Usually they are. Haldane’s Rule notes that in hybrids the sex with two different sex chromosomes (XY) is highly likely to be sterile (there’s been a couple of male mules with what should be viable sperm but it never worked) but on rare occasions females (XX) can have viable offspring if the male they mate with is not a hybrid. Coywolves are generally fertile, tigon/liger females occasionally, female mules have reproduced the least and it’s only been documented a handful of times.

Edit: typo