Summer camera trap records of plains vizcachas (Lagostomus maximus): presence and behaviour at burrow entrances

The objective of our research was to characterize the behaviour of vizcachas near their burrows, considering factors such as sex, age, and time of nocturnal activities.The study colony was located at -31.42679° S, -64.59296° W, elev. 890 m above sea level in central Argentina, in the Chaco Serrano ecoregion (Oyarzabal et al. 2018). The colony had an area of 24 ha and 38 communal burrow systems (vizcacheras), each with 3 to 37 entrances.We randomly selected 8 of the 38 vizcacheras that made up the colony. All active entrances of the selected vizcacheras were monitored with camera traps for one month, from February to March 2 019 (Bushnell Trophy Cam, model 119876). We considered that a burrow entrance was “active” when there were fresh faeces and traces or recent signs of excavation (Branch et al. 1993a). Since vizcachas are mostly nocturnal, camera traps were set up to record video and audio for 30 seconds per detected event (movement) during the night. To record the activity at the entrances of each vizcachera and the close surrounding area, we deployed the cameras pointing at the entrance from an approximately 2-m distance. The cameras were attached to branches or logs from nearby trees at different heights (0.7 to 1.2 m), depending on the slope and orientation of each burrow entrance. The vizcachera entrances were observed for three nights; then, the cameras were moved to a new location. Due to equipment limitations, we monitored one vizcachera at a time, with the exception of vizcacheras 20 and 25, which were monitored simultaneously. The order in which the vizcacheras were sampled was 37, 39, 8, 33, 20-25 (simultaneously), 12, 18. The number of active entrances per vizcachera was 6, 9, 7, 9, 4, 6, 10 and 7, respectively.When watching the videos from the camera traps, we were not able to reliably distinguish between females and males, even when they were adults. This is because the main differences are observed when the adult male is sexually fully developed, namely a darker stripe and whiskers on the face, as well as a squarer and stronger mandible and larger head and body size than females. Young adult males are very similar to females. In addition, infrared cameras produce black and white images at night (low ambient light) and may generate blurred photographs, complicating accurate species identification (Thomas et al. 2020). For these reasons, sex was not used as a variable, and the individuals were classified only by age class according to size and phenotype (adult, juvenile and young).