The production and structure of animal signals may be condition dependent and may provide more than one type of information to receivers. While alarm calls are not typically viewed as condition dependent, recent studies have suggested that their structure, and possibly their propensity to be emitted, depends on an individual’s condition and state. We asked whether the propensity of yellow-bellied marmots (Marmota flaviventer) to emit calls is influenced by their immunological or parasite status, by quantifying both trap-elicited and natural calling rates as a function of their neutrophil to lymphocyte (NL) ratio, the presence of a blood borne trypanosome, and the presence of several intestinal parasites (Eimeria sp., Entamoeba sp., and Ascaris sp.). We fitted linear mixed effects models to determine if the health measures we collected were associated with the probability of calling in a trap and with annual rates of natural alarm calling.
Results/Conclusions
Marmots infected with a blood-borne trypanosome were marginally more likely to call when trapped and called naturally at significantly higher rates, while those infected with the intestinal parasite Ascaris were less likely to call when trapped. NL ratio was not directly associated with in-trap calling probability, but males were more likely to call when they had higher NL ratios. Thus, internal conditions, such as parasite infection and immune system activation, can modulate the production of alarm signals and provide potential information to both predators and prey about the caller’s condition.