His diet is a definite problem. You must try other veggies besides Spring mix. Try kale, watercress, escarole, endive, radicchio, butternut squash, yellow squash, zucchini, sweet potato, red cabbage, sugar snap peas, avocado (no skin or pit they’re toxic), coconut chunks, papaya, apple, pear. Here’s the link to the healthy foods he should be eating.
https://thesquirrelboard.com/forums/...-Pet-Squirrels
Don’t give any nuts till he begins to eat veggies with his blocks. Henrys blocks are loaded with vitamins but they are meant to be eaten as a supplemental block in combination with healthy veggies and fruits…not in combination with nuts. Giving nuts to a squirrel when he doesn’t eat his veggies is like letting a toddler have ice cream instead of veggies.
The hair loss could be from him pushing his nose through the bars of his cage and rubbing it off. It could also be from his diet.
I fear with his diet he is a prime candidate for metabolic bone disease. MBD is the result of not enough calcium in the diet and too many high phosphorus foods, like nuts. The squirrels body tries to maintain the proper calcium to phosphorous ratio, but if he’s not getting enough calcium from foods then his body will pull the calcium from his bones to maintain the proper ratio. MBD is painful, causes hind end paralysis and eventually death if left untreated.