I've not worked on foxes but my gut feeling is that stopping control will lead to foxes recolonising quickly and all the benefits from 10 years of control will be lost. I"m assuming that foxes have relatively large ranges so in the years that you don't see a difference in activity you may have knocked over the residents and then when the control operation stops other foxes move in. Are you using the same monitoring methods in both the controlled and the uncontrolled area? How big is the controlled area in comparison to fox ranges in your area?

Hi Jamie, thanks for your answer. Average home range size is about 1/60th of the study areas, but there are lots of untreated holes (fox control is conducted by private landholders on their own land). All parts of the two study areas are also within reach of foxes dispersing from outside. Also, survival of collared foxes was pretty high after the last two rounds of treatments (c. 70%). Foxes were ubiquitous, but I suspect they occurred at lower densities in the treated areas.

Population modelling suggests that a treatment regime similar to the ones studied here should produce an initial knockdown that can be sustained with minor fluctuations due to seasonal reproduction, immigration and population control. However, these ongoing fluctuations would probably be too small to be detected using the survey methods that have been used here for the past few years. Survey methods were similar at treatment and nil-treatment sites (nil-treatments had less intensity), but they’re still not comparable because detectability could differ between sites.

It’s not possible to give a definitive answer on what’s going on here, but it would be nice to refer to the aforementioned modelling and perhaps a real world example of a similar situation. This might lend some support to the idea of testing whether ongoing fox control could be valuable without each individual control program having a massive impact on the population.

Hi Andrew

I've been racking my brains trying to come up with some similar studies but I've drawn a blank unfortunately. Possibly some of the NZ literature on population recoveries after aerial 1080 drops?

Thanks Jamie,

While looking for examples in the NZ literature, I found something a bit closer to home: foxes in eastern Australia (Claridge, A. W., Cunningham, R. B., Catling, P. C. and Reid, A. M. (2010) Trends in the activity levels of forest-dwelling vertebrate fauna against a background of intensive baiting for foxes. Forest Ecology and Management 260(5), 822-832.)