By Emma Randle
More than a quarter century of pitfall trapping at Arid Recovery reveals the great peaks and troughs of rain-driven cycles in the Australian deserts, with the amazing abundance and diversity of small vertebrates that follow. I had the pleasure of seeing the environment bursting with life. The annual survey at Arid Recovery lives up to the term ‘mad March’, with an intense week of catching and processing animals. Long days, early starts and hot conditions, but the enthusiasm of the staff and volunteers doesn’t waiver.
The annual pitfall trapping surveys at Arid Recovery alternate between swale and dune habitats each year to record both environments. This year swales were surveyed, a habitat of vast clay plains with low chenopod vegetation. It was a bonanza! Over 4 nights we had a total of 1506 captures, consisting of 828 mammals, 678 reptiles and one bird. Two years of good rainfall has stimulated great vegetation growth and breeding across all types of native animals in and around the reserve. Anticipating lots of animals this survey, false floors were used in all of the pits to prevent large rodents from attacking smaller animals that fall into the same pit.
My week of pitfall trapping began with a bogged car. As we rolled out of camp at 6 am, we came to our first sand hill and just stopped. With little more than a sigh, Bridget, our team leader, got out of the car and started digging. We promptly dug ourselves out, let down the tyres and continued to our first site to start the toilsome process of digging in the lines, putting in the drift fence and opening the pits themselves. It didn’t take us long to realise insecticide had been forgotten (used to ensure the animals trapped don’t get ravaged by ants, a slow and grim way to go, to say the least). Bridget later confessed to not being much of a morning person.
As the survey went on, we found pits full of congregations of plains mice (Pseudomys australis) and spinifex hopping mice (Notomys alexis). The most spinifex hopping mice found in a single pit was 15 individuals. These occurrences reminded me of the sociality of these species, both species living in social assemblies in complex burrows. In this survey, we were also thrilled to see some less prevalent rodent species, including sandy inland mice (Pseudomys hermannsburgensis) and desert mice (Pseudomys desertor). In the past, the sandy inland mouse has been found few and far between, with occasional captures every few years, compared to 12 individuals captured this year. The desert mouse wasn’t caught in pitfall surveys for a decade between 2011 and 2021, so it was marvellous to see them again!
The number of mammals might have been higher if it wasn’t for our record-breaking 10 captures of sand goannas (Varanus gouldii). Some of the pit lines were desolate with just a sand goanna in the last pit, indicative of a solid feed from these guys. Goannas were only captured within the reserve, with numbers booming without predation from cats and foxes that would occur on the other side of the fence. A knock-on effect of the boom of sand goannas within the reserve is that the number of small reptiles inside decreases, due to predation.
Due to the sheer number of animals caught in these surveys, we process them back at the lab, in the comfort of air conditioning (beneficial to the animals and the humans). In the hustle and bustle of cleaning up and collecting animals, I watched Kath, our CEO, pick up a toilet roll to be put away, none the wiser that a plains mouse was still tucked up inside. The plains mouse didn’t leave the comfort of its toilet roll and was returned to the bucket safely. Gen, our ecologist, had the most captures of any group. She worked tirelessly processing all the animals even on her birthday. A birthday girl led to a birthday cake, which we were all so grateful for.
My fondest moment from the trapping week was sitting around ogling a tiny smooth earless dragon (Tympanocryptis intima). Not much larger than the size of my fingernail, we were amazed to find it so easily in the pit. We understood just how effective the camouflage of this species is for their survival. When we put this tiny dragon amongst gibber rock, we had to look twice to make sure it was still there.
