It really isn't a problem catching porcupines, just give them a little time to return. The last time I made blind sets with both 15 and 18 inch wide double door beaver traps with a bit of simple drift fencing, which worked fine, got several in a couple of weeks, no bait or lures as usual.
In response to to those who might be experiencing beaver refusals from other beaver cage traps, I surely can't say why they are having issues. Perhaps narrow traps are part of their problem or bulky, conspicuous door systems? With experience under our belt, we have been trapping beaver almost exclusively with wide, low profile swim through beaver cage traps for nearly 10 years now taking a total of 1,336 beaver with no evidence of refusals of any kind, often cleaning entire colonies of 8 or 10 beaver in two nights without issue. Many ADC trappers have taken 100 beaver per year using these cage traps for many years, racking up catches of 300, 500 and more beaver with no evidence or even a suggestion of refusals. These traps also regularly take both otter, beaver and porcupines, even bobcats, fox and coyotes in dry sets, again minus refusals. With so many variables, identifying real problems and solving them should need not be confused with ginning worries about issues that could easily be attributable to many factors.
I don't know of a test for Crypto Chrome molecules in Porcupines. EMF intensity could be a big factor. I would think because of its genetic base and the quills a trap 14 inches wide or more and a door opening height of 14 inches or more would be best if EMF is a factor.
As far as EMF intensity testing for beaver and otter
,a trap should work well on land as well as under water to be the most effective. The only way I have found that to be true is a trap that has a low intensity as the animal moves through the trap. Check your traps using your IPHONE with a tesla magnetometer App.
As far as how effective cage traps can be I took a whole colony of beaver (10) earlier this year myself in 10 days with two cage traps that work equally well on land or in water and underwater.
As far as taking 1300 or more beaver in ten years in cage traps seems to me, based on my experience, to be a very low number if one was targeting water sets and sets on land. I have never found it possible to avoid refusals if the traps being used had a elevated intensity EMF at the traps door or going through the trap when used on land for beaver and otter. Catches of over 100 beaver per month with 12 cages should be consistently possible if the trapper has the area, ability, and corresponding equipment such a truck and supplies. (Cool times of the year)
Where Bobcats are concerned they pay little concern for elevated EMF's inside a trap. To compare under water sets and animals such as cats to traps having a elevated EMF is not accurate. All traps omit a magnetic field. Not all of the models have a reduced field, but many do. These also include the cheaper traps made by so many of the manufacturers.
Check your traps for EMF intensity and find out for yourself. I have never found it to be inaccurate.