Cat baiting using Eradicat and Curiosity… is it working?

Baiting is an effective method of controlling feral cats. To date two types of cat baits have been developed, Eradicat® (dosed with 1080) and Curiosity® [containing an encapsulated pellet known as the ‘Hard Shell Delivery Vehicle’ (HSDV), which contains the toxicant ‘PAPP’ (Para-aminopropiophenone)]. There are other baits in trial programs at the moment (i.e. Hisstory) but they are not approved bait types yet.

When feeding, cat’s generally shear their food into manageable chunks and swallow these portions whole. In contrast, most non-target species typically process food items more thoroughly in the mouth. This makes the HSDV delivery method very effective as non-target species usually reject the pellet. The PAPP toxin is required to be encapsulated within the pellet form. If injected directly into the bait the concentration needs to be increased, therefore increasing the risk to non-target species. The Department of Parks and Wildlife has undertaken a field trial to compare the efficacy of both baits (Algar et al. 2011). Below is a summary of this research, however, if you are interested in reading the article in its entirety it can be viewed here.

Cafeteria pen trials have been undertaken previously at the cat haven to determine a preference between the two baits among semi-feral cats by offering them a choice between the two non-toxic bait mediums. Each cat’s bait preference was recorded during the trial. If a cat consumed both baits, then its first preference was recorded. A total of 43 cats consumed at least one bait type and analysis indicated a significant difference in preference with 40 of the cats consuming Eradicat® first. However, in 40% of the occasions when Eradicat® was consumed first, the cats then also consumed the Curiosity® bait.

To test whether this difference was real, the researchers undertook a field trial. The objective of this trial was to determine whether there was any significant difference in baiting efficacy between the two bait types during an operational baiting campaign. This trial was undertaken at Cape Arid National Park (CRNP) and in the adjoining Nuytsland Nature Reserve (NNR). The sites were selected as past surveys had indicated a high presence of cats, no baiting has occurred in the area previously, there are no non-target species at risk in the area, baiting will assist in the conservation of the Critically Endangered Western Ground Parrot (Pezoporus [wallicus] flaviventris) and the baiting in the area will benefit the financial supporters of the study.

Due to limited financial resources the study area was separated into two areas, a larger area (1,200 km²) was baited with Eradicat® and a smaller area (259 km²) was baited with the more expensive Curiosity® bait. Several weeks prior to the baiting program commencing, feral cats were trapped and fitted with radio-collars throughout both study areas. The baiting program began in April/May to avoid the onset of winter rainfall, which will degrade the baits. Aircrafts dropped the baits at an application rate of 50 baits per km². Resulting in a total of 60,000 Eradicat® baits and 12,950 Curiosity® baits being deployed.

Baiting efficacy was determined by two methods: firstly from the percentage of radio-collared cats found dead post baiting and secondly by the difference in cat activity at sand pads pre- and post-baiting by recording presence / absence of tracks at each survey plot. A total of 10 cats were radio-collared in the Curiosity® trial area and nine cats were radio-collared in the Eradicat® survey area. The results of the study indicated that two of the ten radio-collared cats in the Curiosity® bait cell and two of the eight radio-collared cats in the Eradicat® bait cell are presumed to have died from baiting. The results of the sand pad activity indices for cats, foxes and varanids before and after baiting indicated that there was a significant reduction in the Eradicat® area, but interestingly, there was a non-significant increase within the Curiosity® study area after baiting.

The mortality rate of the radio-collared cats in both study areas was low, therefore the results of the study are inconclusive; however, the study did indicate that Eradicat® baiting had a significant impact on cat activity in the area post-baiting. Unfortunately, a fire within the study area several weeks prior to the baiting program may have impacted the results, particularly regarding the slight increase in activity within the Curiosity® study plot and was likely a limitation of the study.

It is thought that poor bait uptake by cats in either area, in comparison with previous trials, was most likely a result of reduced bait attractiveness/palatability. Both feral cat bait types require preparation by thawing and sweating prior to deployment in the field. To have sufficient baits prepared to suit the timing of flights necessitates that many baits are prepared the day prior to delivery. However, logistical issues make this difficult at times. Unfortunately, the longer baits are left before deployment the greater the chance that mould and rancidity can impact the baits. Decaying baits are not attractive/palatable to cats and bait uptake is therefore significantly reduced.

Suggestions from the study to improve baiting efficacy in more temperate regions recommended that:

• An efficient artificial method to sweat baits in the field is developed as reliance on environmental conditions to sweat baits is likely to result in poor quality baits being distributed;
• A test for bait stability/longevity is undertaken in all future trials to gain some measure of bait availability over time; and
• Trials to assess baiting efficiency during late summer are conducted. Despite the prey resource likely to be more abundant during these warmer months, bait integrity and longevity will be improved and therefore potentially bait uptake.

Fortescue Marsh cat management

DPaW, using environmental offset funds, has undertaken numerous feral cat baiting programs in and around the Fortescue Marsh (Clausen et al. 2015). Clausen et al. (2015) reported to the outcomes of Year 4 of this program.

