I am in PA and would be willing to go up to North Jersey and confirm this BUT the weather is getting cool here in PA and I assume the same goes for North Jersey. Day time temps are rarely reaching mid 70's and night time temps are in the low 60's. Being that Cali's are primary nocturnal it could be hard to locate them with the cool weather looming.
If these guy's get a major foot hold it'll be hard to get rid of them. I personally think they will be able to survive in the Pine Barren's or another other wooded area in NJ. There are some ideal places for them to hybernate but we do have some harsh winters around here sometimes so maybe they would be killed off during the winter but there is a good chance they will do well. They COULD cover the whole state and interbreed with the eastern king and could also wind up slaughtering any local species. Snakes in NJ are getting rare and to think that the cali king has establisted itself and could be killing off NJ natives is disturbing.
If he is seeing more then one it COULD BE that these guys are 2nd or even 3rd gen cali's that were released into the wild. Someone could have been a nickle/dime breeder and let them go which is what I would assume. If they are 2nd gen that means they already survived last winter.
What bothers me the most is cali king's are known to be huge snake eatters.A little more so then the eastern king from what I understand. This could spell doom for some of native locals in NJ such as the copperhead which it's status is unknown,the rare timber rattler,the endangered corn snake(but these two snakes have been KNOWN to mate but I think the king would assume food first) and other snakes like ringnecks,racers,eastern milks..list goes on..while a lot are stable collecters have depleted a lot of herps in the pine barrens over the years and with the cali king roaming around the balance could change serverly over the next 10 years. The cali certainly wouldn't stay up north and would travel south into southern NJ,Del and further down south...They could even wind up in area's of PA.
I copied and pasted this from my other post on the king snake board.
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Reptiles
0.1 - Early 2002 Anery Motley Corn 33 1/2"
1.0 - Late 2003 Yellow Rat Snake 15 2/3"
0.0.1 - 2003 Banded California King Snake 29 2/3"
1.0 Green Anole
0.0.0 House Gecko
0.1 Painted Turtle
Mammals
4 female ferrets,1 male cat and 1 male doberman...and a few kids!
RIP - Nala my Rottie 08/19/2004