to continued use of the range / patch.
Another wild idea of mine concerns territorial marking and reactions by neighbours to the individual’s / group’s scent marks.
In some situations when unwanted changes (affecting our health and therefore the qualities of our droppings/discharges) occur gradually over time, we might become accustomed to our ‘new scent’ and it could take a relative stranger (in this case, a neighbour that has been familiar with one’s scent and can thereby ‘appreciate’ changes in it) to diagnose the new state.
These changes could be followed by the neighbours on border scent-mark sites or latrines.
For example, if the new state is a diseased one, the neighbouring group might begin taking more frequent or otherwise more intense advantage of the potentially weakened status of their neighbours which could, in turn, inform the diseased group of their vulnerability which they have been unable to detect independently due to the transformations being too gradual or too subtle for an observer on daily (but not weekly, monthly as in neighbours) basis.
I have not read too much about inspecting one’s own droppings / discharges as compared to inspecting those of conspecifics / individuals of other species.
Any references have been mostly directed at overmarking of fading scent (as a part of territorial or self-advertising behaviour) or processing own marks in order to access information relevant to, for example, status of food caches etc.
It might be interesting to learn if animals also follow their own health status through long-term inspection of their droppings/discharges as well as the interaction of these produced materials with specific parts of their home ranges and with external (abiotic and biotic) agents.
Notes by Ieva 