Determining Social Rank in Ungulates: A Comparison of Aggressive Interactions Recorded at a Bait Site and under Natural Conditions

Researchers often assume that dyadic interactions at bait sites have similar outcomes to those occurring under natural conditions, but this assumption has seldom been tested. I used aggressive interactions recorded during 1994–97 among marked mountain goats (Oreamnos americanus) to compare dyadic relationships near an artificial salt lick with those observed under natural conditions. I also examined how observations recorded at the lick affected the structure of dominance matrices. The probability of winning an encounter was strongly and positively related to age, both under natural conditions and at the salt lick. The proportion of interactions that adult females lost to 2‐yr‐olds and the proportion won by the youngest individual among adult females, however, more than doubled at the salt lick compared to natural conditions. Two‐year‐old females were 22 times more likely to win interactions against 2‐yr‐old males at the lick than under natural conditions. A decrease in the directional consistency index revealed that the outcomes of repeated encounters of the same dyad were more inconsistent at the salt lick than elsewhere. When interactions recorded at the lick were added to female dominance matrices, the number of inconsistencies more than doubled and the strength of the inconsistencies increased 2–8 times compared to matrices restricted to interactions recorded under natural conditions. Interactions seen at the salt lick caused substantial changes in the hierarchical rank of individual goats. Because interaction rates were high and animals were very concentrated at the trap site, individual recognition may have been difficult, explaining the differences observed in dyadic relationships at the lick compared to natural conditions.