Yes, you need a permit if you intend to spend a night in any of the state forest. This includes backpacking trips on the West Rim Trail and Old Loggers Path. The permit is free and if you are on Tioga County land you can obtain the permit from the local forestry office at Nessmuck Lake located on RT 287 just south of Wellsboro. If you are in another county (i.e. the Old Loggers Path is in Lycoming County) you need to obtain a permit from that county's forestry office. Here is a link to DCNR's website. You can get a permit by mail from their site.
Black bears, rattlsnakes and other creatures do live in abundance in Tioga County. There is a very good chance you will see at least one of them if you spend some time in the canyon area or on any of the other hiking trails in North-Central PA. Remember this, if you leave them alone, they will leave you alone. Snakes are often present on the rail trail when the sun is out during the summer months. Try not to run over them with your bike or horse. We like our snakes and live in harmony with them. Watch for snakes on trails. They are easily mistaken for roots. If you hear a sharp rattling sound stop and try to locate where it is coming from; then move away from that area and go back to enjoying your hike.