Bait monitoring

It might be a subjective distinction but I prefer to use the word ‘lure’ for attractants (consumable or not) that increase detection probability for ringtail possums and the word ‘bait’ for mostly toxic attractants of predators.

Monitoring the effectiveness of predator control is an essential component of management. It is resource intensive but as no established pest has ever been successfully eradicated from mainland Australia, only monitoring can gauge the extent of the problem. (Braysher et al, 2012, Walters and Holling, 1990)

The literature provides some interesting, but not encouraging examples of bait monitoring.

A major problem was that if the bait was taken at all, the species taking the bait could only be identified in a minority of instances even though expensive equipment with high sensitivity and fast trigger speeds was used. (Moseby and Read, 2014)
Even when baits were placed in the centre of the field of view the animal responsible for removing the bait could not be identified in a third of cases.
The camera either did not show the act of removing the bait or the camera did not take photos at all. (Meek et al, 2012) We have the same experience - bait is suddenly gone without any photos of an animal that might have removed it.

The high failure rate of passive motion detectors can be tested by using two or more cameras at the same site. Every camera will most likely produce a differing result – the animal seen on one might not be picked up by the other even if the target animal is as large as a fox. Another advantage of using several cameras is that there is still data if the camera (or the operator) fails. (Stokeld et al, 2015)

Placement in more open areas or along tracks and in spots with high densities of small prey species such as rabbits, will give the best results.

In official research the uptake of bait by non-target species – such as ravens, emu, kangaroo - seems to be higher than by the targeted cats or foxes. Meat, eggs, fish, all attract a variety of species that would potentially be killed. In particular cats have a low uptake rate of bait and even if they clearly found and sometimes investigated the bait, it was rarely ingested.  (Algar et al, 2007, Moseby et al, 2011)
At our release sites, capture of cats in cage traps seems to still have the highest success rate, however we are not licensed to use Eradicat which might be more attractive to cats.

Fox bait (buried eggs and meat bait) is frequently taken at our release sites but we sighted on camera and therefore suspect brushtail possums, quenda, shingleback lizards and heath monitors (Varanus rosenbergi) to take some, hopefully not most of them. The act of ingesting bait was never captured on camera though. We also frequently see kangaroos in the baited area but so far there has never been an indication that they removed any of the bait. 

Foxes are quite camera wary, they stare at the camera, approach, retreat, and usually leave without taking the bait.

When a camera is newly installed, foxes seem to move through fast and only fragments of them are captured. However, they get used to the presence of the camera after a while and ignore it. Young animals tend to be curious and check it out. There is however no doubt that animals notice the camera trap – they seem to hear ultrasound generated by cameras and they see the illumination.