Ventilatory frequency as a measure of the response of tammar wallabies (Macropus eugenii) to the odour of potential predators

This study uses changes in ventilatory frequency to quantify the physiological response of an Australian terrestrial herbivore, the tammar wallaby (Macropus eugenii), to olfactory cues suggesting the presence of potential predators. Ventilatory frequency proved to be a quantifiable measure to assess the response of this macropod marsupial to olfactory cues. Ventilatory frequency increased from mean resting levels of 45 ± 5.1 breaths min–1 to 137 ± 11.2 breaths min–1 during the first minute of exposure to all odours. These physiological responses diminished over time, with ventilatory frequency in the first minute after introduction of the scents greater than that during the subsequent four, suggesting that the initial reaction was due to disturbance and was investigative in nature. However, the ratio of ventilatory frequency in the remaining 4 min after introduction of the odours compared with before was greater for fox (3.58 ± 0.918) and cat (2.44 ± 0.272) odours than for snake (2.27 ± 0.370), distilled water (1.81 ± 0.463) and quoll (1.71 ± 0.245) odours, suggesting that fox and cat odour provoked a greater response. However, the wallabies’ response to the odour of these introduced predators and to horse odour (2.40 ± 0.492) did not differ. Our study indicates that a long period of co-history with particular predators is not a prerequisite for detection of potentially threatening species. We do not find any support for the hypothesis that an inability to interpret olfactory cues to detect and respond to potential predation by introduced predators is responsible for the decline of these macropod marsupials

Predator odour does not influence trappability of southern brown bandicoots (Isoodon obesulus) and common brushtail possums (Trichosurus vulpecula)

Predators cause changes in the behaviour of many prey species. This study investigated whether trappability of wild southern brown bandicoots (Isoodon obesulus) and common brushtail possums (Trichosurus vulpecula) was influenced by odour cues suggesting the presence of potential predators. Trapping success was compared between traps with predator scents and controls in two different experiments. The first measured trapping success of single clean traps, traps with unfamiliar herbivore (horse) odour and traps scented with predator (fox, cat, quoll and dingo) odours, while the second offered three choices (fox, dingo and clean traps) simultaneously. Frequency of capture of bandicoots and possums was not influenced by odour, mass or sex in either experiment. The lack of avoidance response observed in this study suggests that neither southern brown bandicoots nor common brushtail possums alter foraging behaviour in response to olfactory cues that suggest the presence of exotic or Australian predators. This is consistent with previous studies, which indicate that native Australian marsupials do not avoid predator odours