A Reassessment of the Function of Scent Marking in Territories

Abstract

The energetic costs and the risk of injury in agonistic encounters can be reduced by prior assessment of opponents: it will generally pay low quality animals to avoid combat with one of high quality. Following this principle it is suggested that territory owners scent mark their territories to provide intruders with a means of assessment. When the odour of a competitor, or of a mark it is seen to have made, matches that of scent marks encountered in the vicinity, then the competitor is probably the territory owner. Since owners are generally high quality animals, and assuming they have more to gain by retaining a territory than an intruder has in taking it over, it will pay the owner to escalate and the intruder to give up early. The advantage to owners in marking may thus be that by allowing themselves to be identified they reduce the costs of territory defence. Published information on the behaviour of territory owners and intruders is consistent with predictions from this hypothesis. The hypothesis offers an explanation for a number of poorly understood behaviours including ‘self‐anointing’ and scent marking during agonistic encounters. Zusammenfassung Evolutionsbiologische Argumente machen wahrscheinlich, daß Tiere ihre Territorien duftmarkieren, um Eindringlingen die Möglichkeit zu geben, bei Begegnungen den Eigentümer zu identifizieren. Diese Identifikation müßte auf einem Duft‐Vergleich beruhen. Eindringlinge vergleichen den Duft eines Individuums mit dem Duft der häufigsten Duftmarken in der Umgebung. Wenn diese Düfte zusammenpassen, ist das Tier wahrscheinlich der Eigentümer des Territoriums. Der Vorteil für den Eigentümer liegt darin, daß sich Eindringlinge dann vermutlich wieder zurückziehen, da Eigentümer gewöhnlich bereit sind, ihr Revier stark zu verteidigen. Der zur Markierung eines Territoriums nötige Aufwand (hauptsächlich Zeit und Energie) könnte so durch die eingesparten Kosten einer aktiven Verteidigung (hauptsächlich Energieaufwand und Verletzungsgefahr) überwogen werden. Das bekannte Markier‐ und Kampfverhalten verschiedener Tiere wird mit den Voraussagen der Hypothese verglichen. Voraussagen über den Eigentümer sind: 1. er sollte sein Territorium auf eine Weise markieren, die eine maximale Möglichkeit bietet, daß die Marken von einem Eindringling bemerkt werden; 2. er sollte sich selbst mit den zur Markierung des Territoriums verwendeten Substanzen markieren; 3. er sollte sich zum Zwecke eines Duft‐vergleichs dem Eindringling stellen; und 4. er sollte andere Marken im Territorium entfernen oder durch eigene ersetzen. Diese Voraussagen werden in der Regel vom beobachteten Verhalten bestätigt. Voraussagen über das Verhalten von Eindringlingen sind: 1. sie sollten die Duftmarken des Eigentümers ausfindig zu machen suchen; 2. sie sollten bei der Begegnung mit einem möglichen Eigentümer dessen zur Reviermarkierung verwendeten Duft prüfen; 3. sie sollten sich meistens zurückziehen, wenn der Duft des Gegners zum Duft der Markierungen paßt; und 4. Eindringlinge, die um den Besitz des Terri...

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“…Sun and Müller-Schwarze (1998b) showed that beavers' response to AGS from unfamiliar adult males remained at about the same level, but their response to castoreum showed a descending trend. The descending trend in response to the same signal without matching the signaler demonstrates a declining importance of the signal over time, i.e., the scent-matching hypothesis (Gosling, 1982) was supported. The scent-matching hypothesis predicts, among other things, that the territory owner should make itself available for scent matching by the intruder (Gosling, 1982).…”

“…The descending trend in response to the same signal without matching the signaler demonstrates a declining importance of the signal over time, i.e., the scent-matching hypothesis (Gosling, 1982) was supported. The scent-matching hypothesis predicts, among other things, that the territory owner should make itself available for scent matching by the intruder (Gosling, 1982). Sun and Müller-Schwarze (1998a) recently documented that related individuals shared more features in the chemical AGS profile than did unrelated individuals, and Sun and Müller-Schwarze (1998c) also demonstrated that it is possible to use some AGS compounds to classify different families.…”

“…Furthermore, anal glands, which are located in the anus (Svendsen, 1978), may add AGS to the feces when beavers defecate in the water. For instance, the large complex of sebaceous and apocrine glands located in and around the anus of many species of antelope may add individual-specific secretion to feces (Barrette, 1977;Mainoya, 1980;Gosling, 1982).…”

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“…If the smells match, then the animal that the intruder has met must be the territory owner. If the hypothesis were true, one would expect owners to (1) mark where intruders are most likely to encounter marks; (2) mark themselves with the substances used to mark the territory; (3) make themselves available for scent matching by intruders; and (4) remove or replace marks of others (Gosling, 1982).…”

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“…Given the constraints of time and energy, scent marks should not be deployed at random, but instead in an organized pattern that maximizes their chance of being 4 discovered by the individuals to whom they are directed, to give the earliest possible warning to a potential trespasser. Such a place might be territorial borders (Gosling, 1982;Gorman, 1990), and the upstream edge of the territory should be most frequently marked if the movement of dispersing individuals is predominantly downstream. The pay-off to the owner is the reduced costs of competition (Gosling, 1986;Gosling and Mckay, 1990).…”