Abstract
BackgroundThe common grey wolf (Canis lupus) is found throughout the entire Northern hemisphere and preys on many kinds of mammals. The urine of the wolf contains a number of volatile constituents that can potentially be used for predator–prey chemosignalling. Although wolf urine is put to practical use to keep rabbits, rodents, deer and so on at bay, we are unaware of any prior behavioural studies or chemical analyses regarding the fear-inducing impact of wolf urine on laboratory mice.Methodology/Principal FindingsThree wolf urine samples harvested at different times were used in this study. All of them induced stereotypical fear-associated behaviors (i.e., avoidance and freezing) in female mice. The levels of certain urinary volatiles varied widely among the samples. To identify the volatiles that provoked avoidance and freezing, behavioural, chemical, and immunohistochemical analyses were performed. One of the urine samples (sample C) had higher levels of 2,6-dimethylpyrazine (DMP), trimethylpyrazine (TMP), and 3-ethyl-2,5-dimethyl pyrazine (EDMP) compared with the other two urine samples (samples A and B). In addition, sample C induced avoidance and freezing behaviours more effectively than samples A and B. Moreover, only sample C led to pronounced expression of Fos-immunoreactive cells in the accessory olfactory bulb (AOB) of female mice. Freezing behaviour and Fos immunoreactivity were markedly enhanced when the mice were confronted with a mixture of purified DMP, TMP, and EDMP vs. any one pyrazine alone.Conclusions/SignificanceThe current results suggest that wolf urinary volatiles can engender aversive and fear-related responses in mice. Pyrazine analogues were identified as the predominant active components among these volatiles to induce avoidance and freezing behaviours via stimulation of the murine AOB.
Highlights
The common grey wolf (Canis lupus) is found throughout the entire Northern hemisphere and preys on many kinds of mammals, including deer, rabbits, squirrels and mice
To explore the signalling pathway elicited by wolf urine odorants, we examined immunoreactivity for Fos, a marker of neuronal excitation, in the main olfactory bulb (MOB) and the accessory olfactory bulb (AOB)
This study was conducted with three different wolf urine samples, A, B and C
Summary
The common grey wolf (Canis lupus) is found throughout the entire Northern hemisphere and preys on many kinds of mammals, including deer, rabbits, squirrels and mice. Wolf urine induces avoidance behaviour in cattle [3], wild animals [4,5,6,7] and rats [8]. We hypothesized that wolf urine contains additional kairomones that are used in predator-prey chemosignalling. Additional behavioural and immunohistochemical studies were performed to show that these candidate pyrazine analogues, and especially combinations thereof, encouraged significant freezing behaviour in mice, in part by the stimulation of the murine accessory olfactory bulb (AOB). These results support the proposition that wolf urine contains novel kairomones that mediate predator-prey chemosignalling. A cocktail of pyrazine analogues had a similar effect to that of the urine itself, suggesting that the cocktail may prove useful in applications to disperse wild animals
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
