From what I've read, and seen for myself, it seems to be around 8-10 months of age. Tho it can be sooner, or possibly later, depending on the individual chin.
It lasts until his hormones settle, which can take months. In some cases, nothing much happens. In others, if there's a cage mate, they might fight, or you'll see more dominance humping than usual. Some chins will start "loving" your hand, socks, and their stuffed pillows or cuddle buddies.
Most chinchillas are considered adult at 10-12 months, but it doesnt always mean they are done growing. I've seen ebonies continue to grow until 2yrs old or beyond, and I've had a fella here go thru a sudden growth spurt at 3yrs old.
~Barb~