Eradicat® baits were aerially distributed over a 896 km² area of the Fortescue Marsh in mid-July of 2015. Eighteen feral cats trapped within the treatment area were monitored with radio-collars and the probability of occupancy was assessed prior to, and following baiting using camera traps at 44 treatment and 24 control sites. Eradicat® baiting of the Fortescue Marsh resulted in a 30% knock-down of radio-collared feral cats. This impact was supported by occupancy modelling using remote camera data, which also demonstrated a significant effect of baiting in the treatment cell when compared to a control. Random models detected decline in occupancy of approximately 20% and spatial models detected a decline of 15%. (Clausen et al. 2015 p 5). Captures of feral cats in 2015 were similar to those in previous years, with a 2.12% capture success rate, so, given baiting programs occurred in 2012, 2013 and 2014, these data might suggest the baiting programs were having limited impact on reducing the cat population.

Curiosity bait trial in Karijini National Park

Curiosity® baits were aerially distributed over a 268 km² area within Karijini National Park, Western Australia in August 2012 (Johnson et al. 2013). This trial was part of a series of field trials conducted across Australia to assess the efficacy of this bait product and monitoring of the bait efficacy program was undertaken by assessing site occupancy of feral cats prior to and following baiting using automated cameras.  In addition to the camera trap surveys, the survival of eight GPS radio-collared cats was monitored. The study also included replicated counts of birds prior to and following the aerial baiting to determine whether the Curiosity® baits led to a decrease in populations of non-target species. Impacts on reptile populations were expected to be mitigated given that the application of baits was timed for winter when these species were minimally active. The full research report can be view here.

An analysis of site occupancy data showed that there was no significant reduction in the feral cat population after baiting. None of the collared cats died as a result of bait consumption, despite numerous opportunities to encounter the bait as indicated by the GPS datalogged locations. Corvids and dingoes were photographed removing and consuming baits from a limited number of sites, however, as these individuals were not ‘marked’ or otherwise identifiable, it was not possible to monitor their fate throughout the study. Counts of non-target bird species did not show any broad population decline, suggesting that presence of baits did not lead to loss of population viability.

Several problems encountered during the study affected the results:

• The visual lures used with the automated camera surveys were not ideal;
• The baiting aircraft was delayed, which meant that baits were applied in hotter weather. This affected increases in both the desiccation rate of baits and potentially also the abundance of available prey resource particularly with small reptiles;
• Baits developed a putrescent odour and exhibited limited ‘sweating’ (i.e. exudation of the chicken fat component) which reduced bait attractiveness; and
• Insufficient cats were fitted with collars to make confident statements about changes in the feral cat population. Ongoing development efforts are required to confirm that the Curiosity® bait is an effective management tool for reducing feral cat populations in semi-arid Australia.

Ethical issues

Doherty and Ritchie (2016) raise the often forgotten ethical issues associated with wide-spread attempted culls / killing of feral species including cats and foxes as the bycatch / kill resulting from these widespread aerial baiting programs can be significant. For example, Dundas et al. (2014) reported 99% of the monitored 1080 baits (Probait®) laid in the Jarrah forest of south-west Western Australia were taken by non-target species and the threatened quokka took 48% of them. Doherty and Ritchie (2016) explained the logic of these culls is that the benefits to conservation significant species outweigh the impact on the bycatch / kill species. However, they suggest this logic must be challenged when culls fail to have a positive impact on the species they aim to protect. They went on to express concern about the resources spent on these ineffective culls.

So what is an acceptable percentage death rate of the target species relative to the number of deaths of unintended species? Is 10% of non-target species acceptable, if we get 90% of the target species acceptable? As indicated above, aerial baiting is not always effective in culling the target species for a variety of reasons, but an unknown number of non-target species are often killed in these failed or unsuccessful attempts.

Rethinking cat management priorities

Given the Threatened Species Commission has committed the Commonwealth Government to killing 2 million cats by 2020 (Anon. 2015), which will mostly be done using aerial baiting programs, then perhaps we need to rethink how best these funds might be spent in conserving threatened species. Other programs including top-predator conservation and release, maintaining and restoring habitat complexity and ecological refuges, exclusion fences and assisted behavioural and evolutionary ecology may be viable alternatives (Doherty and Ritchie 2016).

Thanks to Andrew Hide for drafting an earlier version of this blog.

Reference

Algar, D., N. Hamilton, M. Onus, S. Hilmer, S. Comer, C. Tiller, L. Bell, J. Pinder, E. Adams, and S. Butler. 2011. Field trial to compare baiting efficacy of Eradicat® and Curiosity® baits. Perth.

Anon. 2015. Threatened Species Strategy. Canberra.

Clausen, L., S. Cowen, J. Pinder, J. Pridham, A. Danks, P. Speldewinde, S. Comer, and D. Algar. 2015. Fortescue Marsh Feral Cat Baiting Program (Christmas Creek Water Management Scheme) Year 4 Annual Report. Perth.

Doherty, T. S., and E. G. Ritchie. 2016. Stop jumping the gun: A call for evidence-based invasive predator management. Conservation Letters.

Dundas, S. J., P. J. Adams, and P. A. Fleming. 2014. First in, first served: uptake of 1080 poison fox baits in south-west Western Australia. Wildlife Research 41:117-126.

Johnston, M., O’Donoghue, M., Holdsworth, M., Robinson, S., Herrod, A., Eklom, K., Gigliotti, F., Bould, L. and Little, N. (2013) Field assessment of the Curiosity® bait for managing feral cats in the Pilbara. Arthur Rylah Institute for Environmental Research Technical Report Series No. 245. Department of Sustainability and Environment, Heidelberg, Victoria.

Photo credit: Top – Pilbara landscape near Karijini; bottom – 1080 bait warning sign